A method for synthesizing olefin copolymers based on microchannel reaction

Abstract

The present invention discloses a method for synthesizing olefin copolymers based on microchannel reaction, belonging to the field of olefin polymerization. This method is carried out in a microchannel reactor and includes: mixing a supported microsphere initiator with solvent A and solvent B in the microchannel reactor at a mixing temperature of 20 - 40 °C, and then introducing tetrafluoroethylene monomer and other comonomers together into the microchannel reactor for polymerization reaction. The polymerization reaction temperature is 60 - 180 °C and the pressure is 0.1 - 5 MPa. Among them, the supported microsphere initiator is a polystyrene / sodium montmorillonite microsphere or a polystyrene / zeolite microsphere loaded with a persulfate initiator; solvent A is selected from organic solvents; solvent B is selected from fluorine-containing ionic liquids. The present invention solves the problems of difficult reaction control, low product molecular weight, and uneven product distribution in the existing methods, and has the characteristics of short reaction time, high synthesis efficiency, high product molecular weight, and narrow distribution.

Description

Technical Field

[0001] The present invention belongs to the field of olefin polymerization, and particularly relates to a method for synthesizing olefin copolymers based on microchannel reaction. Background Art

[0002] Polyolefins have been widely used in packaging, films, pipes, electronics, electrical and automotive fields due to their excellent chemical stability, corrosion resistance, non-toxicity and low cost. Among them, polytetrafluoroethylene is a high molecular polymer prepared by polymerizing tetrafluoroethylene as a monomer. This material has the characteristics of being resistant to acids and alkalis and various organic solvents, and is almost insoluble in all solvents. Due to its outstanding physical and chemical properties, tetrafluoroethylene monomer in polytetrafluoroethylene has been widely used in chemical industry, machinery, electronics, electrical appliances, military, aerospace and environmental protection fields.

[0003] However, in practical applications, although the structures of polyolefins have certain similarities, phase separation structures often occur when different polyolefins or polyolefins are mixed with other polymers, resulting in poor mechanical properties of the polymers. Block copolymers combining polyolefins with different structures and properties have good mechanical properties and processing properties. For example, polytetrafluoroethylene (PTFE) has special "insoluble and infusible" characteristics, making it difficult to process. Copolymerizing tetrafluoroethylene with other monomers to prepare various polytetrafluoroethylene-based copolymers, such as FEP (tetrafluoroethylene-propylene trifluoride copolymer), ETFE (ethylene-tetrafluoroethylene copolymer), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), etc., can improve the processing properties of polytetrafluoroethylene while maintaining its excellent physical and chemical properties. Compared with polytetrafluoroethylene, polytetrafluoroethylene-based copolymers destroy the symmetric structure of PTFE, reducing their crystallinity and melting point, making them more conducive to melt processing and expanding their application scope.

[0004] Currently, the polymerization methods for tetrafluoroethylene copolymers mainly include: emulsion polymerization, high-temperature suspension copolymerization, supercritical polymerization, radiation polymerization, etc. Specifically as follows:

[0005] (1) Emulsion polymerization process generally uses an aqueous medium and is easy to operate to prepare FEP. In this heterogeneous process, perfluorinated surfactants such as perfluorooctanoic acid and gentle stirring can obtain small ellipsoidal particles. Since perfluorinated surfactants have excellent aqueous solution dispersion stability and can reduce the chain transfer reaction to surfactant molecules, they are widely used in the preparation of perfluoroethylenepropylene. Although this method has a fast polymerization rate and high molecular weight, the polymer separation and precipitation process is complicated, there are many types of additives, large dosages, and many residual impurities in the product;

[0006] (2) High-temperature suspension copolymerization is carried out in a stainless-steel autoclave with an anchor stirrer. The polymerization medium is deoxygenated deionized water, and the initiator is a persulfate, such as potassium persulfate, etc. Although this method can increase the stability of the end groups of the polymer product, it is difficult to remove the dispersant from the polymerization product after polymerization, which affects the performance of the polymerization product.

