Method for preparing cycloolefin copolymer through continuous polymerization

Abstract

The invention discloses a method for preparing a cycloolefin copolymer by continuous polymerization, which comprises the following steps: (1) in a reaction kettle, reacting ethylene with a toluene solution of dicyclopentadiene at high temperature and high pressure to synthesize norbornene, so as to obtain a crude norbornene mixed solution, and distilling to obtain a toluene solution of norbornene at the top of a distillation tower and a byproduct at the bottom of the tower; and (2) directly conveying the toluene solution of norbornene obtained in the step (1) into a polymerization kettle, and carrying out a copolymerization reaction with ethylene to prepare the cycloolefin copolymer. According to the invention, the toluene solution of norbornene is directly obtained through distillation, and the solution is liquid, is easier to convey in a pipeline and is copolymerized with ethylene of a next unit, so that continuous preparation of the cycloolefin copolymer is realized, and the method is more economical; and on the other hand, the boiling point difference between the norbornene and the methylbenzene is not large, so that the separation is difficult, the methylbenzene solution of the norbornene is directly obtained, and the operation is more convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical production, and particularly relates to a method for continuously polymerizing to prepare cycloolefin copolymer. Background Art

[0002] Cycloolefin copolymer (abbreviated as COC) is a kind of high-value-added thermoplastic engineering plastic copolymerized from cycloolefin monomers and α-olefins, etc. Compared with traditional polyolefins, due to the introduction of a cyclic structure into the main chain, COC has high transparency, excellent heat resistance, chemical stability, melt fluidity, dimensional stability, etc., and is widely used in the manufacture of various optical lenses, prisms, automotive headlights, optical films for LCDs, contact lenses, etc. In addition, COC also has an extremely low dielectric constant and can be used in the manufacture of 5G communication materials, electronic and electrical components, etc. At the same time, COC has also become one of the emerging pharmaceutical (such as COVID-19 vaccine injection materials) and food packaging materials due to its good moisture barrier property and easy disinfection property.

[0003] For the most widely studied COC material at present - ethylene / norbornene copolymer (abbreviated as ENC), it is obtained through an addition polymerization process. In the addition polymerization process, metallocene catalysts are mostly used, and the polymerization process is solution polymerization. CN1101052A discloses a method for preparing ethylene / norbornene copolymer, which uses a zirconocene main catalyst and a methylaluminoxane cocatalyst. The polymerization process is bulk polymerization, and the reactor is a continuous stirred tank reactor, which has 4 main processes including polymerization, polymer recovery, pelletizing and packaging, and rectification recovery; in the polymerization process, gaseous ethylene supplied by pipelines and molten monomer norbornene are introduced into the polymerization kettle, and then the main catalyst and the methylaluminoxane cocatalyst are mixed in toluene and then pumped into the reaction kettle for reaction; after the reaction is completed, a small amount of soft water is added to the polymer solution to terminate the reaction, and then the copolymer solid is obtained by filtration.

[0004] However, norbornene (abbreviated as NB), an important monomer of cycloolefin copolymer, is mainly obtained by the Diels - Alder reaction of cyclopentadiene (abbreviated as CPD) and ethylene as dienophiles. CPD is unstable at room temperature and exists in the form of a dimer dicyclopentadiene (abbreviated as DCPD). In the reaction process, DCPD is formulated into a solution with a certain concentration, decomposed into CPD under high temperature and high pressure conditions, then copolymerized with ethylene to synthesize norbornene, and then polymer-grade norbornene is obtained through two rectifications. Then, using norbornene as a raw material, after dissolving it in an inert solvent, it is copolymerized with ethylene to synthesize ENC. Moreover, norbornene is a solid at room temperature, and it is inconvenient to transport. It needs to be heated and dissolved first for the next copolymerization step, and the operation is rather troublesome. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for continuously polymerizing to prepare cycloolefin copolymer.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for continuously polymerizing to prepare a cycloolefin copolymer, comprising the following steps:

[0008] (1) In a reaction kettle, ethylene reacts with a toluene solution of dicyclopentadiene at high temperature and high pressure to synthesize norbornene, obtaining a crude norbornene mixture. After distillation, a toluene solution of norbornene is obtained at the top of the distillation column, and the bottom of the column is a by-product;

[0009] (2) The toluene solution of norbornene obtained in step (1) is directly transported to a polymerization kettle to carry out a copolymerization reaction with ethylene to prepare a cycloolefin copolymer.

