A system and method for producing impact-resistant copolymer polypropylene

Abstract

This invention belongs to the field of olefin gas-phase polymerization technology and discloses a system and method for producing impact-resistant copolymer polypropylene. The system includes an intermittent polypropylene unit and a gas supply tank. The intermittent polypropylene unit includes a polymerization reactor. The outlet of the gas supply tank is connected to the inlet of the polymerization reactor via a gas-phase olefin feed pipeline, and the outlet of the polymerization reactor is connected to the gas supply tank via a circulating gas pipeline. The gas supply tank is connected to a propylene feed unit and an ethylene feed unit. The gas supply tank is equipped with a temperature control unit and a first pressure control unit. A circulating compressor is installed on the circulating gas pipeline. This system and method enables the production of impact-resistant copolymer polypropylene using an intermittent liquid-phase bulk polymerization method with relatively low equipment investment, while ensuring the quality of the polypropylene.

Description

Technical Field

[0001] This invention belongs to the field of olefin polymerization technology, and specifically relates to a system and method for producing impact-resistant copolymer polypropylene. Background Technology

[0002] Impact copolymer polypropylene, also known as multiphase copolymer polypropylene, is a high-value-added product in the polypropylene family due to its excellent balance of rigidity and toughness. Its output has maintained a strong growth trend, and the developed grades are increasingly replacing steel and engineering plastics, and are widely used in automobiles, home appliances and other fields.

[0003] Impact-resistant polypropylene is prepared using a multi-reactor series process. First, propylene is homopolymerized in the first-stage reactor to generate a continuous isotactic polypropylene phase. Then, the polymer particles are transferred to subsequent reactors for ethylene / propylene or ethylene / butene copolymerization, resulting in a dispersed copolymer phase on the continuous isotactic polypropylene phase. Currently, impact-resistant copolymer polypropylene can almost only be produced using a continuous polypropylene process.

[0004] The batch liquid-phase bulk polymerization process for polypropylene production is a technology independently developed and successfully implemented in my country. This process mainly includes raw material refining, polymerization reaction, flash deactivation, granulation, and packaging. The polymerization reaction unit includes equipment such as propylene metering tanks, activator feeding tanks, catalyst feeding tanks, hydrogen metering tanks, polymerization kettles, hot water tanks, hot water pumps, cold water pipelines, and steam pipelines. The batch liquid-phase bulk polymerization process for polypropylene does not have very high requirements for the quality of the raw material propylene. It has a simple process, low investment, quick returns, and flexible product grade conversion, making it particularly suitable for the dispersed and abundant gas resources of Chinese refineries. The batch liquid-phase bulk polymerization process can generally only produce homopolymer polypropylene.

[0005] Patent document CN101693756A discloses a production process and apparatus for block copolymer polypropylene. The process involves polymerizing liquid propylene in a homopolymer reactor to produce homopolymer polypropylene. After polymerization, the homopolymer is transferred to a copolymerization gas-phase reactor. After deactivation of the polypropylene particles, ethylene and propylene are introduced to react with the polypropylene in a gas-phase copolymerization reaction, producing block copolymer polypropylene. The production apparatus includes a polymerization system, a gas distribution system, a low-purity nitrogen system, a degassing flash evaporation system, and a circulation system. This method makes the intermittent liquid-gas phase method for producing block copolymer polypropylene a reality. However, this patent document does not describe how to control the gas composition within the polymerization reactor during ethylene-propylene gas-phase copolymerization, which may affect the quality stability of the prepared block copolymer. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a system and method for producing impact-resistant copolymer polypropylene, thereby improving the situation of low-end products and poor profitability of intermittent polypropylene plants, and increasing product added value and market competitiveness.

[0007] A first aspect of the present invention provides a system for producing impact-resistant copolymer polypropylene, the system comprising an intermittent polypropylene unit and a gas supply tank, the intermittent polypropylene unit comprising a polymerization reactor, the outlet of the gas supply tank being connected to the inlet of the polymerization reactor via a gas phase olefin feed line, and the outlet of the polymerization reactor being connected to the gas supply tank via a circulating gas line.

