Anti-clogging microreactor for synthesizing high-viscosity silicone rubber and continuous preparation method

Abstract

The present invention relates to the technical field of high polymer material synthesis, and discloses an anti-clogging microreactor for high viscosity silicone rubber synthesis, the anti-clogging microreactor comprises a microreactor chip, and the interior of the microreactor chip is provided with a tree-shaped bifurcated microchannel network based on fractal structure design; the invention relates to a continuous preparation method of an anti-clogging microreactor for synthesizing high-viscosity silicone rubber. The continuous preparation method comprises the following steps: S1, precisely metering a methyl cyclosiloxane monomer and a vinyl siloxane monomer, and then inputting the methyl cyclosiloxane monomer and the vinyl siloxane monomer into the microreactor; s2, carrying out a controllable ring-opening polymerization reaction in the microchannel; and S3, quickly terminating the reaction by injecting a terminating agent on line, and controlling the molecular weight and distribution of the polymer. Compared with the prior art, the method has the advantages that the problems that an existing microreactor is prone to blockage and difficult to operate stably for a long time when treating a high-viscosity siloxane polymerization system are solved, meanwhile, the method can achieve accurate control over product quality and continuity and intellectualization of the production process, the production efficiency is remarkably improved, and energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer material synthesis, in particular to an anti-blocking micro-reactor for high-viscosity silicone rubber synthesis and a continuous preparation method. BACKGROUND

[0002] Methyl vinyl silicone rubber (MVQ) is widely used in aerospace, new energy vehicles, high-end electronics and medical health fields due to its excellent high and low temperature resistance, weather resistance, electrical insulation and biocompatibility. At present, the production of MVQ in China mainly relies on the traditional batch reaction kettle process. This process has the following inherent defects: low production efficiency, long reaction period and high energy consumption; due to the limitations of mixing, mass transfer and heat transfer efficiency, the product has a wide molecular weight distribution and uneven vinyl content, which ultimately affects the mechanical properties and consistency of the vulcanized rubber; in addition, high-viscosity materials are prone to wall sticking and coking during the reaction, which further affects the stability of product quality and the continuity of the production process.

[0003] To overcome the shortcomings of batch process, the industry has begun to explore continuous production process. For example, Chinese patent CN201810189929.1 discloses a full-automatic continuous production line, but its core polymerization unit still uses traditional kettle or tubular reactors, which cannot fundamentally solve the problem of efficient mixing and heat transfer under high-viscosity system, and the ability to accurately control the product molecular structure is limited. Micro-reactor technology has great potential in chemical process intensification due to its extremely high specific surface area, which can achieve efficient mixing and mass and heat transfer. However, when it is applied to the polymerization system of high-viscosity siloxane, it faces the serious risk of micro-channel blockage, which greatly limits the industrial application of this technology. SUMMARY

[0004] (I) Technical problems to be solved

[0005] The technical problem to be solved by the present application is to provide an anti-blocking micro-reactor for high-viscosity silicone rubber synthesis and a continuous preparation method to solve the problem of easy blocking of existing micro-reactors when processing high-viscosity siloxane polymerization system and difficult long-term stable operation. The method can realize accurate control of product quality, continuous and intelligent production process, and significantly improve production efficiency and reduce energy consumption.

[0006] (II) Technical solutions

[0007] To solve the above technical problems, the technical solution provided by the present application is: an anti-blocking micro-reactor for high-viscosity silicone rubber synthesis, comprising a micro-reactor chip, which is internally provided with a tree-shaped branched micro-channel network based on fractal structure design, the characteristic size of the micro-channel gradually decreases from hundreds of microns at the inlet to tens to hundreds of microns at the reaction section;

[0008] The inner wall of the microchannel is surface-modified and coated with a low surface energy material, so that the contact angle of the inner wall to the high viscosity silicone system is significantly improved to reduce material adhesion and retention;

[0009] The microreactor chip is made of corrosion-resistant metal material and is manufactured by high-precision laser micromachining, precision etching or electroforming process, with a machining precision controlled within microns;

[0010] The microreactor chip packaging structure ensures no leakage under high pressure and wide temperature conditions and has long-term stable operation capability.