[0007] (3) Supercritical polymerization is to dissolve two reactive monomers in supercritical carbon dioxide and add a peroxide as the polymerization initiator to initiate polymerization. This type of peroxide initiator is also an organic perfluorinated peroxide. Although this method has high stability, impact strength, good toughness, and long fatigue life, it has high requirements for the properties of the surfactant, requiring it to be easily soluble in ScCO2 and able to inhibit polymer precipitation.

[0008] (4) Radiation polymerization is also thermal polymerization, which refers to carrying out copolymerization at a temperature of 70 - 350 °C, a pressure above 200 atm, and in the presence of a polymerization promoter. In radiation polymerization, the ray energy is high, which can cause monomers that are difficult to polymerize to polymerize. The resulting polymer has a high purity, but the radiation effect has no selectivity, resulting in a relatively complex reaction.

[0009] In the above four tetrafluoroethylene polymerization methods, there are problems such as difficult reaction control, complex polymerization products, low molecular weight of the products, and uneven product distribution. Tetrafluoroethylene has characteristics such as violent reaction during polymerization, releasing a large amount of heat, making it difficult to control the reaction temperature, which affects the yield and structural properties of the polymerization product.

[0010] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0011] The object of the present invention is to provide a method for synthesizing an olefin copolymer based on microchannel reaction, which solves the problems of difficult reaction control, low molecular weight of the product, and uneven product distribution in the existing methods, and has the characteristics of short reaction time, high synthesis efficiency, high molecular weight of the product, and narrow distribution.

[0012] To achieve the above object, the present invention provides a method for synthesizing an olefin copolymer based on microchannel reaction. This method is carried out in a microchannel reactor and includes: mixing a supported microsphere initiator with solvent A and solvent B in the microchannel reactor at a mixing temperature of 20 - 40 °C, and then introducing tetrafluoroethylene monomer and other comonomers into the microchannel reactor for polymerization reaction. The molar ratio of the tetrafluoroethylene monomer to other comonomers is (0.1 - 1) : (0.05 - 1), and the polymerization reaction temperature is 60 - 180 °C, and the pressure is 0.1 - 5 MPa.

[0013] Among them, the supported microsphere initiator is a polystyrene / sodium montmorillonite microsphere or a polystyrene / zeolite microsphere loaded with a persulfate initiator; the solvent A is selected from organic solvents; the solvent B is selected from fluorine-containing ionic liquids.

[0014] The key technology of the present invention lies in mixing and heating the supported microsphere initiator with the solvent A and the solvent B in a microchannel reactor, using tetrafluoroethylene monomer and olefin comonomer as raw materials, and synthesizing an olefin copolymer under the combined action of the supported microsphere initiator, the solvent A and the solvent B. The present invention uses two solvents, namely a fluorine-containing ionic liquid and an organic solution, to carry out a mixed reaction on different olefins and initiators, which can effectively accelerate the reaction rate. By using the supported microsphere initiator, wherein the initiator is persulfate, the polymerization rate can be accelerated and the polymerization cycle can be shortened. The supported microsphere initiator of the present invention loads the initiator on porous microspheres, with better dispersibility, and has the characteristics of high polymerization efficiency and not easily blocking pipelines. Moreover, by using a microchannel reactor for the polymerization reaction, heat dissipation of the reaction can be effectively carried out, and the polymerization temperature and pressure can be controlled to synthesize the target product. Through the microchannel reactor, the polymerization efficiency and polymerization quality of the copolymer can be effectively improved, and a high-molecular-weight, narrow-distribution product with higher purity and better performance can be obtained, which preferably solves the problems of low molecular weight and uneven distribution of the polymerization product.

[0015] The method of the present invention can synthesize a multi-component copolymer in a microreactor. The copolymer can be an alternating copolymer, a random copolymer or a block copolymer, and the synthesized copolymer has a wide range of applications.

