Method for synthesizing olefin copolymer based on microchannel reaction

Abstract

The invention discloses a method for synthesizing an olefin copolymer based on a microchannel reaction, and belongs to the field of olefin polymerization, the method is carried out in a microchannel reactor, and the method comprises the following steps: mixing a supported microsphere initiator with a solvent A and a solvent B in the microchannel reactor at the mixing temperature of 20-40 DEG C, then, tetrafluoroethylene monomers and other comonomers are introduced into the microchannel reactor together for a polymerization reaction, the polymerization reaction temperature is 60-180 DEG C, and the polymerization reaction pressure is 0.1-5 MPa. Wherein the supported microsphere initiator is a polystyrene / Na-montmorillonite microsphere or a polystyrene / zeolite microsphere loaded with a persulfate initiator; the solvent A is selected from an organic solvent; the solvent B is selected from fluorine-containing ionic liquid. The method solves the problems of difficult reaction control, low product molecular weight and non-uniform product distribution in the existing method, and has the characteristics of short reaction time, high synthesis efficiency, high product molecular weight and narrow distribution.

Description

Technical Field

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

[0002] Polyolefins have been widely used in packaging, film, pipe, 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 made by polymerization of tetrafluoroethylene as a monomer. This material is resistant to acid and alkali, various organic solvents, and is almost insoluble in all solvents. The tetrafluoroethylene monomer in polytetrafluoroethylene has outstanding physical and chemical properties and is widely used in chemical industry, machinery, electronics, electrical appliances, military industry, aerospace and environmental protection.

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

[0004] At present, the polymerization methods of tetrafluoroethylene copolymers mainly include: emulsion polymerization, high temperature suspension copolymerization, supercritical polymerization, radiation polymerization, etc. The details are as follows:

[0005] (1) The emulsion polymerization process generally uses an aqueous medium for easy operation to prepare FEP. In this heterogeneous process, perfluoro surfactants such as perfluorooctanoic acid and gentle stirring can produce small ellipsoidal particles. Perfluoro surfactants have excellent aqueous dispersion stability and can reduce chain transfer reactions on surfactant molecules, so they are widely used in the preparation of polyperfluoroethylene propylene. Although this method has a fast polymerization speed and high molecular weight, the polymer separation and precipitation process is complicated and there are many types of additives, large amounts, and many residual impurities in the product;

[0006] (2) High-temperature suspension copolymerization is carried out in a stainless steel autoclave with anchor stirring. The polymerization medium is deoxygenated deionized water and the initiator is a persulfate, such as potassium persulfate. Although this method can increase the stability of the terminal groups of the polymer product, it is difficult to remove the dispersant from the polymer product after the polymerization is completed, which affects the performance of the polymer product. (3) Supercritical polymerization is to dissolve two reaction monomers in supercritical carbon dioxide and add peroxide as a polymerization initiator to initiate polymerization. This type of peroxide initiator is also an organic perfluoroperoxide. Although this method has high stability, impact strength, good toughness, and long fatigue life, it has high requirements on the properties of the surfactant, requiring it to be easily soluble in ScCO2 and able to inhibit polymer precipitation;

[0007] (4) Radiation polymerization is also known as thermal polymerization, which refers to copolymerization at 70~350℃, pressure above 200atm and in the presence of a polymerization promoter. The radiation energy in radiation polymerization is high, which can polymerize monomers that are difficult to polymerize. The resulting polymer has a high purity, but the radiation effect is non-selective, which will lead to a more complicated reaction.

[0008] The above four tetrafluoroethylene polymerization methods all have problems such as difficult reaction control, complex polymerization products, low product molecular weight, and uneven product distribution. Tetrafluoroethylene has the characteristics of violent reaction during the polymerization process, which will release a large amount of heat, making the reaction temperature difficult to control and affecting the yield and structural properties of the polymerization product.

[0009] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0010] The purpose of the present invention is to provide a method for synthesizing olefin copolymers based on microchannel reaction, which solves the problems of difficult reaction control, low product molecular weight and uneven product distribution in the existing method, and has the characteristics of short reaction time, high synthesis efficiency, high product molecular weight and narrow distribution.

