Device and method for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene

Abstract

The present invention discloses an apparatus and method for plasma polymerization of ultra-high-purity, ultra-high molecular weight polyethylene. The apparatus includes a plasma reaction chamber, a plasma high-energy excitation source, a gas supply system, a vacuum control system, a temperature control system, a product collection system, and a gas circulation system. The plasma coil in the plasma high-energy excitation source is enclosed in the outer ring of the bell-shaped jar of the plasma reaction chamber, providing energy to the plasma reaction chamber and exciting the inner wall of the chamber to generate high-activity, high-energy density plasma. The present invention generates high-activity, high-energy density plasma through high-energy excitation. Ethylene monomer molecules are impacted by high-energy particles in the plasma to form active species, which react with other ethylene monomers or active species. Free radical polymerization forms polyethylene chains, achieving polymerization of ethylene monomers, thereby generating ultra-high molecular weight polyethylene materials in the absence of catalysts. Ultra-high purity polyethylene products can be obtained through precise control of temperature and pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-high purity and ultra-high molecular weight polyethylene preparation, and in particular to a device and method for preparing ultra-high purity and ultra-high molecular weight polyethylene by adopting plasma high energy polymerization technology. Background Art

[0002] Ultra-high molecular weight polyethylene has excellent properties such as puncture resistance, tensile strength, impact resistance, high strength and high toughness. It is a key basic raw material for various high-purity chemical nanofiltration membranes and high-cleanliness packaging barrels, wafer baskets, chemical delivery pipelines, valves, joints, equipment linings, and seals. In high value-added fields such as power battery separators and semiconductor processing, there are higher requirements for the cleanliness and consistency of products, which require ultra-high purity ultra-high molecular weight polyethylene. Traditional methods for preparing ultra-high molecular weight polyethylene include monomer-initiated polymerization, ion polymerization, and para-oxidation polymerization. Taking monomer-initiated polymerization as an example, it is necessary to complete the polymerization reaction under high pressure and high temperature conditions with ethylene monomer as the raw material under the action of a catalyst (such as iron, cobalt, nickel, etc.). Other polymerization methods also require the use of catalysts to promote polymerization reactions through ions or para-oxidation. Traditional methods for synthesizing ultra-high molecular weight polyethylene (UHMWPE) have the following drawbacks: 1) The reaction must be carried out under high temperature and pressure, consuming significant energy and presenting significant operational challenges; 2) Catalyst synthesis is challenging and susceptible to contamination; and 3) The production process itself struggles to meet the stringent standards for cleanliness, separation, and impurity removal required to produce ultra-high-purity UHMWPE. Therefore, a new, economical, environmentally friendly, and green pathway for synthesizing UHMWPE is urgently needed.

[0003] Low-temperature plasma can be generated under mild conditions at atmospheric pressure, and has the advantages of high activity, low pollution, and a high safety factor. High-energy excitation is used to generate high-activity, high-energy-density plasma, which converts monomer molecules into active particles. These active particles undergo addition reactions with each other or with monomers to form polymer chains. No catalyst is required during the reaction, and it is a new green method for preparing polymers. The invention patent (CN117602847A) discloses a mixture of an organosilicon monomer and an oxidizing gas to form a plasma polymerization hydrolysis film under plasma excitation. The invention patent (CN117797310A) discloses a method for polymerization in radio frequency plasma using ethyl acrylate monomer as a precursor, and a polyethyl acrylate coating is deposited on a titanium stent.

[0004] In summary, plasma polymerization can achieve catalyst-free monomer polymerization at room temperature and pressure. However, due to the disordered nature of plasma reactions, it is difficult to control the degree of polymerization and to separate polymers of different molecular chains. This problem is exacerbated by the high reactivity of ethylene monomers. Developing novel plasma polymerization technologies to achieve the production of ultra-high-purity, ultra-high molecular weight polyethylene under catalyst-free conditions is of great significance. Summary of the Invention

