High-transparency ultraviolet-resistant petg film grade chip and preparation method thereof

Abstract

This invention provides a high-transparency, UV-resistant PETG film-grade slicing and its preparation method, belonging to the field of PETG film-grade slicing technology. To achieve high transparency and long-lasting weather resistance in PETG materials, this application introduces epoxy groups to prepare a reactive UV absorber, which can chemically bond with the PETG matrix, thereby reducing migration tendency and providing long-term UV protection. Secondly, hindered amines are grafted onto a phenyl-containing organosilicon framework to prepare a low-migration, highly compatible light stabilizer that efficiently captures free radicals without affecting the material's transparency. By constructing an organic shell compatible with the matrix for nano-cerium dioxide, its aggregation is effectively inhibited, achieving efficient and transparent inorganic UV shielding. Under the processing protection of antioxidants, these three additives form a well-defined, multi-layered three-dimensional protective network, which is beneficial for maintaining high transparency while improving long-term weather resistance.

Description

Technical Field

[0001] This invention belongs to the field of PETG film-grade slicing technology, and relates to a high-transparency, UV-resistant PETG film-grade slice and its preparation method. Background Technology

[0002] Polyethylene terephthalate-1,4-cyclohexanediol (PETG) is a high-performance, non-crystalline copolyester. Due to its high optical transparency, excellent chemical resistance, and easy thermoforming, PETG is widely used in high-end cosmetic packaging, medical devices, electronic product panels, advertising boards, and specialty films. However, similar to many polyester materials, PETG's molecular structure contains easily photodegradable ester groups and benzene rings, resulting in weak resistance to ultraviolet radiation. Prolonged exposure to sunlight or artificial light sources containing ultraviolet radiation leads to photo-oxidative degradation of PETG, macroscopically manifested as yellowing, decreased transparency, surface cracking, and a sharp deterioration in mechanical properties (such as impact strength and tensile strength). This significantly limits its further development in outdoor applications, long-life display panels, and high-end weather-resistant films.

[0003] Currently, the mainstream method to improve the weather resistance of PETG is to add functional additives, such as UV absorbers and hindered amine light stabilizers, through physical blending. While this method can delay material aging to some extent, it also presents several problems: First, traditional weather-resistant additives are mostly small molecules, which do not bind firmly to the PETG matrix and are prone to migration and precipitation during use. This not only causes the material's protective performance to decay over time, losing its long-term effectiveness, but the precipitates can also contaminate the surface of the product, affecting its appearance and function. Second, the additives have poor compatibility with the PETG matrix, especially when adding highly efficient inorganic shielding agents, which are prone to aggregation. These aggregates form light scattering centers, leading to increased haze and decreased transparency, thus damaging the optical value of PETG. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a high-transparency, UV-resistant PETG film-grade chip and its preparation method. This application introduces highly active epoxy groups onto the UV absorber molecule, enabling it to covalently bond with the PETG matrix during melt blending. This chemical anchoring improves the migration problem of traditional absorbers, serving as the first line of defense for long-term UV absorption. Secondly, a hindered amine light stabilizer is prepared by grafting functional units onto a phenyl-containing organosilicon framework. This not only inhibits migration but also ensures uniform dispersion of the phenyl side chains within the matrix, thereby efficiently capturing free radicals without sacrificing transparency, thus constructing a second line of protection. Finally, a core-shell structured cerium dioxide is constructed by coating it with a highly compatible organic polyester shell, solving the problem of decreased transparency caused by nanoparticle aggregation. This provides inorganic UV shielding while also serving as a stable dispersion anchor. These three additives, under the processing protection of antioxidants, form a three-dimensional protective network integrating UV absorption, free radical scavenging, and processing stabilization. Their synergistic effect helps to improve long-term weather resistance while maintaining high transparency.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing high-transparency, UV-resistant PETG film-grade chips, the method comprising:

[0007] S1: Disperse hydroxyphenyltriazine UV absorber in a mixed solvent, add tetrabutylammonium bromide to obtain an organic phase, prepare a sodium hydroxide solution, add epichlorohydrin dropwise to the organic phase, and simultaneously add sodium hydroxide solution to maintain pH to obtain reaction solution A. Stir the reaction, separate the phases, wash, distill under reduced pressure, and dry to obtain a reactive UV absorber.

[0008] S2: A copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was dispersed in toluene to obtain a dispersion. Under nitrogen protection, 4-allyloxy-2,2,6,6-tetramethylpiperidine and Karstedt catalyst were added to obtain reaction solution B. The reaction was stirred, and the mixture was purified by vacuum distillation and dried to obtain a hindered amine stabilizer.

[0009] S3: Cerium dioxide was dispersed in an aqueous ethanol solution, pH was adjusted with acetic acid, KH-560 was added to obtain reaction solution C, reaction was carried out, centrifuged and washed to obtain surface-modified cerium dioxide, which was dispersed in N,N-dimethylformamide, carboxyl-terminated saturated polyester resin and 1,8-diazabicyclo[5.4.0]undec-7-ene were added to obtain reaction solution D, reaction was carried out, filtered, washed and dried to obtain core-shell structured cerium dioxide;

[0010] S4: PETG matrix, reactive UV absorber, hindered amine stabilizer, core-shell structured cerium dioxide and antioxidant are premixed in a high-speed mixer to obtain a mixture, which is then added to a twin-screw extruder for melt blending and granulation to obtain high-transparency, UV-resistant PETG film-grade chips.

