Method for preparing polyphenyl ether

Abstract

According to the method for preparing the polyphenyl ether, methylbenzene and water are used as solvents to produce the polyphenyl ether of which the molecular weight distribution is 2.0 or below, and a water-phase-enriched copper catalyst is used repeatedly, so that the utilization rate of the catalyst is increased, and the amount of wastewater is reduced. The method is simple in process, high in catalyst utilization rate and suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a method for preparing polyphenylene ether. Background Art

[0002] Polyphenylene ether has excellent performance. The molecular chain of polyphenylene ether has high symmetry and low polarity, so it has excellent electrical properties such as low and stable dielectric constant and low dielectric loss. Moreover, since the molecular chain of polyphenylene ether contains a large number of aromatic groups and the main chain is rigid, it has good heat resistance and many characteristics such as self-flame retardancy and low density. Polyphenylene ether is widely used in electrical, automotive, cable, photovoltaic power generation and other fields. In recent years, with the development of 5G communication technology, polyphenylene ether has been widely developed and applied in 5G antenna covers, signal transmission base stations, electronic circuit boards and other communication fields due to its low dielectric constant and low dielectric loss performance, which is conducive to the functional characteristics of low loss and high fidelity in the transmission process of electromagnetic signals.

[0003] Regarding the preparation of polyphenylene ether in two-phase solvents, Percec et al. first reported in the article "Functional Polymers and Sequential Copolymers by Phase Transfer Catalysis" in 1986 that 2,6-dimethylphenol was polymerized in a two-phase medium of water and benzene to synthesize PPO. In 1999, Ahn et al. used copper complex catalysts in the article "Biphasic coupling polymerization of 2,6-dimethylphenol using surface-active copper complex catalysts" to oxidatively polymerize 2,6-dimethylphenol in a two-phase medium of water / chloroform. In 2002, Gamez et al. also reported in their article "A Simple and Selective Biphasic Catalytic System for the Oxidative Polymerization of 2,6-Dimethylphenol" that DMP was oxidatively coupled to obtain PPO in a two-phase medium of water and organic solvents.

[0004] According to existing research, the preparation of PPO by oil-water two-phase medium polymerization has the following advantages: ①The reaction takes place at the interface between the two phases, with high selectivity, high activity and high conversion rate; ② The selection range of organic solvents has been expanded, reducing the use of organic solvents; ③ The reaction speed is faster than that of precipitation polymerization; ④ Since the catalyst works at the oil-water interface, the stereoselectivity of the catalyst can be controlled.

[0005] CN109836568A proposes a method for preparing polyphenylene ether copolymers in an oil / water two-phase medium, and hopes to achieve the regulation of the molecular weight of polyphenylene ether through the polymerization reaction at the interface of the two phases. However, the two-phase reaction of toluene / water is only regarded as a conventional emulsion polymerization, and the advantages of preparing polyphenylene ether in a two-phase solvent in terms of catalyst recovery and material viscosity control are not reflected. In addition, the preparation focus of the patent is always placed on polyphenylene ether with a larger molecular weight, and the advantages of the two-phase solution in the reaction selectivity and product molecular weight distribution when preparing polyphenylene ether with small and medium molecular weight are not reflected.

[0006] CN102604075B and CN103145975B propose a method for preparing polyphenylene ether in water phase, which can avoid using organic solvents and reduce solvent costs. However, due to the low solubility of the polymer in water, the method has to use a large amount of surfactants; in order to increase the reaction rate, the scheme uses a large amount of bases, catalysts, and ligands, and also prolongs the reaction time, which leads to a substantial increase in the actual cost of the scheme and makes the scheme lose its industrial value.

[0007] The post-treatment of polyphenylene ether in the prior art also includes problems such as catalyst recovery, and a certain processing cost is required for this. Therefore, how to develop a suitable method for preparing polyphenylene ether is of great significance. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the catalyst utilization rate in the existing preparation process is low, which is not conducive to large-scale production.

[0009] In order to solve the above technical problems, the present invention provides a method for preparing polyphenylene ether, which comprises the following steps: (1) adding a raw material monomer, a ligand and toluene into a first reaction container and mixing to obtain a mixed material, wherein the raw material monomer has a structure as shown in Formula I; ...Formula I In Formula I, X1 and X2 are each selected from halogen atoms, C1-C 10 Primary alkyl or C1-C 10 Secondary alkyl, C2-C 10 Alkenyl, C3-C 10 Alkenyl alkyl, C2-C 10 Alkynyl, C3-C 10 Alkynylalkyl, C1-C 10 Aminoalkyl or C1-C 10 Any one or a combination of at least two of hydroxyalkyl; Y1 and Y2 are selected from hydrogen, halogen atoms, C1-C 10 Primary alkyl, C1-C10 Secondary alkyl, C2-C 10 Alkenyl, C3-C 10 Alkenyl alkyl, C2-C 10 Alkynyl, C3-C 10 Alkynylalkyl, C1-C 10 Aminoalkyl or C1-C 10 Any one or a combination of at least two of hydroxyalkyl groups; The ligand includes an amine compound and / or a compound represented by formula II; ...Formula II In formula II, R1, R2, R4, and R5 are each independently a hydrogen atom or an alkyl group, the alkyl group is a straight-chain alkyl group or a branched-chain alkyl group, and R3 is a saturated alkyl group of 2 carbon atoms; The reaction solvent includes aromatic hydrocarbons or halogenated hydrocarbons; The mass percentage of the raw material monomer in toluene is 10% to 70%, and the amount of the ligand is 0.1% to 100% of the amount of the raw material monomer; (2) adding a copper catalyst and water into a second reaction vessel, adding the mixed material in step (1) into the second reaction vessel for reaction, and separating the organic phase to obtain a crude product; the amount of the copper catalyst is 0.1% to 100% of the amount of the raw material monomer; the amount of water is 0.1 to 2 times the volume of the mixed material in step (1); (3) adding the crude product obtained in step (2) into a third reaction container, adding a chelating agent and water for washing, and obtaining an organic phase and an aqueous phase after standing and stratification, separating the organic phase into a fourth reaction container, and obtaining the polyphenylene ether after a first precipitation and a second precipitation; The copper catalyst and water added in step (2) can be replaced by the water phase recovered in step (2), and the chelating agent and water added in step (3) can be replaced by the water phase recovered in step (3).