[0005] To address these issues, the present invention aims to provide a plasma high-energy polymerization device and method. This device utilizes pulse modulation technology to selectively "tailor" monomer functional groups, regulating the polymerization reaction pathway. Combined with precise temperature and pressure control, this device separates products of varying molecular weights, thereby producing ultra-high-purity ultra-high molecular weight polyethylene (UHMWPE). Compared to traditional polymerization techniques, this device can synthesize ultra-high-purity UHMWPE without catalysts, resulting in a more economical, environmentally friendly, and greener synthesis method.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A device for preparing ultra-high-purity ultra-high molecular weight polyethylene using plasma high-energy polymerization technology includes a plasma reaction chamber, a plasma high-energy excitation source, a gas supply system, a vacuum control system, a temperature control system, a product collection system, and a gas circulation system. The plasma coil in the plasma high-energy excitation source is sheathed on the outer ring of the bell-shaped jar of the plasma reaction chamber, providing energy to the plasma reaction chamber and exciting the inner wall of the chamber to produce high-activity and high-energy density plasma; an air inlet port is provided on the plasma reaction chamber, connected to the air inlet flange in the gas supply system, and its opening and closing are controlled by the air inlet valve; an air outlet port is provided on the top of the bell-shaped jar in the plasma reaction chamber, connected to the air outlet flange in the product collection system, and its opening and closing are controlled by the air outlet valve; a vacuum pipe joint and a vacuum gauge joint are provided on the plasma reaction chamber, which are respectively connected to the vacuum pipe and vacuum gauge in the vacuum control system. The working state of the mechanical pump and the molecular pump is controlled by setting a vacuum display screen to realize the gas pressure control inside the chamber. The real-time vacuum degree in the chamber is measured by a vacuum gauge, and the signal is fed back to the controller. The controller adjusts the working state of the vacuum pump according to the set value to maintain the required vacuum degree, and the vacuum degree can be as low as 10 -6Torr; a heating wire interface and a temperature probe interface are provided on the plasma reaction chamber, which are respectively connected to the heating wire and temperature probe of the temperature control system. The temperature probe is used to measure the real-time temperature of multiple positions in the chamber, and the signal is fed back to the temperature head with a high-precision control algorithm. The temperature head adjusts the heating output in real time according to the set value. Through the feedback of the temperature probe and the regulation of the temperature head, the heating wires evenly arranged in the plasma reaction chamber are controlled, thereby realizing precise control of the temperature inside the chamber with a control accuracy of ±0.1°C; a gas circulation port is opened on the plasma reaction chamber, which is connected to the gas flange in the gas circulation system. Its switch is controlled by the gas valve, and the carrier gas, unreacted gas and product gas with substandard molecular weight are collected and reintroduced into the intake system for recycling.

[0008] The plasma reaction chamber includes a bell-shaped cover, an air inlet port, an air outlet port, a metal cavity, a vacuum pipe joint, a vacuum gauge joint, a heating wire joint, a temperature probe joint and a gas circulation port; the plasma high-energy excitation source includes a plasma coil and a high-voltage joint; the gas supply system includes an air inlet flange and an air inlet valve; the vacuum control system includes a vacuum gauge, a vacuum pipe, a vacuum degree display screen, a mechanical pump and a molecular pump; the temperature control system includes a heating wire, a temperature probe and a temperature gauge head; the product collection system includes an air outlet flange and an air outlet valve; and the gas circulation system includes a gas flange and a gas valve.

[0009] A method for using an apparatus for preparing ultra-high-purity and ultra-high-molecular-weight polyethylene using plasma high-energy polymerization technology, the method comprising the following steps:

[0010] Step 1. Turn on the vacuum control system, set the vacuum display, turn on the mechanical pump, and pump negative pressure into the plasma reaction device until the gas pressure drops to 10 -2 Pa, turn on the molecular pump until the gas pressure drops to 10 -3 Pa, close the vacuum system;

[0011] Step 2. Open the gas inlet valve and introduce the reaction gas into the reaction chamber using ethylene monomer as the precursor and inert gas as the working gas. The mixing ratio of inert gas to ethylene monomer does not exceed 10:1. The gas flow rate is controlled at 100-3000 sccm, and the pressure in the chamber is maintained in the range of 1000-3000 Pa.

