A method for one-pot preparation of ethylene-norbornene copolymers

Abstract

This invention provides a one-pot method for preparing ethylene-norbornene copolymer, comprising: (1) replacing the air in the reactor with nitrogen, then replacing the nitrogen in the reactor with ethylene, then adding toluene solvent, introducing ethylene, starting stirring and heating to 180-200℃, continuing to introduce ethylene and pressurizing to 18-20 MPa; adding a toluene solution of dicyclopentadiene at a uniform rate, and reacting for 1 hour after the addition is complete to obtain a norbornene mixture; (2) lowering the temperature of the reaction system to 40-70℃ and the pressure to 0.1-0.6 MPa, then introducing the main catalyst and co-catalyst to carry out the polymerization reaction; after the reaction is completed, depressurizing, transferring the product to a product tank, adding acidified ethanol to generate a white precipitate, filtering, washing and vacuum drying to obtain the ethylene-norbornene copolymer. This invention directly uses dicyclopentadiene and ethylene as raw materials to prepare the copolymer in a one-pot process. The cyclic olefins do not need to be separated and purified, and directly participate in the polymerization, which has the characteristics of simple process, reduced energy consumption and higher efficiency.

Description

Technical Field

[0001] This invention relates to the field of chemical production technology, and in particular to a one-pot method for preparing ethylene-norbornene copolymer. Background Technology

[0002] Cyclic olefin polymers are a series of amorphous, transparent polymeric materials obtained by the self-polymerization or copolymerization of cyclic olefin monomers with other olefins. There are two main preparation processes: metallocene-catalyzed addition polymerization (COC) and ring-opening shift polymerization (COP). COC is obtained by copolymerizing cyclic olefin monomers with ethylene or α-olefins, while COP is obtained by hydrogenating the unsaturated bonds in cyclic olefin monomers after ring-opening shift polymerization. COC / COP was first reported in the 1990s. Due to its excellent optical properties such as high transparency and low birefringence, as well as its excellent properties such as low water absorption, high biocompatibility, dimensional stability, and low density, it has attracted widespread attention from industry and academia.

[0003] The most widely studied COC material, ethylene-norbornene copolymer (ENC), is obtained through addition polymerization. The production process includes the following three steps: (1) Preparation of norbornene (NB) product: Cyclopentadiene (CPD) and ethylene undergo a Diels-Alder cyclization reaction under high temperature and pressure to obtain NB product; (2) Separation and purification of NB: During the synthesis of NB, tetracyclic dodecene and cyclopentadiene trimer byproducts are generated. By multi-stage distillation, the byproducts and solvent are separated to obtain high-purity NB; (3) Copolymerization of COC: NB and ethylene undergo a copolymerization reaction under metallocene catalysis to prepare cyclic olefin copolymers. For example, the COC production process of Ticona Company uses a solution polymerization process catalyzed by metallocene catalysts, including distillation, polymerization, catalyst separation and devolatification. Multi-stage distillation is used to ensure the ultra-high purity of monomers and solvents. The monomer norbornene (NB) is dissolved in solvent and added to the reactor. By adjusting the concentration ratio of monomers in the reactor, the content of each monomer in the polymer is controlled, thereby controlling the polymer's properties. ENC is then obtained through post-processing. This process requires multiple distillations of the monomer NB to ensure high purity, increasing equipment investment and operating costs, generating significant energy consumption, and resulting in high production costs. Therefore, simplifying the process, improving production efficiency, and reducing production costs are key areas of focus.

[0004] Patent CN103664470A describes a method for preparing norbornene. A solution of ethylene and dicyclopentadiene (DCPD) is first premixed in a high-temperature and high-pressure batch reactor. The residence time of the premixing is 1 to 60 minutes, the temperature of the premixing is 50 to 180°C, and the pressure of the premixing is absolute pressure of 60 to 100 bar. Then, the mixture is introduced into a tubular reactor. The molar ratio of α-olefin, DCPD, and solvent is 1:(1 / 50 to 1):(1 / 250 to 3). The residence time of the reactants in the tubular reactor is 1 to 10 minutes. Crude norbornene is generated at a reaction temperature of 160 to 300°C and a reaction pressure of 100 to 500 bar.

