An ultraviolet absorber and PET plastic

Abstract

This application relates to the field of PET plastics technology, and more particularly to a UV absorber and PET plastic. The UV absorber is prepared by the following method: under a protective gas atmosphere, alkyl α-cyano-4-hydroxy-3-alkoxycinnamic acid, an inorganic base, and an epoxy chain extender are dissolved in a polar aprotic solvent, and the mixture is stirred and reacted at 100°C~120°C for 2~8 hours. After the reaction, acidification, filtration, washing, and drying are performed sequentially. The solution provided in this application can effectively improve the dispersion stability of the UV absorber in the PET matrix, reduce the risk of migration and precipitation, and maintain the advantage of high material transparency.

Description

Technical Field

[0001] This application relates to the field of PET plastics technology, and more particularly to an ultraviolet absorber and PET plastic. Background Technology

[0002] Polyethylene terephthalate (PET) is widely used in packaging, fiber, and industrial films worldwide due to its excellent transparency, mechanical strength, gas barrier properties, and recyclability. However, the ester groups and benzene rings in the PET molecular structure are prone to photochemical degradation under long-term sunlight exposure, leading to polymer chain breakage and a decrease in molecular weight. Macroscopically, this manifests as yellowing, decreased transparency, deterioration of mechanical properties, and increased brittleness.

[0003] Furthermore, in photovoltaic and packaging applications, ultraviolet (UV) radiation can penetrate PET materials and adversely affect the contents. For example, it can accelerate the photo-oxidation of sensitive components such as vitamins, pigments, and flavorings in food and beverages, leading to loss of nutritional value, flavor deterioration, and shortened shelf life. Therefore, adding UV-shielding additives to PET to build an effective protective barrier has significant technical and commercial value in protecting both the PET material itself and its contents.

[0004] Existing UV shielding additives function through three pathways: UV absorption, shielding / reflection, and excited-state quenching. Commonly used types include benzophenones, benzotriazoles, triazines, and inorganic nanoparticles.

[0005] In existing technologies, various patents have proposed different PET UV protection solutions. For example, Chinese patent CN107418159A uses organic UV absorbers (such as UV-9) and nano-metal oxides (such as Al2O3) to prepare BOPET shielding masterbatch, achieving 100% UV blocking rate, but the metal oxides reduce the transparency of the product. Chinese patent CN108456947A uses hollow porous microspheres with composite organic UV absorbers to prepare UV-resistant PET fibers, but the hollow microspheres significantly reduce the transparency of the product. Chinese patent CN103788597A uses UV absorbers and dyes to prepare UV-color blocking PET bottles, but there are problems with large addition amounts and easy precipitation. Chinese patent CN110982051A prepares PET with a molecular structure containing UV-resistant and flame-retardant units, but there are problems with multiple reaction steps, complex processes, and difficulty in large-scale promotion. Summary of the Invention

[0006] One of the purposes of this application is to provide a UV absorber that avoids the shortcomings of the prior art, effectively improves the dispersion stability of the UV absorber in the PET matrix, reduces the risk of migration and precipitation, and maintains the advantage of high material transparency.

[0007] The second objective of this application is to provide a PET plastic.

[0008] One of the objectives of this application is to achieve the following technical solution:

[0009] An ultraviolet absorber is provided, which is prepared by the following method: under a protective gas atmosphere, alkyl α-cyano-4-hydroxy-3-alkoxycinnamic acid, an inorganic base and an epoxy chain extender are dissolved in a polar aprotic solvent and stirred at 100°C to 120°C for 2 to 8 hours. After the reaction is completed, acidification, filtration, washing and drying are performed in sequence.

[0010] In some embodiments, based on 100 parts by mass of α-cyano-4-hydroxy-3-alkoxycinnamic acid alkyl ester, the amount of inorganic base added is 6 to 8 parts by mass, the amount of polar aprotic solvent added is 220 to 280 parts by mass, and the amount of epoxy chain extender added is 275 to 325 parts by mass.