[0011] As a preferred technical solution of the present invention, in step S1, the volume ratio of dichloromethane to toluene in the mixed solvent is 1:(1-3), for example, it can be 1:1.0, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2.0, 1:2.2, 1:2.4, 1:2.6, 1:2.8 or 1:3.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] In some optional embodiments, the amount of tetrabutylammonium bromide added is 0.5-1% of the mass of the hydroxyphenyltriazine UV absorber, for example, it can be 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.90%, 0.95% or 1.00%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0013] In some optional embodiments, the mass fraction of the sodium hydroxide solution is 40-50%, for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0014] In some optional embodiments, the temperature at which epichlorohydrin is added dropwise to the organic phase is 30-50°C, for example, at 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C or 50°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] In some alternative embodiments, sodium hydroxide solution is added to the organic phase to maintain the pH value to 12-13, for example, to maintain the pH value to 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9 or 13.0, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0016] In some optional embodiments, the molar ratio of epichlorohydrin to hydroxyphenyltriazine UV absorber is (6-12):1, for example, it can be 6.0:1, 6.6:1, 7.2:1, 7.8:1, 8.4:1, 9.0:1, 9.6:1, 10.2:1, 10.8:1, 11.4:1 or 12.0:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0017] In some optional embodiments, the reaction time of the reaction solution A is 2-4 hours, for example, it can be 2.0 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] As a preferred technical solution of the present invention, in step S2, the mass fraction of the dispersion is 20-30 wt.%, for example, it can be 20 wt.%, 21 wt.%, 22 wt.%, 23 wt.%, 24 wt.%, 25 wt.%, 26 wt.%, 27 wt.%, 28 wt.%, 29 wt.%, or 30 wt.%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In some optional embodiments, the molar ratio of the hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane copolymer to 4-allyloxy-2,2,6,6-tetramethylpiperidine is (1-1.2):1, for example, it can be 1.00:1, 1.02:1, 1.04:1, 1.06:1, 1.08:1, 1.10:1, 1.12:1, 1.14:1, 1.16:1, 1.18:1 or 1.20:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0020] In some optional embodiments, the amount of the Karstedt catalyst fed is 5-15 ppm of the total mass of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane with 4-allyloxy-2,2,6,6-tetramethylpiperidine, for example, 5 ppm, 6 ppm, 7 ppm, 8 ppm, 9 ppm, 10 ppm, 11 ppm, 12 ppm, 13 ppm, 14 ppm or 15 ppm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] In some optional embodiments, the temperature of the reaction mixture B during stirring is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] In some optional embodiments, the reaction time of the reaction solution B is 6-10 hours, for example, 6.0 hours, 6.4 hours, 6.8 hours, 7.2 hours, 7.6 hours, 8.0 hours, 8.4 hours, 8.8 hours, 9.2 hours, 9.6 hours, or 10.0 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] As a preferred technical solution of the present invention, in step S3, the particle size of the cerium dioxide is 5-10nm, for example, it can be 5.0nm, 5.5nm, 6.0nm, 6.5nm, 7.0nm, 7.5nm, 8.0nm, 8.5nm, 9.0nm, 9.5nm or 10.0nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] In some alternative embodiments, the cerium dioxide is dispersed in an aqueous ethanol solution and then the pH is adjusted to 4.3-4.8 with acetic acid. For example, the pH can be adjusted to 4.30, 4.35, 4.40, 4.45, 4.50, 4.55, 4.60, 4.65, 4.70, 4.75 or 4.80, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the volume ratio of ethanol to deionized water in the ethanol-water solution is (90:10) to (95:5), for example, it can be (90.0, 90.5, 91.0, 91.5, 92.0, 92.5, 93.0, 93.5, 94.0, 94.5 or 95.0):(10.0, 9.5, 9.0, 8.5, 8.0, 7.5, 7.0, 6.5, 6.0, 5.5 or 5.0), but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0026] In some optional embodiments, the mass ratio of cerium dioxide to KH-560 is 1:(0.2-0.3), for example, it can be 1:0.20, 1:0.21, 1:0.22, 1:0.23, 1:0.24, 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29 or 1:0.30, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the reaction temperature of the reaction solution C is 60-80°C, for example, it can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0028] In some optional embodiments, the reaction time of the reaction solution C is 4-6 hours, for example, 4.0 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.4 hours, 5.6 hours, 5.8 hours, or 6.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the surface-modified cerium dioxide dispersed in N,N-dimethylformamide has a mass fraction of 8-15 wt.%, for example, it can be 8 wt.%, 8.5 wt.%, 9 wt.%, 9.5 wt.%, 10 wt.%, 10.5 wt.%, 11 wt.%, 11.5 wt.%, 12 wt.%, 12.5 wt.%, 13 wt.%, 13.5 wt.%, 14 wt.%, 14.5 wt.%, or 15 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] In some optional embodiments, the mass ratio of the carboxyl-terminated saturated polyester resin to the surface-modified cerium dioxide is (0.15-0.3):1, for example, it can be 0.150:1, 0.165:1, 0.180:1, 0.195:1, 0.210:1, 0.225:1, 0.240:1, 0.255:1, 0.270:1, 0.285:1 or 0.300:1, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene fed is 0.5-1% of the mass of the carboxyl-terminated saturated polyester resin, for example, it can be 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.90%, 0.95% or 1.00%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the reaction temperature of the reaction solution D is 120-130°C, for example, it can be 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C or 130°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the reaction time of the reaction solution D is 6-8 hours, for example, it can be 6.0 hours, 6.2 hours, 6.4 hours, 6.6 hours, 6.8 hours, 7.0 hours, 7.2 hours, 7.4 hours, 7.6 hours, 7.8 hours or 8.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0034] As a preferred technical solution of the present invention, in step S4, the mass fraction of the reactive ultraviolet absorber in the mixture is 8-12%, for example, it can be 8.0%, 8.4%, 8.8%, 9.2%, 9.6%, 10.0%, 10.4%, 10.8%, 11.2%, 11.6% or 12.0%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] In some optional embodiments, the mass fraction of the hindered amine stabilizer in the mixture is 2-4%, for example, it can be 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, 3.0%, 3.2%, 3.4%, 3.6%, 3.8% or 4.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some optional embodiments, the mass fraction of core-shell structured cerium dioxide in the mixture is 6-8%, for example, it can be 6.0%, 6.2%, 6.4%, 6.6%, 6.8%, 7.0%, 7.2%, 7.4%, 7.6%, 7.8% or 8.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the antioxidant mass fraction in the mixture is 0.3-0.5%, for example, it can be 0.30%, 0.32%, 0.34%, 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, 0.48% or 0.50%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] The antioxidant 1010 and antioxidant 626 are in a mass ratio of 1:2.