[0010] The preparation method provided by the present invention uses toluene and water as solvents to produce polyphenylene ether with a molecular weight distribution of less than 2.0. The copper catalyst enriched in the water phase is repeatedly applied to increase the catalyst utilization rate and reduce the amount of waste water. The method has a simple process, a high catalyst utilization rate, and is suitable for large-scale production.

[0011] In the present invention, the reaction solvent includes substances that can dissolve the polymerization monomers and catalysts, including aromatic hydrocarbons (such as benzene, toluene, ethylbenzene, xylene), halogenated hydrocarbons (such as chloroform, dichloroethane, trichloroethane, chlorobenzene); preferably toluene.

[0012] The amounts used in the reaction of the present invention are all molar amounts except for the volumes or masses specifically marked.

[0013] Preferably, the raw material monomer in step (1) is 2,6-dimethylphenol; the mass percentage of the raw material monomer in the solvent is 50%.

[0014] Preferably, the ligand in step (1) is a combination of an amine compound and a compound represented by formula II; the amount of the ligand is: the amine compound is 1% of the amount of the raw material monomer, and the compound represented by formula II is 1% of the amount of the raw material monomer.

[0015] In the present invention, the use of amines, on the one hand, a higher proportion of amine ligands can significantly increase the selectivity of the polymerization reaction and reduce the generation of by-product quinone substances; on the other hand, increasing the polarity and alkalinity of the solvent also has a significant positive effect on the selectivity of the reaction. At the same time, the amine compound also acts as a phase transfer catalyst, which helps the reaction between the oil / water phases.

[0016] The compound shown in formula II is a diamine compound. The complex constant of diamine compounds with copper is higher than that of ordinary amine ligands. The use of diamine compounds can significantly reduce the amount of ligands used, while achieving higher reaction selectivity. During the multiple application of the aqueous phase of the reaction solution, the amine ligands that are weakly bound to copper ions are mostly lost to the organic phase during the phase separation process, so they need to be supplemented in the raw materials, while the loss of diamine compounds is low during the phase separation process, and there is no need to make frequent supplements during the aqueous phase application process.

[0017] Preferably, the amine compound includes any one of primary amine, tertiary amine or secondary amine. The primary amine includes any one of n-propylamine, isopropylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine or cyclohexylamine.

[0018] The secondary amine includes any one of di-n-propylamine, di-n-butylamine, di-tert-butylamine, n-butyl-n-pentylamine, morpholine or di-n-hexylamine, preferably morpholine. Among them, morpholine, as a cyclic secondary amine, can provide the same complexing ability as secondary amines such as piperidine, and has stronger water solubility, so that the proportion of loss in the toluene solvent in the water / toluene two-phase system is lower, and the prepared polyphenylene ether has less impurities enclosed.

[0019] The tertiary amine includes any one of triethylamine, tri-n-propylamine, tri-n-butylamine, dimethyl-n-butylamine or dimethyl-n-pentylamine.

[0020] Preferably, the compound represented by formula II is N , N , N ´, N ´-Tetramethyl-1,3-diaminopropane or N , N ´-Di-tert-butylethylenediamine.

[0021] Preferably, the copper catalyst in step (2) comprises any one or a combination of at least two of cuprous compounds, copper compounds or copper salts; Preferably, the copper catalyst is any one of cuprous chloride, cuprous bromide, cupric chloride or cupric bromide; Preferably, the amount of the copper catalyst used is 2% of the amount of the raw material monomer.

[0022] In the present invention, copper catalyst and water are added to the reactor, stirred and dissolved, and the materials in the mixing kettle are mixed and added to the reactor. After nitrogen replacement of the reactor is maintained while stirring, the oxygen content is reduced to less than 2%, the temperature in the kettle is raised to the reaction temperature, the two phases are mixed by heat preservation and stirring, and oxygen is introduced to start the reaction, the monomer raw material is gradually converted into the product polyphenylene ether, and the viscosity of the system gradually increases. The reaction time is determined according to the molecular weight of the target product. After the reaction is completed, the oxygen input is stopped, the stirring is turned off, and the reaction solution is allowed to stand to stratify. The upper organic phase of the reactor is pumped into the washing kettle, and the lower aqueous phase is retained, which can be applied multiple times.