[0012] Step 3. Adjust the plasma reaction parameters. The operating voltage range is 5-30kV, the discharge frequency is 2-100kHz, the pulse rise time is 50-100ns, and the pulse duty cycle is 0.3-0.9. Turn on the plasma power supply and discharge in the plasma reaction chamber to generate a highly active, high-energy-density plasma. The discharge time is 30-180 minutes. The ethylene monomer molecules are impacted by the high-energy particles (such as electrons and ions) in the plasma, causing the molecular bonds to break and forming active species (free radicals and ions). These react with other ethylene monomers or active species, and the free radicals polymerize to form polyethylene chains, thereby achieving the polymerization of ethylene monomers. By adjusting the plasma reaction parameters, a narrow or wide molecular weight distribution can be adjusted: when the duty cycle is 0.3-0.6, the monomer molecules react incompletely, forming short-chain polymers with a molecular weight of 400,000 to 1.5 million; when the duty cycle is 0.6-0.9, the monomer molecules dissociate more fully, forming long-chain polymers with a molecular weight greater than 1.5 million.

[0013] Step 4. After the discharge is complete, turn on the temperature control system, set the temperature control meter parameters, maintain the temperature for 5 to 30 minutes, increase the pressure in the chamber to 1.3 to 1.5 MPa, and begin product separation and collection. The temperature is adjusted between 222 and 260°C to sublimate long-chain polymers with a molecular weight greater than 1.5 million into gas. The outlet valve is opened, and the high-molecular-weight products are collected through the product collection system. The temperature is then raised to 270 to 300°C to sublimate short-chain polymers with a molecular weight of 400,000 to 1.5 million into gas. The low-molecular-weight products are collected through the product collection system. This staged temperature change allows for the separation of polyethylene molecules of different molecular weights, as well as the separation of polyethylene molecules from unreacted ethylene gas, resulting in polyethylene with a purity of ppb.

[0014] Step 5. After the product collection is completed, continue to adjust the temperature and pressure in the cavity, set the temperature control head parameters so that the temperature in the cavity is 20°C higher than the product collection set temperature, open the gas valve, and collect the carrier gas, unreacted gas, and product gas with substandard molecular weight through the gas circulation system and re-introduce it into the air intake system for recycling.

[0015] The beneficial effects of the present invention are:

[0016] First, the present invention proposes high-energy plasma polymerization technology and pulse modulation technology to control the excitation, ionization and polymerization reaction paths of monomer molecules. High-energy excitation generates highly active and high-energy-density plasma. Ethylene monomer molecules are impacted by high-energy particles (such as electrons and ions) in the plasma, causing molecular bonds to break and forming active species (free radicals and ions). These react with other ethylene monomers or active species, and the free radicals polymerize to form polyethylene chains, achieving polymerization of the ethylene monomers, thereby producing ultra-high molecular weight polyethylene materials in the absence of catalysts.

[0017] Secondly, the present invention proposes to precisely control temperature and pressure regulation to separate products of different molecular weights. The gas pressure inside the cavity is controlled by setting a vacuum display to control the working status of the mechanical pump and molecular pump. A vacuum gauge is used to measure the real-time vacuum degree in the cavity and the signal is fed back to the controller. The controller adjusts the working status of the vacuum pump according to the set value to maintain the required vacuum degree. The minimum vacuum degree can reach 10 -6 Torr uses temperature probes to measure the real-time temperature at multiple locations within the chamber and feeds the signal back to a temperature gauge equipped with a high-precision control algorithm. The temperature gauge adjusts the heating output in real time based on the set value. Through the feedback from the temperature probe and the regulation of the temperature gauge, the uniformly arranged heating wires within the plasma reaction chamber are controlled, thereby achieving precise control of the internal temperature of the chamber with a control accuracy of ±0.1°C. Through precise control of temperature and pressure, ultra-high molecular weight polyethylene products of different molecular weights can be sublimated in stages, resulting in ultra-high purity polyethylene products.

[0018] Third, the method for synthesizing ultra-high-purity and ultra-high molecular weight polyethylene proposed in the present invention does not require expensive technical equipment such as high-temperature and high-pressure equipment and special catalysts in traditional processes. The production process is simple, green, economical, efficient, and has lower costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a layout diagram of an apparatus for preparing ultra-high purity and ultra-high molecular weight polyethylene using plasma high-energy polymerization technology according to the present invention;

[0020] Figure 2 This is a three-dimensional schematic diagram of the installation of a plasma reaction chamber and a plasma high-energy excitation source of an apparatus for preparing ultra-high-purity ultra-high molecular weight polyethylene using plasma high-energy polymerization technology according to the present invention;

[0021] Figure 3 for Figure 2 a front view of the device shown;

[0022] Figure 4 for Figure 2 a left side view of the device shown;

[0023] Figure 5 for Figure 2 Top view of the device shown.