[0039] In some alternative embodiments, the melting temperature is 200-230°C, for example, 200°C, 203°C, 206°C, 209°C, 212°C, 215°C, 218°C, 221°C, 224°C, 227°C or 230°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0040] In some alternative embodiments, the screw rotation speed is 200-300 rpm, for example, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm or 300 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] Secondly, the present invention provides a high-transparency, UV-resistant PETG film-grade chip.

[0042] This application presents a reactive UV absorber designed to impart long-term, non-migrating UV protection to the PETG matrix. Traditional physically added UV absorbers suffer from diminishing protective effects over time due to migration and precipitation, impacting the surface quality of the product. This application utilizes a chemical reaction to introduce highly reactive epoxy groups onto the hydroxyphenyltriazine UV absorber molecule, transforming it from an inert additive into a chemically reactive monomer. These introduced epoxy groups act as chemical anchors, chemically bonding with the end groups of the PETG molecular chain during subsequent melt blending. This chemical anchoring embeds the UV absorber molecule into the polymer network through partial covalent bonding, thereby reducing migration tendency and better maintaining UV protection during long-term use, contributing to durable and stable weather resistance.

[0043] This application presents a highly compatible hindered amine light stabilizer designed to address the migration issues inherent in traditional hindered amines and ensure uniform dispersion within a PETG matrix to maintain high transparency. Its function is achieved by chemically grafting the hindered amine functional units onto a specific organosilicon framework. First, this organosilicon framework inhibits migration; second, the numerous phenyl side chains on its molecular chain act as built-in compatibilizers, enhancing compatibility through a chemical structure similar to the PETG matrix. This ensures uniform dispersion rather than aggregation of the stabilizer, thereby protecting the material's optical properties. Furthermore, the low surface energy of the organosilicon backbone allows for enrichment at material interfaces, enabling the construction of highly efficient free radical trapping regions on vulnerable material surfaces.

[0044] This application constructs a core-shell structured cerium dioxide nanoparticle to overcome the severe agglomeration problem caused by the difference in surface properties of inorganic nanoparticles in organic polymers. This agglomeration is the root cause of the sharp decline in material transparency. Through dual surface coating, an organic shell compatible with PETG is encapsulated around the inorganic cerium dioxide core. The inner layer is a chemical bridge formed by a silane coupling agent, connecting the organic shell to the surface of the inorganic core. The outer layer is grafted with a saturated polyester resin, whose chemical structure is highly similar to the PETG matrix. This outer shell allows the modified cerium dioxide particles to be accepted by the PETG matrix, thus uniformly and stably dispersing them in the form of nanoscale primary particles. This effectively performs its ultraviolet shielding function while reducing visible light scattering caused by agglomeration, maintaining the original high transparency of the material.

[0045] The three functional additives constructed in this application, together with the PETG matrix, form a synergistic system with a clear division of labor and multiple layers of protection, thus constructing a three-dimensional protective network. First, at the UV protection level, the chemically anchored reactive UV absorber and the nano-dispersed core-shell structured cerium dioxide work synergistically, complementing each other across different mechanisms and wavelengths to form a relatively broad-spectrum, highly efficient, and durable UV shielding system. Second, at the light stabilization level, when UV light penetrates the shielding layer and generates destructive free radicals, the uniformly distributed hindered amine light stabilizer immediately comes into play, efficiently capturing free radicals, terminating the polymer degradation chain reaction, and protecting the material's chemical structure and physical properties. At the processing stability level, the compounded antioxidant system protects the PETG matrix and all functional additives from thermal oxidative degradation during high-temperature melt blending, ensuring the successful implementation of the entire synergistic system and guaranteeing the high transparency and low color of the final product.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] This application presents a reactive UV absorber designed to improve the long-term performance degradation caused by migration in traditional additives. By introducing epoxy groups, the absorber can chemically bond with PETG during processing, thereby becoming immobilized in the polymer network and ensuring the long-lasting and stable UV protection function of the material.