[0011] In order to achieve the above-mentioned object, the present invention provides a method for synthesizing olefin copolymers based on microchannel reaction, which is carried out in a microchannel reactor, comprising: mixing a supported microsphere initiator with a solvent A and a solvent B in a 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, 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 0.1-5 MPa.

[0012] Wherein, the loaded microsphere initiator is polystyrene / sodium-montmorillonite microsphere or polystyrene / zeolite microsphere loaded with persulfate initiator; the solvent A is selected from organic solvents; and the solvent B is selected from fluorine-containing ionic liquids.

[0013] The key technology of the present invention is that a loaded microsphere initiator is mixed and heated with solvent A and solvent B in a microchannel reactor, and tetrafluoroethylene monomer and olefin comonomer are used as raw materials to synthesize olefin copolymers under the joint action of the loaded microsphere initiator, solvent A and solvent B. The present invention uses two solvents, fluorine-containing ionic liquid and organic solution, to carry out mixed reactions on different olefins and initiators, which can effectively accelerate the reaction rate. The loaded microsphere initiator is used, wherein the initiator is persulfate, which can accelerate the polymerization rate and shorten the polymerization cycle. The loaded microsphere initiator of the present invention loads the initiator on porous microspheres, has better dispersibility, and has the characteristics of high polymerization efficiency and not easy to block pipelines. Moreover, the polymerization reaction is carried out by using a microchannel reactor, which can effectively dissipate the heat of the reaction, control the polymerization temperature and pressure to synthesize the target product, and the copolymer polymerization efficiency and polymerization quality can be effectively improved by the microchannel reactor, so as to obtain a high molecular weight and narrow distribution product with higher purity and better performance, and better solve the problems of low molecular weight and uneven distribution of the polymerized product.

[0014] The method of the present invention can synthesize a multi-component copolymer in a microreactor. The copolymer can be alternating copolymerization, random copolymerization or block copolymerization. The synthesized copolymer has a wide application range.

[0015] Preferably, the polymerization reaction temperature is 60-150°C.

[0016] Preferably, the pressure is 2.2~3.7MPa.

[0017] Preferably, the persulfate is selected from any one or more of potassium persulfate, sodium persulfate and ammonium persulfate.

[0018] Preferably, the supported microsphere initiator is prepared by the following method: (1) Preparation of polystyrene / sodium-montmorillonite microspheres or polystyrene / zeolite microspheres The sodium montmorillonite or zeolite and water are stirred evenly, centrifuged, the supernatant is taken and a porogen is added, and the mixture is heated. When the reaction temperature is 30° C., a dispersant is added, and when the temperature rises to 70° C., styrene and an organic peroxide are added and the temperature is rapidly raised to 80° C. After the reaction is completed, vacuum filtration is performed, washing, and drying are performed to obtain the polystyrene / sodium montmorillonite microspheres or polystyrene / zeolite microspheres; (2) Initiator loading The polystyrene / sodium-montmorillonite microspheres or polystyrene / zeolite microspheres are dispersed in water and stirred at a constant temperature of 20-40° C., allowed to stand, and then an inorganic salt initiator is added, stirred sufficiently, and dried at low temperature in a vacuum oven. The obtained powder is called a supported initiator.

[0019] Preferably, the porogen is selected from any one or more of polyethylene glycol, polyurethane and urea; or / and, the dispersant is selected from polyvinyl alcohol.

[0020] Preferably, the fluorine-containing ionic liquid is composed of a combination of cations and anions; the cations include: any one of alkyl quaternary ammonium ions, pyridinium salt cations, imidazolium salt cations and alkyl triazole ions, 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.

[0021] Preferably, the organic solvent is selected from any one or more of benzene, toluene, phenol, cyclohexane, dichlorobenzene and acetonitrile.

[0022] Preferably, the molar ratio of the supported microsphere initiator to solvent A or solvent B is (1-5): (2-4); or / and, the molar ratio of solvent A or solvent B is 1: 1; or / and, the molar ratio of the supported microsphere initiator to tetrafluoroethylene monomer or other comonomer is (1-3): (2-5).

[0023] Preferably, the volume ratio of the tetrafluoroethylene monomer to other comonomers is 1:1.