[0016] Preferably, the polymerization reaction temperature is 60-150 °C.

[0017] Preferably, the pressure is 2.2-3.7 MPa.

[0018] Preferably, the persulfate is selected from any one or more of potassium persulfate, sodium persulfate and ammonium persulfate.

[0019] Preferably, the supported microsphere initiator is prepared by the following method:

[0020] (1) Preparation of polystyrene / sodium montmorillonite microspheres or polystyrene / zeolite microspheres

[0021] Mix sodium montmorillonite or zeolite and water evenly, centrifuge, take the supernatant and add a pore-forming agent, heat, add a dispersant when the reaction temperature is 30 °C, add styrene and an organic peroxide when the temperature rises to 70 °C and quickly raise the temperature to 80 °C. After the reaction ends, carry out vacuum filtration, washing and drying to obtain the polystyrene / sodium montmorillonite microspheres or polystyrene / zeolite microspheres;

[0022] (2) Initiator loading

[0023] Disperse the polystyrene / sodium montmorillonite microspheres or polystyrene / zeolite microspheres in water, stir at a constant temperature of 20~40°C, let it stand, then add an inorganic salt initiator, stir well, and dry at low temperature in a vacuum oven. The obtained powder is called a supported initiator.

[0024] Preferably, the pore-forming agent is selected from any one or more of polyethylene glycol, polyurethane, and urea; and / or, the dispersant is selected from polyvinyl alcohol.

[0025] Preferably, the fluorine-containing ionic liquid is composed of a combination of a cation and an anion; the cation includes: any one of alkyl quaternary ammonium ions, pyridinium cations, imidazolium cations, and alkyl triazole ions, and the number of carbon atoms in the alkyl group of the alkyl triazole ion is 1~3; the anion includes: BF4 — 、PF6 — 、any one of trifluoromethylsulfonamide ions and trifluoromethanesulfonic acid ions.

[0026] Preferably, the organic solvent is selected from any one or more of benzene, toluene, phenol, cyclohexane, dichlorobenzene, and acetonitrile.

[0027] Preferably, the molar ratio of the supported microsphere initiator to solvent A or solvent B is (1~5):(2~4); and / or, the molar ratio of solvent A or solvent B is 1:1; and / or, the molar ratio of the supported microsphere initiator to tetrafluoroethylene monomer or other comonomers is (1~3):(2~5).

[0028] Preferably, the volume ratio of the tetrafluoroethylene monomer to other comonomers is 1:1.

[0029] Preferably, the mixing time of the supported microsphere initiator with solvent A and solvent B is 0.1~2h; and / or, for the polymerization reaction, the feeding amount of the tetrafluoroethylene monomer and other comonomers is 20~200 mL, the monomer feeding flow rate is 5~30 mL / min, the feeding time interval of the polymerization monomers is 10~240 s, and the reaction time is 5~120 min.

[0030] In the present invention, by controlling the flow rate and dosage of the tetrafluoroethylene monomer and other olefin comonomers introduced into the microchannel reactor (such as controlled by a metering pump), and at the same time by controlling the time interval of entering the microchannel reactor, the synthesis of different types of copolymers is realized.

[0031] Preferably, the chemical structural formula of the other comonomer is CF2=CFR1 or CH2=CHR2; wherein, R1 and R2 are independently selected from: H, fluorinated or non-fluorinated alkyl groups, fluorinated or non-fluorinated vinyl groups, and the carbon chain lengths of the fluorinated or non-fluorinated alkyl groups and fluorinated or non-fluorinated vinyl groups are C1~C6; the fluorinated or non-fluorinated alkyl groups and fluorinated or non-fluorinated vinyl groups may or may not contain oxygen atoms between carbon atoms.

[0032] Specifically, the fluorinated or non-fluorinated alkyl groups and fluorinated or non-fluorinated vinyl groups may or may not have substituents.