[0048] This application presents a high-performance light stabilizer prepared by grafting hindered amine functional units onto an organosilicon framework. This stabilizer inhibits migration and, thanks to the phenyl structure in the framework, achieves excellent compatibility with the PETG matrix, ensuring high transparency and ultimately providing long-lasting and efficient light-stabilizing protection for the material.

[0049] By coating inorganic cerium dioxide nanoparticles with an organic shell compatible with their PETG matrix, this application solves the problem of particle aggregation in polymers. This core-shell structure design improves the dispersion state of the nanoparticles, thereby maintaining the original high transparency of the material while efficiently exerting its ultraviolet shielding function.

[0050] This application constructs a synergistic system composed of three functional additives. First, the UV absorber and nano-cerium dioxide together form a highly efficient and durable UV shielding layer; second, the hindered amine light stabilizer is responsible for scavenging free radicals generated by penetrating UV rays; finally, the antioxidant provides stability assurance for the entire system during processing, improving the overall weather resistance of the material under UV aging conditions. Detailed Implementation

[0051] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to 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 this application. These technical solutions include technical solutions that employ any obvious substitutions and modifications made to the embodiments described herein.

[0052] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0053] Example 1

[0054] This embodiment provides a high-transparency, UV-resistant PETG film-grade slice and its preparation method. The preparation method of the high-transparency, UV-resistant PETG film-grade slice specifically includes the following steps:

[0055] S1: Disperse the hydroxyphenyl triazine UV absorber in a mixed solvent. The hydroxyphenyl triazine UV absorber is Tinuvin® 400. Add tetrabutylammonium bromide to obtain an organic phase. The volume ratio of dichloromethane to toluene in the mixed solvent is 1:2.5. The amount of tetrabutylammonium bromide added is 0.8% of the mass of the hydroxyphenyl triazine UV absorber. Prepare a 48% sodium hydroxide solution. Add epichlorohydrin dropwise to the organic phase at 45°C. Simultaneously, add sodium hydroxide solution to maintain the pH at 12.8 to obtain reaction solution A. The molar ratio of epichlorohydrin to hydroxyphenyl triazine UV absorber is 10:1. Stir the reaction for 3.5 h, separate the phases, wash, distill under reduced pressure, and dry to obtain the reactive UV absorber.

[0056] S2: A dispersion of a copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was dispersed in toluene to obtain a dispersion with a mass fraction of 28 wt.%. The copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was of the type Gelest HPM-502. Under nitrogen protection, 4-allyloxy-2,2,6,6-tetramethylpiperidine and Karstedt catalyst were added to obtain reaction solution B. The molar ratio of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane to 4-allyloxy-2,2,6,6-tetramethylpiperidine was 1.15:1. The amount of Karstedt catalyst added was 12 ppm of the total mass of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane and 4-allyloxy-2,2,6,6-tetramethylpiperidine. The reaction was stirred at 75 °C for 9 h. The mixture was then purified by vacuum distillation and dried to obtain a hindered amine stabilizer.

[0057] S3: Cerium dioxide with a particle size of 8 nm was dispersed in an ethanol-water solution, and the pH was adjusted to 4.7 with acetic acid. KH-560 was added to obtain reaction solution C, wherein the volume ratio of ethanol to deionized water in the ethanol-water solution was 92:8, and the mass ratio of cerium dioxide to KH-560 was 1:0.28. The reaction was carried out at 72℃ for 5.5 h, centrifuged, and washed to obtain surface-modified cerium dioxide, which was dispersed in N,N-dimethylformamide, wherein the mass fraction of surface-modified cerium dioxide dispersed in N,N-dimethylformamide was 8 wt.%. Carboxyl-terminated saturated polyester resin and 1,8-diazabicyclo[5.4.0]undec-7-ene were added to obtain reaction solution D, wherein the carboxyl-terminated saturated polyester resin was Allnex CRYLCOAT®. 2441-2, the mass ratio of carboxyl-terminated saturated polyester resin to surface-modified cerium dioxide is 0.25:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene fed is 0.9% of the mass of carboxyl-terminated saturated polyester resin, the reaction is carried out at 128℃ for 7.5h, filtered, washed and dried to obtain core-shell structured cerium dioxide;

[0058] S4: PETG matrix, reactive UV absorber, hindered amine stabilizer, core-shell cerium dioxide, and antioxidant are premixed in a high-speed mixer to obtain a mixture. The mass fraction of reactive UV absorber in the mixture is 11%, the mass fraction of hindered amine stabilizer is 3.5%, the mass fraction of core-shell cerium dioxide is 7.5%, and the mass fraction of antioxidant is 0.45%. The antioxidant is composed of antioxidant 1010 and antioxidant 626 in a mass ratio of 1:2. This mixture is added to a twin-screw extruder for melt blending and granulation to obtain high-transparency, UV-resistant PETG film-grade chips. The melt temperature is 225℃, and the screw speed is 280 rpm.