[0024] Preferably, the mixing time of the supported microsphere initiator with solvent A and solvent B is 0.1-2h; or / and, in the polymerization reaction, the amount of tetrafluoroethylene monomer and other comonomers introduced is 20-200mL, the monomer introduction flow rate is 5-30mL / min, the time interval for introducing the polymerization monomer is 10-240s, and the reaction time is 5-120min.

[0025] The present invention realizes the synthesis of different types of copolymers by controlling the flow rate and amount of tetrafluoroethylene monomer and other olefin comonomers entering the microchannel reactor (such as controlled by a metering pump) and by controlling the time interval of entering the microchannel reactor.

[0026] Preferably, the chemical formula of the other comonomer is CF2=CFR1 or CH2=CHR2; wherein R1 and R2 are independently selected from: H, fluorine-containing or non-fluorine-containing alkyl, fluorine-containing or non-fluorine-containing vinyl, the carbon chain length of the fluorine-containing or non-fluorine-containing alkyl, fluorine-containing or non-fluorine-containing vinyl is C1~C6; the fluorine-containing or non-fluorine-containing alkyl, fluorine-containing or non-fluorine-containing vinyl contains or does not contain oxygen atoms between carbon atoms.

[0027] Specifically, the fluorine-containing or non-fluorine-containing alkyl group and the fluorine-containing or non-fluorine-containing vinyl group may or may not have a substituent.

[0028] The present invention realizes copolymerization of tetrafluoroethylene monomer and other olefins by using different polymer monomers. Preferably, the material of the microchannel reactor is nickel or its alloy; or / and, the inner diameter of the microchannel reactor is 2~4mm, and the length is 500~5000mm; or / and, the microchannel reactor contains 3~5 raw material replenishment points for replenishing solvents, initiators and polymer monomers.

[0029] The method for synthesizing olefin copolymers based on microchannel reaction of the present invention solves the problems of difficult reaction control, low product molecular weight and uneven product distribution in the existing method, and has the following advantages: (1) The present invention uses a supported microsphere initiator to participate in the polymerization reaction, which can effectively improve the polymerization efficiency and avoid clogging the reactor; (2) The present invention uses two solvents, fluorinated ionic liquid and organic solution, to carry out mixed reaction of different olefins and initiators, which can effectively accelerate the reaction rate; (3) The present invention adopts a microchannel reactor to carry out polymerization reaction, which can effectively dissipate heat from the reaction and control the polymerization temperature to synthesize the target product. The microchannel reactor can effectively improve the polymerization efficiency and polymerization quality of the copolymer, and better solve the problems of low molecular weight and uneven distribution of the polymerization product; (4) The present invention can synthesize a multi-polymer in a microreactor by controlling the flow rate and amount of the polymerization monomers and the time interval for the polymerization monomers to enter the microchannel reactor. The copolymer can be an alternating copolymer, a random copolymer or a block copolymer. The synthesized copolymer has a wide range of applications. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] It should be noted that if the specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased from the market.

[0032] In the present invention, all features defined in the form of numerical ranges or percentage ranges, such as values, quantities, contents and concentrations, are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0033] 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 the scope of this specification. Each feature disclosed in the specification can be replaced by any alternative feature that can provide the same, equal or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equal or similar features.

[0034] The present invention provides a method for synthesizing olefin copolymers based on microchannel reaction, which is carried out in a microchannel reactor, comprising: mixing a supported microsphere initiator with solvent A and solvent B in a microchannel reactor, the mixing temperature being 20-40°C, and then introducing tetrafluoroethylene monomer and other comonomers into the microchannel reactor for polymerization, the molar ratio of tetrafluoroethylene monomer to other comonomers being (0.1-1): (0.05-1), the polymerization temperature being 60-180°C, and the pressure being 0.1-5MPa. The supported microsphere initiator is polystyrene / sodium montmorillonite microspheres or polystyrene / zeolite microspheres loaded with persulfate initiator; solvent A is selected from organic solvents; and solvent B is selected from fluorine-containing ionic liquids.

[0035] A microchannel reactor is a heat exchanger with a channel equivalent diameter of 10~1000μm. There are dozens of tiny flow channels in the flat tubes of this heat exchanger, which are connected to circular headers at both ends. Through this heat exchanger, the heat generated during the reaction can be effectively and timely discharged to maintain a certain reaction temperature. In addition, microchannel reactor technology can effectively enhance the mass transfer effect of the material system, and miniaturize and micronize large-scale reaction processes, easily realize the rapid adjustment of material system concentration, pressure, and temperature, and finally realize the flexible adjustment of product properties.

