Method for preparing modified cyclic olefin copolymer and curved screen prepared thereby

Abstract

The application belongs to the technical field of organic polymer compound synthesis, and particularly relates to a preparation method of modified cycloolefin copolymer and a prepared curved screen. The preparation method comprises the following steps: S1, mixing a functional monomer, a cycloolefin monomer, a main catalyst and a cocatalyst, introducing alpha-olefin to perform a polymerization reaction, and obtaining a functional cycloolefin copolymer; S2, adding maleic anhydride and a free radical initiator to the functional cycloolefin copolymer to perform grafting, and obtaining a maleic anhydride functional cycloolefin copolymer; S3, stirring and activating the maleic anhydride functional cycloolefin copolymer, a polymerization initiator and an organic solvent, and then adding styrene to perform modification, and obtaining a modified cycloolefin copolymer. The modified cycloolefin copolymer is prepared by sequentially performing 4-vinylphenyl anisole functionalization, maleic anhydride functionalization and grafting polystyrene modification, so that the prepared modified cycloolefin copolymer effectively improves the toughness while maintaining high transparency, high heat resistance and low moisture absorption.

Description

Technical Field

[0001] This invention belongs to the field of organic polymer synthesis technology, specifically relating to a method for preparing a modified cyclic olefin copolymer and the resulting curved screen. Background Technology

[0002] Cyclic olefin copolymers, or COCs for short, are a class of high-performance, high-value-added thermoplastic engineering plastics. The molecular chains of COCs consist of flexible aliphatic segments and rigid cyclic structures, a unique structure that endows the material with a range of excellent comprehensive properties. Cyclic olefin copolymers possess advantages such as high transparency, high heat resistance, low moisture absorption, and good dimensional stability, and are widely used in automotive lenses, AR / VR optical lenses and waveguides, backlight modules for LCD displays, and polarizing protective films. Industrially, the production of cyclic olefin copolymers commonly employs chain copolymerization, which involves using ethylene (or α-olefins) and cyclic olefin monomers (usually norbornene) as raw materials, undergoing a copolymerization reaction under the action of a catalyst.

[0003] HUD curved screens made from cyclic olefin copolymers offer superior display effects and strong adaptability, leading to their increasingly widespread application in civilian vehicles. HUD curved screens have stringent requirements for the transmittance, low moisture absorption, and heat resistance of optical materials. Compared to materials like polycarbonate, polymethyl methacrylate, or glass, cyclic olefin copolymers offer advantages such as high transmittance, low water absorption, aging resistance, and lightweight construction. Furthermore, their glass transition temperature is adjustable, perfectly meeting the needs of this field. However, as an in-vehicle safety component, HUDs must pass wide-temperature-range mechanical shock and random vibration tests, while also withstanding assembly stress and long-term thermal cycling stress. Unmodified cyclic olefin copolymers suffer from high brittleness and poor impact resistance. Moreover, existing modification methods, while improving the impact resistance of cyclic olefin copolymers, significantly reduce their transparency and heat resistance. Therefore, effectively toughening cyclic olefin copolymers while maintaining high transparency and heat resistance is one of the core challenges in material design.

[0004] Chinese patent CN118063697A discloses a method for preparing a cyclic olefin-ethylene copolymer. The method involves mixing toluene, a cyclic olefin, a main catalyst, and a co-catalyst to obtain a reaction solution; introducing hydrogen gas and ethylene into the reaction solution to react and obtain a polymer solution; adding an acidic aqueous solution containing p-sulfonylbenzoic acid and HCl to the polymer solution and reacting, followed by washing to obtain an acid-treated polymer solution; adding an alkaline aqueous solution containing sodium sulfobutyl-β-cyclodextrin and NaOH to the acid-treated polymer solution and reacting, followed by washing to obtain an alkaline-treated polymer solution; and then treating the alkaline-treated polymer solution with a silica gel-filled adsorption column, followed by distillation and vacuum drying to obtain the cyclic olefin-ethylene copolymer product.