[0059] Example 2

[0060] This embodiment provides a high-transparency, UV-resistant PETG film-grade slice and its preparation method. The preparation method of the high-transparency, UV-resistant PETG film-grade slice specifically includes the following steps:

[0061] S1: Disperse the hydroxyphenyl triazine UV absorber in a mixed solvent. The hydroxyphenyl triazine UV absorber is Tinuvin® 400. Add tetrabutylammonium bromide to obtain an organic phase. The volume ratio of dichloromethane to toluene in the mixed solvent is 1:1. The amount of tetrabutylammonium bromide added is 0.5% of the mass of the hydroxyphenyl triazine UV absorber. Prepare a 40% sodium hydroxide solution. Add epichlorohydrin dropwise to the organic phase at 30°C. At the same time, add sodium hydroxide solution to maintain the pH to 12 to obtain reaction solution A. The molar ratio of epichlorohydrin to hydroxyphenyl triazine UV absorber is 6:1. Stir the reaction for 2 hours, separate the phases, wash, distill under reduced pressure, and dry to obtain the reactive UV absorber.

[0062] S2: A dispersion of 20 wt.% of a copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was obtained by dispersing the copolymer in toluene. The copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was of the type Gelest HPM-502. Under nitrogen protection, 4-allyloxy-2,2,6,6-tetramethylpiperidine and Karstedt catalyst were added to obtain reaction solution B. The molar ratio of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane to 4-allyloxy-2,2,6,6-tetramethylpiperidine was 1:1. The amount of Karstedt catalyst added was 5 ppm of the total mass of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane and 4-allyloxy-2,2,6,6-tetramethylpiperidine. The reaction was stirred at 60 °C for 6 h, purified by vacuum distillation, and dried to obtain the hindered amine stabilizer.

[0063] S3: Cerium dioxide with a particle size of 5 nm was dispersed in an ethanol-water solution, and the pH was adjusted to 4.3 with acetic acid. KH-560 was added to obtain reaction solution C, wherein the volume ratio of ethanol to deionized water in the ethanol-water solution was 95:5, and the mass ratio of cerium dioxide to KH-560 was 1:0.2. The reaction was carried out at 60 °C for 4 h, centrifuged, and washed to obtain surface-modified cerium dioxide, which was dispersed in N,N-dimethylformamide, wherein the mass fraction of surface-modified cerium dioxide dispersed in N,N-dimethylformamide was 15 wt.%. Carboxyl-terminated saturated polyester resin and 1,8-diazabicyclo[5.4.0]undec-7-ene were added to obtain reaction solution D, wherein the carboxyl-terminated saturated polyester resin was Allnex CRYLCOAT®. 2441-2, the mass ratio of carboxyl-terminated saturated polyester resin to surface-modified cerium dioxide is 0.15:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene fed is 0.5% of the mass of carboxyl-terminated saturated polyester resin, the reaction is carried out at 120℃ for 6h, filtered, washed and dried to obtain core-shell structured cerium dioxide;

[0064] S4: PETG matrix, reactive UV absorber, hindered amine stabilizer, core-shell cerium dioxide, and antioxidant are premixed in a high-speed mixer to obtain a mixture. The mass fraction of reactive UV absorber in the mixture is 8%, the mass fraction of hindered amine stabilizer is 2%, the mass fraction of core-shell cerium dioxide is 6%, and the mass fraction of antioxidant is 0.3%. The antioxidant is composed of antioxidant 1010 and antioxidant 626 in a mass ratio of 1:2. This mixture is added to a twin-screw extruder for melt blending and granulation to obtain high-transparency, UV-resistant PETG film-grade chips. The melt temperature is 200℃ and the screw speed is 200rpm.

[0065] Example 3

[0066] This embodiment provides a high-transparency, UV-resistant PETG film-grade slice and its preparation method. The preparation method of the high-transparency, UV-resistant PETG film-grade slice specifically includes the following steps:

[0067] S1: Disperse the hydroxyphenyl triazine UV absorber in a mixed solvent. The hydroxyphenyl triazine UV absorber is Tinuvin® 400. Add tetrabutylammonium bromide to obtain an organic phase. The volume ratio of dichloromethane to toluene in the mixed solvent is 1:2. The amount of tetrabutylammonium bromide added is 0.6% of the mass of the hydroxyphenyl triazine UV absorber. Prepare a 42% sodium hydroxide solution. Add epichlorohydrin dropwise to the organic phase at 35°C. At the same time, add sodium hydroxide solution to maintain the pH to 12.2 to obtain reaction solution A. The molar ratio of epichlorohydrin to hydroxyphenyl triazine UV absorber is 8:1. Stir the reaction for 2.5 h, separate the phases, wash, distill under reduced pressure, and dry to obtain the reactive UV absorber.

[0068] S2: A dispersion of a copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was dispersed in toluene to obtain a dispersion with a mass fraction of 22 wt.%. The copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was of the type Gelest HPM-502. Under nitrogen protection, 4-allyloxy-2,2,6,6-tetramethylpiperidine and Karstedt catalyst were added to obtain reaction solution B. The molar ratio of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane to 4-allyloxy-2,2,6,6-tetramethylpiperidine was 1.05:1. The amount of Karstedt catalyst added was 8 ppm of the total mass of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane and 4-allyloxy-2,2,6,6-tetramethylpiperidine. The reaction was stirred at 65 °C for 7 h. The mixture was then purified by vacuum distillation and dried to obtain a hindered amine stabilizer.