[0011] In some embodiments, the method further includes adding an alkyl primary alcohol in a volume ratio of 1:4 to the volume of the polar aprotic solvent.

[0012] In some embodiments, the alkyl primary alcohol includes at least one selected from methanol, ethanol, n-propanol, n-butanol, dodecyl alcohol, and octadecyl alcohol.

[0013] In some embodiments, the alkyl α-cyano-4-hydroxy-3-alkoxycinnamate includes any one of methyl α-cyano-4-hydroxy-3-methoxycinnamate, ethyl α-cyano-4-hydroxy-3-methoxycinnamate, ethyl α-cyano-4-hydroxy-3-ethoxycinnamate, propyl α-cyano-4-hydroxy-3-propoxycinnamate, butyl α-cyano-4-hydroxy-3-butoxycinnamate, and hexyl α-cyano-4-hydroxy-3-methoxycinnamate.

[0014] The epoxy chain extender includes at least one of ADR-4370, ADR-4468, ADR-4368, and ADR-4400.

[0015] In some embodiments, the polar aprotic solvent includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone;

[0016] The inorganic base includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate.

[0017] The ultraviolet absorber provided in this application has the following beneficial effects:

[0018] (1) The ultraviolet absorber provided in this application can effectively shield ultraviolet rays from 250nm to 400nm and can cover the UVA and UVB bands. The molecular structure of the ultraviolet absorber contains epoxy groups, which can undergo grafting reaction with PET resin, thereby improving the tensile strength of plastic products and significantly reducing the risk of precipitation. In addition, the ultraviolet absorber does not contain inorganic particles or hollow structures, and will not reduce the visible light transmittance of PET plastic products, making it suitable for transparent packaging, film and other application scenarios.

[0019] (2) This application uses a one-step reaction process to prepare ultraviolet absorbers. No complicated modification steps are required. High-purity products can be obtained by simply acidifying, filtration, washing and drying. The operating cost is low, there are no additional complicated separation processes, the process is simple and controllable, and it is easy to industrialize.

[0020] The second objective of this application is achieved through the following technical solution:

[0021] A PET plastic is provided, comprising 90 to 99.9 parts by weight of PET resin, 0.05 to 5 parts by weight of a first ultraviolet absorber, and 0.05 to 5 parts by weight of a second ultraviolet absorber; wherein the first ultraviolet absorber is the aforementioned ultraviolet absorber.

[0022] In some embodiments, the second ultraviolet absorber includes at least one of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, triazines, and hindered amines.

[0023] In some embodiments, it also includes at least one of antioxidants, antistatic agents, antihydrolysis agents, toughening agents, colorants, fillers, and flame retardants.

[0024] In some embodiments, the PET plastic is obtained by mixing the components evenly in a high-speed mixer and then melt-extruded it through a twin-screw extruder at 270°C to 280°C to obtain the PET plastic.

[0025] The PET plastic provided in this application has the following beneficial effects:

[0026] The PET plastic provided in this application achieves efficient shielding with a low amount of the first UV absorber, covering the 300nm~400nm wavelength band. The first UV absorber exhibits good compatibility with PET, with minimal leaching after immersion in ethanol at 70℃ for 24 hours, demonstrating high long-term stability. Furthermore, the PET plastic containing the first UV absorber has higher tensile strength than traditional UV-resistant PET, achieving a balance between UV resistance and mechanical properties. This application optimizes the reaction system and component ratio to construct a UV absorber structure with better compatibility with the PET matrix. Applying this structure to PET solves the technical problems of easy migration and leaching of traditional UV absorbers and their impact on transparency, resulting in improved material weather resistance and optical properties. Attached Figure Description

[0027] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0028] Figure 1 This refers to the light transmittance of 0.1 mm samples prepared from various embodiments and comparative examples of this application. Detailed Implementation

[0029] Preferred embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0030] PET is widely used in transparent packaging, fibers, industrial films and photovoltaic module encapsulation, where there are strict requirements for the material's transparency, long-term stability and mechanical properties.