[0005] The patented cyclic olefin-ethylene copolymer is mainly composed of two monomers, norbornene and ethylene, without introducing other energy-dissipating flexible or rigid phases. Therefore, it is difficult to improve the toughness of the cyclic olefin-ethylene copolymer at the molecular level, which is not conducive to optimizing the impact resistance of the cyclic olefin-ethylene copolymer. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing modified cyclic olefin copolymers, which effectively improves the toughness of cyclic olefin copolymers while maintaining their high transparency, high heat resistance, and low moisture absorption. This invention also provides curved screens made from modified cyclic olefin copolymers.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The method for preparing the modified cyclic olefin copolymer of the present invention includes the following steps: S1. Under the protection of an inert gas, the functionalized monomer, cyclic olefin monomer, main catalyst and co-catalyst are mixed and α-olefin is introduced to carry out a polymerization reaction to obtain a functionalized cyclic olefin copolymer. S2. Under inert gas protection, maleic anhydride and a free radical initiator are added to the functionalized cyclic olefin copolymer for grafting to obtain maleic anhydride functionalized cyclic olefin copolymer. S3. Under inert gas protection, maleic anhydride functionalized cyclic olefin copolymer, polymerization initiator and organic solvent are stirred and activated, and then styrene is added for modification to obtain modified cyclic olefin copolymer.

[0008] in: In S1, the functionalized monomer is 4-vinylanisole, the cyclic olefin monomer is norbornene, the α-olefin is ethylene, and the organic solvent is toluene; the main catalyst is diphenylmethylene (cyclopentadiene) (9-fluorenyl)zirconium dichloride, and the co-catalyst is a methylaluminoxane solution with a concentration of 10-15 wt%.

[0009] In S1, the ratio of the added amounts of functionalized monomer, cyclic olefin monomer, organic solvent, α-olefin, main catalyst, and co-catalyst is 10:(1000~1500):(3000~4000):(0.8~1.0):(0.075~0.1):(30~40); the organic solvent and co-catalyst are in mL, the functionalized monomer, cyclic olefin monomer, and main catalyst are in g, and the α-olefin is in MPa.

[0010] In S1, the polymerization reaction temperature is 90~110℃, and the reaction time is 25~50min. After the polymerization reaction is completed, a post-processing step is also included: after the reaction is completed, sodium hydroxide and ethanol are added to terminate the reaction, and after precipitation and filtration, functionalized cyclic olefin copolymer is obtained; the ratio of the amount of cyclic olefin monomer, sodium hydroxide and ethanol added is (1000~1500):(90~120):(300~400), and the cyclic olefin monomer and sodium hydroxide are calculated in g, and the ethanol is calculated in mL.

[0011] In the S2 described above, the free radical initiator is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.

[0012] In the S2, the addition is carried out in steps: the maleic anhydride and free radical initiator are added in 4 to 10 batches, and the mass of maleic anhydride and free radical initiator added in different batches is the same. The ratio of maleic anhydride to free radical initiator added in each batch is (5 to 30): 1 (the last batch adds all the remaining maleic anhydride), with an interval of 3 to 10 minutes between each addition.

[0013] In S2, the grafting temperature is 170~180℃, the grafting time is 15~25min, and the mass ratio of functionalized cyclic olefin copolymer, maleic anhydride and free radical initiator is 200:(20~50):(1~4).

[0014] In S3, the polymerization initiator is a n-butyllithium solution with a concentration of 1.8~2.0M, and the organic solvent is toluene.

[0015] In S3, the ratio of maleic anhydride functionalized cyclic olefin copolymer, polymerization initiator, organic solvent and styrene is 150:(160~200):(4000~5000):(180~200), where styrene, polymerization initiator and organic solvent are in mL and maleic anhydride functionalized cyclic olefin copolymer is in g.

[0016] In S3, the stirring activation temperature is 30~35℃, and the stirring activation time is 6~8h.

[0017] In step S3, the modification temperature is 30-50℃ and the modification time is 30-60 min. After modification, a post-processing step is included: adding methanol to terminate the reaction, followed by a first solvent removal, a second solvent removal, and granulation to obtain the modified cyclic olefin copolymer.