[0023] Since the copper salt can be used multiple times by phase separation, the amount of the catalyst can be increased to increase the polymerization reaction rate. The present invention can control the reaction rate by the amount of the copper salt.

[0024] Preferably, in step (2), an inorganic salt is dissolved in the water; the mass percentage of the inorganic salt in the water is 0.1% to 30%.

[0025] The inorganic salt can specifically be sodium chloride, potassium chloride, sodium bromide, potassium bromide, lithium chloride, sodium sulfate, calcium chloride, ammonium chloride, preferably sodium chloride. The addition of alkaline inorganic salts to the aqueous phase provides a polar environment for the solution to maintain the activity of the catalyst, and on the other hand increases the density of the aqueous phase, which helps the two-phase separation. In the present invention, the mass percentage of the inorganic salt is preferably 10%. Too low a mass percentage will result in difficulty in emulsification; too high a mass percentage will affect the stirring and mixing effect, and the reaction rate is low.

[0026] Preferably, the reaction temperature in step (2) is 30-70°C, preferably 50°C.

[0027] Preferably, the reaction time in step (2) is 20 to 150 min, preferably 40 to 80 min.

[0028] Preferably, the reaction in step (2) is carried out in an atmosphere with an oxygen volume concentration of 21% to 100%, preferably 90% to 100%.

[0029] In the present invention, the amount of oxygen used per hour is 2.2 times the equivalent of the raw material monomer.

[0030] Preferably, the chelating agent in step (3) comprises any one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, trisodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium citrate or trisodium nitrilotriacetate.

[0031] Preferably, the mass concentration of the chelating agent in water is 1% to 20%, preferably 5%.

[0032] In the third reaction container, the total amount of the chelating agent and water is 0.1 to 2 times, preferably 0.5 times, of the reaction solution in the previous step.

[0033] Preferably, a poor solvent is used in both the first precipitation and the second precipitation.

[0034] Preferably, the poor solvent comprises C1-C4 alcohol and / or water, preferably a methanol aqueous solution.

[0035] Preferably, in the first precipitation, the mass ratio of the organic phase to the poor solvent is (0.2-5):1, preferably 0.8:1.

[0036] Preferably, in the second precipitation, the mass ratio of the organic phase to the poor solvent is (0.2-1.2):1, preferably 0.7:1.

[0037] In the present invention, the material is discharged from the precipitation kettle and is subjected to steps such as filtration and drying to obtain a powdered polyphenylene ether product.

[0038] During the first precipitation, the slurry needs to be maintained at 40-70°C and stirred for 30 minutes after precipitation. On the one hand, the solvent residue in the particles is reduced, and on the other hand, residual small molecular impurities, including quinone by-products, are removed by washing. The clear liquid in the kettle is discharged by standing and using the solid to settle to the bottom. The clear liquid contains a small amount of low molecular weight polyphenylene ether and most of the quinone by-products. This step separates the low molecular weight products in the product, further reducing the molecular weight distribution of the product polyphenylene ether; During the second precipitation, after adding the poor solvent, the mixture is quickly stirred to form a slurry containing both solid and liquid polyphenylene ether, and finally filtered and dried to obtain a solid product. Dividing the precipitation step into two steps not only saves the amount of poor solvent used, but also separates impurities and low molecular weight products in the solid product, thereby further reducing the molecular weight of the product step by step.

[0039] In the present invention, the first reaction container is generally a mixing kettle, the second reaction container is generally a reaction kettle, the third reaction container is generally a washing kettle, and the fourth reaction container is generally a precipitation kettle.

[0040] In the preparation process of the present invention, a slurry containing both solid and liquid polyphenylene ether is usually formed after precipitation. The filtration method generally adopts a conventional method for separating the solid and liquid phases, such as a suction filter barrel, optional filtration, centrifugal filtration, etc.

[0041] The above-mentioned method for drying the polyphenylene ether may be vacuum drying, nitrogen drying or other known industrial drying methods, or known industrial dryers such as drum dryers may be used.

[0042] In the process of repeated use and application, only raw material monomers and amine ligands need to be added to the mixing kettle without adding diamine ligands, and the water phases of the reaction kettle and the washing kettle can be used multiple times.

[0043] The implementation of the present invention has the following beneficial effects: (1) Polyphenylene ether is obtained by polymerization reaction in a toluene / water mixture. On the one hand, due to the difference in solubility of the catalyst copper complex in the organic phase and the aqueous phase, the raw monomer has a considerable solubility in water. In the early stage of the reaction, the reaction is mainly oxidative coupling in the aqueous phase. As the degree of polymerization of the reaction product increases, the reaction gradually turns to proceed only at the interface between the two phases, the reaction rate decreases significantly, and the process is controllable. On the other hand, the product is enriched in the organic phase. Since the long chain of polyphenylene ether is difficult to contact and combine with the catalyst in the aqueous phase, the redistribution reaction between the polymer chains is inhibited, which greatly reduces the increase in the molecular weight distribution of the polymer caused by the redistribution reaction.