[0033] In the present invention, by using different polymer monomers, copolymerization of tetrafluoroethylene monomer and other olefins is achieved.

[0034] Preferably, the material of the microchannel reactor is nickel or its alloy; or / and, the inner diameter of the microchannel reactor is 2~4 mm and the length is 500~5000 mm; or / and, the microchannel reactor is provided with 3~5 raw material supplement points for supplementing solvents, initiators and polymer monomers.

[0035] The method for synthesizing olefin copolymers based on microchannel reaction in the present invention solves the problems of difficult reaction control, low product molecular weight and uneven product distribution in the existing methods, and has the following advantages:

[0036] (1) In the present invention, a supported microsphere initiator is used to participate in the polymerization reaction, which can effectively improve the polymerization efficiency and avoid blocking the reactor at the same time;

[0037] (2) In the present invention, two solvents, namely fluorinated ionic liquid and organic solution, are used to mix and react different olefins and initiators, which can effectively accelerate the reaction rate;

[0038] (3) In the present invention, a microchannel reactor is used for the polymerization reaction, which can effectively dissipate heat from the reaction, control the polymerization temperature to synthesize the target product, and can effectively improve the copolymerization efficiency and polymerization quality of the copolymer through the microchannel reactor, and better solve the problems of low molecular weight and uneven distribution of the polymerization product;

[0039] (4) In the present invention, by controlling the flow rate and dosage of the polymerized monomers and simultaneously controlling the time interval for the polymerized monomers to enter the microchannel reactor, a multi-component copolymer can be synthesized in the microreactor, and the copolymer can be alternating copolymerization, random copolymerization or block copolymerization, and the synthesized copolymer has a wide range of applications. Specific embodiments

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] It should be noted that: for those not specifying specific conditions in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0042] In the present invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of simplicity and convenience. Accordingly, the description of the numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0043] The features mentioned in the present invention can be combined arbitrarily as long as there is no contradiction in the combination of these features. All possible combinations should be considered as being within the scope described in this specification. Each feature disclosed in the specification can be replaced by any alternative feature that can provide the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equivalent or similar features.

[0044] The present invention provides a method for synthesizing an olefin copolymer based on microchannel reaction. This method is carried out in a microchannel reactor and includes: mixing a supported microsphere initiator with solvent A and solvent B in the microchannel reactor at a mixing temperature of 20-40°C, and then introducing tetrafluoroethylene monomer and other comonomers into the microchannel reactor for polymerization reaction. The molar ratio of tetrafluoroethylene monomer to other comonomers is (0.1-1):(0.05-1), the polymerization reaction temperature is 60-180°C, and the pressure is 0.1-5 MPa. Among them, the supported microsphere initiator is a polystyrene / sodium montmorillonite microsphere or a polystyrene / zeolite microsphere loaded with a persulfate initiator; solvent A is selected from organic solvents; solvent B is selected from fluorinated ionic liquids.

[0045] A microchannel reactor is a heat exchanger with a channel equivalent diameter of 10-1000 μm. There are dozens of fine channels in the flat tube of this heat exchanger, which are connected to circular headers at both ends of the flat tube. Through this heat exchanger, the heat generated during the reaction process can be effectively exported in time to maintain a certain reaction temperature. In addition, the microchannel reactor technology can effectively enhance the mass transfer effect of the material system, miniaturize and microscale large-scale reaction processes, easily realize the rapid adjustment of the concentration, pressure, and temperature of the material system, and ultimately realize the flexible adjustment of the product properties.

[0046] The present invention can effectively realize the copolymerization of tetrafluoroethylene monomer and other olefins through a microchannel reactor, and can produce a high molecular weight and narrow distribution product with higher purity and better performance by controlling parameters such as temperature and pressure.

[0047] The following is a detailed description of a method for synthesizing olefin copolymers based on microchannel reaction provided by the present invention through experimental examples, embodiments and comparative examples.