[0008] The gas supply tank is connected to a propylene feeding unit and an ethylene feeding unit. The gas supply tank is equipped with a temperature control unit and a first pressure control unit. A circulating compressor is installed on the circulating gas pipeline.

[0009] A second aspect of the present invention provides a method for producing impact-resistant copolymer polypropylene using the above-described system, the method comprising:

[0010] 1) The propylene feeding unit introduces liquid propylene into the gas supply tank, the gas supply tank is heated, and the liquid propylene is partially vaporized; the ethylene feeding unit introduces gaseous ethylene into the gas supply tank, and controls the temperature and pressure of the gas supply tank so that the vaporized liquid propylene and gaseous ethylene form a mixed olefin gas that is copolymerized.

[0011] 2) Add materials containing liquid propylene and catalyst system into the polymerization reactor to carry out homopolymerization of propylene. After the homopolymerization reaction is completed, flash evaporate and recover the unreacted propylene monomer.

[0012] 3) Introduce the mixed olefin gas into the polymerization reactor and circulate the gas between the polymerization reactor and the gas supply tank through a circulating compressor. The polymerization reactor undergoes a copolymerization reaction. As the copolymerization reaction proceeds, gaseous ethylene is continuously introduced into the gas supply tank, and liquid propylene is continuously vaporized. The temperature and pressure of the gas supply tank are maintained at the same level as in step 1).

[0013] 4) After the copolymerization reaction is completed, gradually reduce the pressure of the polymerization reactor, stop the gas circulation, close the gas inlet and outlet of the polymerization reactor, discharge the polymerization product and perform post-processing to obtain impact-resistant copolymer polypropylene.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) For the copolymerization reaction of olefins, the difference in the reactivity ratio of different olefin monomers leads to different consumption rates of different olefin monomers in the polymerization reactor, which makes it difficult to stabilize the gas composition during the copolymerization process. In the system of the present invention, the gas supply tank can provide a stable mixture of propylene and ethylene gas. By adding a circulating compressor between the polymerization reactor and the gas supply tank and selecting an appropriate circulating gas speed, the gas can be circulated between the polymerization reactor and the gas distribution tank. On the one hand, this achieves the effect of maintaining the basic stability of the gas composition in the polymerization reactor, and on the other hand, it also helps to remove the heat of polymerization, which is beneficial to the temperature control of the polymerization reactor during gas-phase polymerization.

[0016] (2) The system and method for producing impact copolymer polypropylene of the present invention enables the production of impact copolymer polypropylene products by intermittent liquid phase bulk method with relatively small equipment investment. Compared with the prior art, process control and product performance can be optimized, which improves the situation of low-end products and poor profitability of intermittent polypropylene equipment, and increases product added value and market competitiveness.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a system for producing impact-resistant copolymer polypropylene.

[0019] Explanation of reference numerals in the attached drawings: 1-Propylene storage tank; 2-Propylene pump; 3-Polymerization reactor; 4-Hydrogen cylinder; 5-Hydrogen inlet pressure reducing valve; 6-Auxiliary agent feed port; 7-High-pressure ethylene cylinder; 8-Ethylene inlet pressure reducing valve; 9-Ethylene inlet regulating valve; 10-Gas supply tank; 11-Propylene inlet regulating valve; 12-Gas supply tank outlet pressure reducing valve; 13-Mixed gas inlet regulating valve; 14-Circulating compressor; 15-Heat exchanger; 16-Deactivation tank; 17-Propylene recovery system. Detailed Implementation

[0020] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0021] According to a first aspect of the present invention, the present invention provides a system for producing impact-resistant copolymer polypropylene, the system comprising an intermittent polypropylene unit and a gas supply tank, the intermittent polypropylene unit comprising a polymerization reactor, the outlet of the gas supply tank being connected to the inlet of the polymerization reactor via a gas phase olefin feed line, and the outlet of the polymerization reactor being connected to the gas supply tank via a circulating gas line.

[0022] The gas supply tank is connected to a propylene feeding unit and an ethylene feeding unit. The gas supply tank is equipped with a temperature control unit and a first pressure control unit. A circulating compressor is installed on the circulating gas pipeline.