[0024] In the figure, 1. Plasma reaction chamber; 101. Bell jar; 102. Gas inlet port; 103. Gas outlet port; 104. Metal chamber; 105. Vacuum pipe connector; 106. Vacuum gauge connector; 107. Heating wire connector; 108. Temperature probe connector; 109. Gas circulation port; 2. Plasma high-energy excitation source; 201. Plasma coil; 202. High-voltage connector; 3. Gas supply system; 301. Gas inlet flange; 302. Gas inlet valve; 303. Working gas storage tank; 304. Ethylene gas storage tank; 4. Vacuum control system; 401. Vacuum gauge; 402. Vacuum pipe; 403. Vacuum degree display screen; 404. Mechanical pump; 405. Molecular pump; 5. Temperature control system; 501. Heating wire; 502. Temperature probe; 503. Temperature gauge; 6. Product collection system; 601. Gas outlet flange; 602. Gas outlet valve; 603. Product collection tank; 7. Gas circulation system; 701. Gas flange; 702. Gas valve; 703. Gas storage tank. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] The present invention provides a device for preparing ultra-high purity and ultra-high molecular weight polyethylene using plasma high energy polymerization technology, such as Figure 1-2 As shown, it includes a plasma reaction chamber 1, a plasma high-energy excitation source 2, a gas supply system 3, a vacuum control system 4, a temperature control system 5, a product collection system 6, and a gas circulation system 7. The plasma coil 201 in the plasma high-energy excitation source 2 is sleeved on the outer ring of the bell-shaped jar 101 of the plasma reaction chamber 1 to provide energy for the plasma reaction chamber 1 and generate highly active plasma on the inner wall of the chamber. Figure 2-5As shown; an air inlet port 102 is provided on the plasma reaction chamber 1, which is connected to the air inlet flange 301 in the air supply system 3, and its switch is controlled by the air inlet valve 302; an air outlet port 103 is provided on the top of the bell-shaped cover 101 in the plasma reaction chamber 1, which is connected to the air outlet flange 601 in the product collection system 6, and its switch is controlled by the air outlet valve 602; a vacuum pipe connector 105 and a vacuum gauge connector 106 are provided on the plasma reaction chamber 1, which are respectively connected to the vacuum pipe 402 and the vacuum gauge 401 in the vacuum control system 4, and the working state of the mechanical pump 404 and the molecular pump 405 is controlled by setting a vacuum degree display screen 403 to realize the control of the gas pressure inside the chamber. The plasma reaction chamber 1 is provided with a heating wire interface 107 and a temperature probe interface 108, which are respectively connected to the heating wire 501 and the temperature probe 502 of the temperature control system 5. The heating wire 501 uniformly arranged in the plasma reaction chamber is controlled by the feedback of the temperature probe 502 and the regulation of the temperature gauge 503, thereby achieving precise control of the temperature inside the chamber. The plasma reaction chamber 1 is provided with a gas circulation port 109, which is connected to the gas flange 701 in the gas circulation system 7. Its switch is controlled by the gas valve 702, and the carrier gas, unreacted gas and product gas with substandard molecular weight are collected and reintroduced into the air intake system for recycling.

[0027] The plasma reaction chamber 1 includes a bell jar 101, an air inlet port 102, an air outlet port 103, a metal cavity 104, a vacuum pipe joint 105, a vacuum gauge joint 106, a heating wire interface 107, a temperature probe interface 108 and a gas circulation port 109. Figure 2-5 As shown; the plasma high-energy excitation source 2 includes a plasma coil 201 and a high-voltage connector 202; the gas supply system 3 includes an air inlet flange 301 and an air inlet valve 302; the vacuum control system 4 includes a vacuum gauge 401, a vacuum pipe 402, a vacuum degree display screen 403, a mechanical pump 404 and a molecular pump 405; the temperature control system 5 includes a heating wire 501, a temperature probe 502 and a temperature gauge head 503; the product collection system 6 includes an air outlet flange 601 and an air outlet valve 602; the gas circulation system 7 includes a gas flange 701 and a gas valve 702.