[0010] Further, the specific method for synthesizing norbornene in step (1) is as follows: After replacing the air in the reaction kettle with nitrogen, replacing the nitrogen in the reaction kettle with ethylene, then adding 210 g - 315 g of pure toluene solvent per liter of the reaction kettle, and then adding a toluene solution of ethylene and DCPD to carry out the reaction to obtain norbornene; the reaction conditions are: the pressure of the reaction kettle is 15 - 20 MPa, the temperature is 220 - 250 °C, and the cumulative concentration of DCPD throughout the reaction process is 20% - 40%;

[0011] In step (1), the distillation temperature for distillation is 100 - 120 °C;

[0012] In step (2), ethylene is introduced into the toluene solution of norbornene, and a metallocene catalyst and a cocatalyst are added to start the polymerization reaction.

[0013] Further, in step (1), before reaching the reaction conditions, ethylene is introduced into the reaction kettle for heating and stirring to reach the reaction conditions, and stirring is maintained during the reaction; the toluene solution of DCPD is added evenly through a liquid metering pump after the pressure and temperature in the reaction kettle both reach the reaction conditions; after the dropping of the toluene solution of DCPD is completed, the reaction continues for 20 min, and then the reaction is terminated; after the reaction ends, the reaction kettle is cooled, the stirring is turned off, the pressure in the reaction kettle is discharged, and the reaction product is collected to obtain a crude norbornene mixture.

[0014] Further, the specific method for preparing the cycloolefin copolymer in step (2) is as follows: directly transfer the toluene solution of norbornene obtained in step (1) into a polymerization kettle, and heat it to 60 °C; introduce ethylene into the toluene solution of norbornene, and stir to fully dissolve ethylene in the solution. Subsequently, add a metallocene catalyst and a cocatalyst to start the polymerization reaction, and increase the pressure to 0.2 MPa; during the polymerization process, ethylene is continuously introduced into the polymerization kettle to maintain the pressure at 0.2 MPa; after reacting for 40 min, relieve the pressure, add acidified ethanol to generate a white precipitate, filter, wash, and dry it under vacuum to obtain the cycloolefin copolymer.

[0015] Further, the metallocene catalyst is one or more of bis(1-indenyl)zirconium dichloride, bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride, bis(isopropylcyclopentadienyl)zirconium dichloride, and bis(2-methylindenyl)zirconium dichloride.

[0016] Further, the cocatalyst is one or more of methylaluminoxane, triethylaluminum, and triisobutylaluminum.

[0017] Further, the metallocene catalyst is bis(1-indenyl)zirconium dichloride, and the cumulative concentration of bis(1-indenyl)zirconium dichloride in the toluene solution of norbornene is 8×10 -5 mol / L.

[0018] Further, the cocatalyst is methylaluminoxane, and the cumulative concentration of methylaluminoxane in the toluene solution of norbornene is 1.6×10 -1 mol / L.

[0019] Further, the metallocene catalyst is bis(1-indenyl)zirconium dichloride, the cocatalyst is methylaluminoxane, the cumulative concentration of bis(1-indenyl)zirconium dichloride in the toluene solution of norbornene is 8×10 -5 mol / L, and the cumulative concentration of methylaluminoxane in the toluene solution of norbornene is 1.6×10 -1 mol / L.

[0020] Further, the temperature of the vacuum drying is 70 °C and the drying time is 24 h.

[0021] Further, the stirring time in step (2) is 30 min.

[0022] The method for continuously preparing the cycloolefin copolymer according to the present invention is characterized in that:

[0023] The present invention first synthesizes norbornene, and obtains a toluene solution of norbornene through distillation separation. Without further separation, it directly polymerizes with ethylene in a polymerization kettle to obtain a cycloolefin copolymer. Since the solvents for synthesizing norbornene in the first unit and preparing COC in the second unit are both toluene, taking advantage of this feature, it is not necessary to refine to obtain a pure product of polymerization-grade norbornene in the first unit. Instead, a toluene solution of norbornene is obtained through simple distillation and can be directly used to prepare COC. The boiling points of norbornene and toluene in the present invention differ significantly from those of the heavy components such as by-products. The toluene solution of norbornene directly obtained through distillation is a liquid (pure polymerization-grade norbornene is a solid at room temperature), which is easier to transport in pipelines. The directly obtained toluene solution of norbornene is transported to the second unit and copolymerizes with ethylene to achieve the continuous preparation of cycloolefin copolymer, which is more economical. On the other hand, since the boiling points of norbornene and toluene are not very different, separation is difficult, while directly obtaining the toluene solution of norbornene is more convenient in operation. Compared with the prior art of directly refining to obtain polymerization-grade norbornene and then preparing a toluene solution of norbornene to prepare COC, this invention connects these two reactions in series, simplifies the process flow, and realizes the continuous preparation of COC. The operation is simpler, energy is saved, and the economy is higher. Detailed implementation manners

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with embodiments. However, it should be understood that these embodiments are only used to illustrate the present invention and do not constitute a limitation to the scope of the present invention.

