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CN-121975049-A - Method and apparatus for preparing ethylene-vinyl acetate copolymer using loop reactor

CN121975049ACN 121975049 ACN121975049 ACN 121975049ACN-121975049-A

Abstract

The invention discloses a method and a device for preparing an ethylene-vinyl acetate copolymer by using a loop reactor, and belongs to the field of polymerization. According to the invention, a loop reactor is adopted to carry out solution polymerization reaction of ethylene and vinyl acetate, ethylene, vinyl acetate, a solvent and an initiator are pressurized and then enter the loop reactor, the reaction temperature is controlled to be 50-150 ℃, the reaction pressure is controlled to be 10-50 MPa, and a polymer is generated, and the reaction operation parameters are regulated in real time or intermittently according to the measured values of temperature, pressure, viscosity and density, so that the stabilization of a polymerization process is realized. The invention can prepare the ethylene-vinyl acetate copolymer with high molecular weight and high VA content. The invention can actively prevent and online scale removal, overcomes the problems of difficult cleaning of wall-sticking materials and complex operation and maintenance of the existing reactor, is beneficial to avoiding phenomena of explosion aggregation, wall sticking, reaction runaway and the like of the loop reactor, and improves the stability of the loop reactor and the continuity of the reaction.

Inventors

  • FAN XIAOQIANG
  • ZHOU HONGKE
  • YANG YAO
  • WANG JINGDAI

Assignees

  • 浙江大学

Dates

Publication Date
20260505
Application Date
20260130

Claims (10)

  1. 1. A process for preparing an ethylene-vinyl acetate copolymer using a loop reactor, comprising: (1) Providing a loop reactor for the solution polymerization reaction of ethylene and vinyl acetate, wherein the loop reactor is a single loop reactor, a double loop reactor or a combination of the two, and comprises a low temperature zone with jacket heat exchange and a high temperature zone without jacket heat exchange; (2) Ethylene and vinyl acetate are separately pressurized and then enter the loop reactor, a solvent and an initiator enter the loop reactor after being pressurized by a pump, the reaction temperature is controlled to be 50-150 ℃, the reaction pressure is controlled to be 10-50 MPa, and monomers are contacted under the action of the initiator to carry out polymerization reaction to generate a polymer; (3) Measuring the reaction temperature and pressure in real time by an online thermometer and a pressure sensor, and measuring the viscosity and density of the polymer solution by an online viscometer and an online densimeter; Wherein, according to the measured values of temperature, pressure, viscosity and density, at least one of reaction temperature, reaction pressure, solvent feeding flow, initiator feeding flow, ethylene feeding flow and vinyl acetate feeding flow is regulated in real time or intermittently, so as to realize the stabilization of the polymerization process.
  2. 2. The method of claim 1, wherein the in-line viscometer is positioned at a point of a material outlet in the tube in the low temperature zone.
  3. 3. The method according to claim 1, wherein the solvent is an alcohol solvent having 1 to 4 carbon atoms, and the mass ratio of the solvent to the vinyl acetate used is 10:1 to 1:3.
  4. 4. The method of claim 1, wherein the reaction time in step (2) is 3 to 8 hours.
  5. 5. The method according to claim 1, further comprising separating and granulating the polymer in sequence to obtain the ethylene-vinyl acetate copolymer.
  6. 6. The method according to claim 1, wherein the initiator is a peroxide initiator or an azo initiator, the peroxide initiator is at least one of tert-butyl peroxybenzoate, di-tert-butyl peroxide, methyl ethyl ketone peroxide, diisobutyryl peroxide, tert-butyl peroxyneodecanoate, tert-amyl peroxyneodecanoate, tervalyl peroxypivalate, terbutyl peroxyacetate, tert-butyl peroxy-2-ethylhexanoate and the like, and the azo initiator is at least one of azobisisobutyronitrile, azobisisovaleronitrile, azobisisobutyronitrile, and azobisisobutyric acid dimethyl ester and the like.
  7. 7. The method of claim 1, wherein the polymer solution has a flow rate in the range of 2 to 10m/s and a viscosity in the range of 10 to 500cp.
  8. 8. The method of claim 1, wherein when the on-line viscometer detects that the viscosity of the low temperature zone material is greater than a set threshold, the viscosity of the material is reduced by controlling the water temperature, flow rate of the jacket in the low temperature zone or by temporarily increasing the flow rate of the material in the tube, the solvent feed rate.
  9. 9. An apparatus for carrying out the method according to any one of claims 1 to 8, comprising a raw material supply unit, a polymerization reaction unit and a separation and purification unit connected in this order; the raw material supply unit is provided with an ethylene compressor and a pump for conveying an initiator, a solvent and vinyl acetate; the polymerization reaction unit is a loop reactor, a feed inlet of which is communicated with outlet pipelines of the ethylene compressor and the pump, the loop reactor is a single loop reactor, a double loop reactor or a combination of the two, the loop reactor is provided with an online viscometer and an online densimeter, and the loop reactor comprises a low temperature zone with jacket heat exchange and a high temperature zone without jacket heat exchange, and the online viscometer is arranged at least in the low temperature zone; The separation and purification unit comprises at least two stages of flash tanks, an inlet of the first stage flash tank is connected with an outlet of the loop reactor, and a discharge hole of the first stage flash tank is connected with a feed inlet of the second stage flash tank.
  10. 10. The apparatus of claim 9, wherein the on-line viscometer is one of a vibrating type or a rotating type, the on-line viscometer is built-in with a thermocouple or mounted at a distance of 0.01-0.5 meters from the thermocouple, and the on-line densimeter is one of an ultrasonic densimeter, a capacitive densimeter, a radial densimeter, and a resonant densimeter, the on-line densimeter is built-in with a thermocouple or mounted at a distance of 0.01-0.5 meters from the thermocouple.