[0069] S3: Cerium dioxide with a particle size of 6 nm was dispersed in an ethanol-water solution, and the pH was adjusted to 4.4 with acetic acid. KH-560 was added to obtain reaction solution C, wherein the volume ratio of ethanol to deionized water in the ethanol-water solution was 91:9, and the mass ratio of cerium dioxide to KH-560 was 1:0.22. The reaction was carried out at 68℃ for 4.5 h, centrifuged, and washed to obtain surface-modified cerium dioxide, which was dispersed in N,N-dimethylformamide, wherein the mass fraction of surface-modified cerium dioxide dispersed in N,N-dimethylformamide was 10 wt.%. Carboxyl-terminated saturated polyester resin and 1,8-diazabicyclo[5.4.0]undec-7-ene were added to obtain reaction solution D, wherein the carboxyl-terminated saturated polyester resin was Allnex CRYLCOAT®. 2441-2, the mass ratio of carboxyl-terminated saturated polyester resin to surface-modified cerium dioxide is 0.2:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene fed is 0.6% of the mass of carboxyl-terminated saturated polyester resin, the reaction is carried out at 122℃ for 6.5h, filtered, washed and dried to obtain core-shell structured cerium dioxide;

[0070] S4: PETG matrix, reactive UV absorber, hindered amine stabilizer, core-shell cerium dioxide, and antioxidant are premixed in a high-speed mixer to obtain a mixture. The mass fraction of reactive UV absorber in the mixture is 9%, the mass fraction of hindered amine stabilizer is 2.5%, the mass fraction of core-shell cerium dioxide is 6.5%, and the mass fraction of antioxidant is 0.35%. The antioxidant is composed of antioxidant 1010 and antioxidant 626 in a mass ratio of 1:2. This mixture is added to a twin-screw extruder for melt blending and granulation to obtain high-transparency, UV-resistant PETG film-grade chips. The melt temperature is 210℃, and the screw speed is 220rpm.

[0071] Example 4

[0072] This embodiment provides a high-transparency, UV-resistant PETG film-grade slice and its preparation method. The preparation method of the high-transparency, UV-resistant PETG film-grade slice specifically includes the following steps:

[0073] S1: Disperse the hydroxyphenyl triazine UV absorber in a mixed solvent. The hydroxyphenyl triazine UV absorber is Tinuvin® 400. Add tetrabutylammonium bromide to obtain an organic phase. The volume ratio of dichloromethane to toluene in the mixed solvent is 1:3. The amount of tetrabutylammonium bromide added is 1% of the mass of the hydroxyphenyl triazine UV absorber. Prepare a 50% sodium hydroxide solution. Add epichlorohydrin dropwise to the organic phase at 50°C. At the same time, add sodium hydroxide solution to maintain the pH to 13 to obtain reaction solution A. The molar ratio of epichlorohydrin to hydroxyphenyl triazine UV absorber is 12:1. Stir the reaction for 4 hours. Separate the phases, wash, distill under reduced pressure, and dry to obtain the reactive UV absorber.

[0074] S2: A 30 wt.% dispersion of a copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was obtained by dispersing it in toluene. The copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was of the type Gelest HPM-502. Under nitrogen protection, 4-allyloxy-2,2,6,6-tetramethylpiperidine and Karstedt catalyst were added to obtain reaction solution B. The molar ratio of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane to 4-allyloxy-2,2,6,6-tetramethylpiperidine was 1.2:1. The amount of Karstedt catalyst added was 15 ppm of the total mass of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane and 4-allyloxy-2,2,6,6-tetramethylpiperidine. The reaction was stirred at 80 °C for 10 h, purified by vacuum distillation, and dried to obtain a hindered amine stabilizer.

[0075] S3: Cerium dioxide with a particle size of 10 nm was dispersed in an ethanol-water solution, and the pH was adjusted to 4.8 with acetic acid. KH-560 was added to obtain reaction solution C, wherein the volume ratio of ethanol to deionized water in the ethanol-water solution was 90:10, and the mass ratio of cerium dioxide to KH-560 was 1:0.3. The reaction was carried out at 80℃ for 6 h, centrifuged, and washed to obtain surface-modified cerium dioxide, which was dispersed in N,N-dimethylformamide, wherein the mass fraction of surface-modified cerium dioxide dispersed in N,N-dimethylformamide was 12 wt.%. Carboxyl-terminated saturated polyester resin and 1,8-diazabicyclo[5.4.0]undec-7-ene were added to obtain reaction solution D, wherein the carboxyl-terminated saturated polyester resin was Allnex CRYLCOAT®. 2441-2, the mass ratio of carboxyl-terminated saturated polyester resin to surface-modified cerium dioxide is 0.3:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene fed is 1% of the mass of carboxyl-terminated saturated polyester resin, and the reaction is carried out at 130℃ for 8h. After filtration, washing and drying, core-shell structured cerium dioxide is obtained.