[0005] Patent CN104692993A discloses a method for synthesizing norbornene using a microchannel reactor. The microchannel reactor includes a reaction section, and the reaction channel of the reaction section has two or more inlets along the material flow direction. The method includes the following steps: adding a dicyclopentadiene solution into the reaction channel of the reaction section through any one of the inlets; adding ethylene into the reaction channel of the reaction section through the first inlet; the reaction temperature in the reaction channel is 180℃-300℃, the pressure is 5-30 MPa, the residence time in the reaction section is 0.5-10 minutes, and the molar ratio of ethylene to dicyclopentadiene solution is 1-10:1. Using the method of this invention, norbornene can be synthesized safely and efficiently using a microchannel reactor.

[0006] The above technologies all target norbornene as the product. In addition to norbornene, the reaction products also contain small amounts of tetracyclic dodecene and cyclopentadiene trimer byproducts. To obtain high-purity norbornene, distillation is required to remove the byproducts, which increases energy consumption.

[0007] Copolymerization (COC) uses cyclic olefin monomers and α-olefins as raw materials, employing metallocene catalysts and MAO co-catalysts for polymerization. Metallocene catalysts are highly sensitive to air and humidity, easily deactivating in air and leading to reaction failure; therefore, they must be stored in a low-temperature, inert environment. Thus, the polymerization reaction requires strict anhydrous and oxygen-free treatment of the raw materials and solvents to ensure the reaction proceeds. In the synthesis of NB, the raw materials DCPD, ethylene, and solvent toluene do not require further treatment. However, for continuous polymerization to prepare COC, the raw materials and solvents must be dehydrated and deoxygenated to ensure anhydrous and oxygen-free conditions throughout the system.

[0008] Patent CN 117362501A reports a method for directly preparing cyclic olefin copolymers from cyclopentadiene and ethylene using a continuous flow reactor. The method primarily utilizes a continuous flow reactor to efficiently produce norbornene and its derivatives from ethylene and dicyclopentadiene, which are then reacted with excess ethylene to obtain cyclic olefin copolymers. Patent CN 117720679A reports a method and system for preparing a high-heat-resistant cyclic olefin polymer. Cyclopentadiene reacts with ethylene to form a first-stage reaction product, and then reacts with the first-stage product to form a second-stage reaction product. This process is repeated to achieve a multi-stage Diels-Alder reaction with gradually increasing temperatures, resulting in a mixture of tetracyclododecene containing norbornene. Under the action of a catalyst, this mixture is then polymerized with ethylene to obtain a high-heat-resistant cyclic olefin polymer.

[0009] The above techniques all involve first preparing norbornene and its derivatives in a reactor, then transferring them to a next-stage reactor for polymerization to obtain cyclic olefin polymers. Although the norbornene mixture obtained in the first-stage reaction does not need to be separated, it still requires additional reactors for the polymerization stage, resulting in more equipment and a larger investment. Summary of the Invention

[0010] To address the problems of long, complex, and costly processes in the current preparation of cyclic olefin polymers, the present invention aims to provide a one-pot method for preparing ethylene-norbornene copolymers, thereby obtaining norbornene and ethylene-norbornene copolymers in one step.

[0011] To achieve the above objectives, the present invention provides a one-pot method for preparing ethylene-norbornene copolymer, comprising the following steps:

[0012] (1) After replacing the air in the reactor with nitrogen, replace the nitrogen in the reactor with ethylene. Then add 210-315g of pure toluene solvent per liter of reactor, introduce ethylene, start stirring and heat to a preset temperature of 180-200℃, continue to introduce ethylene and pressurize to a preset pressure of 18-20MPa, then add a toluene solution of 80% dicyclopentadiene at a uniform rate for 20-60min. After the addition is complete, continue the reaction for 1 hour to obtain a norbornene mixture. During the reaction, maintain the preset reaction temperature and continuously introduce ethylene to maintain the preset pressure.

[0013] (2) Reduce the temperature of the reaction system to 40-70℃ and the pressure to 0.1-0.6MPa. Then, introduce the main catalyst and the co-catalyst into the reactor. The norbornene mixture is then polymerized with ethylene for 20-60 minutes. After the reaction is completed, depressurize and transfer the product to the product tank. Add acidified ethanol to generate a white precipitate. After filtration, washing and vacuum drying, ethylene-norbornene copolymer is obtained.

[0014] The ethylene, dicyclopentadiene, and toluene are all deoxygenated and dehydrated before being introduced into the reactor to ensure that their respective water and oxygen content is less than 10 ppm.

[0015] After the reaction in step (1) is completed and a mixture of norbornene is obtained, without separation, after the temperature and pressure are reduced in step (2), the main catalyst and the main catalyst can be directly added to allow norbornene to undergo a polymerization reaction with ethylene to obtain an ethylene-norbornene copolymer. The ethylene participating in the polymerization reaction in step (2) is the ethylene that did not react in step (1).

