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CN-122011248-A - Method for continuously preparing optical-grade polymethyl methacrylate by microreactor-light control combination

CN122011248ACN 122011248 ACN122011248 ACN 122011248ACN-122011248-A

Abstract

The application discloses a method for continuously preparing optical-grade polymethyl methacrylate by combining a microreactor and light control, belonging to the technical field of high polymer material synthesis. The method comprises the steps of conveying reaction liquid containing methyl methacrylate monomers, photoinitiators and chain transfer agents into a micro-reactor system formed by connecting at least two stages of micro-reactors in series, carrying out polymerization in each stage of micro-reactors through illumination, wherein the hydraulic diameter and illumination intensity of a micro-channel of a subsequent micro-reactor are higher than those of a previous stage of micro-reactor, monitoring the material viscosity at an outlet of at least one micro-reactor in real time by adopting an online viscometer, and adjusting the illumination intensity and/or the material flow rate according to monitoring data through feedback by a closed-loop control system. The method can realize the accurate control of the continuous polymerization process, and the polymethyl methacrylate product with narrow molecular weight distribution and stable optical performance is prepared.

Inventors

  • LI XICHUN
  • WANG MIN
  • CUI YUNLONG
  • LIU XUEQIANG
  • WANG JIANQIANG
  • LI YUAN

Assignees

  • 山东宏旭化学股份有限公司
  • 山东胜利职业学院
  • 万达集团股份有限公司
  • 山东真卓科技有限公司

Dates

Publication Date
20260512
Application Date
20260413

Claims (10)

  1. 1. A method for continuously preparing optical-grade polymethyl methacrylate by microreactor-light control combination, which is characterized by comprising the following steps: a) Conveying a reaction solution containing methyl methacrylate monomer, a photoinitiator and a chain transfer agent into a micro-reactor system formed by at least two stages of micro-reactors connected in series; b) In the micro-reactor system, polymerization reaction is carried out through illumination, wherein the hydraulic diameter of a micro-channel of a subsequent micro-reactor is larger than that of a micro-channel of a previous micro-reactor, and the illumination intensity applied by the subsequent micro-reactor is larger than that applied by the previous micro-reactor; c) At the outlet of at least one micro-reactor, an online viscometer is arranged to monitor the viscosity of the material in real time, and the illumination intensity and/or the material flow rate are/is adjusted through a closed-loop control system according to the feedback of the monitored data based on a preset viscosity-molecular weight-conversion rate relation model; The viscosity-molecular weight-conversion relationship model satisfies the equation: Wherein, the For the dynamic viscosity of the system measured in real time, In order to achieve the conversion of the monomers, In order to obtain the number average molecular weight of the polymer, And (3) with All are constants obtained through early sampling calibration; d) After the materials leave the micro-reactor system, rapidly quenching active free radicals in the system by adopting physical or chemical means so as to rapidly terminate the polymerization reaction; e) And (3) carrying out stabilization treatment, melting devolatilization and granulation on the material after termination to obtain the optical-grade polymethyl methacrylate.
  2. 2. The method of claim 1, wherein the online viscometer is a vibrating viscometer or a rotary viscometer, and the control system sets the target viscosity range based on monitoring data of the online viscometer.
  3. 3. A method according to claim 1 or 2, wherein the control system completes the parameter adjustment of the illumination intensity and/or the material flow rate within 10 seconds when the monitored viscosity deviates from the target viscosity range.
  4. 4. The method of claim 1, wherein the physical means is irradiation with ultraviolet light having a wavelength of less than 300nm, or the chemical means is injection of a photoactivated chemical terminator into the material and irradiation with a light source.
  5. 5. The method of claim 1, wherein the hydraulic diameter of the microchannels of the second stage microreactor is 1.2 to 3 times the hydraulic diameter of the microchannels of the first stage microreactor, and the illumination intensity of the second stage microreactor is 1.5 to 5 times the illumination intensity of the first stage microreactor.
  6. 6. The method of claim 1, wherein a static mixer is provided between each stage of microreactor.
  7. 7. The method of claim 1, wherein the microreactor is made of quartz glass, sapphire or transparent polycarbonate, and the illumination wavelength is 365nm, 385nm, 405nm or 450nm matched with the photoinitiator absorption wavelength.
  8. 8. The method according to claim 1, wherein the photoinitiator is selected from one or more of 2, 2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl ] -2- (4-morpholinyl) -1-propanone, phenyl bis (2, 4, 6-trimethylbenzoyl) phosphine oxide, and the addition amount is 0.01% -0.5% of the mass of methyl methacrylate monomer.
  9. 9. The method according to claim 1, wherein the chain transfer agent is selected from one or more of n-butyl mercaptan, isobutyl mercaptan, n-octyl mercaptan, isooctyl mercaptan, n-dodecyl mercaptan and t-dodecyl mercaptan, and the addition amount is 0.05% -0.5% of the mass of the methyl methacrylate monomer.
  10. 10. The process of claim 1 wherein the first stage microreactor has a microchannel hydraulic diameter of 100 to 1000 microns, a reaction temperature of 20 to 60 ℃, a residence time of 0.5 to 10 minutes, a prepolymerization stage conversion of 10 to 30%, and the second stage microreactor has a microchannel hydraulic diameter of 200 to 2000 microns, a reaction temperature of 40 to 80 ℃, a residence time of 2 to 20 minutes, and a total conversion of 60 to 85%.