[0025] In addition, 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. The test methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise specified, all percentages and parts are by weight.

[0026] The norbornene synthesis device in the first unit is a high-temperature and high-pressure reaction kettle with a volume of 1 L, a design pressure of 30 MPa, and a design temperature of 350 °C. The entire system uses nitrogen as the protective gas.

[0027] Since the copolymerization of ethylene and cyclopentadiene requires high-pressure conditions to increase the solubility of ethylene in the solution, this can improve the conversion rate and selectivity of the reaction and reduce the generation of by-products. Under high-temperature and high-pressure conditions (pressure of 15 - 20 MPa, temperature of 220 - 250 °C), the conversion rate of this copolymerization reaction is close to 100%, and the selectivity > 90%. Therefore, the main component in the reaction mixture is norbornene, containing unreacted raw material ethylene and a small amount of by-products such as cyclopentadiene trimer and tetracyclododecene. Since the boiling points of the by-products differ greatly from those of norbornene and toluene, the by-products can be easily removed by atmospheric distillation to obtain a toluene solution of norbornene for the next copolymerization reaction.

[0028] The volume of the polymerization kettle in the second unit is 500 mL, and the designed pressure is 0.6 MPa. The entire system is protected by nitrogen gas. During the reaction, ethylene is introduced into the toluene solution of norbornene in advance for a period of time. On the one hand, it is to dissolve the ethylene gas in the solution; on the other hand, the introduction of ethylene can expel the air in the kettle, making the kettle filled with ethylene gas to avoid the influence of air on the metallocene catalyst and the cocatalyst. Then, the metallocene catalyst and the cocatalyst are added to start the reaction, and the pressure is increased to the preset reaction pressure. During the polymerization process, ethylene is continuously introduced into the reaction kettle to maintain the pressure stability.

[0029] DCPD conversion rate = amount of DCPD participating in the reaction / total amount of DCPD input into the reaction kettle;

[0030] Norbornene selectivity = amount of DCPD participating in the formation of norbornene / total amount of DCPD input into the reaction kettle.

[0031] Example 1

[0032] First unit: After replacing the air in the reaction kettle with nitrogen, replace the nitrogen in the reaction kettle with ethylene. Pump in 315 g of pure toluene solvent through a liquid metering pump, introduce ethylene into the reactor through a gas booster feeding system, turn on the stirrer and heat up to 220 °C. When the temperature rises to 220 °C, continue to add ethylene through the gas booster system to increase the pressure to 15 MPa. After reaching the preset pressure, add 105 g of a toluene solution of dicyclopentadiene with a concentration of 80% evenly through a liquid metering pump to start the reaction. The dropping time is 40 min. After the dropping is completed, continue the reaction for 20 min, and then terminate the reaction. After the reaction is over, turn on the cooling water for cooling, then turn off the stirrer, discharge the pressure in the reaction kettle, and collect the reaction product. The DCPD conversion rate of the reaction is 98.5%, and the norbornene selectivity is 95.5%. The reaction product is subjected to atmospheric distillation, the distillation temperature is 110 °C, and the mixed solution of norbornene and toluene is distilled out at the top of the column, and the heavy components remain in the column kettle. Through gas phase analysis, the concentration of the toluene solution of norbornene is 25%.

[0033] Unit 2: After replacing the air in the polymerization kettle with nitrogen, 200 mL of the toluene solution of norbornene obtained from Unit 1 was added to the polymerization kettle. Stirring was started and the temperature was raised to 60 °C. Ethylene was introduced into the solution, and stirring was carried out for 30 min to fully dissolve ethylene in the solution. Subsequently, the main metallocene catalyst ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration of 8×10 -5 mol / L) and the cocatalyst methylaluminoxane (cumulative concentration of 1.6×10 -1 mol / L) were added. The pressure was raised to 0.2 MPa and the reaction was started for 40 min. During the polymerization process, ethylene was continuously introduced into the polymerization kettle to maintain a stable pressure. After the reaction, the pressure was released, and the reaction product was fed into the product tank. Acidified ethanol was added to form a white precipitate. The product was filtered, washed, and vacuum-dried at 70 °C for 24 h to obtain a white solid, which was a cycloolefin copolymer.