[0018] The primary desolventizing temperature is 110~120℃ and the primary desolventizing pressure is -0.09MPa; the secondary desolventizing temperature is 180~200℃ and the secondary desolventizing pressure is -0.095MPa; the granulation speed is 300~500rpm and the particle diameter is 3~5mm.

[0019] The curved screen described in this invention is prepared from the modified cyclic olefin copolymer. The preparation process of the curved screen involves mixing the modified cyclic olefin copolymer with a color masterbatch to form a sheet. The sheet is then hot-pressed and post-treated to obtain the curved screen.

[0020] in: The mass ratio of the modified cyclic olefin copolymer to the color masterbatch is (15~20):1, the hot pressing temperature is 170~180℃, and the hot pressing time is 8~15min.

[0021] The beneficial effects of this invention are as follows: This invention introduces 4-vinylanisole during the reaction of cyclic olefin monomers with α-olefins to obtain functionalized cyclic olefin copolymers. Based on this, maleic anhydride functionalization modification is performed, and finally, polystyrene is grafted onto the copolymers to obtain modified cyclic olefin copolymers. 4-Vinyl anisole participates in the copolymerization process of cyclic olefin monomers and α-olefins. By introducing anisole groups onto the side chains of conventional COC, tertiary carbon active anchors can be formed on the main chain of conventional COC. In the second step of maleic anhydride functionalization, the alkoxy radicals generated by the decomposition of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane will abstract tertiary carbon hydrogens. At the same time, the p-π conjugation effect in the anisole group can stabilize the active site after losing tertiary carbon hydrogens, reducing the side reactions of main chain breakage and degradation.

[0022] This functionalization modification of 4-vinyl anisole and the p-π conjugation effect in the anisole group directly solve the industry pain points of "few grafting sites, low grafting rate, and many side reactions" when grafting maleic anhydride with ordinary COC free radicals, which significantly improves the conversion rate of maleic anhydride monomer and provides a further active site basis for the third step reaction.

[0023] Grafting maleic anhydride monomers avoids the physical damage to the optical transparency of COC caused by long-chain self-polymers. In addition, the carbonyl group on the grafted maleic anhydride monomer has an inductive effect, forming an interaction system with the anisole group. This causes a significant shift in the electron cloud of the CH bond on the tertiary carbon of the adjacent anisole group, resulting in a decrease in bond energy and an increase in polarity. This polarization effect ultimately benefits the grafting of methyl groups onto the anisole group of polystyrene.

[0024] Finally, by introducing polystyrene segments, multiple improvements are achieved in toughness, rigidity, optical properties, and processing performance: under impact loads, polystyrene branches can extend and shift their orientation, effectively dissipating impact energy; simultaneously, the branches can act as molecular-level stress transfer points, dispersing local stress concentration and preventing brittle fracture; the polystyrene branches and the COC main chain are covalently connected by chemical bonds, without forming significant phase separation; all modifications occur in the side chains, the rigid alicyclic structure of the COC main chain remains intact, and the heat-resistant core is preserved; the grafted polystyrene branches act as "intramolecular lubricants," increasing the free volume between COC main chains, reducing main chain entanglement, reducing molding internal stress and optical distortion, and adapting to the precision molding requirements of large-size HUD curved screens. Attached Figure Description

[0025] Figure 1 Here is a photograph of the modified cyclic olefin copolymer from Example 1; Figure 2 This is a physical image of the curved screen prepared in Example 4. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the embodiments.

[0027] The raw materials used in the following examples and comparative examples are all commercially available products.

[0028] Example 1 S1. Add 10g of 4-vinylanisole, 1200g of norbornene, and 4000mL of toluene to reactor A, then add 35mL of methylaluminoxane solution (methylaluminoxane concentration of 10wt%, toluene solvent) and 90mg of diphenylmethylene (cyclopentadiene) (9-fluorenyl)zirconium dichloride; continuously introduce ethylene at a pressure of 1.0MPa, heat the reactor to 90℃ and react for 50min. After the reaction is completed, add 90g of sodium hydroxide and 360mL of ethanol (terminating agent) to the mixture. After precipitation and filtration, functionalized cyclic olefin copolymer is obtained.