[0031] Existing small-molecule UV absorbers (such as benzotriazole UV360 and benzoxazolone UV3638) have poor compatibility with PET resin and are prone to leaching from plastic products in practical applications. This not only reduces the long-term effectiveness of UV protection but may also contaminate the contents of food, beverages, and other products. At the same time, poor compatibility leads to the deterioration of the mechanical properties of PET plastic products. In addition, some existing solutions use inorganic particles or hollow microspheres to improve the shielding effect, but this significantly reduces the transparency of PET plastic products and cannot meet the needs of transparent packaging and other scenarios.

[0032] To address the aforementioned issues, this application provides a UV absorber that can effectively improve the dispersion stability of the UV absorber in the PET matrix, reduce the risk of migration and precipitation, and maintain the advantage of high material transparency.

[0033] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0034] The present application will be further described in detail below with reference to the embodiments. All components described in the present application are obtained commercially. The components described in the specific embodiments or examples are mass ratios or mass parts.

[0035] In a typical embodiment of this application, an ultraviolet absorber is provided, which is prepared by the following method: under a protective gas atmosphere, alkyl α-cyano-4-hydroxy-3-alkoxycinnamic acid, an inorganic base and an epoxy chain extender are dissolved in a polar aprotic solvent and stirred at 100°C to 120°C for 2 to 8 hours. After the reaction is completed, acidification, filtration, washing and drying are performed in sequence.

[0036] Specifically, the protective gas can be one of nitrogen, argon, or helium. Alkyl α-cyano-4-hydroxy-3-alkoxycinnamic acid esters are derivatives of cinnamic esters, wherein the alkoxy group is a C1-C4 alkyl group, specifically methyl (-OCH3), ethyl (-OC2H5), propyl (-OC3H7), and butyl (-OC4H9), and the alkyl ester is a C1-C6 alkyl group, specifically methyl ester (-COOCH3), ethyl ester (-COOC2H5), propyl ester (-COOC3H7), and hexyl ester (-COOC6H9). 13 Acidification refers to washing with one of dilute hydrochloric acid, dilute sulfuric acid, or dilute phosphoric acid, preferably with a mass fraction of 5% to 10% dilute hydrochloric acid. The washing step involves washing the filtered solid with distilled water until the filtrate is neutral. The drying step involves vacuum drying at 60°C to 80°C for 4 to 6 hours.

[0037] In this embodiment, α-cyano-4-hydroxy-3-alkoxy alkyl cinnamate is a derivative of cinnamic ester. α-cyano-4-hydroxy-3-alkoxy alkyl cinnamate can be obtained directly from commercially available products or prepared through organic synthesis. Its hydroxyl and carboxyl groups can participate in subsequent chain extension reactions. An inorganic base acts as a catalyst in the reaction, promoting the cross-linking reaction between the epoxy group and the carboxyl group. For example, sodium hydroxide or sodium carbonate can be used as an inorganic base. An epoxy chain extender is a compound containing epoxy groups, whose main function is to form high molecular weight products through chain extension reactions. Other types of epoxy resins or polyols can be used as alternatives. A polar aprotic solvent is used to dissolve the reaction components and also promotes homogeneous reaction. N,N-dimethylformamide, dimethyl sulfoxide, or other solvents with similar properties can be used. The reaction is stirred at 100℃~120℃ for 2~8 hours. Based on reaction kinetics, this temperature range and time window ensures the reaction proceeds fully while avoiding thermal decomposition. After the reaction, acidification is performed primarily to neutralize any residual alkalinity in the reaction system, causing the target product to precipitate in solid form. The filtration, washing, and drying steps are mainly used to remove unreacted substances and impurities, ensuring the purity of the final product. Similar effects can be achieved through methods such as centrifugation or vacuum drying.