[0034] Example 2

[0035] Unit 1: After replacing the air in the reaction kettle with nitrogen, the nitrogen in the reaction kettle was replaced with ethylene. 262 g of pure toluene solvent was pumped in through a liquid metering pump, and ethylene was introduced into the reactor through a gas booster feeding system. Stirring was started and the temperature was raised to 220 °C. When the temperature reached 220 °C, ethylene was continuously added through the gas booster system to increase the pressure to 15 MPa. After reaching the preset pressure, 157 g of an 80% toluene solution of dicyclopentadiene was added evenly through a liquid metering pump to start the reaction. The dropping time was 40 min. After the dropping was completed, the reaction was continued for 20 min, and then the reaction was terminated. After the reaction, cooling water was turned on for cooling, then stirring was turned off, the pressure in the reaction kettle was released, and the reaction product was collected. The conversion rate of DCPD in the reaction was 98.0%, and the selectivity of norbornene was 94.5%. The reaction product was subjected to atmospheric distillation. The distillation temperature was 110 °C, and the mixture of norbornene and toluene was distilled out at the top of the column, and the heavy components remained in the bottom of the column. By gas phase analysis and detection, the concentration of the toluene solution of norbornene was 33%.

[0036] Unit 2: After replacing the air in the polymerization kettle with nitrogen, 200 mL of the toluene solution of norbornene obtained from Unit 1 was added to the polymerization kettle. Stirring was started and the temperature was raised to 60 °C. Ethylene was introduced into the solution, and stirring was carried out for 30 min to fully dissolve ethylene in the solution. Subsequently, the main metallocene catalyst ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration of 8×10 -5 mol / L) and the cocatalyst methylaluminoxane (cumulative concentration of 1.6×10 -1mol / L). Raise the pressure to 0.2 MPa and start the reaction for 40 min. During the polymerization process, ethylene is continuously introduced into the polymerization kettle to maintain a stable pressure. After the reaction is completed, release the pressure. The reacted material enters the product tank, acidified ethanol is added to form a white precipitate. The product is filtered, washed, and vacuum dried at 70 °C for 24 h to obtain a white solid, which is a cycloolefin copolymer.

[0037] Example 3

[0038] First unit: After replacing the air in the reaction kettle with nitrogen, replace the nitrogen in the reaction kettle with ethylene. Pump 210 g of pure toluene solvent into the reactor through a liquid metering pump. Introduce ethylene into the reactor through a gas booster feeding system, turn on the stirrer and heat up to 220 °C. When the temperature reaches 220 °C, continue to add ethylene through the gas booster system to increase the pressure to 15 MPa. After reaching the preset pressure, add 210 g of a toluene solution of dicyclopentadiene with a concentration of 80% into the reactor through a liquid metering pump at a uniform speed to start the reaction. The dropping time is 40 min. After the dropping is completed, continue the reaction for 20 min, and then terminate the reaction. After the reaction is completed, turn on the cooling water for cooling, then turn off the stirrer, release the pressure in the reaction kettle, and collect the reaction product. The conversion rate of DCPD in the reaction is 97.0%, and the selectivity of norbornene is 92.5%. The reaction product is distilled at atmospheric pressure, and the distillation temperature is 110 °C. The mixed solution of norbornene and toluene is distilled out at the top of the column, and the heavy components remain in the bottom of the column. By gas phase analysis, the concentration of norbornene in the toluene solution is 46%.

[0039] Second unit: After replacing the air in the polymerization kettle with nitrogen, add 200 mL of the toluene solution of norbornene obtained from the first unit into the polymerization kettle, turn on the stirrer and heat up to 60 °C; introduce ethylene into the solution and stir for 30 min to fully dissolve ethylene in the solution. Subsequently, add the main metallocene catalyst ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration of 8×10 -5 mol / L) and the cocatalyst methylaluminoxane (cumulative concentration of 1.6×10 -1 mol / L). Raise the pressure to 0.2 MPa and start the reaction for 40 min. During the polymerization process, ethylene is continuously introduced into the polymerization kettle to maintain a stable pressure. After the reaction is completed, release the pressure. The reacted material enters the product tank, acidified ethanol is added to form a white precipitate. The product is filtered, washed, and vacuum dried at 70 °C for 24 h to obtain a white solid, which is a cycloolefin copolymer.