[0029] S2. Nitrogen gas is introduced into reactor B and pressure is maintained. 200g of functionalized cyclic olefin copolymer is added, and stirring is started. After the reactor temperature is raised to 170℃, maleic anhydride and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator) are added. The addition is carried out in four batches using a stepwise feeding method. The mass of maleic anhydride and free radical initiator added in different batches is the same. The ratio of maleic anhydride to free radical initiator added in each batch is 30:1 (the last batch adds all the remaining maleic anhydride). Each batch is 10min apart, and a total of 50g of maleic anhydride and 1g of free radical initiator are added. After all the addition is completed, stirring is continued for 18min. After the reaction is completed, the mixture is naturally cooled to room temperature, and the insoluble matter is filtered out to obtain maleic anhydride functionalized cyclic olefin copolymer.

[0030] S3. Nitrogen gas is introduced into reactor C and pressure is maintained. 150g of maleic anhydride functionalized cyclic olefin copolymer, 4000mL of toluene and 200mL of 1.8M n-butyllithium solution (solvent is toluene) are added. The mixture is stirred at 35℃ for 7h. 187mL of styrene is added and the mixture is stirred at 30℃ for 60min to obtain a mixture containing modified cyclic olefin copolymer.

[0031] Methanol was added to terminate the reaction, and then the mixture was passed into a flash evaporator for a first-stage solvent removal process at 120°C and -0.09 MPa to remove solvents such as toluene, with residual solvent ≤5%. The mixture was then fed into a vacuum extruder for a second-stage solvent removal process at 180°C and -0.095 MPa, with residual solvent ≤0.03%. Finally, granulation was performed at a cutting speed of 500 rpm to obtain particles with a diameter of 5 mm, yielding a modified cyclic olefin copolymer. The modified cyclic olefin copolymer exhibited an appearance free of charred particles and impurities.

[0032] Example 2 S1. Add 10g of 4-vinyl anisole, 1000g of norbornene, and 3000mL of toluene to reactor A, then add 40mL of methylaluminoxane solution (methylaluminoxane concentration of 12wt%, toluene solvent) and 100mg of diphenylmethylene (cyclopentadiene) (9-fluorenyl)zirconium dichloride; continuously introduce ethylene at a pressure of 0.9MPa, heat the reactor to 100℃ and react for 25min. After the reaction is completed, add 120g of sodium hydroxide and 300mL of ethanol (terminating agent) to the mixture. After precipitation and filtration, functionalized cyclic olefin copolymer is obtained.

[0033] S2. Nitrogen gas is introduced into reactor B and pressure is maintained. 200g of functionalized cyclic olefin copolymer is added, and stirring is started. After the reactor is heated to 180℃, maleic anhydride and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator) are added. The addition is carried out in 8 batches using a stepwise feeding method. The mass of maleic anhydride and free radical initiator added in different batches is the same. The ratio of maleic anhydride to free radical initiator added in each batch is 5:1. Each batch is added at 6-minute intervals, for a total of 20g of maleic anhydride and 4g of free radical initiator. After all the addition is completed, stirring is continued for 15 minutes. After the reaction is completed, the mixture is naturally cooled to room temperature, and the insoluble matter is filtered out to obtain maleic anhydride functionalized cyclic olefin copolymer.

[0034] S3. Nitrogen gas is introduced into reactor C and pressure is maintained. 150g of maleic anhydride functionalized cyclic olefin copolymer, 5000mL of toluene and 160mL of 1.9M n-butyllithium solution (solvent is toluene) are added. The mixture is stirred at 30℃ for 8h. 200mL of styrene is added and the mixture is stirred at 40℃ for 45min to obtain a mixture containing modified cyclic olefin copolymer.

[0035] Methanol was added to terminate the reaction, and then the mixture was passed into a flash evaporator for a first-stage solvent removal process at 110°C and -0.09 MPa to remove solvents such as toluene, with residual solvent ≤5%. The mixture was then fed into a vacuum extruder for a second-stage solvent removal process at 200°C and -0.095 MPa, with residual solvent ≤0.03%. Finally, granulation was performed at a cutting speed of 300 rpm to obtain particles with a diameter of 3 mm, yielding a modified cyclic olefin copolymer. The modified cyclic olefin copolymer exhibited an appearance free of charred particles and impurities.