[0011] A continuous preparation method of an anti-clogging microreactor for high-viscosity silicone rubber synthesis, characterized in that it comprises the following steps:

[0012] S1, precisely measuring methylcyclosiloxane monomers and vinylsiloxane monomers and inputting them into the microreactor;

[0013] S2, performing controllable ring-opening polymerization reaction in the microchannel, with residence time controlled within several minutes and single-pass conversion rate stabilized at more than 98%;

[0014] S3, achieving rapid termination of the reaction by online injection of a terminating agent, controlling the molecular weight and its distribution of the polymer, and making the molecular weight distribution index PDI less than 1.8;

[0015] S4, integrating a near-infrared spectrum online detection system to monitor the vinyl content and molecular weight distribution in real time, and adjusting process parameters through a closed-loop feedback control system to ensure that the vinyl content is controlled within the target range and the distribution coefficient of variation is not higher than 3%;

[0016] S5, realizing full-process continuous operation from raw material input to product output, shortening the single-pass production cycle to within 6 hours, and significantly reducing the comprehensive energy consumption per unit product compared with the traditional batch kettle process.

[0017] As an improvement, the fractal microchannel network has at least a three-level branching structure, through the step-by-step division and recombination of fluid, the radial mixing efficiency of high-viscosity fluid in it reaches more than 95%.

[0018] As an improvement, the low surface energy material is a fluorine-containing polymer or silane coating coated by chemical vapor deposition or sol-gel method.

[0019] As an improvement, the microreactor chip is integrated with temperature and pressure sensors and interlocked with an external temperature control system and back pressure valve to realize accurate control of reaction temperature and stable maintenance of system pressure.

[0020] As an improvement, in the step S1, the methylcyclosiloxane monomer and the vinylsiloxane monomer are subjected to a pretreatment of precision filtration, deep drying and removal of dissolved oxygen.

[0021] As an improvement, in the step S4, the closed-loop feedback control system performs the following operation: based on the real-time predicted vinyl content or molecular weight distribution data of the near-infrared spectrum, dynamically adjusts one or more parameters of the monomer feed ratio, the catalyst injection rate or the reaction temperature.

[0022] As an improvement, in the step S3, the terminating agent is an accurately metered acidic substance or a compound capable of deactivating the catalyst, and the injection point is in the outlet section of the microreactor, and the reaction termination is completed within milliseconds.

[0023] As an improvement, the method is implemented in a modular continuous flow process system comprising a precision premixing module, a polymerization reaction module, an online functionalization module and a rapid termination module, and each module is seamlessly connected through micro-pipes.

[0024] (III) Beneficial effects

[0025] The present application has the advantages compared with the prior art: through the synergistic effect of "fractal microchannel structure reinforced mixing" and "low surface energy inner wall coating reduces adhesion", the plugging problem of the microreactor in the synthesis of high viscosity silicone rubber is fundamentally solved, the long period stable operation of the system is ensured, the inherent high mass transfer and heat transfer efficiency of the microreactor, combined with online monitoring and closed-loop feedback control system, can accurately control the key quality attributes such as vinyl content, molecular weight and molecular weight distribution (PDI), and the product consistency is extremely high. DETAILED DESCRIPTION

[0026] The invention content of the present application will be further described in detail below in conjunction with specific embodiments, but it should not be understood that the scope of the subject matter of the present application is limited to only the following examples.

[0027] Example 1: Manufacture of anti-plugging microreactor

[0028] 316L stainless steel is selected as the base material. First, a three-stage tree-shaped fractal microchannel network is processed on it by using a high-precision fiber laser microprocessing system. The size of the inlet main channel is 700 μm, after two-stage branching, the final reaction section channel width is 80 μm, the depth is 100 μm, and the processing precision is controlled within ± 5 μm. Subsequently, a layer of perfluorooctyltrichlorosilane is uniformly coated on the inner wall of the microchannel by chemical vapor deposition method to form a low surface energy coating. Finally, the microreactor chip and the cover plate are packaged by high temperature and high pressure sealing technology, and the helium mass spectrometer leak detector is tested to ensure that there is no leakage under the condition of 10 MPa, 180℃.

[0029] Example 2: Continuous production of methyl vinyl silicone rubber

[0030] The precision filtered and deeply dried octamethylcyclotetrasiloxane (D4) and tetramethyltetra-vinylcyclotetrasiloxane were fed into the system in a predetermined ratio.

[0031] In the S1 step, the raw materials were metered by high-precision gear pumps and then entered the pretreatment module for the final stage of deoxygenation treatment.

[0032] In the S2 step, the material and the catalyst ammonium hydroxide base glue were fed into the microreactor to perform ring-opening polymerization at 120 DEG C under a certain back pressure, with a residence time of about 5 minutes and a conversion rate of 99.2%.