[0044] (2) Compared with the precipitation method for preparing polyphenylene ether, the toluene / water phase reaction environment has two advantages. First, the molecular weight distribution is narrower, and low molecular weight polyphenylene ether is soluble in the organic phase and can participate in the polymerization more evenly, while in non-aqueous phase reaction or precipitation method reaction, only the outer layer of the particles participates in the polymerization; second, polyphenylene ether with a molecular weight of 10,000-20,000 can be prepared, which can prepare more types of polyphenylene ether products compared with aqueous phase reaction or precipitation method reaction.

[0045] (3) Compared with the homogeneous method for preparing polyphenylene ether, the toluene / water system can reduce the amount of solvent toluene, which can meet the requirements of ensuring stirring efficiency while using less toluene, and avoid the excessive viscosity of the system causing stirring difficulties after reducing the amount of toluene, which in turn leads to insufficient mixing of the system, local overheating that increases side reactions, and uneven reactions that increase the molecular weight distribution of the product.

[0046] (4) The polyphenylene ether preparation method proposed in the present invention reduces the catalyst recovery step. The cuprous salt catalyst can be recovered by simple separation, and the aqueous phase containing the catalyst can be reused multiple times, thereby reducing unnecessary costs caused by catalyst loss. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0048] Example 1 This embodiment provides a method for preparing 8000 Dalton polyphenylene ether (1) A 15L mixing kettle was used. 4.98 kg (40 mol, 98%) of the raw material monomer 2,6-dimethylphenol and 5 kg of the reaction solvent toluene were added into the kettle. Stirring was started to mix the materials evenly.

[0049] (2) The reactor is a 25L reactor. 40.4g of cuprous bromide (0.4mol, 98%), 40g (0.4mol) of catalyst ligand morpholine and 68.4g (0.4mol) of N,N-di-tert-butylethylenediamine, 500g of sodium chloride (10%) and 4.5kg of water are added to the reactor and stirred to dissolve and mix evenly. After mixing, the materials in the mixing kettle are pumped into the reactor. Stirring is maintained while nitrogen is replaced in the reactor to reduce the oxygen content to less than 2%. The temperature in the reactor is raised to 50°C. After being stirred for 5 minutes, oxygen is introduced from the oxygen inlet at the bottom of the reactor at an oxygen rate of 2.82kg / h. After the reaction starts, the stirring power is increased to prevent the aqueous phase and the organic phase from stratification. As the monomer raw material is gradually converted into the product polyphenylene ether, the viscosity of the system gradually increases. After 55 minutes of reaction time from the start of oxygen introduction, the oxygen input is stopped and nitrogen is introduced to purge the oxygen content above the liquid surface to less than 2%. Turn off the stirring and let it stand for 15 minutes to allow the reaction liquid to separate into layers. Pump the upper organic phase of the reaction kettle into the washing kettle through a pump. The lower aqueous phase in the kettle is retained and can be used multiple times. Take a sample of the aqueous phase and titrate to determine the cuprous ion content.

[0050] (3) The washing kettle is a 25L kettle. Add 4.75kg of water and 250g of chelating agent disodium ethylenediaminetetraacetic acid (5%) into it, stir to dissolve and mix evenly. After the upper organic phase in the reaction kettle is pumped into the washing kettle, start stirring to mix the two phases. Heat the mixed solution to 45°C, keep stirring vigorously for 30 minutes, and then let it stand for 15 minutes to separate the organic phase and the aqueous phase. Pump the upper organic phase of the washing kettle into the precipitation kettle. The lower aqueous phase in the washing kettle can be retained and reused multiple times. Take a sample of the aqueous phase in the washing kettle and titrate to measure the EDTA content of the aqueous phase.

[0051] (4) The precipitation kettle is a 30L kettle. The upper organic phase of the washing kettle is pumped into the precipitation kettle. After the solution temperature is lowered to below 30°C, 12.5kg of 95% methanol is added to the kettle. Stirring is maintained during the period to precipitate the polyphenylene ether solid. After stirring for 30 minutes, the polyphenylene ether solid is allowed to stand for 15 minutes to precipitate. A total of 15.3kg of the upper clear liquid of the material is removed by pump. 10kg of 95% methanol water (0.7:1) is added to the kettle again, and vigorously stirred for 30 minutes to complete the precipitation. After filtering, the obtained wet product is placed in a vacuum drying drum dryer with a temperature gradually increased from 40°C to 120°C for drying until the volatile matter of the product is reduced to less than 0.5wt%, and a total of 5.35kg of polyphenylene ether powder is obtained. The intrinsic viscosity of the polymer is measured and calculated using an Ubbelohde viscometer according to the method in GBT1632-1993. The molecular weight of the polymer is Mn=7780 and the molecular weight distribution D=1.81.

[0052] Example 2 In this example, the waste liquid in Example 1 was used as the reaction liquid for the reaction. (1) Add 4.98 kg (40 mol, 98%) of monomer 2,6-dimethylphenol and 5 kg of reaction solvent toluene into a mixing kettle, and start stirring to mix the materials evenly.