[0038] This application synthesizes an absorber that effectively protects polyethylene terephthalate (PET) materials from UV damage and improves their mechanical strength through specific reaction system design and process control. Compared with existing technologies, this method avoids the problem of reduced transparency caused by the addition of inorganic nanoparticles or dyes, while simplifying the process and reducing the risk of UV absorber migration and precipitation in PET materials, thereby maintaining the optical and mechanical properties of plastic products over a long period.

[0039] Further, based on 100 parts by mass of α-cyano-4-hydroxy-3-alkoxycinnamic acid alkyl ester, the amount of inorganic base added is 6-8 parts by mass, the amount of polar aprotic solvent added is 220-280 parts by mass, and the amount of epoxy chain extender added is 275-325 parts by mass.

[0040] Specifically, the core function of the inorganic base is to catalyze the cross-linking reaction between the epoxy group and the alkyl ester of α-cyano-4-hydroxy-3-alkoxycinnamic acid. Designing the inorganic base to have a concentration in the range of 6-8 ensures sufficient catalytic activity, allowing the reaction to proceed fully at 100-120°C for 2-8 hours. Insufficient base concentration results in low catalytic efficiency, incomplete reaction, a wide molecular weight distribution of the product, and negatively impacts UV absorption performance and compatibility with PET. Excessive base concentration leads to overly alkaline reaction systems, which can cause hydrolysis of the epoxy chain extender and subsequent side reactions.

[0041] The role of polar aprotic solvents is to dissolve all reaction components and create a homogeneous reaction environment. Using a polar aprotic solvent in the range of 220-280 parts per cubic meter ensures complete dissolution of the raw materials. If the amount is below 220 parts per cubic meter, some raw materials (such as the chain extender ADR) may not dissolve sufficiently, leading to precipitation, uneven local reactions, inconsistent product structures, and affecting the UV shielding effect. If the amount is above 280 parts per cubic meter, there is a problem of over-dilution, resulting in a decrease in the reaction rate.

[0042] The core function of epoxy chain extenders is to react with the hydroxyl / carboxyl groups of esters to form high molecular weight products, thereby improving compatibility with PET. Targeting the amount of epoxy chain extender within the range of 275-325 ensures sufficient chain extension and the formation of products with adequate molecular weight. Insufficient dosage results in low molecular weight products that are prone to precipitating from PET. Excessive dosage leads to over-chain extension, resulting in excessively cross-linked products that negatively impact subsequent processing (e.g., poor flowability during melt extrusion).

[0043] Furthermore, the method further includes adding an alkyl primary alcohol to replace part of the polar aprotic solvent, wherein the volume ratio of the alkyl primary alcohol to the polar aprotic solvent is 1:4.

[0044] Specifically, alkyl primary alcohols refer to a class of straight-chain or branched alcohol compounds with terminal hydroxyl groups. In the preparation of UV absorbers, the introduction of alkyl primary alcohols allows them to interact with polar aprotic solvents (such as N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone), promoting phase separation or precipitation of the reaction mixture. This facilitates more effective removal of solvent residues in subsequent filtration and washing steps, preventing impurities from affecting product performance. By replacing some of the polar aprotic solvent with alkyl primary alcohols, the purity of the product can be improved, thereby enhancing the application stability of the UV absorber and improving the transparency and long-term performance of PET materials. In practice, the replacement of some polar aprotic solvents with alkyl primary alcohols can be adjusted according to the viscosity of the system.

[0045] Further, the alkyl primary alcohol includes at least one selected from methanol, ethanol, n-propanol, n-butanol, dodecyl alcohol, and octadecyl alcohol. In some embodiments, methanol or ethanol is preferred, as UV absorbers prepared from these two alkyl primary alcohols have better compatibility with PET.