[0048] Experimental Example 1

[0049] 1. Preparation of supported microsphere initiator

[0050] The preparation method of polystyrene / sodium-montmorillonite microspheres loaded with potassium persulfate is as follows:

[0051] (1) Weigh 100 g of sodium montmorillonite, add 100 mL of deionized water and stir evenly, then centrifuge with a high-speed centrifuge, take the supernatant and put it in a three-necked flask, add 5 g of polyethylene glycol (porogen), add 0.5 g of polyvinyl alcohol (dispersant) when the reaction temperature is 30 °C, and when the temperature rises to 70 °C, weigh 10 g of styrene and 0.5 g of benzoyl peroxide (initiator) and add them to the three-necked flask and quickly heat it to 80 °C. After reacting for 2 h, vacuum filter and wash the obtained sample with deionized water several times. After vacuum drying at 80 °C, white polystyrene / sodium montmorillonite microspheres are obtained;

[0052] (2) The polystyrene / sodium-montmorillonite microspheres are dispersed in 100 mL of deionized water and stirred at a constant temperature of 20-40°C. The mixture is allowed to stand for 24 h, and then 50 g of potassium persulfate is added. The mixture is stirred thoroughly and dried at 60°C in a vacuum oven. The resulting powder is polystyrene / sodium-montmorillonite microspheres loaded with potassium persulfate, i.e., a loaded microsphere initiator.

[0053] The preparation methods of ammonium persulfate-loaded polystyrene / sodium-montmorillonite microspheres and potassium persulfate-loaded polystyrene / zeolite microspheres refer to the preparation method of potassium persulfate-loaded polystyrene / sodium-montmorillonite microspheres.

[0054] 2. Structural characterization

[0055] Some microsphere samples were analyzed using a specific surface area and pore size analyzer (BSD-660S). The data are shown in Table 1. From the pore volume and specific surface area data before and after microsphere loading, it can be found that polystyrene / sodium montmorillonite microspheres / zeolite microspheres all have relatively developed pore structures and specific surface areas, and the specific surface area and porosity are slightly reduced after loading persulfate.

[0056] Table 1 Pore volume and specific surface area data of supported microsphere initiator

[0057]

[0058] Example 1

[0059] A method for synthesizing olefin copolymer based on microchannel reaction, the inner diameter of the microchannel reactor used is 3 mm, and the length of the microchannel reactor is 3000 mm. This method includes:

[0060] First, 0.05 mol of polystyrene / sodium montmorillonite microspheres loaded with potassium persulfate (initiator), 0.1 mol of benzene (solvent A), and 0.2 mol of pyridinium cation and BF4 — liquid (solvent B) are mixed and heated in the microchannel reactor. The mixing temperature is 30 °C, and the mixing time is 1 h. Then, 0.15 mol of tetrafluoroethylene and 0.05 mol of ethylene are successively introduced into the microchannel reactor for polymerization reaction to obtain a block copolymer. The feeding flow rate of tetrafluoroethylene monomer is 30 mL / min, the feeding flow rate of ethylene monomer is 5 mL / min, the feeding time interval between polymerization monomers is 240 s, the polymerization reaction temperature is 100 °C, the reaction residence time is 10 min, and the pressure is 2.2 MPa.

[0061] After the reaction is completed, the reaction solution is degassed and desolvated, and then the polymerization product is analyzed by high-temperature gel chromatography (PL-GPC220). The results are as follows: The molecular weight M of the prepared olefin copolymer n =11.2×10 4 , and the molecular weight distribution PDI = 1.34.