Description

Method and apparatus for preparing ethylene-vinyl acetate copolymer using loop reactor Technical Field The invention relates to the technical field of polymer preparation by solution polymerization, in particular to a method and a device for preparing an ethylene-vinyl acetate copolymer by using a loop reactor. Background Ethylene-vinyl acetate copolymer is a thermoplastic resin obtained by copolymerization of ethylene and vinyl acetate monomer, has excellent mechanical properties, low temperature resistance and hot melt processability, and is widely applied as a hot melt adhesive and an elastomer in the fields of packaging materials, electronics, medical treatment, automobile manufacturing and the like. At present, most of enterprises at home and abroad adopt a high-pressure continuous bulk polymerization process to produce the ethylene-vinyl acetate copolymer. The high pressure continuous bulk polymerization process can be generally classified into two processes, a tubular process and a kettle process, depending on the reactor employed. Wherein the kettle reactor can be used for preparing ethylene-vinyl acetate elastomer with high Vinyl Acetate (VA) content, and the existing ethylene-vinyl acetate copolymer product with VA content higher than 50% can only be produced by adopting the kettle method. However, the investment cost of production equipment, the operation and maintenance cost, the occupied area and the process stability are relatively high, and the production efficiency is relatively low. The loop reactor has the advantages of good mixing, heat transfer and mass transfer characteristics, simple structure, high heat transfer efficiency, uniform flow field distribution, easy realization of automatic control and continuous operation, high space assembly precision, good interface sealing performance, less material residence time, better utilization of reaction volume, production efficiency improvement and the like. According to the structural form of the loop reactor, the loop reactor is divided into a single loop reactor and a double loop reactor, wherein a second reactor is not arranged in the single loop reactor, materials directly enter the next process after circulating in the loop, the double loop reactor is formed by connecting a first reactor and the second reactor in series, and the materials enter the second reactor for circulation after circulating in the first reactor and then enter the next process. In the loop reactor, the reaction medium circularly flows to promote the reaction raw materials to be in a fully mixed flow state, so that the sufficiency of the polymerization reaction is further improved, and meanwhile, the mobility of the polymerization reaction is taken into consideration. Chinese patent CN202211017647.6 proposes a method for preparing ethylene-vinyl acetate copolymer using a loop reactor, which adopts a bulk polymerization method, and the reaction pressure and reaction temperature in the loop reactor are high, resulting in thicker wall thickness, short residence time, poor heat transfer of the loop reactor, and only low VA content copolymer can be produced. In addition, the viscosity of the ethylene-vinyl acetate copolymer is difficult to control, the problems of wall sticking, reaction runaway and the like of the copolymer are easily caused, and no effective prevention or solution means exists in the prior art. Disclosure of Invention In view of the above, the present invention provides a method and apparatus for preparing ethylene vinyl acetate copolymer using a loop reactor. According to one aspect of the present invention, there is provided a process for preparing an ethylene-vinyl acetate copolymer using a loop reactor comprising: (1) Providing a loop reactor for the solution polymerization reaction of ethylene and vinyl acetate, wherein the loop reactor is a single loop reactor, a double loop reactor or a combination of the two, and comprises a low temperature zone with jacket heat exchange and a high temperature zone without jacket heat exchange; (2) Ethylene and vinyl acetate are separately pressurized and then enter the loop reactor, a solvent and an initiator enter the loop reactor after being pressurized by a pump, the reaction temperature is controlled to be 50-150 ℃, the reaction pressure is controlled to be 10-50 MPa, and monomers are contacted under the action of the initiator to carry out polymerization reaction to generate a polymer; (3) Measuring the reaction temperature and pressure in real time by an online thermometer and a pressure sensor, and measuring the viscosity and density of the polymer solution by an online viscometer and an online densimeter; Wherein, according to the measured values of temperature, pressure, viscosity and density, at least one of reaction temperature, reaction pressure, solvent feeding flow, initiator feeding flow, ethylene feeding flow and vinyl acetate feeding flow is regulated in real time or intermittently, so as to re