[0028] The present invention discloses a method for preparing ultra-high purity ultra-high molecular weight polyethylene using plasma high energy polymerization technology, comprising the steps of: 1. opening a vacuum control system 4, setting a vacuum degree display screen 403, opening a mechanical pump 404, and pumping negative pressure into the plasma reaction device until the gas pressure is reduced to 10 -2 Pa, open the molecular pump 405 until the gas pressure drops to 10 -3 Pa, close the vacuum system;

[0029] Step 2. Open the gas inlet valve 302 and introduce ethylene monomer as the precursor and inert gas as the working gas into the reaction chamber. The mixing ratio of inert gas to ethylene monomer does not exceed 10:1. The gas flow rate is controlled at 100-3000 sccm. The pressure in the chamber is maintained in the range of 1000-3000 Pa.

[0030] Step 3. Adjust the plasma reaction parameters to an operating voltage range of 5-30 kV, a discharge frequency of 2-100 kHz, a pulse rise time of 50-100 ns, and a pulse duty cycle of 0.3-0.9. Turn on the plasma power supply and discharge within the plasma reaction chamber 1 for 30-180 minutes to achieve polymerization of ethylene monomers. Adjusting the plasma reaction parameters to achieve a narrow or broad molecular weight distribution: when the duty cycle is 0.3-0.6, the monomer molecules do not react completely, forming short-chain polymers with a molecular weight of 400,000 to 1.5 million. When the duty cycle is 0.6-0.9, the monomer molecules dissociate more fully, forming long-chain polymers with a molecular weight greater than 1.5 million.

[0031] Step 4. After the discharge is complete, turn on the temperature control system 5, set the parameters of the temperature control meter 503, maintain the temperature for 5 to 30 minutes, increase the pressure in the chamber to 1.3 to 1.5 MPa, and begin product separation and collection. The temperature is adjusted between 222 and 260°C to sublimate long-chain polymers with a molecular weight greater than 1.5 million into gas. The outlet valve 602 is opened, and the high-molecular-weight products are collected through the product collection system 6. The temperature is then raised to 270 to 300°C to sublimate short-chain polymers with a molecular weight of 400,000 to 1.5 million into gas. The low-molecular-weight products are collected through the product collection system 6. This staged temperature change allows for the separation of polyethylene molecules of different molecular weights, as well as the separation of polyethylene molecules from unreacted ethylene gas, resulting in polyethylene with a purity of ppb.

[0032] Step 5. After the product collection is completed, continue to adjust the temperature and pressure in the cavity, set the parameters of the temperature control head 503, so that the temperature in the cavity is 20°C higher than the product collection set temperature, open the gas valve 702, and collect the carrier gas, unreacted gas and product gas with substandard molecular weight through the gas circulation system 7 and re-introduce them into the air intake system for recycling.

[0033] Example 1

[0034] The present invention discloses a method for preparing ultra-high purity ultra-high molecular weight polyethylene using plasma high energy polymerization technology. Specifically, the vacuum control system is turned on, a vacuum degree display screen is set, a mechanical pump is turned on, and a negative pressure is pumped from the plasma reaction device until the gas pressure is reduced to 10 -2 Pa, turn on the molecular pump until the gas pressure drops to 10 -3Pa, close the vacuum system; open the gas inlet valve, use ethylene monomer as the precursor and argon as the working gas, introduce the reaction gas into the reaction chamber, the mixing ratio of argon to ethylene monomer is 5:1, the gas flow rate is controlled at 300 sccm, and the gas pressure in the chamber is maintained at 1000 Pa; adjust the plasma reaction parameters, the working voltage range is 8 kV, the discharge frequency is 10 kHz, the pulse rising edge is 50 ns, and the pulse duty cycle is 0.5, turn on the plasma power supply, discharge in the chamber, and the discharge time is 120 min to achieve polymerization of ethylene monomer to form a short-chain polymer with a molecular weight of about 700,000; after the discharge is completed, stop the molecular pump, wait for the speed to decrease and then turn off the mechanical pump, turn on the temperature switch, set the temperature of the temperature control head, adjust the temperature range to 280°C, keep warm for 10 minutes, increase the pressure in the chamber to 1.5 MPa to start product separation and collection, so that the short-chain polymer product is sublimated into gas, and collect the low molecular weight product through the product collection system. The obtained polyethylene has a purity of 1.2 ppb.