[0062] Example 2

[0063] A method for synthesizing olefin copolymer based on microchannel reaction, the microchannel reactor used is the same as that in Example 1. This method includes:

[0064] First, 0.3 mol of polystyrene / sodium montmorillonite microspheres loaded with ammonium persulfate (initiator), 0.5 mol of toluene (solvent A), and 0.5 mol of pyridinium cation and BF4 — liquid (solvent B) are mixed and heated in the microchannel reactor. The mixing temperature is 30 °C, and the mixing time is 0.5 h. Then, 1 mol of tetrafluoroethylene and 1 mol of ethylene are successively introduced into the microchannel reactor for polymerization reaction to obtain an alternating copolymer. The feeding flow rate of tetrafluoroethylene monomer is 15 mL / min, the feeding flow rate of ethylene is 5 mL / min, the feeding time interval between polymerization monomers is 20 s, the polymerization reaction temperature is 120 °C, the reaction residence time is 60 min, and the pressure is 2.9 MPa.

[0065] After the reaction, the reaction solution was degassed and desolvated, and then the polymerization product was analyzed by high-temperature gel permeation chromatography (PL-GPC220). The results were as follows: The molecular weight M of the prepared olefin copolymer n = 13.2×10 4 , and the polydispersity index PDI = 1.56.

[0066] Example 3

[0067] A method for synthesizing an olefin copolymer based on microchannel reaction, using the same microchannel reactor as in Example 1. This method includes:

[0068] First, 0.3 mol of polystyrene / zeolite microspheres loaded with potassium persulfate (initiator), 0.5 mol of toluene (solvent A), and 0.5 mol of alkyl quaternary ammonium ion and trifluoromethylsulfonamide ionic liquid (solvent B) were mixed and heated in the microchannel reactor at a mixing temperature of 30 °C for 0.5 h. Then, 1 mol of tetrafluoroethylene and 0.5 mol of ethylene were successively introduced into the microchannel reactor for polymerization to obtain a random copolymer. The monomer feed flow rate was 5 mL / min, the time interval between the introduction of polymerization monomers was 10 s, the polymerization reaction temperature was 150 °C, the reaction residence time was 60 min, and the pressure was 3.7 MPa.

[0069] After the reaction, the reaction solution was degassed and desolvated, and then the polymerization product was analyzed by high-temperature gel permeation chromatography (PL-GPC220). The results were as follows: The number-average molecular weight Mn of the prepared olefin copolymer = 9.7×10 4 , and the polydispersity index PDI = 1.26.

[0070] Example 4

[0071] A method for synthesizing an olefin copolymer based on microchannel reaction, using the same microchannel reactor as in Example 1. This method includes:

[0072] First, 0.3 mol of polystyrene / zeolite microspheres loaded with potassium persulfate (initiator), 0.1 mol of benzene (solvent A), and 0.5 mol of alkyl quaternary ammonium ion and trifluoromethylsulfonamide ionic liquid (solvent B) were mixed and heated in the microchannel reactor at a mixing temperature of 30 °C for 0.5 h. Then, 1 mol of tetrafluoroethylene and 0.1 mol of hexafluoropropylene were successively introduced into the microchannel reactor for polymerization to obtain a random copolymer. The monomer feed flow rate was 5 mL / min, the time interval between the introduction of polymerization monomers was 10 s, the polymerization reaction temperature was 60 °C, the reaction residence time was 30 min, and the pressure was 2.1 MPa.

[0073] After the reaction is completed, the reaction solution is degassed and desolvated, and then the polymerization product is analyzed by high-temperature gel permeation chromatography (PL-GPC220). The results are as follows: the molecular weight of the prepared olefin copolymer Mn = 9.3×10 4 , and the polydispersity index PDI = 1.23.

[0074] Comparative Example 1

[0075] A method for synthesizing an olefin copolymer, which is basically the same as that of Example 1, except that:

[0076] A 1L high-pressure reactor is used for the reaction.

[0077] After the reaction is completed, the reaction solution is degassed and desolvated, and then the polymerization product is analyzed by high-temperature gel permeation chromatography (PL-GPC220). The results are as follows: the molecular weight of the prepared olefin copolymer M n = 9.3×10 3 , and the polydispersity index PDI = 3.02. Compared with Example 1, the product of the method for synthesizing an olefin copolymer using a microchannel reactor in Example 1 of the present invention has a higher molecular weight and a more concentrated product distribution.