[0040] Example 4

[0041] Unit 1: After replacing the air in the reaction kettle with nitrogen, replace the nitrogen in the reaction kettle with ethylene. Pump in 315 g of pure toluene solvent through a liquid metering pump. Introduce ethylene into the reactor through a gas booster feeding system. Turn on the stirrer and heat up to 220 °C. When the temperature reaches 220 °C, continue to add ethylene through the gas booster system to increase the pressure to 20 MPa. After reaching the preset pressure, add 105 g of a toluene solution of dicyclopentadiene with a concentration of 80% evenly through a liquid metering pump to start the reaction. The dropping time is 40 min. After the dropping is completed, continue the reaction for 20 min, and then terminate the reaction. After the reaction is completed, turn on the cooling water for cooling, then turn off the stirrer, release the pressure in the reaction kettle, and collect the reaction product. The DCPD conversion rate of the reaction is 99.2%, and the norbornene selectivity is 97.2%. The reaction product is subjected to atmospheric distillation. The distillation temperature is 100 °C. The mixed solution of norbornene and toluene is distilled out at the top of the column, and the heavy components remain in the column kettle. By gas phase analysis, the concentration of the norbornene toluene solution is 25%.

[0042] Unit 2: After replacing the air in the polymerization kettle with nitrogen, add 200 g of the toluene solution of norbornene obtained from Unit 1 to the polymerization kettle. Turn on the stirrer and heat up to 60 °C; introduce ethylene into the solution and stir for 30 min to fully dissolve ethylene in the solution. Subsequently, add the main metallocene catalyst ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration of 8×10 -5 mol / L) and the cocatalyst methylaluminoxane (cumulative concentration of 1.6×10 -1 mol / L). Raise the pressure to 0.2 MPa and start the reaction for 40 min. During the polymerization process, ethylene is continuously introduced into the polymerization kettle to maintain the pressure stable. After the reaction is completed, release the pressure. The reacted material enters the product tank, add acidified ethanol to generate a white precipitate. The product is filtered, washed, and vacuum dried at 70 °C for 24 h to obtain a white solid, which is a cycloolefin copolymer.

[0043] Example 5

[0044] Unit 1: After replacing the air in the reaction kettle with nitrogen, replace the nitrogen in the reaction kettle with ethylene. Pump in 315 g of pure toluene solvent through a liquid metering pump, introduce ethylene into the reactor through a gas booster feeding system, turn on the stirrer and heat up to 250 °C. When the temperature rises to 250 °C, continue to add ethylene through the gas booster system to increase the pressure to 20 MPa. After reaching the preset pressure, uniformly add 105 g of a toluene solution of dicyclopentadiene with a concentration of 80% through a liquid metering pump to start the reaction. The dropping time is 40 min. After the dropping is completed, continue the reaction for 20 min, and then terminate the reaction. After the reaction is completed, turn on the cooling water for cooling, then turn off the stirrer, discharge the pressure in the reaction kettle, and collect the reaction product. The DCPD conversion rate of the reaction is 99.6%, and the norbornene selectivity is 96.8%. The reaction product is subjected to atmospheric distillation. The distillation temperature is 120 °C. The mixture of norbornene and toluene is distilled out at the top of the column, and the heavy components remain in the column kettle. By gas phase analysis, the concentration of the norbornene toluene solution is 25%.

[0045] Unit 2: After replacing the air in the polymerization kettle with nitrogen, add 200 g of the toluene solution of norbornene obtained from Unit 1 to the polymerization kettle, turn on the stirrer and heat up to 60 °C; introduce ethylene into the solution and stir for 30 min to fully dissolve ethylene in the solution. Subsequently, add the main metallocene catalyst ethylene bis(1-indenyl)zirconium dichloride (cumulative concentration of 8×10 -5 mol / L) and the cocatalyst methylaluminoxane (cumulative concentration of 1.6×10 -1 mol / L). Raise the pressure to 0.2 MPa and start the reaction for 40 min. During the polymerization process, ethylene is continuously introduced into the polymerization kettle to maintain the pressure stable. After the reaction is completed, release the pressure. The reaction material after the reaction enters the product tank, add acidified ethanol to generate a white precipitate. The product is filtered, washed, and vacuum dried at 70 °C for 24 h to obtain a white solid, which is a cycloolefin copolymer.