[0046] Further, the alkyl α-cyano-4-hydroxy-3-alkoxycinnamate includes any one of methyl α-cyano-4-hydroxy-3-methoxycinnamate, ethyl α-cyano-4-hydroxy-3-methoxycinnamate, ethyl α-cyano-4-hydroxy-3-ethoxycinnamate, propyl α-cyano-4-hydroxy-3-propoxycinnamate, butyl α-cyano-4-hydroxy-3-butoxycinnamate, and hexyl α-cyano-4-hydroxy-3-methoxycinnamate;

[0047] The epoxy chain extender includes at least one of ADR-4370, ADR-4468, ADR-4368, and ADR-4400.

[0048] Furthermore, the polar aprotic solvent includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone;

[0049] The inorganic base includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate.

[0050] This application's embodiments involve a chain extension reaction between alkyl α-cyano-4-hydroxy-3-alkoxycinnamate and an epoxy chain extender under a protective gas atmosphere. This, combined with the catalytic effect of an inorganic base and a homogeneous reaction environment using a polar aprotic solvent, generates a high-molecular-weight UV absorber. This design significantly improves the compatibility of the UV absorber with the polyethylene terephthalate matrix, avoiding the problem of easy migration and precipitation of small-molecule additives. It also maintains the high transparency of plastic products, overcoming the optical performance degradation caused by the addition of inorganic nanoparticles or dyes in existing technologies. Furthermore, by optimizing the reaction temperature and time window, the process flow is simplified, reducing the need for multi-step synthesis or complex post-processing, providing an efficient and stable solution for industrial production.

[0051] In another embodiment, this application also discloses a PET plastic comprising the following components in parts by weight: 90-99.9 parts by weight of PET resin, 0.05-5 parts by weight of a first ultraviolet absorber, and 0.05-5 parts by weight of a second ultraviolet absorber; wherein the first ultraviolet absorber is the aforementioned ultraviolet absorber; and the second ultraviolet absorber may include one or more of benzotriazoles, benzoxazolones, and triazines.

[0052] Specifically, the PET resin substrate is a polyethylene terephthalate (PET) polymer, which may include homopolymers, copolymers, or mixtures of two or more PET polymers, preferably homopolymers. The homopolymer refers to a PET polymer composed solely of repeating polyethylene terephthalate units, which possesses excellent transparency, mechanical strength, and gas barrier properties, making it particularly suitable for film-grade, bottle-grade, and fiber-grade applications.

[0053] Furthermore, the intrinsic viscosity of PET resin is preferably 0.68–1.0 dL / g, which balances the processing fluidity and mechanical strength of PET plastic, and is suitable for molding requirements of different application scenarios such as film and bottle.

[0054] Furthermore, the PET resin can be one or more of film-grade, bottle-grade, and fiber-grade, with film-grade PET resin being preferred. Film-grade PET resin has superior transparency and tensile properties, making it particularly suitable for applications with stringent optical and mechanical performance requirements, such as packaging films and photovoltaic encapsulation films.

[0055] Furthermore, the second ultraviolet absorber includes at least one of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, triazines, and hindered amines.

[0056] Furthermore, it also includes at least one of antioxidants, antistatic agents, anti-hydrolysis agents, toughening agents, colorants, fillers, and flame retardants.

[0057] It is understandable that the selection, addition method, and dosage of antioxidants, antistatic agents, anti-hydrolysis agents, toughening agents, colorants, fillers, and flame retardants are conventional techniques that those skilled in the art can master.

[0058] Furthermore, the PET plastic is obtained by the following method: after the components are mixed evenly in a high-speed mixer, the mixture is melt-extruded through a twin-screw extruder at 270°C to 280°C to obtain the PET plastic.