[0078] Comparative Example 2

[0079] A method for synthesizing an olefin copolymer based on microchannel reaction, using the same microchannel reactor as in Example 1, and this method is basically the same as that of Example 1, except that:

[0080] Only benzene is used as the solvent, and no fluorine-containing ionic liquid is added as the solvent.

[0081] After the reaction is completed, the reaction solution is degassed and desolvated, and then the polymerization product is analyzed by high-temperature gel permeation chromatography (PL-GPC220). The results are as follows: the molecular weight of the prepared olefin copolymer M n = 11.2×10 3 , and the polydispersity index PDI = 2.14. Compared with Example 1, in Example 1 of the present invention, benzene and a fluorine-containing ionic liquid are used together as the solvent, and the resulting product has a higher molecular weight and a more concentrated product distribution.

[0082] Comparative Example 3

[0083] A method for synthesizing an olefin copolymer based on microchannel reaction, using the same microchannel reactor as in Example 1, and this method is basically the same as that of Example 1, except that:

[0084] The polymerization reaction temperature is 210 °C.

[0085] After the reaction is completed, the reaction solution is degassed and desolvated, and then the polymerization product is analyzed by high-temperature gel permeation chromatography (PL-GPC220). The results are as follows: the molecular weight M of the prepared olefin copolymer n = 14.1×10 3 , and the polydispersity index PDI = 2.63. It can be seen that high-temperature polymerization will cause damage to the molecular structure and produce polymers of lower quality.

[0086] Comparative Example 4

[0087] A method for synthesizing an olefin copolymer based on microchannel reaction, using the same microchannel reactor as in Example 1. This method is basically the same as that in Example 1, except that:

[0088] The initiator used in this comparative example is potassium persulfate, and no microspheres are used for loading.

[0089] After the reaction is completed, the reaction solution is degassed and desolvated, and then the polymerization product is analyzed by high-temperature gel permeation chromatography (PL-GPC220). The results are as follows: the molecular weight M of the prepared olefin copolymer n = 10.4×10 3 , and the polydispersity index PDI = 2.56. Compared with Example 1, in Example 1 of the present invention, polystyrene / sodium montmorillonite microspheres loaded with potassium persulfate are used as the initiator, and the obtained product has a higher molecular weight and a more concentrated product distribution.

[0090] From the test data of the above examples and comparative examples: compared with the comparative examples, in the examples of the present invention, microchannel reaction is used to polymerize tetrafluoroethylene and other comonomers in two solvents and at a suitable polymerization temperature, and the prepared copolymer has a higher molecular weight and a narrower molecular weight distribution.