[0036] Example 3 S1. Add 10g of 4-vinylanisole, 1500g of norbornene, and 3800mL of toluene to reactor A, then add 30mL of methylaluminoxane solution (methylaluminoxane concentration of 15wt%, toluene solvent) and 75mg of diphenylmethylene (cyclopentadiene) (9-fluorenyl)zirconium dichloride; continuously introduce ethylene at a pressure of 0.8MPa, heat the reactor to 110℃ and react for 35min. After the reaction is completed, add 110g of sodium hydroxide and 400mL of ethanol (terminating agent). After precipitation and filtration, functionalized cyclic olefin copolymer is obtained.

[0037] S2. Nitrogen gas is introduced into reactor B and pressure is maintained. 200g of functionalized cyclic olefin copolymer is added, and stirring is started. After the reactor temperature is raised to 175℃, maleic anhydride and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (free radical initiator) are added. The addition is carried out in 10 batches using a stepwise feeding method. The mass of maleic anhydride and free radical initiator added in different batches is the same. The ratio of maleic anhydride to free radical initiator added in each batch is 10:1 (the last batch adds all the remaining maleic anhydride). Each batch is added at 4min intervals, for a total of 35g of maleic anhydride and 2g of free radical initiator. After all the addition is completed, stirring is continued for 25min. After the reaction is completed, the mixture is naturally cooled to room temperature, and the insoluble matter is filtered out to obtain maleic anhydride functionalized cyclic olefin copolymer.

[0038] S3. Nitrogen gas is introduced into reactor C and pressure is maintained. 150g of maleic anhydride functionalized cyclic olefin copolymer, 4300mL of toluene and 180mL of 2.0M n-butyllithium solution (solvent is toluene) are added. The mixture is stirred at 32℃ for 6h. 180mL of styrene is added and the mixture is stirred at 50℃ for 30min to obtain a mixture containing modified cyclic olefin copolymer.

[0039] Methanol was added to terminate the reaction, and then the mixture was passed into a flash evaporator for a first-stage solvent removal process at 115°C and -0.09 MPa to remove solvents such as toluene, with residual solvent ≤5%. The mixture was then fed into a vacuum extruder for a second-stage solvent removal process at 190°C and -0.095 MPa, with residual solvent ≤0.03%. Finally, granulation was performed at a cutting speed of 400 rpm to obtain particles with a diameter of 4 mm, yielding a modified cyclic olefin copolymer. The modified cyclic olefin copolymer exhibited an appearance free of charred particles and impurities.

[0040] The unreacted norbornene, maleic anhydride, and toluene solvent in Examples 1, 2, and 3 can all be recycled.

[0041] Example 4 The modified cyclic olefin copolymer obtained in Example 1 was fed into a twin-screw extruder. The modified cyclic olefin copolymer was mixed with black masterbatch at a mass ratio of 20:1. After melt extrusion and casting, a sheet was obtained. After the sheet was cut, it was placed in a hot press mold with a curved cavity, heated to 170°C, and held for 8 minutes. Then, the upper and lower molds were closed and pressed. Finally, the sheet was demolded, shaped, and coated on the surface to obtain a HUD curved screen.

[0042] Example 5 The modified cyclic olefin copolymer obtained in Example 1 was fed into a twin-screw extruder. The modified cyclic olefin copolymer was mixed with black masterbatch at a mass ratio of 18:1. After melt extrusion and casting, a sheet was obtained. After the sheet was cut, it was placed in a hot press mold with a curved cavity, heated to 175°C, and held for 15 minutes. Then, the upper and lower molds were closed and pressed. Finally, the sheet was demolded, shaped, and coated on the surface to obtain a HUD curved screen.