[0059] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0060] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0061] Example 1

[0062] 1. Preparation of the first ultraviolet absorber: Under nitrogen protection, 0.1 mol of methyl α-cyano-4-hydroxy-3-methoxycinnamate, 1.7 g of potassium hydroxide, 60 mL of N,N-dimethylformamide, and 72.5 g of polyfunctional epoxy chain extender ADR-4468 were added to a 250 mL three-necked flask. The mixture was stirred and heated to 100-120 °C and reacted at a constant temperature for 4 hours. After the reaction was completed, the solution was acidified to pH 2-3 with 5%-10% dilute hydrochloric acid. The solution was then filtered, washed with distilled water until the filtrate was neutral, and dried under vacuum at 60-80 °C for 4 hours to obtain the first ultraviolet absorber.

[0063] 2. Preparation of PET plastic: Take 93.5 parts by weight of dry PET resin and 6.5 parts by weight of the above-mentioned macromolecular ultraviolet absorber, and mix them in a high-speed mixer for 5 minutes; the mixture is melt-extruded and granulated by a twin-screw extruder with an extruder temperature of 270~280℃, a die temperature of 260℃, and a screw speed of 300r / min.

[0064] Example 2

[0065] 1. Preparation of the first ultraviolet absorber: Same as in Example 1.

[0066] 2. Preparation of PET plastic: Take 99.8 parts by weight of dried PET resin and 0.2 parts by weight of the above-mentioned first ultraviolet absorber, mix and extrude granulate in the same way as in Example 1.

[0067] Example 3

[0068] 1. Preparation of the first ultraviolet absorber: Same as in Example 1.

[0069] 2. Preparation of PET plastic: Take 98.8 parts by weight of dried PET resin, 1 part by weight of the above-mentioned first ultraviolet absorber and 0.2 parts by weight of benzotriazole UV360, mix and extrude granulate in the same way as in Example 1.

[0070] Comparative Example 1

[0071] Take 98.8 parts by weight of dried PET resin and 1.2 parts by weight of benzotriazole UV360, mix and extrude granulate in the same way as in Example 1.

[0072] Comparative Example 2

[0073] Take 93.5 parts by weight of dried PET resin and 6.5 parts by weight of benzoxazolone UV3638, mix them, and extrude and granulate them using the same process as in Example 1.

[0074] The UV-resistant PET plastics of Examples 1-3 and Comparative Examples 1-2 were subjected to transmittance tests, exudation tests, and mechanical property tests:

[0075] Specifically, the transmittance test involved vacuum drying the PET plastic obtained above at 120℃ for 4 hours, followed by casting at 280℃ to prepare a 0.1mm thick sample. The transmittance from 300 to 450 nm was measured using a Shimadzu UV-3600 UV-Vis spectrometer. The test results are shown below. Figure 1 .

[0076] Specifically, the precipitation test involved placing the prepared PET plastic under vacuum drying at 120°C for 4 hours, casting at 280°C to prepare a 0.1 mm thick sample, and then cutting it into 90 cm pieces. 2 The sample was then immersed in 50 mL of anhydrous ethanol and kept at 70°C for 24 hours. The absorbance of the extract at the maximum absorption wavelength was measured by spectrophotometry, and the results are detailed in Table 1.

[0077] Specifically, the mechanical property test involves injection molding dumbbell-shaped strips of the PET plastic prepared above according to ISO 527 standard, and testing the tensile strength using a universal testing machine. The test results are detailed in Table 1.

[0078] Table 1: Absorbance and tensile strength of each embodiment and comparative example

[0079]

[0080] according to Figure 1 The transmittance test results show that Examples 1-3 all achieved a shielding rate of over 99% for ultraviolet light in the 300-400nm band; Example 2, with only 0.2% of the first ultraviolet absorber added, achieved a 23% higher ultraviolet shielding rate at 350nm compared to Comparative Example 1, which added 1.2% of benzotriazole UV360; the ultraviolet shielding range of Example 1 can be extended to 410nm, covering the entire UVA band and part of the visible light edge, providing a wider protection range.