[0033] In the S3 step, the reactor outlet was injected with an accurately metered phosphate ester terminator, and the reaction was terminated within tens of milliseconds.

[0034] In the S4 step, the near-infrared probe monitored the flow material in real time, and the data were transmitted to the PLC control system. When the prediction model showed that the vinyl content deviated slightly, the system automatically fine-tuned the rate of the vinyl monomer feed pump to achieve closed-loop control.

[0035] The final product (S5) was detected, with a vinyl content of 0.18% (target range 0.15% to 0.20%), a distribution variation coefficient of 2.1%, a PDI of 1.65, and a tensile strength of 12.5 MPa. The entire production cycle was about 5.5 hours, and the unit product energy consumption was reduced by about 40% compared to the same capacity batch kettle. Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents. In general, if a person skilled in the art is inspired by it, without creating creativity, similar structural ways and embodiments are designed without departing from the purpose of the present application, which should belong to the protection scope of the present application.

Claims

1. An anti-clogging microreactor for the synthesis of high-viscosity silicone rubber, characterized in that: The microreactor chip has a tree-like branching microchannel network based on a fractal structure design inside. The characteristic size of the microchannels decreases stepwise from hundreds of micrometers at the inlet to tens to hundreds of micrometers in the reaction section. The inner wall of the microchannel is surface modified and coated with a low surface energy material, which significantly increases the contact angle of the inner wall with the high viscosity siloxane system, thereby reducing material adhesion and retention. The microreactor chip is made of corrosion-resistant metal material and is manufactured by high-precision laser micromachining, precision etching or electroforming processes, with the processing accuracy controlled within the micrometer level. The microreactor chip packaging structure ensures that it is leak-free and has long-term stable operation capability under high pressure and wide temperature range conditions.

2. The continuous preparation method of an anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 1, characterized in that, Includes the following steps: S1. Methylcyclosiloxane monomer and vinylsiloxane monomer are precisely metered and then fed into the microreactor; S2. Controllable ring-opening polymerization reaction is carried out in microchannels, with residence time controlled within a few minutes, and single-pass conversion rate stably reaches over 98%. S3. Rapid termination of the reaction is achieved by injecting a terminator online, controlling the molecular weight and distribution of the polymer, and making the molecular weight distribution index (PDI) less than 1.

8. S4. An integrated near-infrared spectroscopy online detection system monitors vinyl content and molecular weight distribution in real time, and adjusts process parameters through a closed-loop feedback control system to ensure that vinyl content is controlled within the target range and the coefficient of variation of distribution is not higher than 3%. S5. Enables continuous operation throughout the entire process from raw material input to product output, shortening the single-process production cycle to less than 6 hours, and significantly reducing the overall energy consumption per unit product compared to traditional batch reactor processes.

3. The anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 1, characterized in that: The fractal microchannel network has at least a three-level branching structure, and through the progressive division and recombination of fluids, the radial mixing efficiency of high-viscosity fluids in it reaches more than 95%.

4. The anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 1, characterized in that: The low surface energy material is a fluoropolymer or silane coating applied by chemical vapor deposition or sol-gel method.

5. The anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 1, characterized in that: The microreactor chip integrates temperature and pressure sensors and is interlocked with an external temperature control system and back pressure valve to achieve precise control of the reaction temperature and stable maintenance of system pressure.

6. A continuous preparation method for an anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 2, characterized in that, In step S1, the methylcyclosiloxane monomer and vinylsiloxane monomer are subjected to precision filtration, deep drying and pretreatment to remove dissolved oxygen.

7. A continuous preparation method for an anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 2, characterized in that, In step S4, the closed-loop feedback control system performs the following operation: dynamically adjusting one or more parameters among monomer feed ratio, catalyst injection rate, or reaction temperature based on real-time prediction of vinyl content or molecular weight distribution data from near-infrared spectroscopy.

8. A continuous preparation method for an anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 2, characterized in that, In step S3, the terminator is a precisely measured acidic substance or a compound that can deactivate the catalyst, and its injection point is at the outlet section of the microreactor, with the termination reaction completed within milliseconds.

9. A continuous preparation method for an anti-clogging microreactor for the synthesis of high-viscosity silicone rubber according to claim 2, characterized in that, The method is implemented in a modular continuous flow process system comprising a precision premixing module, a polymerization reaction module, an online functionalization module, and a rapid termination module, with each module seamlessly connected via microchannels.