Description

Method for continuously preparing optical-grade polymethyl methacrylate by microreactor-light control combination Technical Field The application relates to the technical field of high polymer material synthesis, in particular to a method for continuously preparing optical-grade polymethyl methacrylate by combining a microreactor and light control. Background Polymethyl methacrylate is an indispensable key material for preparing optical lenses, light guide plates, high-end display devices and other products due to its excellent light transmittance, weather resistance and processability. At present, continuous bulk polymerization is widely used in industry to produce polymethyl methacrylate in large kettle reactors. However, such conventional tank reactor processes have inherent technical drawbacks. First, bulk polymerization of methyl methacrylate is a strongly exothermic reaction, and the heat transfer area to volume ratio of the tank reactor is small, resulting in low heat dissipation efficiency and extremely easy formation of local hot spots inside the reactor. This may not only cause safety accidents such as bursting, but also lead to degradation or carbonization of the polymer, generating impurities that affect the optical properties of the final product. Secondly, the fluid mixing pattern in the tank reactor is complex, and there is generally a dead zone for the return and flow, resulting in a very wide residence time distribution of the material in the reactor. This results in insufficient polymerization of some of the materials and excessive polymerization of another part, and thus the molecular weight distribution of the final product is broadened, and its polymer dispersion index is usually greater than 2.0, severely affecting the optical uniformity, light transmittance and haze of the material. In addition, although the idea of improving the stability of the product by monitoring the reaction parameters and performing feedback control has been proposed in some polymerization processes, for a system in which the bulk polymerization of methyl methacrylate is rapidly and strongly exothermic with a sharp increase in viscosity, a conventional thermally initiated polymerization system is sensitive to temperature change and has a slow response, and when the product specifications need to be adjusted, the process switching process is long, resulting in poor production flexibility and a lot of transition materials. Therefore, it is difficult to stably produce the optical grade polymethyl methacrylate with the highest quality in the prior art. Disclosure of Invention The application aims to provide a method for continuously preparing optical-grade polymethyl methacrylate by combining a micro-reactor and light control, which aims to solve the technical problems of wide polymer molecular weight distribution, unstable optical performance of a product, poor batch consistency, low production safety and insufficient process flexibility caused by difficult polymerization heat management and uneven material residence time distribution when the optical-grade polymethyl methacrylate is continuously prepared by adopting a kettle-reactor in the prior art. In order to achieve the above object, the present application provides a method for continuously preparing optical grade polymethyl methacrylate by microreactor-light control combination, comprising the following steps: a) Conveying a reaction solution containing methyl methacrylate monomer, a photoinitiator and a chain transfer agent into a micro-reactor system formed by at least two stages of micro-reactors connected in series; b) In the micro-reactor system, polymerization reaction is carried out through illumination, wherein the hydraulic diameter of a micro-channel of a subsequent micro-reactor is larger than that of a micro-channel of a previous micro-reactor, and the illumination intensity applied by the subsequent micro-reactor is larger than that applied by the previous micro-reactor; c) At the outlet of at least one micro-reactor, an online viscometer is arranged to monitor the viscosity of the material in real time, and the illumination intensity and/or the material flow rate are/is adjusted through a closed-loop control system according to the feedback of the monitored data based on a preset viscosity-molecular weight-conversion rate relation model; The viscosity-molecular weight-conversion relationship model satisfies the equation: Wherein, the For the dynamic viscosity of the system measured in real time,In order to achieve the conversion of the monomers,In order to obtain the number average molecular weight of the polymer,And (3) withAll are constants obtained by early sampling calibration. D) After the materials leave the micro-reactor system, rapidly quenching active free radicals in the system by adopting physical or chemical means so as to rapidly terminate the polymerization reaction; e) And (3) carrying out stabilization treatment, melting devol