[0053] (2) The remaining aqueous phase after the separation in Example 1 is retained in the reactor. The materials in the mixing kettle are pumped into the reactor. Stirring is maintained while the reactor is replaced with nitrogen to reduce the oxygen content to less than 2%. The temperature in the reactor is raised to 50°C. After being kept warm and stirred for 5 minutes, oxygen is introduced from the oxygen inlet at the bottom of the reactor at an oxygen rate of 2.82 kg / h. After the reaction starts, the stirring power is increased to allow the aqueous phase and the organic phase to be fully mixed. As the monomer raw material is gradually converted into the product polyphenylene ether, the viscosity of the system gradually increases. After 55 minutes of reaction time from the start of oxygen introduction, the oxygen input is stopped, and nitrogen is introduced to purge the oxygen content above the liquid surface to less than 2%. Stirring is turned off, and the reaction solution is allowed to stand for 15 minutes to separate into layers. The upper organic phase of the reactor is pumped into the washing kettle by a pump. The lower aqueous phase in the kettle is retained, and the aqueous phase is sampled and titrated to determine the cuprous ion content.

[0054] (3) The remaining EDTA solution after separation in Example 1 is retained in the washing kettle, and the upper organic phase of the reaction kettle is pumped into the washing kettle. Stirring is started to mix the two phases, and the mixed solution is heated to 45°C. After vigorous stirring for 30 minutes, it is allowed to stand for 15 minutes to separate the organic phase and the aqueous phase. The upper organic phase of the washing kettle is pumped into the precipitation kettle by a pump. The lower aqueous phase in the washing kettle is retained, and the aqueous phase of the washing kettle is sampled and the EDTA content of the aqueous phase is measured by titration.

[0055] (4) The upper organic phase of the washing kettle was pumped into the precipitation kettle, and the poor solvent was added in batches to precipitate the product in the same manner as in Example 1, and then filtered and dried to obtain a total of 5.35 kg of polyphenylene ether powder. The intrinsic viscosity of the polymer was measured and calculated using an Ubbelohde viscometer according to the method in GBT1632-1993, and the molecular weight of the polymer was Mn=7975, and the molecular weight distribution D=1.85.

[0056] Example 3, Example 4 and Example 5 The steps of Example 2 were repeated, and the aqueous phase of the reaction kettle and the washing kettle was used multiple times. The aqueous phase of the reaction kettle and the washing kettle was sampled and titrated in the same manner as in Example 2 to determine the cuprous content and EDTA content. The intrinsic viscosity of the polymer was determined using an Ubbelohde viscometer, and the molecular weight and molecular weight distribution of the polymer were calculated.

[0057] Example 6 This embodiment provides a method for preparing 16000 Dalton polyphenylene ether (1) Add 4.98 kg (40 mol, 98%) of 2,6-dimethylphenol and 7.5 kg of toluene as the reaction solvent into a mixing kettle, and start stirring to mix the materials evenly.

[0058] (2) The remaining aqueous phase after the separation in Example 5 is retained in the reactor. The materials in the mixing kettle are pumped into the reactor. Stirring is maintained while the reactor is replaced with nitrogen to reduce the oxygen content to less than 2%. The temperature in the reactor is raised to 50°C. After being kept warm and stirred for 5 minutes, oxygen is introduced from the oxygen inlet at the bottom of the reactor at an oxygen rate of 2.82 kg / h. After the reaction starts, the stirring power is increased to allow the aqueous phase and the organic phase to be fully mixed. As the monomer raw material is gradually converted into the product polyphenylene ether, the viscosity of the system gradually increases. After 80 minutes of reaction time from the start of oxygen introduction, the oxygen input is stopped, and nitrogen is introduced to purge to reduce the oxygen content above the liquid surface to less than 2%. Stirring is turned off, and the reaction solution is allowed to stand for 15 minutes to separate into layers. The upper organic phase of the reactor is pumped into the washing kettle by a pump. The lower aqueous phase in the kettle is retained, and the aqueous phase is sampled and titrated to determine the cuprous ion content.

[0059] (3) The remaining EDTA solution after separation in Example 1 is retained in the washing kettle, and the upper organic phase of the reaction kettle is pumped into the washing kettle. Stirring is started to mix the two phases, and the mixed solution is heated to 50°C. After vigorous stirring for 30 minutes, it is allowed to stand for 15 minutes to separate the organic phase and the aqueous phase. The upper organic phase of the washing kettle is pumped into the precipitation kettle by a pump. The lower aqueous phase in the washing kettle is retained, and the aqueous phase of the washing kettle is sampled and the EDTA content of the aqueous phase is measured by titration.

[0060] (4) Pump the upper organic phase of the washing kettle into the precipitation kettle, lower the solution temperature to below 30°C, add 15.6 kg of 95% methanol to the kettle, keep stirring during the period, and precipitate the polyphenylene ether solid. Stir for 30 minutes and let it stand for 15 minutes to precipitate the polyphenylene ether solid. Use a pump to remove 21 kg of the upper clear liquid of the material. Add 5 kg of 95% methanol water (0.7:1) to the kettle again, and stir vigorously for 30 minutes to complete the precipitation. Then filter and dry according to the same method as Example 1 to obtain a total of 5.35 kg of polyphenylene ether powder. According to the method in GBT1632-1993, the intrinsic viscosity of the polymer was determined using an Ubbelohde viscometer and calculated to obtain the molecular weight of the polymer Mn=15753 and the molecular weight distribution D=1.94.