[0023] The system of this invention is implemented by adding a gas supply tank to an intermittent polypropylene unit. Intermittent polypropylene units are conventional setups in the art, including those containing a polymerization reactor, propylene feeding facilities, and a propylene recovery system, which will not be described in detail here. The gas supply tank of this invention provides the polymerization reactor with propylene and ethylene gaseous feedstocks of a specific composition required for copolymerization. The size of the gas supply tank is not strictly required; generally, the volume ratio of the gas supply tank to the polymerization reactor is 0.01 to 5:1, preferably 0.05 to 0.5:1.

[0024] According to the present invention, the propylene feeding unit intermittently or continuously supplies liquid olefin feedstock to the gas supply tank. If the pressure of the propylene source is lower than the operating pressure of the gas supply tank, the feeding unit can use an explosion-proof diaphragm pump as the power source; if the pressure of the propylene source is higher than the operating pressure of the gas supply tank, the feeding unit can utilize the pressure difference to achieve feedstock transportation without additional power equipment. The gas supply tank is equipped with a level gauge, and a third regulating valve is provided on the connecting pipeline between the propylene feeding unit and the gas supply tank. The third regulating valve is electrically connected to the level gauge signal of the gas supply tank to achieve continuous feeding of liquid olefins. This propylene feeding unit can be a propylene feeding facility shared with an intermittent polypropylene unit.

[0025] In this invention, the ethylene feeding unit continuously supplies ethylene gas to the gas supply tank. The pressure of the ethylene source is higher than the operating pressure of the gas supply tank. The gas supply tank is equipped with a pressure gauge, and the first pressure control unit is a pressure reducing valve (such as a self-regulating pressure reducing valve) and / or a first regulating valve located on the pipeline connecting the ethylene feeding unit and the gas supply tank. The first regulating valve is electrically connected to the pressure gauge signal of the gas supply tank to stabilize the pressure of the gas supply tank at a set value.

[0026] According to the present invention, the gas supply tank is equipped with a temperature instrument, and the temperature control unit maintains the temperature of the material inside the gas supply tank at a set value near the gas supply tank. The temperature control unit may include a jacketed water system disposed on the outer surface of the gas supply tank and / or a heat exchanger disposed on the circulating gas return pipeline.

[0027] The jacket water system is a conventional temperature control system, which includes instruments to control the temperature and flow rate of the jacket water, so that the temperature of the air supply tank can be maintained within a certain range of the set temperature value. The heat exchange medium of the heat exchanger is circulating water.

[0028] In one specific embodiment, the temperature control unit comprises only a heat exchanger located on the circulating gas pipeline, with a crossover connecting the gaseous olefin feed pipeline and the circulating gas pipeline. The heat exchanger includes instruments for controlling the flow rate and temperature of the heat exchange medium. The crossover allows the circulating gas to circulate only between the gas supply tank, the circulating compressor, and the heat exchanger, thereby achieving temperature control of the material in the gas supply tank. These features are all achievable with reference to existing technologies.

[0029] In this invention, the circulating compressor is the power source for circulating the reaction gas between the polymerization reactor and the gas supply tank, and a centrifugal compressor is generally selected.

[0030] According to the present invention, a second pressure control unit is provided on the gas phase olefin feed line, the second pressure control unit includes a pressure reducing valve and / or a second regulating valve, and the second regulating valve is electrically connected to the pressure gauge signal of the polymerization reactor.

[0031] According to a second aspect of the present invention, the present invention provides a method for producing impact-resistant copolymer polypropylene using the above-described system, the method comprising:

[0032] 1) The propylene feeding unit introduces liquid propylene into the gas supply tank, the gas supply tank is heated, and the liquid propylene is partially vaporized; the ethylene feeding unit introduces gaseous ethylene into the gas supply tank, and controls the temperature and pressure of the gas supply tank so that the vaporized liquid propylene and gaseous ethylene form a mixed olefin gas that is copolymerized.

[0033] 2) Add materials containing liquid propylene and catalyst system into the polymerization reactor to carry out homopolymerization of propylene. After the homopolymerization reaction is completed, flash evaporate and recover the unreacted propylene monomer.