[0016] As an example, the deoxygenation and dehydration treatment method is as follows: the ethylene, dicyclopentadiene and toluene are sequentially passed through a column packed with deoxygenation and dehydration molecular sieves.

[0017] For example, the main catalyst mentioned in step (2) is one or more of the following: ethylene bis(1-indenyl)zirconia, ethylene bis(4,5,6,7-tetrahydro-1-indenyl)zirconia, bis(isopropylcyclopentadienyl)zirconia, and bis(2-methylindenyl)zirconia.

[0018] For example, the co-catalyst mentioned in step (2) is one or more of methylaluminoxane, triethylaluminum, and triisobutylaluminum.

[0019] Preferably, the main catalyst in step (2) is ethylene bis(1-indenyl)zirconia, and the co-catalyst is methylaluminoxane; wherein the cumulative concentration of ethylene bis(1-indenyl)zirconia in the norbornene mixture is 8 × 10⁻⁶. - 5 The cumulative concentration of methylaluminoxane in the norbornene mixture was 1.6 × 10 mol / L. -1 mol / L.

[0020] Preferably, the polymerization reaction time in step (2) is 30-40 min.

[0021] For example, the vacuum drying conditions in step (2) are vacuum drying at 70°C for 24 hours.

[0022] Preferably, the cumulative concentration of DCPD in the norbornene mixture in step (1) is 20%-40%.

[0023] Without violating common sense in the field, the above-described implementation conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0024] The method for preparing ethylene-norbornene copolymer in one pot according to the present invention is characterized by:

[0025] The method provided by this invention uses dicyclopentadiene and ethylene as raw materials. In a single reactor, by controlling the process conditions, the cyclic olefin monomers do not need to be separated and purified, but directly participate in the polymerization reaction to achieve the preparation of norbornene and ethylene-norbornene copolymer. It has the advantages of simple process, reduced energy consumption, higher efficiency, low production cost, simpler operation, and is conducive to industrial production.

[0026] The method for preparing norbornene provided by this invention uses high temperature and high pressure process conditions to bring ethylene to a supercritical state. Ethylene in the supercritical state has excellent mass transfer and dispersion in toluene solution, which reduces the production of by-products and results in high conversion rate and selectivity of the product. The generated norbornene can be used for the preparation of ethylene-norbornene copolymer without purification.

[0027] The raw materials used in this invention, dicyclopentadiene and ethylene, and the toluene solution, are all treated to be anhydrous and oxygen-free before use. The reaction system is sealed, and no water or oxygen enters during the reaction. After the norbornene is generated, it can be directly used in the next polymerization reaction to generate an ethylene-norbornene polymer.

[0028] The method provided by this invention allows the solvent and excess ethylene used in monomer preparation to be directly used in the polymerization reaction, avoiding solvent recovery, waste liquid generation, and energy waste. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. However, it should be understood that these embodiments are for illustrative purposes only and do not constitute a limitation on the scope of this invention.

[0030] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, all percentages and parts are by weight.

[0031] DCPD conversion rate = Amount of DCPD participating in the reaction / Total amount of DCPD added to the reactor;

[0032] Norbornene selectivity = Amount of DCPD involved in norbornene formation / Total amount of DCPD added to the reactor.

[0033] In the following examples and comparative examples, the ethylene, dicyclopentadiene, and toluene used were sequentially passed through columns equipped with deoxygenation and dehydration molecular sieves before being introduced into the reactor to ensure that their water and oxygen content was each below 10 ppm.

[0034] Example 1

[0035] After purging the air in the reactor with nitrogen, the nitrogen was replaced with ethylene. 315g of pure toluene solvent was pumped in using a liquid metering pump, and ethylene was introduced into the reactor through a gas-pressurized feeding system. Stirring was started and the temperature was raised to 200℃. When the temperature reached 200℃, ethylene was continued to be added through the gas-pressurized system to increase the pressure to 18MPa. After reaching the preset pressure, 105g of a toluene solution with a concentration of 80% dicyclopentadiene was added at a uniform rate using a liquid metering pump to initiate the reaction. The addition time was 40min, and after the addition was complete, the reaction continued for 1h to obtain a norbornene mixture. After the reaction was completed, the temperature was lowered to 60℃ and the pressure was lowered to 0.2MPa. The main metallocene catalyst, ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration 8×10⁻⁶), was added through a liquid metering pump. -5 (mol / L) and co-catalyst methylaluminoxane (cumulative concentration of 1.6 × 10⁻⁶ mol / L) and -1 After the mol / L (ethanol) was added, the polymerization reaction began and lasted for 40 minutes. After the reaction was completed, the pressure was released, the product entered the product tank, acidified ethanol was added, a white precipitate was formed, the product was filtered, washed, and vacuum dried at 70°C to obtain a white solid, which was an ethylene-norbornene copolymer.