[0061] Example 7 This embodiment provides a method for preparing 4000 Dalton polyphenylene ether (1) Add 4.98 kg (40 mol, 98%) of monomer 2,6-dimethylphenol and 4 kg of reaction solvent toluene into a mixing kettle, and start stirring to mix the materials evenly.

[0062] (2) The remaining aqueous phase after the separation in Example 6 is retained in the reactor. The materials in the mixing kettle are pumped into the reactor. Stirring is maintained while the reactor is replaced with nitrogen to reduce the oxygen content to less than 2%. The temperature in the kettle is raised to 50°C. After being kept warm and stirred for 5 minutes, oxygen is introduced from the oxygen inlet at the bottom of the kettle at an oxygen rate of 2.82 kg / h. After the reaction starts, the stirring power is increased to allow the aqueous phase and the organic phase to be fully mixed. As the monomer raw material is gradually converted into the product polyphenylene ether, the viscosity of the system gradually increases. After 40 minutes of timing reaction from the start of oxygen introduction, the oxygen input is stopped, and nitrogen is introduced to purge to reduce the oxygen content above the liquid surface to less than 2%. Stirring is turned off, and the reaction solution is allowed to stand for 15 minutes to separate into layers. The upper organic phase of the reactor is pumped into the washing kettle by a pump. The lower aqueous phase in the kettle is retained, and the aqueous phase is sampled and titrated to determine the cuprous ion content.

[0063] (3) The remaining EDTA solution after separation in Example 1 is retained in the washing kettle, and the upper organic phase of the reaction kettle is pumped into the washing kettle. Stirring is started to mix the two phases, and the mixed solution is heated to 40°C. After vigorous stirring for 30 minutes, it is allowed to stand for 15 minutes to separate the organic phase and the aqueous phase. The upper organic phase of the washing kettle is pumped into the precipitation kettle by a pump. The lower aqueous phase in the washing kettle is retained, and the aqueous phase of the washing kettle is sampled and the EDTA content of the aqueous phase is measured by titration.

[0064] (4) Pump the upper organic phase of the washing kettle into the precipitation kettle, lower the solution temperature to below 30°C, add 11.2 kg of 95% methanol to the kettle, keep stirring during the period, and precipitate the polyphenylene ether solid. Stir for 30 minutes and let it stand for 15 minutes to precipitate the polyphenylene ether solid. Use a pump to remove the upper clear liquid of the material, a total of 13.1 kg. Add 5 kg of 95% methanol water (0.7:1) to the kettle again, and stir vigorously for 30 minutes to complete the precipitation. Then filter and dry according to the same method as Example 1 to obtain a total of 5.35 kg of polyphenylene ether powder. According to the method in GBT1632-1993, the intrinsic viscosity of the polymer was determined using an Ubbelohde viscometer and calculated to obtain the molecular weight of the polymer Mn=3887 and the molecular weight distribution D=1.72.

[0065] Example 8 The difference between this embodiment and embodiment 1 is that the ligand of the catalyst is replaced by 1.2 mol of triethylamine, and the other raw material dosages or operation steps are consistent with those of embodiment 1. After phase separation, washing and precipitation steps, a total of 5.35 kg of polyphenylene ether powder is obtained, with a molecular weight Mn=7142 and a molecular weight distribution D=1.87. The copper ion concentration of the aqueous phase of the reactor is calculated by titration to be 7.43×10 - 2 mol / L, catalyst loss was 7.12%.

[0066] Example 9 The difference between this embodiment and embodiment 1 is that the amine ligand is replaced by 1.2 mol of di-n-propylamine, and the other raw material dosages or operation steps are consistent with those of embodiment 1. After phase separation, washing and precipitation steps, a total of 5.35 kg of polyphenylene ether powder is obtained, with a molecular weight Mn=7325 and a molecular weight distribution D=1.91. The copper ion concentration of the aqueous phase of the reactor is calculated by titration to be 7.21×10 -2 mol / L, catalyst loss was 9.88%.

[0067] Example 10 The difference between this embodiment and embodiment 1 is that the amine ligand is replaced by 1.2 mol of n-propylamine, and the other raw material dosages or operation steps are consistent with those of embodiment 1. After phase separation, washing and precipitation steps, a total of 5.35 kg of polyphenylene ether powder is obtained, with a molecular weight Mn=6854 and a molecular weight distribution D=1.85. The copper ion concentration of the aqueous phase of the reactor is calculated by titration to be 6.55×10 -2 mol / L, catalyst loss was 18.12%.

[0068] Wastewater treatment (1) There is a total of 5.25 kg of waste water in the reactor. Add 30 g of sodium sulfide and heat and stir to precipitate copper sulfide solid. After filtering out the solid, the remaining liquid can be used again.

[0069] (2) Add 30g of sodium sulfide to the 5.25kg wastewater in the reactor, heat and stir, precipitate copper sulfide solid, filter out the copper sulfide solid and recover it. Distill the remaining liquid to increase the concentration and then cool it down to precipitate sodium chloride solid and recover it.

[0070] Comparative Example 1 This comparative example uses the precipitation method to synthesize polyphenylene ether (1) Add 4.98 kg (40 mol, 98%) of the raw material monomer 2,6-dimethylphenol and 15 kg of the reaction solvent methanol into a mixing kettle, and start stirring to mix the materials evenly.