[0081] Regarding precipitation performance and tensile strength, the precipitation amounts in Examples 1-3 were significantly lower than those in the comparative example. Specifically, the absorbance of the precipitate in Example 2 was 0, while the absorbance in Example 1 was <0.1, attributed to the excellent compatibility between the first UV absorber and the PET resin. The core mechanism lies in the fact that the first UV absorber has a macromolecular structure with a significantly higher relative molecular weight than the traditional small-molecule UV360. Furthermore, the introduction of epoxy functional groups into the molecular chain allows it to undergo covalent grafting reactions with the terminal hydroxyl / carboxyl groups of the PET molecular chain at PET processing temperatures, forming stable chemical bonds. This anchors the UV absorbing groups within the PET molecular network, effectively inhibiting the migration and precipitation of the UV absorber. The tensile strength of Example 1 reached 71.3 MPa, an increase of 11.2% compared to Comparative Example 1. This result indicates that the macromolecular chain of the first UV absorber enhances the intermolecular forces of the PET molecular chains through grafting reactions, thereby improving the mechanical properties of the material.

[0082] In summary, Example 2 achieves a superior UV shielding effect compared to Comparative Example 1 by adding only 0.2% of the first UV absorber, significantly reducing the dosage while ensuring protective performance, thus offering better cost-effectiveness.

[0083] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A UV absorber, characterized in that, The ultraviolet absorber is prepared by the following method: under a protective gas atmosphere, 100 parts by weight of alkyl α-cyano-4-hydroxy-3-alkoxycinnamic acid ester, 6-8 parts by weight of inorganic base, and 275-325 parts by weight of epoxy chain extender are dissolved in 220-280 parts by weight of polar aprotic solvent, and the mixture is stirred and reacted at 100℃-120℃ for 2-8 hours. After the reaction is completed, acidification, filtration, washing and drying are performed in sequence. The epoxy chain extender includes at least one of ADR-4370, ADR-4468, ADR-4368, and ADR-4400.

2. The ultraviolet absorber according to claim 1, characterized in that, The method further includes adding an alkyl primary alcohol to replace part of the polar aprotic solvent, wherein the volume ratio of the alkyl primary alcohol to the polar aprotic solvent is 1:

4.

3. The ultraviolet absorber according to claim 2, characterized in that, The alkyl primary alcohols include at least one of methanol, ethanol, n-propanol, n-butanol, dodecanol, and octadecyl alcohol.

4. The ultraviolet absorber according to claim 1, characterized in that, The alkyl α-cyano-4-hydroxy-3-alkoxycinnamate includes any one of methyl α-cyano-4-hydroxy-3-methoxycinnamate, ethyl α-cyano-4-hydroxy-3-methoxycinnamate, ethyl α-cyano-4-hydroxy-3-ethoxycinnamate, propyl α-cyano-4-hydroxy-3-propoxycinnamate, butyl α-cyano-4-hydroxy-3-butoxycinnamate, and hexyl α-cyano-4-hydroxy-3-methoxycinnamate.

5. The ultraviolet absorber according to claim 1, characterized in that, The polar aprotic solvent includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone; The inorganic base includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, and sodium bicarbonate.

6. A PET plastic, characterized in that, It includes 90-99.9 parts by weight of PET resin, 0.05-5 parts by weight of a first ultraviolet absorber, and 0.05-5 parts by weight of a second ultraviolet absorber; The first ultraviolet absorber is the ultraviolet absorber according to any one of claims 1 to 5.

7. The PET plastic according to claim 6, characterized in that, The second ultraviolet absorber includes at least one of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, triazines, and hindered amines.

8. The PET plastic according to claim 6, characterized in that, It also includes at least one of antioxidants, antistatic agents, anti-hydrolysis agents, toughening agents, colorants, fillers, and flame retardants.

9. The PET plastic according to claim 6, characterized in that, The PET plastic is obtained by the following method: after the components are mixed evenly in a high-speed mixer, the mixture is melt-extruded through a twin-screw extruder at 270°C to 280°C to obtain the PET plastic.

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