[0091] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and substitutions to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A method for synthesizing olefin copolymers based on microchannel reaction, characterized in that: The method is carried out in a microchannel reactor and comprises: The supported microsphere initiator is mixed with solvent A and solvent B in a microchannel reactor at a mixing temperature of 20-40° C., and then tetrafluoroethylene monomer and other comonomers are introduced into the microchannel reactor for polymerization reaction, wherein the molar ratio of the tetrafluoroethylene monomer to the other comonomer is (0.1-1): (0.05-1), the polymerization reaction temperature is 60-180° C., and the pressure is 2.2-3.7 MPa; Wherein, the loaded microsphere initiator is polystyrene / sodium montmorillonite microspheres or polystyrene / zeolite microspheres loaded with a persulfate initiator; the persulfate is selected from any one or more of potassium persulfate, sodium persulfate and ammonium persulfate; The preparation method of polystyrene / sodium-montmorillonite microspheres loaded with potassium persulfate is as follows: (1) Weigh 100 g of sodium montmorillonite, add 100 mL of deionized water and stir evenly, then centrifuge with a high-speed centrifuge, take the supernatant and put it in a three-necked flask, add 5 g of polyethylene glycol, add 0.5 g of polyvinyl alcohol when the reaction temperature is 30 °C, and when the temperature rises to 70 °C, weigh 10 g of styrene and 0.5 g of benzoyl peroxide and add them to the three-necked flask and quickly heat it to 80 °C. After reacting for 2 h, vacuum filter and wash the obtained sample with deionized water several times, and vacuum dry at 80 °C to obtain white polystyrene / sodium montmorillonite microspheres; (2) The polystyrene / sodium-montmorillonite microspheres are dispersed in 100 mL of deionized water and stirred at a constant temperature of 20-40°C for 24 hours, and then 50 g of potassium persulfate is added, stirred thoroughly, and dried at 60°C in a vacuum oven. The resulting powder is polystyrene / sodium-montmorillonite microspheres loaded with potassium persulfate, i.e., a loaded microsphere initiator; The preparation methods of polystyrene / sodium-montmorillonite microspheres loaded with ammonium persulfate and polystyrene / zeolite microspheres loaded with potassium persulfate refer to the preparation method of polystyrene / sodium-montmorillonite microspheres loaded with potassium persulfate; The solvent A is selected from organic solvents; The solvent B is selected from fluorine-containing ionic liquids.

2. The method for synthesizing olefin copolymers based on microchannel reaction according to claim 1, characterized in that: The fluorine-containing ionic liquid is composed of cations and anions; The cation includes any one of an alkyl quaternary ammonium ion, a pyridinium salt cation, an imidazolium salt cation and an alkyl triazole ion, wherein the carbon number of the alkyl group in the alkyl triazole ion is 1 to 3; The anions include: BF4 — PF6 — , trifluoromethylsulfonamide ion and trifluoromethylsulfonate ion.

3. The method for synthesizing olefin copolymers based on microchannel reaction according to claim 1, characterized in that: The organic solvent is selected from any one or more of benzene, toluene, phenol, cyclohexane, dichlorobenzene and acetonitrile.

4. The method for synthesizing olefin copolymers based on microchannel reaction according to claim 1, characterized in that: The molar ratio of the supported microsphere initiator to the solvent A or solvent B is (1-5): (2-4); Or / and, the molar ratio of the solvent A to the solvent B is 1: 1; Or / and, the molar ratio of the supported microsphere initiator to the tetrafluoroethylene monomer is (1-3): (2-5).

5. The method for synthesizing olefin copolymers based on microchannel reaction according to claim 1, characterized in that: The mixing time of the supported microsphere initiator, solvent A and solvent B is 0.1 to 2 hours; Or / and, in the polymerization reaction, the amount of tetrafluoroethylene monomer and other comonomers introduced is 20-200 mL, the monomer introduction flow rate is 5-30 mL / min, the time interval for introducing the polymerization monomers is 10-240 s, and the reaction time is 5-120 min.

6. The method for synthesizing olefin copolymers based on microchannel reaction according to claim 1, characterized in that: The chemical structural formula of the other comonomer is CF2=CFR1 or CH2=CHR2; Wherein, R1 and R2 are independently selected from: H, fluorinated or non-fluorinated alkyl, fluorinated or non-fluorinated vinyl, wherein the carbon chain length of the fluorinated or non-fluorinated alkyl, fluorinated or non-fluorinated vinyl is C1 to C6; The fluorine-containing or non-fluorine-containing alkyl group and the fluorine-containing or non-fluorine-containing vinyl group may or may not contain oxygen atoms between carbon atoms.

7. The method for synthesizing olefin copolymers based on microchannel reaction according to any one of claims 1 to 6, characterized in that: The microchannel reactor is made of nickel or its alloy; Or / and, the inner diameter of the microchannel reactor is 2-4 mm, and the length is 500-5000 mm; Or / and, the microchannel reactor comprises 3 to 5 raw material replenishing points for replenishing solvent, initiator and polymer monomer.

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