[0043] Example 6 The modified cyclic olefin copolymer obtained in Example 1 was fed into a twin-screw extruder. The modified cyclic olefin copolymer was mixed with black masterbatch at a mass ratio of 15:1. After melt extrusion and casting, a sheet was obtained. After the sheet was cut, it was placed in a hot press mold with a curved cavity, heated to 180°C, and held for 10 minutes. Then, the upper and lower molds were closed and pressed. Finally, the sheet was demolded, shaped, and coated on the surface to obtain a HUD curved screen.

[0044] Comparative Example 1 Without adding 4-vinyl anisole, the remaining steps are the same as in Example 1, to obtain a cyclic olefin copolymer.

[0045] Comparative Example 2 Similar to S1 in Example 1, a functionalized cyclic olefin copolymer was obtained, but without subsequent maleic anhydride functionalization and styrene modification.

[0046] Comparative Example 3 Similar to S1 in Example 1, a functionalized cyclic olefin copolymer was obtained, which was directly modified with styrene (without prior maleic anhydride functionalization).

[0047] Comparative Example 4 Similar to S1 in Example 1, a functionalized cyclic olefin copolymer was obtained. Styrene was first added for modification, and then maleic anhydride was used for functionalization.

[0048] Implementation effect evaluation The modified cyclic olefin copolymers obtained in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests according to relevant industry or national testing standards.

[0049] 1. Physical and basic properties, including density, melt flow rate (260℃, 2.16kg) and water absorption rate.

[0050] 2. Thermal properties, including glass transition temperature (Tg) and heat distortion temperature (0.45 MPa).

[0051] 3. Optical properties, including transmittance and refractive index.

[0052] 4. Mechanical properties, including tensile properties (tensile strength / tensile modulus / elongation at break), flexural properties (flexural strength / flexural modulus), and impact resistance (impact resistance of simply supported beams).

[0053] Table 1 shows the reference standards for each test item, and Table 2 shows the performance test results. The test numbers in Table 2 correspond one-to-one with the test numbers and test items in Table 1.

[0054] Table 1 Test Items and Reference Standards

[0055] Table 2 Performance Test Results

[0056] As can be seen from the data in Table 1, the present invention achieves excellent results by first modifying with 4-vinyl anisole and maleic anhydride, and then grafting polystyrene segments. 1. Addressing the core defects of traditional COC, such as high brittleness and easy cracking, this invention improves the toughness of COC while maintaining its high transparency, high heat resistance, and low moisture absorption. In the embodiment, the impact strength of a simply supported beam reaches 18~24 kJ / m. 2 The impact resistance is greatly improved; the elongation at break in the example reaches 2.0%~2.6%, and the tensile strength is greatly improved; the rigidity indicators such as bending strength and bending modulus are maintained at a high level, and there is no decrease in rigidity due to toughening. The overall mechanical properties are enhanced through the grafted polystyrene branch structure.

[0057] 2. Traditional blending and toughening often leads to a decrease in light transmittance due to phase separation. This invention achieves a positive improvement in optical performance while toughening and modifying. The modified cyclic olefin copolymer prepared in the example has high light transmittance and the refractive index is maintained within a reasonable range, which enables the prepared curved screen to have low light scattering loss.

[0058] 3. All grafting and modification reactions in this invention occur in the side chain, causing minimal damage to the saturated alicyclic structure of the COC main chain and fully preserving the core heat resistance. The heat distortion temperature (0.45MPa) of the example is 128~133℃. The grafting of maleic anhydride and the introduction of polystyrene side chains effectively compensate for the decrease in heat resistance caused by the copolymerization of functional monomers.

[0059] 4. This invention is based on two modifications, and then introduces polystyrene branches, thereby increasing the free volume between molecular chains, reducing the entanglement of the main chain, and effectively reducing the melt viscosity. In the example, the melt flow rate (260℃, 2.16kg) reaches 35~38g / 10min. The lower melt viscosity can reduce the processing temperature and pressure of hot pressing of curved screens, reduce the internal stress and optical distortion of the molding, and adapt to the precision molding requirements of large-size curved screens.