[0034] 3) Introduce the mixed olefin gas into the polymerization reactor and circulate the gas between the polymerization reactor and the gas supply tank through a circulating compressor. The polymerization reactor undergoes a copolymerization reaction. As the copolymerization reaction proceeds, gaseous ethylene is continuously introduced into the gas supply tank, and liquid propylene is continuously vaporized. The temperature and pressure of the gas supply tank are maintained at the same level as in step 1).

[0035] 4) After the copolymerization reaction is completed, gradually reduce the pressure of the polymerization reactor, stop the gas circulation, close the gas inlet and outlet of the polymerization reactor, discharge the polymerization product and perform post-processing to obtain impact-resistant copolymer polypropylene.

[0036] In this invention, the temperature, pressure, and liquid propylene volume of the gas supply tank can be determined as needed, as long as the mixed olefin gas for copolymerization can be continuously supplied. For example, the liquid volume in the gas supply tank accounts for 10% to 90% of the gas supply tank volume, the temperature of the gas supply tank is 0 to 50°C, and the pressure of the gas supply tank is 0.5 to 4.0 MPa.

[0037] According to the present invention, the feeding of liquid propylene into the gas supply tank can be done only once before copolymerization, and not again during copolymerization; or it can be continued intermittently multiple times during copolymerization; or it can be continuously fed throughout the process through automatic control of the liquid level in the gas supply tank via a regulating valve. Preferably, liquid propylene is continuously introduced into the gas supply tank through an electrical connection between the regulating valve and the liquid level gauge signal of the gas supply tank, so that the liquid level in the gas supply tank remains constant at a set value.

[0038] In this invention, the final polymerization reactor pressure after flash propylene recovery during homopolymerization affects the establishment of initial equilibrium in the subsequent ethylene-propylene copolymerization. Therefore, this pressure should be as low as possible, and its selection depends on the capacity of the propylene recovery system. Generally, after homopolymerization, flash evaporation is stopped when the polymerization reactor pressure is below 2.0 MPa; preferably, it is stopped when it is below 1.0 MPa.

[0039] According to the present invention, during the copolymerization reaction, the temperature fluctuation of the material inside the gas supply tank relative to the set temperature of the gas supply tank is less than 10°C, preferably less than 5°C, and more preferably less than 2°C. The temperature of the material inside the gas supply tank is the actual temperature displayed on the temperature monitoring instrument.

[0040] In this invention, hydrogen gas needs to be introduced during homopolymerization and copolymerization, which is a conventional operation in the art, and the amount of hydrogen gas used can be selected as needed. The conditions for homopolymerization can also refer to the conventional conditions in the prior art.

[0041] According to the present invention, the circulating gas flow rate of the circulating compressor during the copolymerization process should be as large as possible. This is beneficial to the stability of the gas composition inside the polymerization reactor and the removal of polymerization heat, but the corresponding equipment cost will also increase. The gas velocity of the circulating compressor is selected according to the size of the polymerization reactor, and is generally 1 to 80 m / s². 3 / min.

[0042] In this invention, the copolymerization temperature is 50-100℃ and the copolymerization pressure is 0.1-2.0MPa. The higher the copolymerization pressure, the higher the polymerization rate, but the copolymerization pressure must be lower than the gas supply tank pressure.

[0043] According to the present invention, after the copolymerization reaction is completed, the pressure of the polymerization reactor is gradually reduced. This can be achieved by gradually reducing the flow rate of the reaction gas entering the polymerization reactor from the gas supply tank, while the gas velocity of the circulating compressor remains constant. The reduced pressure of the polymerization reactor should be sufficient to allow for smooth discharge. Generally, after the copolymerization reaction is completed, gas circulation is stopped when the pressure of the polymerization reactor is below 1.0 MPa; preferably, gas circulation is stopped when it is below 0.5 MPa. The impact-resistant copolymer polypropylene obtained by polymerization is discharged to a deactivation tank using the residual pressure in the polymerization reactor. After nitrogen purging and deactivation, it is packaged.