[0071] (2) The reactor is a 25L reactor. Add 40.4g of cuprous bromide (0.4mol, 98%), 40g (0.4mol) of catalyst ligand morpholine and 68.4g (0.4mol) of N,N-di-tert-butylethylenediamine, and 100g of methanol as solvent. Stir and dissolve to mix evenly. After mixing, pump the materials in the mixing kettle into the reactor. Keep stirring and replace the reactor with nitrogen to reduce the oxygen content to less than 2%. Raise the temperature in the kettle to 50°C. After keeping the temperature and stirring for 5min, introduce oxygen from the oxygen inlet at the bottom of the kettle at an oxygen rate of 2.82kg / h. After the reaction starts, increase the stirring power. As the monomer raw material gradually converts into the product polyphenylene ether, solid particles gradually precipitate in the system. After 55min of reaction time from the start of oxygen introduction, stop the oxygen input and introduce nitrogen to purge the oxygen content above the liquid surface to less than 2%. Turn off the stirring and let it stand for 15min to allow the reaction liquid to separate. The supernatant was removed using a pump, 5 kg of toluene was injected into the kettle, and the solid was dissolved by stirring, and the solution was introduced into the washing kettle.

[0072] (3) Keep the remaining EDTA solution after the previous batch of reaction separation in the washing kettle, pump the reaction kettle solution into the washing kettle, heat and stir and wash in the same way, let it stand for phase separation, and pump the upper organic phase of the washing kettle into the precipitation kettle.

[0073] (4) The upper organic phase of the washing kettle was pumped into the precipitation kettle, and the poor solvent was added in batches to precipitate the product in the same manner as in Example 1, and then filtered and dried to obtain a total of 5.35 kg of polyphenylene ether powder. The intrinsic viscosity of the polymer was measured and calculated using an Ubbelohde viscometer according to the method in GBT1632-1993, and the molecular weight of the polymer was Mn=4189, and the molecular weight distribution D=2.25.

[0074] Comparative Example 2 This comparative example uses a homogeneous method to synthesize polyphenylene ether (1) Add 1.0 kg (8 mol, 98%) of the raw material monomer 2,6-dimethylphenol and 5 kg of the reaction solvent toluene into a mixing kettle, and start stirring to mix the materials evenly.

[0075] (2) The reactor is a 25L reactor. Add 8.1g of cuprous bromide (0.08mol, 98%), 8.0g (0.08mol) of catalyst ligand morpholine and 13.7g (0.08mol) of N,N-di-tert-butylethylenediamine, and 20g of methanol as solvent. Stir and dissolve to mix evenly. After mixing, pump the materials in the mixing kettle into the reactor. Keep stirring and replace the reactor with nitrogen to reduce the oxygen content to less than 2%. Raise the temperature in the kettle to 50°C. After keeping the temperature and stirring for 5min, introduce oxygen from the oxygen inlet at the bottom of the kettle at an oxygen rate of 2.82kg / h. After the reaction starts, increase the stirring power. As the monomer raw material is gradually converted into the product polyphenylene ether, the viscosity of the material in the system gradually increases. After 35min of reaction time from the start of oxygen introduction, stop the oxygen input and introduce nitrogen to purge the oxygen content above the liquid surface to less than 2%. Turn off the stirring and introduce the solution into the washing kettle.

[0076] (3) Keep the remaining EDTA solution after the previous batch of reaction separation in the washing kettle, pump the reaction kettle solution into the washing kettle, heat and stir and wash in the same way, let it stand for phase separation, and pump the upper organic phase of the washing kettle into the precipitation kettle.

[0077] (4) Pump the upper organic phase of the washing kettle into the precipitation kettle, lower the solution temperature to below 30°C, add 7.5 kg of 95% methanol to the kettle, keep stirring during the process, and precipitate the polyphenylene ether solid. Stir for 30 minutes and let it stand for 15 minutes to precipitate the polyphenylene ether solid. Use a pump to remove the upper clear liquid of the material, a total of 12.1 kg. Add 1 kg of 95% methanol water (0.7:1) to the kettle again, and stir vigorously for 30 minutes to complete the precipitation. Then filter and dry according to the same method as Example 1 to obtain a total of 1.05 kg of polyphenylene ether powder. According to the method in GBT1632-1993, the intrinsic viscosity of the polymer was determined using an Ubbelohde viscometer and calculated to obtain the molecular weight of the polymer Mn=7627 and the molecular weight distribution D=1.89.

[0078] The molecular weight distribution of the products of the above examples and comparative examples was calculated, and the results are shown in Table 1 below: Table 1 Molecular weight distribution data of products of Examples and Comparative Examples

[0079] From the data in Table 1 we can see that: The sampling and titration data of the aqueous phase in the reactor indicate that the copper catalyst has low losses during multiple reactions and phase separation, which can meet the needs of multiple applications. Examples 1-7 show that multiple applications of the aqueous phase in the scheme of the present invention do not significantly affect the reaction activity, and the scheme can stably obtain polyphenylene ether products. In Examples 8-10, different ligands were used to prepare the reaction catalyst. In addition to having a certain effect on the reaction activity, the change of the ligand during the implementation of the scheme also affects the proportion of the catalyst lost during the scheme.