[0036] 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.

[0037] 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.

[0038] Experimental Example 1 1. Preparation of supported microsphere initiator 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 (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; (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.

[0039] 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.

[0040] 2. Structural characterization 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.

[0041] Table 1 Pore volume and specific surface area data of supported microsphere initiator

[0042] Example 1 A method for synthesizing olefin copolymers based on microchannel reaction, wherein the inner diameter of the microchannel reactor used is 3 mm and the length of the microchannel reactor is 3000 mm, and the method comprises: First, 0.05 mol of potassium persulfate-loaded polystyrene / sodium-montmorillonite microspheres (initiator), 0.1 mol of benzene (solvent A), and 0.2 mol of pyridinium cations and BF4 — The liquid (solvent B) was mixed and heated in a microchannel reactor at a mixing temperature of 30°C for a mixing time of 1 h. Then, 0.15 mol of tetrafluoroethylene and 0.05 mol of ethylene were sequentially introduced into the microchannel reactor for polymerization to obtain a block copolymer. The tetrafluoroethylene monomer introduction rate was 30 mL / min, the ethylene monomer introduction rate was 5 mL / min, the introduction time interval between the polymerized monomers was 240 s, the polymerization reaction temperature was 100°C, the reaction residence time was 10 min, and the pressure was 2.2 MPa.

[0043] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was M n =11.2×10 4 , molecular weight distribution PDI=1.34.

[0044] Example 2 A method for synthesizing olefin copolymers based on microchannel reaction, the microchannel reactor used is the same as that in Example 1, and the method comprises: 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 cations and BF4 — The liquid (solvent B) was mixed and heated in a microchannel reactor at a mixing temperature of 30°C and a mixing time of 0.5 h. Then, 1 mol of tetrafluoroethylene and 1 mol of ethylene were sequentially introduced into the microchannel reactor for polymerization to obtain an alternating copolymer. The tetrafluoroethylene monomer introduction rate was 15 mL / min, the ethylene introduction rate was 5 mL / min, the introduction time interval between the polymerized monomers was 20 s, the polymerization reaction temperature was 120°C, the reaction residence time was 60 min, and the pressure was 2.9 MPa.

[0045] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was M n =13.2×10 4 , molecular weight distribution PDI=1.56.

[0046] Example 3 A method for synthesizing olefin copolymers based on microchannel reaction, the microchannel reactor used is the same as that in Example 1, and the method comprises: First, 0.3 mol of potassium persulfate-loaded polystyrene / zeolite microspheres (initiator), 0.5 mol of toluene (solvent A), and 0.5 mol of alkyl quaternary ammonium ions and trifluoromethylsulfonamide ionic liquid (solvent B) were mixed and heated in a microchannel reactor at a mixing temperature of 30°C for a mixing time of 0.5 h. Then, 1 mol of tetrafluoroethylene and 0.5 mol of ethylene were sequentially introduced into the microchannel reactor for polymerization to obtain a random copolymer. The monomer introduction flow rate was 5 mL / min, the introduction time interval between the polymerized 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.

[0047] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was Mn = 9.7×10 4 , molecular weight distribution PDI=1.26.

[0048] Example 4 A method for synthesizing olefin copolymers based on microchannel reaction, the microchannel reactor used is the same as that in Example 1, and the method comprises: First, 0.3 mol of potassium persulfate-loaded polystyrene / zeolite microspheres (initiator), 0.1 mol of benzene (solvent A), and 0.5 mol of alkyl quaternary ammonium ions and trifluoromethylsulfonamide ionic liquid (solvent B) were mixed and heated in a microchannel reactor at a mixing temperature of 30°C for a mixing time of 0.5 h. Then, 1 mol of tetrafluoroethylene and 0.1 mol of hexafluoropropylene were sequentially introduced into the microchannel reactor for polymerization to obtain a random copolymer. The monomer introduction flow rate was 5 mL / min, the introduction time interval between the polymerized 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.

[0049] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was Mn = 9.3×10 4 , molecular weight distribution PDI=1.23.