[0060] 5. The low moisture absorption and lightweight properties are fully retained, with excellent dimensional stability. Extremely low water absorption maintains dimensional stability: the water absorption rate of the example is only 0.008%~0.010%, ensuring the dimensional accuracy of the curved screen in high humidity environments and avoiding optical distortion caused by water absorption. The density of the example is 1.015~1.025 g / cm³. 3 Compared with ordinary COC (1.014g / cm³), 3 The results are almost identical, and the material weight has not increased due to the modification, which is in line with the development trend of lightweight vehicle components.

Claims

1. A method for producing a modified cyclic olefin copolymer, characterized by, Includes the following steps: S1. Under the protection of an inert gas, the functionalized monomer, cyclic olefin monomer, organic solvent, main catalyst and co-catalyst are mixed and then introduced into an α-olefin to carry out a polymerization reaction to obtain a functionalized cyclic olefin copolymer. S2. Under inert gas protection, maleic anhydride and free radical initiator are added to the functionalized cyclic olefin copolymer and then grafted to obtain maleic anhydride functionalized cyclic olefin copolymer. S3. Under inert gas protection, maleic anhydride functionalized cyclic olefin copolymer, polymerization initiator and organic solvent are stirred and activated, and then styrene is added for modification to obtain modified cyclic olefin copolymer.

2. The method for preparing the modified cyclic olefin copolymer according to claim 1, characterized in that, In S1, the functionalized monomer is 4-vinylanisole, the cyclic olefin monomer is norbornene, the α-olefin is ethylene, and the organic solvent is toluene; the main catalyst is diphenylmethylene (cyclopentadiene) (9-fluorenyl)zirconium dichloride, and the co-catalyst is a methylaluminoxane solution with a concentration of 10~15wt%.

3. The method for preparing the modified cyclic olefin copolymer according to claim 1, characterized in that, In S1, the ratio of the added amounts of functionalized monomer, cyclic olefin monomer, organic solvent, α-olefin, main catalyst, and co-catalyst is 10:(1000~1500):(3000~4000):(0.8~1.0):(0.075~0.1):(30~40); the organic solvent and co-catalyst are expressed in mL, the functionalized monomer, cyclic olefin monomer, and main catalyst are expressed in g, and the α-olefin is expressed in MPa.

4. The method for preparing the modified cyclic olefin copolymer according to claim 1, characterized in that, In S1, the polymerization reaction temperature is 90~110℃ and the polymerization reaction time is 25~50min.

5. The method for preparing the modified cyclic olefin copolymer according to claim 1, characterized in that, In S2, the free radical initiator is 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; the grafting temperature is 170~180℃, the grafting time is 15~25min, and the mass ratio of the functionalized cyclic olefin copolymer, maleic anhydride and free radical initiator is 200:(20~50):(1~4).

6. The method for preparing the modified cyclic olefin copolymer according to claim 1, characterized in that, In S3, the polymerization initiator is a n-butyllithium solution with a concentration of 1.8~2.0M, and the organic solvent is toluene.

7. The method for preparing the modified cyclic olefin copolymer according to claim 1, characterized in that, In S3, the ratio of maleic anhydride-functionalized cyclic olefin copolymer, polymerization initiator, organic solvent, and styrene is 150:(160~200):(4000~5000):(180~200), where styrene, polymerization initiator, and organic solvent are expressed in mL, and maleic anhydride-functionalized cyclic olefin copolymer is expressed in g.

8. The method for preparing the modified cyclic olefin copolymer according to claim 1, characterized in that, In S3, the stirring activation temperature is 30~35℃ and the stirring activation time is 6~8h; the modification temperature is 30~50℃ and the modification time is 30~60min.

9. A curved screen, characterized in that, It is prepared from a modified cyclic olefin copolymer, which is obtained by the preparation method of the modified cyclic olefin copolymer according to any one of claims 1-8; the curved screen preparation process is to mix the modified cyclic olefin copolymer with a color masterbatch to make a sheet; the sheet is hot-pressed and post-treated to obtain a curved screen.

10. The curved screen according to claim 9, characterized in that, The mass ratio of the modified cyclic olefin copolymer to the color masterbatch is (15~20):1, the hot pressing temperature is 170~180℃, and the hot pressing time is 8~15min.

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