[0036] Example 2

[0037] After purging the air in the reactor with nitrogen, the nitrogen was replaced with ethylene. 262g of pure toluene solvent was pumped in using a liquid metering pump, and ethylene was introduced into the reactor through a gas-pressurized feeding system. Stirring was started and the temperature was raised to 200℃. When the temperature reached 200℃, ethylene was continued to be added through the gas-pressurized system to increase the pressure to 18MPa. After reaching the preset pressure, 105g of a toluene solution with a concentration of 80% dicyclopentadiene was added uniformly using a liquid metering pump to initiate the reaction. The addition time was 40min, and after the addition was complete, the reaction continued for 1h to obtain a norbornene mixture. After the reaction was completed, the temperature was lowered to 40℃ and the pressure was lowered to 0.2MPa. The main metallocene catalyst, ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration 8×10⁻⁶), was added through a liquid metering pump. -5 (mol / L) and co-catalyst methylaluminoxane (cumulative concentration of 1.6 × 10⁻⁶ mol / L) and -1 After the mol / L (ethanol) was added, the polymerization reaction began and lasted for 50 minutes. After the reaction was completed, the pressure was released, the product entered the product tank, acidified ethanol was added, a white precipitate was formed, the product was filtered, washed, and vacuum dried at 70°C to obtain a white solid, which was an ethylene-norbornene copolymer.

[0038] Example 3

[0039] After purging the air in the reactor with nitrogen, the nitrogen was replaced with ethylene. 262g of pure toluene solvent was pumped in using a liquid metering pump, and ethylene was introduced into the reactor through a gas-pressurized feeding system. Stirring was started and the temperature was raised to 200℃. When the temperature reached 200℃, ethylene was continued to be added through the gas-pressurized system to increase the pressure to 20MPa. After reaching the preset pressure, 105g of a toluene solution with a concentration of 80% dicyclopentadiene was added uniformly using a liquid metering pump to initiate the reaction. The addition time was 40min, and after the addition was complete, the reaction continued for 1h to obtain a norbornene mixture. After the reaction was completed, the temperature was lowered to 70℃ and the pressure was lowered to 0.4MPa. The main metallocene catalyst, ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration 8×10⁻⁶), was added through a liquid metering pump. -5 (mol / L) and co-catalyst methylaluminoxane (cumulative concentration of 1.6 × 10⁻⁶ mol / L) and -1 After the mol / L (ethanol) was added, the polymerization reaction began and lasted for 20 minutes. After the reaction was completed, the pressure was released, the product entered the product tank, acidified ethanol was added, a white precipitate was formed, the product was filtered, washed, and vacuum dried at 70°C to obtain a white solid, which was an ethylene-norbornene copolymer.

[0040] Example 4

[0041] After purging the air in the reactor with nitrogen, the nitrogen was replaced with ethylene. 210g of pure toluene solvent was pumped in using a liquid metering pump, and ethylene was introduced into the reactor through a gas-pressurized feeding system. Stirring was started and the temperature was raised to 180°C. When the temperature reached 180°C, ethylene was continued to be added through the gas-pressurized system to increase the pressure to 20MPa. After reaching the preset pressure, 210g of a toluene solution with a concentration of 80% dicyclopentadiene was added at a uniform rate using a liquid metering pump to initiate the reaction. The addition time was 40 min, and after the addition was complete, the reaction continued for 1 h to obtain a norbornene mixture. After the reaction was completed, the temperature was lowered to 60°C and the pressure was lowered to 0.4MPa. The main metallocene catalyst, ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration 8×10⁻⁶), was added through a liquid metering pump. -5 (mol / L) and co-catalyst methylaluminoxane (cumulative concentration of 1.6 × 10⁻⁶ mol / L) and -1 After the mol / L (ethanol) was added, the polymerization reaction began and lasted for 40 minutes. After the reaction was completed, the pressure was released, the product entered the product tank, acidified ethanol was added, a white precipitate was formed, the product was filtered, washed, and vacuum dried at 70°C to obtain a white solid, which was an ethylene-norbornene copolymer.