[0050] Comparative Example 1 A method for synthesizing an olefin copolymer, the reaction is substantially the same as that of Example 1, except that: The reaction was carried out in a 1 L high pressure reactor.

[0051] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was Mn =9.3×10 3 , molecular weight distribution PDI=3.02. Compared with Example 1, the product molecular weight of the method for synthesizing olefin copolymers using a microchannel reactor in Example 1 of the present invention is higher and the product distribution is more concentrated.

[0052] Comparative Example 2 A method for synthesizing olefin copolymers based on microchannel reaction, the microchannel reactor used is the same as that in Example 1, and the method is basically the same as that in Example 1, except that: Only benzene was used as the solvent, and no fluorine-containing ionic liquid was added as the solvent.

[0053] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was M n =11.2×10 3 , molecular weight distribution PDI=2.14. Compared with Example 1, Example 1 of the present invention uses benzene and fluorine-containing ionic liquid as solvents, and the obtained product has a higher molecular weight and a more concentrated product distribution.

[0054] Comparative Example 3 A method for synthesizing olefin copolymers based on microchannel reaction, the microchannel reactor used is the same as that in Example 1, and the method is basically the same as that in Example 1, except that: The polymerization temperature was 210°C.

[0055] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was M n =14.1×10 3 , molecular weight distribution PDI = 2.63. It can be seen that high-temperature polymerization will lead to the destruction of the molecular structure and produce polymers of lower quality.

[0056] Comparative Example 4 A method for synthesizing olefin copolymers based on microchannel reaction, the microchannel reactor used is the same as that in Example 1, and the method is basically the same as that in Example 1, except that: The initiator used in this comparative example is potassium persulfate, and no microspheres are used for loading.

[0057] After the reaction, the reaction solution was degassed and desolventized, and then the polymerization product was analyzed by high temperature gel chromatography (PL-GPC220). The results showed that the molecular weight of the prepared olefin copolymer was M n =10.4×10 3, molecular weight distribution PDI=2.56. Compared with Example 1, Example 1 of the present invention uses polystyrene / sodium-montmorillonite microspheres loaded with potassium persulfate as an initiator, and the obtained product has a higher molecular weight and a more concentrated product distribution.

[0058] From the test data of the above embodiments and comparative examples, it can be seen that compared with the comparative examples, the microchannel reaction is adopted in the embodiments of the present invention 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.

[0059] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited 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 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; Wherein, the supported microsphere initiator is polystyrene / sodium-montmorillonite microspheres or polystyrene / zeolite microspheres loaded with persulfate initiator; 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 persulfate is selected from any one or more of potassium persulfate, sodium persulfate and ammonium persulfate.

3. The method for synthesizing olefin copolymers based on microchannel reaction according to claim 1, characterized in that: The supported microsphere initiator is prepared by the following method: (1) Preparation of polystyrene / sodium-montmorillonite microspheres or polystyrene / zeolite microspheres The sodium montmorillonite or zeolite and water are stirred evenly, centrifuged, the supernatant is taken and a porogen is added, and the mixture is heated. When the reaction temperature is 30° C., a dispersant is added, and when the temperature rises to 70° C., styrene and an organic peroxide are added and the temperature is rapidly raised to 80° C. After the reaction is completed, vacuum filtration is performed, washing, and drying are performed to obtain the polystyrene / sodium montmorillonite microspheres or polystyrene / zeolite microspheres; (2) Initiator loading The polystyrene / sodium-montmorillonite microspheres or polystyrene / zeolite microspheres are dispersed in water and stirred at a constant temperature of 20-40° C., allowed to stand, and then an inorganic salt initiator is added, fully stirred, and dried. The resulting powder is called a supported initiator.

4. The method for synthesizing olefin copolymers based on microchannel reaction according to claim 3, characterized in that: The porogen is selected from any one or more of polyethylene glycol, polyurethane and urea; Or / and, the dispersant is selected from polyvinyl alcohol.

5. 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.

6. 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.

7. 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 tetrafluoroethylene monomer or other comonomer is (1-3): (2-5).

8. 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.

9. 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.

10. The method for synthesizing olefin copolymers based on microchannel reaction according to any one of claims 1 to 9, 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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