[0035] Example 2

[0036] The present invention discloses a method for preparing ultra-high purity ultra-high molecular weight polyethylene using plasma high energy polymerization technology. Specifically, the vacuum control system is turned on, a vacuum degree display screen is set, a mechanical pump is turned on, and a negative pressure is pumped from the plasma reaction device until the gas pressure is reduced to 10 -2 Pa, turn on the molecular pump until the gas pressure drops to 10 -3Pa, turn off the vacuum system; open the working gas tank and the ethylene monomer gas tank valves, open the air inlet valve, use ethylene monomer as the precursor and argon as the working gas, introduce the mixed reaction gas into the reaction chamber, the mixing ratio of argon to ethylene monomer is 10:1, the gas flow rate is controlled at 100sccm, and the gas pressure in the chamber is maintained at 1000Pa; adjust the plasma reaction parameters, the working voltage range is 6kV, the discharge frequency is 8kHz, the pulse rising edge is 100ns, the pulse duty cycle is 0.8, turn on the plasma power supply, discharge in the chamber, the discharge time is 60min, realize the polymerization of ethylene monomer, and some ethylene monomers are polymerized to form long-chain polymers with a molecular weight of 1.6 million; stop the molecular pump after the discharge is completed, and turn off the mechanical Pump, turn on the temperature switch, set the temperature of the temperature control head, adjust the temperature range to 240℃, keep warm for 20 minutes, increase the pressure in the cavity to 1.5MPa to start product separation and collection, so that the longer-chain polymer product is sublimated into gas, and is introduced into the product collection tank through the product collection system to collect high molecular weight products. The obtained polyethylene has a purity of 1.5ppb; after the product collection is completed, close the outlet valve, continue to adjust the temperature and pressure in the cavity, set the temperature control head parameters, and continue to increase the temperature in the cavity to 260℃, open the gas valve, and collect the carrier gas, unreacted ethylene monomer and product gas with unqualified molecular weight through the gas circulation system and re-introduce them into the gas storage tank, and then continue to introduce them into the air intake system to continue the polymerization reaction, thereby realizing continuous recycling.

[0037] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will appreciate that the present invention is susceptible to variations within the parameters set forth herein. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A device for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene, characterized by: The invention comprises a plasma reaction chamber, a plasma high-energy excitation source, a gas supply system, a vacuum control system, a temperature control system, a product collection system and a gas circulation system. The plasma reaction chamber comprises a bell-shaped jar, an air inlet port, an air outlet port, a metal cavity, a vacuum pipe joint, a vacuum gauge joint, a heating wire joint, a temperature probe joint and a gas circulation port. The plasma high-energy excitation source comprises a plasma coil and a high-voltage joint. The gas supply system comprises an air inlet flange and an air inlet valve. The vacuum control system comprises a vacuum gauge, a vacuum pipe, a vacuum display screen, a mechanical pump and a molecular pump. The temperature control system comprises a heating wire, a temperature probe and a temperature gauge head. The product collection system comprises an air outlet flange and an air outlet valve. The gas circulation system comprises a gas flange and a gas valve. The plasma coil in the plasma high-energy excitation source is sheathed on the outer ring of the bell-shaped jar of the plasma reaction chamber to provide energy for the plasma reaction chamber and stimulate the inner wall of the chamber to generate high-activity and high-energy-density plasma. The plasma reaction chamber is provided with an air inlet port connected to the air inlet flange in the gas supply system and its opening and closing are controlled by the air inlet valve. The bell-shaped jar in the plasma reaction chamber is provided with an air outlet port on its top to connect to the product collection system. The outlet flange is connected to the outlet valve, and the switch is controlled by the outlet valve; the plasma reaction chamber is provided with a vacuum pipe joint and a vacuum gauge joint, which are respectively connected to the vacuum pipe and vacuum gauge in the vacuum control system. The working status of the mechanical pump and the molecular pump is controlled by setting the vacuum degree display to realize the gas pressure control inside the cavity. The real-time vacuum degree in the cavity is measured by the vacuum gauge, and the signal is fed back to the controller. The controller adjusts the working status of the vacuum pump according to the set value to maintain the required vacuum degree; the plasma reaction chamber is provided with a heating wire interface and a temperature probe interface, which are respectively connected to the heating wire and temperature probe of the temperature control system Then, a temperature probe is used to measure the real-time temperature of multiple locations in the cavity, and the signal is fed back to a temperature head with a high-precision control algorithm. The temperature head adjusts the heating output in real time according to the set value. Through the feedback of the temperature probe and the regulation of the temperature head, the uniformly arranged heating wires in the plasma reaction cavity are controlled, thereby achieving precise control of the temperature inside the cavity; a gas circulation port is opened on the plasma reaction cavity, which is connected to the gas flange in the gas circulation system. Its switch is controlled by a gas valve, and the carrier gas, unreacted gas and product gas with substandard molecular weight are collected and reintroduced into the intake system for recycling.