[0042] Example 5

[0043] After purging the air in the reactor with nitrogen, the nitrogen was replaced with ethylene. 315g of pure toluene solvent was pumped in using a liquid metering pump, and ethylene was introduced into the reactor through a gas-pressurized feeding system. Stirring was started and the temperature was raised to 190°C. When the temperature reached 190°C, ethylene was continued to be added through the gas-pressurized system to increase the pressure to 18MPa. After reaching the preset pressure, 105g of a toluene solution with a concentration of 80% dicyclopentadiene was added uniformly using a liquid metering pump to initiate the reaction. The addition time was 40 min, and after the addition was complete, the reaction continued for 1 h to obtain a norbornene mixture. After the reaction was completed, the temperature was lowered to 60°C and the pressure was lowered to 0.1MPa. The main metallocene catalyst, ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration 8 × 10⁻⁶), was added through a liquid metering pump. -5 (mol / L) and co-catalyst methylaluminoxane (cumulative concentration of 1.6 × 10⁻⁶ mol / L) and -1 After the mol / L (ethanol) was added, the polymerization reaction began and lasted for 40 minutes. After the reaction was completed, the pressure was released, the product entered the product tank, acidified ethanol was added, a white precipitate was formed, the product was filtered, washed, and vacuum dried at 70°C to obtain a white solid, which was an ethylene-norbornene copolymer.

[0044] Example 6

[0045] After purging the air in the reactor with nitrogen, the nitrogen was replaced with ethylene. 315g of pure toluene solvent was pumped in using a liquid metering pump, and ethylene was introduced into the reactor through a gas-pressurized feeding system. Stirring was started and the temperature was raised to 200℃. When the temperature reached 200℃, ethylene was continued to be added through the gas-pressurized system to increase the pressure to 20MPa. After reaching the preset pressure, 105g of a toluene solution with a concentration of 80% dicyclopentadiene was added uniformly using a liquid metering pump to initiate the reaction. The addition time was 40min, and after the addition was complete, the reaction continued for another 40min to obtain a norbornene mixture. After the reaction was completed, the temperature was lowered to 60℃ and the pressure was lowered to 0.2MPa. The main metallocene catalyst, ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration 8×10⁻⁶), was added through a liquid metering pump. -5 (mol / L) and co-catalyst methylaluminoxane (cumulative concentration of 1.6 × 10⁻⁶ mol / L) and -1 After the mol / L (ethanol) was added, the polymerization reaction began and lasted for 40 minutes. After the reaction was completed, the pressure was released, the product entered the product tank, acidified ethanol was added, a white precipitate was formed, the product was filtered, washed, and dried at 70°C to obtain a white solid, which was an ethylene-norbornene copolymer.

[0046] Comparative Example 1

[0047] After purging the air in the reactor with nitrogen, the nitrogen was replaced with ethylene. 315g of pure toluene solvent was pumped in using a liquid metering pump, and ethylene was introduced into the reactor through a gas-pressurized feeding system. Stirring was started and the temperature was raised to 180°C. When the temperature reached 180°C, ethylene was continued to be added through the gas-pressurized system to increase the pressure to 5MPa. After reaching the preset pressure, 105g of a toluene solution with a concentration of 80% dicyclopentadiene was added at a uniform rate using a liquid metering pump to initiate the reaction. The addition time was 40 min, and after the addition was complete, the reaction continued for 1 h to obtain a norbornene mixture. After the reaction was completed, the temperature was lowered to 60°C and the pressure was lowered to 0.2MPa. The main metallocene catalyst, ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration 8×10⁻⁶), was added through a liquid metering pump. -5 (mol / L) and co-catalyst methylaluminoxane (cumulative concentration of 1.6 × 10⁻⁶ mol / L) and -1 After the mol / L (ethanol) was added, the polymerization reaction began and lasted for 40 minutes. After the reaction was completed, the pressure was released, the product entered the product tank, acidified ethanol was added, a white precipitate was formed, the product was filtered, washed, and dried at 70°C to obtain a white solid, which was an ethylene-norbornene copolymer.

[0048] Table 1. Cyclopentadiene conversion and selectivity of norbornene mixture in the reactor.