[0044] Components, ingredients and parameters not limited in this invention can be selected according to existing technology and are conventional technical means in this field.

[0045] The present invention will be further described below with reference to embodiments. However, the invention is not limited to these embodiments.

[0046] Example

[0047] Process flow as follows Figure 1 As shown. The system for producing impact-resistant copolymer polypropylene includes an intermittent polypropylene unit and a gas supply tank 10. The intermittent polypropylene unit includes a polymerization reactor 3. The outlet of the gas supply tank is connected to the inlet of the polymerization reactor via a gaseous olefin feed pipeline, and the outlet of the polymerization reactor is connected to the gas supply tank via a circulating gas pipeline. The gas supply tank is connected to a propylene feed unit (propylene storage tank 1) and an ethylene feed unit (high-pressure ethylene cylinder 7). The gas supply tank is equipped with a temperature control unit and a first pressure control unit. A circulating compressor 14 is installed on the circulating gas pipeline. The gas supply tank is equipped with a temperature instrument. The temperature control unit includes a heat exchanger 15 located on the circulating gas pipeline. A crossover line connects the gaseous olefin feed pipeline and the circulating gas pipeline. The gas supply tank is equipped with a pressure instrument. The first pressure control unit includes an ethylene feed pressure reducing valve 8 and an ethylene feed regulating valve 9 located on the pipeline connecting the ethylene feed unit and the gas supply tank. The ethylene feed regulating valve is electrically connected to the pressure instrument signal of the gas supply tank. A second pressure control unit is installed on the gas phase olefin feed line. The second pressure control unit includes a pressure reducing valve 12 at the gas supply tank outlet and a mixed gas inlet regulating valve 13. The mixed gas inlet regulating valve is electrically connected to the pressure gauge signal of the polymerization reactor. A level gauge is installed on the gas supply tank. A propylene feed regulating valve 11 is installed on the connection line between the propylene feed unit and the gas supply tank. The propylene feed regulating valve is electrically connected to the level gauge signal of the gas supply tank.

[0048] The specific process steps include: the gas supply tank has a volume of 2 liters, the liquid level in the gas supply tank 10 is set to 50%, and its liquid level is automatically controlled in conjunction with the opening of the propylene feed regulating valve 11. Then, liquid propylene is continuously introduced from the propylene storage tank 1 into the gas supply tank 10 through the propylene pump 2. The temperature of the gas supply tank 10 is set to 30℃, and its temperature is cascaded with the circulating water temperature of the heat exchanger 15. The circulating gas compressor is started, and the gas supply tank is heated. After the temperature of the gas supply tank 10 reaches the set value and stabilizes, the pressure of the gas supply tank 10 is set to 1.75MPa, and its pressure is automatically controlled in conjunction with the opening of the ethylene feed regulating valve 9. Then, ethylene gas is continuously introduced from the high-pressure ethylene cylinder 7 into the gas supply tank through the ethylene feed pressure reducing valve 8 and the ethylene feed regulating valve 9.

[0049] The polymerization reactor is a 5-liter reactor. 3.0 mmol of triethylaluminum, 0.3 mmol of the external electron donor cyclohexylmethyldimethoxysilane, and 12.0 mg of DQ catalyst are added to the polymerization reactor 3 through the additive feed port 6. Then, 0.25 g of hydrogen is added to the polymerization reactor 3 from the hydrogen cylinder 4 via the hydrogen feed pressure reducing valve 5. Finally, 2.5 liters of liquid propylene are added to the polymerization reactor 3 from the propylene storage tank 1 via the propylene pump 2. The mixture is heated to 70°C under stirring, and the liquid propylene is polymerized in the polymerization reactor for 60 minutes to produce homopolymer polypropylene. Unreacted propylene in the polymerization reactor is then recovered via the propylene recovery system 17.

[0050] After the pressure in polymerization reactor 3 drops below 0.5 MPa, close the propylene recovery valve, open the inlet and outlet valves on polymerization reactor 3, then close the valve on the cross-line, add 0.05 g of hydrogen into the polymerization reactor, and finally set the polymerization reactor temperature to 70℃ and the pressure to 1.4 MPa. Automatically adjust the opening of the mixing gas inlet regulating valve 13 to allow the ethylene and propylene in polymerization reactor 3 to copolymerize. The copolymerization time is 60 minutes, and gas samples are taken from the polymerization reactor at the beginning, 20 minutes, 40 minutes, and before the end of the copolymerization process.