[0076] S4: PETG matrix, reactive UV absorber, hindered amine stabilizer, core-shell cerium dioxide, and antioxidant are premixed in a high-speed mixer to obtain a mixture. The mass fraction of reactive UV absorber in the mixture is 12%, the mass fraction of hindered amine stabilizer is 4%, the mass fraction of core-shell cerium dioxide is 8%, and the mass fraction of antioxidant is 0.5%. The antioxidant is composed of antioxidant 1010 and antioxidant 626 in a mass ratio of 1:2. This mixture is added to a twin-screw extruder for melt blending and granulation to obtain high-transparency, UV-resistant PETG film-grade chips. The melt temperature is 230℃ and the screw speed is 300 rpm.

[0077] Comparative Example 1

[0078] This comparative example provides a high-transparency, UV-resistant PETG film-grade slice. The difference from Example 1 is that an unmodified hydroxyphenyltriazine UV absorber is used instead of a reactive UV absorber. Other operating steps and process parameters are exactly the same as in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides a high-transparency, UV-resistant PETG film-grade chip. The difference from Example 1 is that a conventional small-molecule hindered amine is used instead of the hindered amine stabilizer. Other operating steps and process parameters are exactly the same as in Example 1.

[0081] Comparative Example 3

[0082] This comparative example provides a high-transparency, UV-resistant PETG film-grade slice. The difference from Example 1 is that unmodified nano-cerium dioxide is used to replace the core-shell structured cerium dioxide. Other operating steps and process parameters are exactly the same as in Example 1.

[0083] Comparative Example 4

[0084] This comparative example provides a high-transparency, UV-resistant PETG film-grade chip. The difference between this example and Example 1 is that no reactive UV absorber is added, while the other operating steps and process parameters are exactly the same as in Example 1.

[0085] Comparative Example 5

[0086] This comparative example provides a high-transparency, UV-resistant PETG film-grade chip. The difference between this example and Example 1 is that no hindered amine stabilizer is added, while the other operating steps and process parameters are exactly the same as in Example 1.

[0087] Comparative Example 6

[0088] This comparative example provides a high-transparency, UV-resistant PETG film-grade slice. The difference from Example 1 is that no core-shell structured cerium dioxide is added, while the other operating steps and process parameters are exactly the same as in Example 1.

[0089] The performance of the high-transparency, UV-resistant PETG film-grade slices from Examples 1-4 and Comparative Examples 1-6 was tested, and the specific process is as follows:

[0090] The transmittance of the sample was tested according to ASTM D1003;

[0091] The UV aging resistance of the samples was tested according to ASTM G154.

[0092] The notched impact strength of untreated samples and samples after UV aging was tested according to ASTM D256, and the retention rate was calculated.

[0093] The elongation at break of untreated samples and samples after UV aging were tested according to ASTM D638, and their retention rate was calculated.

[0094] The test results are shown in Table 1.

[0095] Table 1. Performance test results of high-transparency UV-resistant PETG film-grade slices prepared in Examples 1-4 and Comparative Examples 1-6

[0096]

[0097] As shown in Table 1, the test results of Example 1 and Comparative Example 1 indicate that replacing the reactive UV absorber with an unmodified hydroxyphenyltriazine UV absorber did not significantly change the initial optical properties, but the weather resistance decreased. This is because the unbonded UV absorber migrates and volatilizes under long-term humid and hot light conditions, resulting in a decrease in its protective effect on the PETG matrix over time. With the weakening of UV protection, the photo-oxidative degradation of the polymer backbone intensifies, leading to yellowing. Microscopically, this manifests as molecular chain breakage, thus reducing its elongation at break and notched impact strength retention.

[0098] As shown in Table 1, the test results of Example 1 and Comparative Example 2 indicate that replacing the hindered amine stabilizer prepared in this scheme with a traditional small-molecule hindered amine also leads to performance defects due to additive migration. During aging, the small-molecule hindered amine gradually precipitates and leaks from the matrix, significantly weakening its ability to scavenge free radicals and interrupt the degradation chain reaction. Since hindered amines are crucial for maintaining the integrity of the polymer backbone, the loss of their function directly leads to the deterioration of material toughness, exhibiting a clear embrittlement trend after UV aging. Therefore, both its elongation at break and notched impact strength retention decrease.

[0099] As shown in Table 1, the test results of Example 1 and Comparative Example 3 indicate that replacing the core-shell structured cerium dioxide with unmodified nano-cerium dioxide caused the inorganic filler to agglomerate due to interfacial incompatibility between the strongly polar surface and the weakly polar matrix. These micron-sized agglomerates form light scattering centers, disrupting the optical homogeneity of the material and thus reducing its transmittance, resulting in the loss of PETG's high transparency. Its weather resistance remains largely unchanged due to the inherent function of cerium dioxide.

[0100] As shown in Table 1, the test results of Example 1 and Comparative Example 4 indicate that the absence of a reactive UV absorber leads to a decrease in the overall weather resistance of the material. Without this core broad-spectrum organic UV absorption barrier, inorganic shielding and free radical capture alone are insufficient to completely block all harmful UV wavelengths. More UV radiation penetrates and triggers photodegradation of the polymer, causing yellowing of the material. Simultaneously, the degradation of the molecular chains also impairs its mechanical properties, resulting in a decrease in both elongation at break and notched impact strength retention.