2. The device for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene according to claim 1, characterized in that: The minimum vacuum degree inside the cavity is 10 -6 Torr.

3. The device for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene according to claim 1, characterized in that: The temperature control accuracy inside the cavity reaches ±0.1℃.

4. A method for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene, using the apparatus for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene according to claim 1, characterized in that The method comprises the following steps: Step 1. Turn on the vacuum control system, set the vacuum display, turn on the mechanical pump, and pump negative pressure into the plasma reaction device until the gas pressure drops to 10 -2 Pa, turn on the molecular pump until the gas pressure drops to 10 -3 Pa, close the vacuum system; Step 2. Open the gas inlet valve and introduce the reaction gas into the reaction chamber using ethylene monomer as the precursor and inert gas as the working gas. The mixing ratio of inert gas to ethylene monomer does not exceed 10:

1. The gas flow rate is controlled at 100-3000 sccm, and the pressure in the chamber is maintained in the range of 1000-3000 Pa. Step 3. Adjust the plasma reaction parameters to an operating voltage range of 5 to 30 kV, a discharge frequency of 2 to 100 kHz, a pulse rise time of 50 to 100 ns, and a pulse duty cycle of 0.3 to 0.

9. Turn on the plasma power supply to discharge in the plasma reaction chamber to generate a highly active and high-energy-density plasma for a discharge time of 30 to 180 minutes. Ethylene monomer molecules are struck by high-energy particles in the plasma, causing molecular bonds to break and forming active species. These species react with other ethylene monomers or active species to form polyethylene chains through free radical polymerization, thereby achieving polymerization of the ethylene monomer. Step 4. After the discharge is completed, the temperature control system is turned on, the temperature control meter parameters are set, and the temperature is maintained for 5 to 30 minutes. The pressure in the chamber is increased to 1.3 to 1.5 MPa, and product separation and collection are started. The separation of polyethylene molecules of different molecular weights and the separation of polyethylene molecules from unreacted ethylene gas are achieved by staged temperature changes. The purity of the obtained polyethylene is at the ppb level. Step 5. After the product collection is completed, continue to adjust the temperature and pressure in the cavity, set the temperature control head parameters so that the temperature in the cavity is 20°C higher than the product collection set temperature, open the gas valve, and collect the carrier gas, unreacted gas, and product gas with substandard molecular weight through the gas circulation system and re-introduce it into the air intake system for recycling.

5. The method for plasma polymerization of ultra-high purity ultra-high molecular weight polyethylene according to claim 4, characterized in that: When the duty cycle in step 3 is 0.3 to 0.6, the monomer molecules do not react completely, forming short-chain polymers with a molecular weight of 400,000 to 1.5 million.

6. The method for plasma polymerization of ultra-high purity ultra-high molecular weight polyethylene according to claim 4, characterized in that: In step 3, the duty cycle is 0.6 to 0.9, and the monomer molecules are fully dissociated to form long-chain polymers with a molecular weight greater than 1.5 million.

7. The method for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene according to claim 4, characterized in that: In step 4, the temperature range is controlled to be 222-260° C. to sublimate the long-chain polymer with a molecular weight greater than 1.5 million into gas, and the gas outlet valve is opened to collect the high molecular weight product through the product collection system.

8. The method for plasma polymerization of ultra-high purity and ultra-high molecular weight polyethylene according to claim 7, characterized in that: The temperature is raised to 270-300°C to sublime the short-chain polymer product with a molecular weight of 400,000-1.5 million into gas, and the low molecular weight product is collected through a product collection system.

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