[0051] After copolymerization, gradually reduce the pressure in the polymerization reactor until it reaches 0.3 MPa. Then, close the inlet and outlet valves on polymerization reactor 3, and open the discharge valve from polymerization reactor 3 to deactivation tank 16 to discharge the generated impact-resistant copolymer polypropylene into deactivation tank 16. After nitrogen purging and deactivation, the polypropylene product in deactivation tank 16 can be discharged and packaged.

[0052] The temperature of the polymerization reactor was stably controlled during the copolymerization process, and 505 grams of polymer were finally obtained. Analysis of the polymer revealed an ethylene content of 12.38% and a rubber phase content of 26.39%. The chromatographic analysis results of the gas samples are shown in Table 1.

[0053] Comparative Example

[0054] The difference from the previous example is as follows: After the pressure in polymerization reactor 3 drops below 0.1 MPa, the propylene recovery valve is closed, and the pressure in the polymerization reactor is released to atmospheric pressure through venting. After adjusting the mixed gas inlet regulating valve 13 to 100%, the inlet valve on polymerization reactor 3 is opened, while the outlet valve on polymerization reactor 3 is kept closed. Ethylene-propylene mixed gas is introduced into the polymerization reactor, followed by the addition of 0.05 g of hydrogen. The polymerization reactor temperature is set to 70°C, and the pressure reducing valve 12 at the outlet of the gas supply tank is adjusted to bring the polymerization reactor pressure to 1.4 MPa, initiating the copolymerization reaction for 60 minutes. Gas samples are taken from the polymerization reactor at the beginning, 20 minutes, 40 minutes, and before the end of the copolymerization. After copolymerization, the inlet valve on the polymerization reactor is closed, and the pressure in the polymerization reactor is released to 0.3 MPa. The discharge valve from polymerization reactor 3 to deactivation tank 16 is opened, and the generated impact-resistant copolymer polypropylene is discharged into deactivation tank 16, where it is released after displacement and deactivation. The rest is the same as in Example 1.

[0055] During the copolymerization process, the temperature of the polymerization reactor could not be steadily controlled. Initially, the highest temperature reached 96℃, gradually decreasing later, but still reaching a high of 82℃ at the end. A total of 478 grams of polymer was obtained. Analysis of the polymer revealed an ethylene content of 10.25% and a rubber phase content of 25.01%. The chromatographic analysis results of the gas samples are shown in Table 1.

[0056] Table 1

[0057]

[0058] As shown in Table 1, the system and method of this invention maintain a very stable volume ratio of ethylene to propylene in the polymerization reactor during the copolymerization process, with a variation range within 2%, which is beneficial for improving the quality of the polymer product. In the comparative copolymerization process, the volume ratio of ethylene to propylene in the polymerization reactor continuously decreases; at the end of gas-phase polymerization, the volume ratio of ethylene to propylene is reduced by 43% compared to the beginning. The system and method of this invention for producing impact-resistant copolymer polypropylene can improve the situation of low-end products and poor profitability in batch polypropylene plants, thereby increasing product added value and market competitiveness.