[0101] As shown in Table 1, the test results of Example 1 and Comparative Example 5 indicate that the absence of the hindered amine stabilizer leads to a decrease in the mechanical properties of the material. Even with an effective UV shielding layer, the free radicals triggered by the penetrating UV light can still undergo chain reactions, significantly severing the polymer backbone. This results in macroscopic embrittlement of the material, consequently causing a significant decrease in its elongation at break and notched impact strength retention, and the appearance of numerous microcracks on the surface due to the release of internal stress.

[0102] As shown in Table 1, the test results of Example 1 and Comparative Example 6 reveal that the absence of core-shell cerium dioxide weakens the overall efficiency and durability of the protective system. Although the initial transmittance change is not significant, the degree of yellowing and mechanical property degradation deteriorate after long-term aging. Relying solely on organic UV absorbers may result in insufficient absorption bandwidth or self-photobleaching under prolonged irradiation. The addition of cerium dioxide, however, can synergistically complement the organic absorber through a different mechanism, broadening the protective bandwidth and improving the overall stability of the system. Therefore, the absence of this component leads to a decrease in the long-term weather resistance of the material.

[0103] The above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing high-transparency, UV-resistant PETG film-grade slices, characterized in that, The preparation method includes: S1: Disperse the hydroxyphenyltriazine UV absorber in a mixed solvent, add tetrabutylammonium bromide to obtain an organic phase, prepare a sodium hydroxide solution, and add epichlorohydrin dropwise to the organic phase. The molar ratio of epichlorohydrin to hydroxyphenyltriazine UV absorber is (6-12):

1. Simultaneously, add sodium hydroxide solution to maintain pH to obtain reaction solution A. Stir the reaction, separate the phases, wash, distill under reduced pressure, and dry to obtain the reactive UV absorber. S2: A dispersion of a copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane was dispersed in toluene. Under nitrogen protection, 4-allyloxy-2,2,6,6-tetramethylpiperidine and Karstedt catalyst were added to obtain reaction solution B. The molar ratio of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane to 4-allyloxy-2,2,6,6-tetramethylpiperidine was (1-1.2):

1. The mixture was stirred, distilled under reduced pressure, purified, and dried to obtain a hindered amine stabilizer. S3: Cerium dioxide is dispersed in an aqueous ethanol solution, pH is adjusted with acetic acid, KH-560 is added to obtain reaction solution C, reaction is carried out, centrifugation is performed, and washing is performed to obtain surface-modified cerium dioxide, which is dispersed in N,N-dimethylformamide, and carboxyl-terminated saturated polyester resin and 1,8-diazabicyclo[5.4.0]undec-7-ene are added to obtain reaction solution D, wherein the mass ratio of carboxyl-terminated saturated polyester resin to surface-modified cerium dioxide is (0.15-0.3):1, reaction is performed, filtration is performed, washing is performed, and drying is performed to obtain core-shell structured cerium dioxide; S4: PETG matrix, reactive UV absorber, hindered amine stabilizer, core-shell structured cerium dioxide and antioxidant are premixed in a high-speed mixer to obtain a mixture, which is then added to a twin-screw extruder for melt blending and granulation to obtain high-transparency, UV-resistant PETG film-grade chips.

2. The method for preparing a high-transparency, UV-resistant PETG film-grade slice according to claim 1, characterized in that, In S1: The volume ratio of dichloromethane to toluene in the mixed solvent is 1:(1-3); The amount of tetrabutylammonium bromide added is 0.5-1% of the mass of the hydroxyphenyltriazine UV absorber.

3. The method for preparing a high-transparency, UV-resistant PETG film-grade slice according to claim 1, characterized in that, In S1: Sodium hydroxide solution was added to the organic phase to maintain the pH value at 12-13.

4. The method for preparing a high-transparency, UV-resistant PETG film-grade slice according to claim 1, characterized in that, In S2: The Karstedt catalyst is fed at a rate of 5-15 ppm of the total mass of the copolymer of hydrogen-terminated methylhydrosiloxane and phenylmethylsiloxane and 4-allyloxy-2,2,6,6-tetramethylpiperidine.

5. The method for preparing a high-transparency, UV-resistant PETG film-grade slice according to claim 1, characterized in that, In S3: The cerium dioxide has a particle size of 5-10 nm; The mass ratio of cerium dioxide to KH-560 is 1:(0.2-0.3).

6. The method for preparing a high-transparency, UV-resistant PETG film-grade slice according to claim 1, characterized in that, In S3: The amount of 1,8-diazabicyclo[5.4.0]undec-7-ene fed is 0.5-1% of the mass of the carboxyl-terminated saturated polyester resin.

7. The method for preparing a high-transparency, UV-resistant PETG film-grade slice according to claim 1, characterized in that, In S4: The mass fraction of reactive ultraviolet absorber in the mixture is 8-12%; The mass fraction of hindered amine stabilizer in the mixture is 2-4%; The mass fraction of core-shell structured cerium dioxide in the mixture is 6-8%.

8. The method for preparing a high-transparency, UV-resistant PETG film-grade slice according to claim 1, characterized in that, In S4: The antioxidant in the mixture has a mass fraction of 0.3-0.5%; The antioxidant 1010 and antioxidant 626 are in a mass ratio of 1:

2.

9. A high-transparency, UV-resistant PETG film-grade slice prepared by the preparation method according to any one of claims 1-8.

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