[0049] Example CPD conversion rate (%) Product selectivity (%) Example 1 99.1 95.2 Example 2 99.6 95.8 Example 3 99.9 97.2 Example 4 98.6 94.9 Example 5 99.2 95.7 Example 6 97.9 96.1 Comparative Example 1 98.7 79.3

[0050] As shown in Table 1, at 18-20 MPa and 180-200 °C, the conversion rate of cyclopentadiene was above 98.0% for a reaction time of 1 h. Under the same conditions, the reaction time in Example 6 was shortened to 40 min compared to Example 1, resulting in a slight decrease in the conversion rate of cyclopentadiene to 97.9%, but an improvement in selectivity. This is mainly because the extended reaction time increases the formation of byproducts while improving the conversion rate. In Comparative Example 1, compared to Example 1, the selectivity of the product decreased significantly when the pressure was reduced from 18 MPa to 5 MPa. This is because the increased pressure increases the molar ratio of ethylene / CPD, thus improving selectivity; another reason is that ethylene under high pressure can effectively improve the heat and mass transfer of the system, thereby increasing the reaction selectivity.

[0051] As shown in Table 1, under these reaction conditions, the conversion rate of CPD is close to 100% and the product selectivity is >95%. The reaction system contains very few byproducts, mainly toluene solution of norbornene. When the process conditions are changed, the polymerization reaction can be continued directly in the reactor without further treatment to obtain ethylene-norbornene copolymer.

[0052] Although embodiments of the present invention have been described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications and substitutions to the above embodiments without departing from the concept of the present invention.

Claims

1. A method for preparing ethylene-norbornene copolymer in a one-pot process, characterized in that, Includes the following steps: (1) After replacing the air in the reactor with nitrogen, replace the nitrogen in the reactor with ethylene. Then add 210-315g of pure toluene solvent per liter of reactor, introduce ethylene, start stirring and heat to a preset temperature of 180-200℃, continue to introduce ethylene and pressurize to a preset pressure of 18-20MPa, then add a toluene solution of 80% dicyclopentadiene at a uniform rate for 20-60min. After the addition is complete, continue the reaction for 1 hour to obtain a norbornene mixture. During the reaction, maintain the preset reaction temperature and continuously introduce ethylene to maintain the preset pressure. (2) Reduce the temperature of the reaction system to 40-70℃ and the pressure to 0.1-0.6MPa. Then, introduce the main catalyst and the co-catalyst into the reactor. The norbornene mixture is then polymerized with ethylene for 20-60 minutes. After the reaction is completed, depressurize and transfer the product to the product tank. Add acidified ethanol to generate a white precipitate. After filtration, washing and vacuum drying, ethylene-norbornene copolymer is obtained. The ethylene, dicyclopentadiene, and toluene are all deoxygenated and dehydrated before being introduced into the reactor to ensure that their respective water and oxygen content is less than 10 ppm.

2. The method according to claim 1, characterized in that, The deoxygenation and dehydration treatment is carried out by sequentially passing the ethylene, dicyclopentadiene, and toluene through a column packed with deoxygenation and dehydration molecular sieves.

3. The method according to claim 1 or 2, characterized in that, The main catalyst mentioned in step (2) is one or more of the following: ethylene bis(1-indenyl)zirconia, ethylene bis(4,5,6,7-tetrahydro-1-indenyl)zirconia, bis(isopropylcyclopentadienyl)zirconia, and bis(2-methylindenyl)zirconia.

4. The method according to claim 1 or 2, characterized in that, The cocatalyst mentioned in step (2) is one or more of methylaluminoxane, triethylaluminum, and triisobutylaluminum.

5. The method according to claim 1 or 2, characterized in that, The main catalyst mentioned in step (2) is ethylene bis(1-indenyl)zirconium dichloride, and the co-catalyst is methylaluminoxane; The cumulative concentration of ethylene bis(1-indenyl)zirconium dichloride in the norbornene mixture was 8 × 10⁻⁶. -5 The cumulative concentration of methylaluminoxane in the norbornene mixture was 1.6 × 10 mol / L. -1 mol / L.

6. The method according to claim 1 or 2, characterized in that, The polymerization reaction time in step (2) is 30-40 min.

7. The method according to claim 1 or 2, characterized in that, In step (2), the vacuum drying conditions are 70°C for 24 hours.

8. The method according to claim 1 or 2, characterized in that, The cumulative concentration of DCPD in the norbornene mixture in step (1) is 20%-40%.

9. The method according to claim 5, characterized in that, The cumulative concentration of DCPD in the norbornene mixture in step (1) is 20%-40%; the polymerization reaction time in step (2) is 30-40 min, and the vacuum drying conditions are vacuum drying at 70℃ for 24 h.

10. An ethylene-norbornene copolymer, characterized in that, The copolymer is prepared by the method described in any one of claims 1 to 9.