[0046] Although the embodiments of the present invention have been described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can still make changes, modifications, and substitutions to the above embodiments without departing from the concept of the present invention.

Claims

1. A method for continuously polymerizing to prepare a cycloolefin copolymer, characterized in that, It includes the following steps: (1) In a reactor, ethylene reacts with a toluene solution of dicyclopentadiene at high temperature and high pressure to synthesize norbornene, obtaining a crude norbornene mixture. After distillation, a toluene solution of norbornene is obtained at the top of the distillation column, and the bottom of the column is the by-product; (2) Directly transport the toluene solution of norbornene obtained in step (1) to a polymerization kettle to carry out a copolymerization reaction with ethylene to prepare a cycloolefin copolymer.

2. The method according to claim 1, characterized in that The specific method for synthesizing norbornene in step (1) is as follows: After purging the air in the reactor with nitrogen, purge the nitrogen in the reactor with ethylene, then add 210 g - 315 g of pure toluene solvent per liter of the reactor, and then add a toluene solution of ethylene and DCPD to carry out the reaction to obtain norbornene; The reaction conditions are: the pressure of the reactor is 15 - 20 MPa, the temperature is 220 - 250 °C, and the cumulative concentration of DCPD during the whole reaction process is 20% - 40%; In step (1), the distillation temperature for distillation is 100 - 120 °C; In step (2), introduce ethylene into the toluene solution of norbornene, add a metallocene catalyst and a cocatalyst to start the polymerization reaction.

3. The method according to claim 2, wherein In step (1), before reaching the reaction conditions, introduce ethylene into the reactor for heating and stirring to reach the reaction conditions, and keep stirring during the reaction; The toluene solution of DCPD is added uniformly by a liquid metering pump after the pressure and temperature in the reactor both reach the reaction conditions; After the dropping of the toluene solution of DCPD is completed, continue the reaction for 20 min, and then terminate the reaction; After the reaction ends, cool the reactor, turn off the stirring, release the pressure in the reactor, and collect the reaction product to obtain a crude norbornene mixture.

4. The method according to claim 2 or 3, characterized in that, The specific method for preparing the cycloolefin copolymer in step (2) is as follows: Directly transport the toluene solution of norbornene obtained in step (1) to a polymerization kettle and heat it to 60 °C; Introduce ethylene into the toluene solution of norbornene, stir to fully dissolve ethylene in the solution, then add a metallocene catalyst and a cocatalyst to start the polymerization reaction, and raise the pressure to 0.2 MPa; During the polymerization process, ethylene is continuously introduced into the polymerization kettle to maintain the pressure at 0.2 MPa; After reacting for 40 min, relieve the pressure, add acidified ethanol to form a white precipitate, filter, wash, and dry in vacuum to obtain the cycloolefin copolymer.

5. The method according to claim 2 or 3, characterized in that, The metallocene catalyst is one or several of ethylene bis(1 - indenyl) zirconium dichloride, ethylene bis(4,5,6,7 - tetrahydro - 1 - indenyl) zirconium dichloride, bis(isopropylcyclopentadienyl) zirconium dichloride, bis(2 - methylindenyl) zirconium dichloride.

6. The method according to claim 2 or 3, characterized in that, The cocatalyst is one or several of methylaluminoxane, triethylaluminum, triisobutylaluminum.

7. The method according to claim 5, characterized in that The metallocene catalyst is ethylene bis(1-indenyl)zirconium dichloride, and the cumulative concentration of the ethylene bis(1-indenyl)zirconium dichloride in the toluene solution of norbornene is 8×10 -5 mol / L.

8. The method according to claim 6, wherein The cocatalyst is methylaluminoxane, and the cumulative concentration of the methylaluminoxane in the toluene solution of norbornene is 1.6×10 -1 mol / L.

9. The method according to claim 4, wherein The metallocene catalyst is ethylene bis(1-indenyl)zirconium dichloride, the cocatalyst is methylaluminoxane, and the cumulative concentration of ethylene bis(1-indenyl)zirconium dichloride in the toluene solution of norbornene is 8×10 -5 mol / L, and the cumulative concentration of methylaluminoxane in the toluene solution of norbornene is 1.6×10 -1 mol / L.

10. The method according to claim 4, wherein The temperature for vacuum drying is 70 °C and the drying time is 24 h.