[0080] Examples 6-7 show that the method proposed in the present invention can meet the production of polyphenylene ether with a molecular weight range of 4000-16000. Different types of polyphenylene ether products can be obtained by simply adjusting the amount of solvent in the mixing kettle and changing the reaction time during the reaction.

[0081] Comparative Examples 1-2 show that the polyphenylene ether preparation method proposed in the present invention can reduce the amount of solvent toluene, increase the efficiency of catalyst use, and obtain a high-quality polyphenylene ether product that is nearly equivalent to that of the homogeneous polymerization method.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing polyphenylene ether, characterized in that: The method comprises the following steps: (1) adding a raw material monomer, a ligand and toluene into a first reaction container and mixing to obtain a mixed material, wherein the raw material monomer has a structure as shown in Formula I; …Formula I In Formula I, X1 and X2 are each selected from halogen atoms, C1-C 10 Primary alkyl or C1-C 10 Secondary alkyl, C2-C 10 Alkenyl, C3-C 10 Alkenyl alkyl, C2-C 10 Alkynyl, C3-C 10 Alkynylalkyl, C1-C 10 Aminoalkyl or C1-C 10 Any one or a combination of at least two of hydroxyalkyl; Y1 and Y2 are selected from hydrogen, halogen atoms, C1-C 10 Primary alkyl, C1-C 10 Secondary alkyl, C2-C 10 Alkenyl, C3-C 10 Alkenyl alkyl, C2-C 10 Alkynyl, C3-C 10 Alkynylalkyl, C1-C 10 Aminoalkyl or C1-C 10 Any one or a combination of at least two of hydroxyalkyl groups; The ligand includes an amine compound and / or a compound represented by formula II; ...Formula II In formula II, R1, R2, R4, and R5 are each independently a hydrogen atom or an alkyl group, the alkyl group is a straight-chain alkyl group or a branched-chain alkyl group, and R3 is a saturated alkyl group of 2 carbon atoms; The reaction solvent includes aromatic hydrocarbons or halogenated hydrocarbons; The mass percentage of the raw material monomer in toluene is 10% to 70%, and the amount of the ligand is 0.1% to 100% of the amount of the raw material monomer; (2) adding a copper catalyst and water into a second reaction vessel, adding the mixed material in step (1) into the second reaction vessel for reaction, and separating the organic phase to obtain a crude product; the amount of the copper catalyst is 0.1% to 100% of the amount of the raw material monomer; the amount of water is 0.1 to 2 times the volume of the mixed material in step (1); (3) adding the crude product obtained in step (2) into a third reaction container, adding a chelating agent and water for washing, and obtaining an organic phase and an aqueous phase after standing and stratification, separating the organic phase into a fourth reaction container, and obtaining the polyphenylene ether after a first precipitation and a second precipitation; The copper catalyst and water added in step (2) can be replaced by the water phase recovered in step (2), and the chelating agent and water added in step (3) can be replaced by the water phase recovered in step (3).

2. The method according to claim 1, characterized in that The raw material monomer in step (1) is 2,6-dimethylphenol; the mass percentage of the raw material monomer in the solvent is 50%.

3. The method according to claim 1, characterized in that The ligand in step (1) is a combination of an amine compound and a compound represented by formula II; the amount of the ligand is: the amine compound is 1% of the amount of the raw material monomer, and the compound represented by formula II is 1% of the amount of the raw material monomer.

4. The method according to claim 1 or 3, characterized in that: The amine compound includes any one of a primary amine, a tertiary amine or a secondary amine; The primary amine includes any one of n-propylamine, isopropylamine, n-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine or cyclohexylamine; The secondary amine includes any one of di-n-propylamine, di-n-butylamine, di-tert-butylamine, n-butyl-n-pentylamine, morpholine or di-n-hexylamine; The tertiary amine includes any one of triethylamine, tri-n-propylamine, tri-n-butylamine, dimethyl-n-butylamine or dimethyl-n-pentylamine.

5. The method according to claim 1 or 3, characterized in that: The compound represented by formula II is N , N , N ´, N ´-Tetramethyl-1,3-diaminopropane or N , N ´-Di-tert-butylethylenediamine.

6. The method according to claim 1, characterized in that The copper catalyst in step (2) includes any one of cuprous compounds, copper compounds or copper salts, or a combination of at least two of them.

7. The method according to claim 6, characterized in that The copper catalyst is any one of cuprous chloride, cuprous bromide, cupric chloride or cupric bromide; the amount of the copper catalyst used is 2% of the amount of the raw material monomer.

8. The method according to claim 1, characterized in that In step (2), an inorganic salt is dissolved in the water; the mass percentage of the inorganic salt in the water is 0.1% to 30%.

9. The method according to claim 1, characterized in that: The chelating agent in step (3) includes any one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, trisodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, sodium citrate or trisodium nitrilotriacetate; the mass concentration of the chelating agent in water is 1% to 20%.

10. The method according to claim 1, characterized in that In the fourth reaction container, the first precipitation and the second precipitation both use a poor solvent; the poor solvent includes a C1-C4 alcohol and / or water; In the first precipitation, the mass ratio of the organic phase to the poor solvent is (0.2-5):1; in the second precipitation, the mass ratio of the organic phase to the poor solvent is (0.2-1.2):1.

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