[0059] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A process for the production of an impact copolymer polypropylene, characterized in that, The system used in this method includes an intermittent polypropylene unit and a gas supply tank. The intermittent polypropylene unit includes a polymerization reactor. The outlet of the gas supply tank is connected to the inlet of the polymerization reactor via a gaseous olefin feed pipeline, and the outlet of the polymerization reactor is connected to the gas supply tank via a circulating gas pipeline. The gas supply tank is connected to a propylene feed unit and an ethylene feed unit. The gas supply tank is equipped with a temperature control unit and a first pressure control unit. A circulating compressor is installed on the circulating gas pipeline. The method includes: 1) The propylene feeding unit introduces liquid propylene into the gas supply tank, the gas supply tank is heated, and the liquid propylene is partially vaporized; the ethylene feeding unit introduces gaseous ethylene into the gas supply tank, and controls the temperature and pressure of the gas supply tank so that the vaporized liquid propylene and gaseous ethylene form a mixed olefin gas that is copolymerized. 2) Add materials containing liquid propylene and catalyst system into the polymerization reactor to carry out homopolymerization of propylene. After the homopolymerization reaction is completed, flash evaporate and recover the unreacted propylene monomer. 3) Introduce the mixed olefin gas into the polymerization reactor and circulate the gas between the polymerization reactor and the gas supply tank through a circulating compressor. The polymerization reactor undergoes a copolymerization reaction. As the copolymerization reaction proceeds, gaseous ethylene is continuously introduced into the gas supply tank, and liquid propylene is continuously vaporized. The temperature and pressure of the gas supply tank are maintained at the same level as in step 1). 4) After the copolymerization reaction is completed, gradually reduce the pressure of the polymerization reactor, stop the gas circulation, close the gas inlet and outlet of the polymerization reactor, discharge the polymerization product and perform post-processing to obtain impact-resistant copolymer polypropylene.

2. The method for producing impact-resistant copolymer polypropylene according to claim 1, wherein, The gas supply tank is equipped with a temperature instrument, and the temperature control unit includes a jacketed water system located on the outer surface of the gas supply tank and / or a heat exchanger located on the circulating gas pipeline.

3. The process for producing an impact copolymer polypropylene according to claim 2, wherein, The temperature control unit includes a heat exchanger located on the circulating gas pipeline and a crossover line connecting the gas phase olefin feed pipeline and the circulating gas pipeline.

4. The process for producing an impact copolymer polypropylene according to claim 1, wherein, The gas supply tank is equipped with a pressure gauge. The first pressure control unit includes a pressure reducing valve and / or a first regulating valve located on the pipeline connecting the ethylene feed unit and the gas supply tank. The first regulating valve is electrically connected to the pressure gauge signal of the gas supply tank.

5. The process for producing an impact copolymer polypropylene according to claim 1 wherein, The gas phase olefin feed line is equipped with a second pressure control unit, which includes a pressure reducing valve and / or a second regulating valve. The second regulating valve is electrically connected to the pressure gauge signal of the polymerization reactor.

6. The process for producing an impact copolymer polypropylene according to claim 1, wherein, The gas supply tank is equipped with a level gauge, and a third regulating valve is provided on the connecting pipeline between the propylene feeding unit and the gas supply tank. The third regulating valve is electrically connected to the level gauge signal of the gas supply tank.

7. The process for producing an impact copolymer polypropylene according to claim 1 wherein, After the homopolymerization reaction is completed, flash evaporation is stopped when the pressure in the polymerization reactor is below 2.0 MPa.

8. The process for producing an impact copolymer polypropylene according to claim 7, wherein, After the homopolymerization reaction is completed, flash evaporation is stopped when the pressure in the polymerization reactor is below 1.0 MPa.

9. The process for producing an impact copolymer polypropylene according to claim 1, wherein, The liquid volume in the gas supply tank accounts for 10% to 90% of the tank volume, the temperature of the gas supply tank is 0 to 50℃, and the pressure of the gas supply tank is 0.5 to 4.0 MPa.

10. The method for producing impact-resistant copolymer polypropylene according to claim 1, wherein, The air velocity of the circulation compressor is 1-80 m 3 / min.

11. The process for producing an impact copolymer polypropylene according to claim 1, wherein, The copolymerization reaction temperature is 50~100℃, and the copolymerization reaction pressure is 0.1~2.0MPa. The copolymerization reaction pressure is lower than the gas supply tank pressure.

12. The process for producing an impact copolymer polypropylene according to claim 1, wherein, After the copolymerization reaction is completed, gas circulation is stopped when the pressure in the polymerization reactor is below 1.0 MPa.

13. The process for producing an impact copolymer polypropylene according to claim 12 wherein, After the copolymerization reaction is completed, gas circulation is stopped when the pressure in the polymerization reactor is below 0.5 MPa.

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