Process for the preparation of polyphenylene ether

Abstract

The present invention provides a preparation method capable of reducing energy consumption by eliminating the need for a separate process to isolate and purify o-methylphenol produced after phenol alkylation reaction, and also capable of preparing polyphenylene ether in an excellent yield under mild oxidative coupling reaction conditions.

Description

Technical Field

[0001] Cross-referencing related applications

[0002] This application is based on and claims priority to Korean Patent Applications 10-2021-0087374 and 10-2021-0087375, both filed on July 2, 2021, the disclosures of which are incorporated herein by reference in their entirety.

[0003] This invention relates to a method for preparing polyphenylene ether. Background Technology

[0004] Polyphenylene oxide (PPO) is an engineering plastic exhibiting chemical resistance, high heat resistance, and excellent mechanical and electrical properties. Commercial PPO typically has a number-average molecular weight of 20,000 g / mol to 60,000 g / mol and is synthesized through oxidative coupling of phenolic monomers. Commercial PPO consists of oligomers with a number-average molecular weight of 1300 g / mol to 2700 g / mol and polymers with a number-average molecular weight of 17,000 g / mol to 29,000 g / mol.

[0005] Meanwhile, in the preparation of PPO, 2,6-dimethylphenol is obtained through the alkylation of phenol. In this case, in addition to 2,6-dimethylphenol, byproducts o-cresol and 2,4,6-trimethylphenol are also generated. Therefore, a process for separating and purifying these byproducts is required. However, because the boiling point difference between these byproducts and 2,6-dimethylphenol is approximately 10°C, separation and purification are difficult and expensive. In particular, to separate the main byproduct o-cresol, a 140-stage column or azeotropic distillation with decane is used, which is the main reason for the increased cost of preparing 2,6-dimethylphenol and using 2,6-dimethylphenol to prepare PPO.

[0006] Therefore, there is a need to develop a method for preparing PPO that can reduce energy consumption. Summary of the Invention

[0007] Technical issues

[0008] This invention provides a method for preparing polyphenylene ether, which reduces energy consumption by eliminating the need for a separate process for separating and purifying o-methylphenol generated after the alkylation reaction of phenol, and also enables the preparation of polyphenylene ether in excellent yield under mild oxidative coupling reaction conditions.

[0009] Technical solution

[0010] This invention provides a method for preparing polyphenylene ether, the method comprising: step 1, preparing a mixture comprising 2,6-dimethylphenol and o-methylphenol by an alkylation reaction of phenol and methanol; step 2, carrying out an oxidative coupling reaction of the mixture in the presence of a copper catalyst and an amine additive; and step 3, separating o-methylphenol from the reaction product obtained in step 2, and obtaining a polyphenylene ether composed of repeating units represented by the following chemical formula 1, wherein the mixture comprises o-methylphenol in a molar ratio of 0.2 to 0.8 relative to 1 mole of 2,6-dimethylphenol, and the amine additive comprises a secondary amine, a pyridine compound, or a mixture thereof.

[0011] [Chemical Formula 1]

[0012]

[0013] In chemical formula 1, n is an integer greater than or equal to 1.

[0014] In this invention, the terms "first," "second," etc., are used to describe various compounds, and these terms are used only to distinguish a particular component from other components.

[0015] Furthermore, the terminology used in this specification is for the purpose of explaining exemplary embodiments only and is not intended to limit the invention.

[0016] Unless otherwise stated in the context, a singular expression may include a plural expression.

[0017] It must be understood that the terms “comprising,” “equipped,” or “having” in this specification are used only to specify the presence of a valid feature, number, step, component, or combination thereof, and do not preclude the presence or possibility of adding more than one different feature, number, step, component, or combination thereof.

[0018] This invention can be modified and taken in various forms, and specific exemplary embodiments are illustrated and described in detail in the following specification. However, it is not intended to limit the invention to the specific exemplary embodiments, and it must be understood that the invention includes every modification, equivalent, or substitution within its spirit and technical scope.

[0019] The present invention will be described in detail below.

[0020] The method for preparing polyphenylene ether according to the present invention comprises: step 1, preparing a mixture comprising 2,6-dimethylphenol and o-methylphenol by alkylation reaction of phenol and methanol; step 2, carrying out an oxidative coupling reaction of the mixture in the presence of a copper catalyst and an amine additive; and step 3, separating o-methylphenol from the reaction product obtained in step 2, and obtaining polyphenylene ether composed of repeating units represented by the following chemical formula 1.

[0021] The mixture comprises o-methylphenol in a molar ratio of 0.2 to 0.8 relative to 1 mole of 2,6-dimethylphenol, and

[0022] Amine additives include secondary amines, pyridine compounds, or mixtures thereof:

[0023] [Chemical Formula 1]

[0024]

[0025] In chemical formula 1, n is an integer greater than or equal to 1.

[0026] The inventors have discovered that when preparing polyphenylene ether via the oxidative coupling reaction of 2,6-dimethylphenol, 2,6-dimethylphenol prepared by the alkylation reaction of phenol and present in a mixture with o-methylphenol produced by a side reaction, and by controlling the content ratio of o-methylphenol to 2,6-dimethylphenol through the alkylation reaction conditions, and by using the oxidative coupling reaction catalyst together with an amine additive that acts as a ligand for the catalyst, polyphenylene ether with excellent processability can be prepared in high yield.

[0027] Typically, o-methylphenol and 2,6-dimethylphenol have small boiling point differences, making them difficult to separate and purify, and requiring high costs for separation and purification. In contrast, in this invention, the process of separating and purifying 2,6-dimethylphenol from o-methylphenol can be omitted. After producing polyphenylene ether via oxidative coupling, residual o-methylphenol in the reaction system is separated and removed using the boiling point difference, thereby significantly reducing energy consumption.

[0028] In addition, compared with the prior art, the oxidative coupling reaction can be carried out under mild conditions in this invention, thereby improving process stability.

[0029] Meanwhile, in this invention, the above steps can be carried out through a series of continuous reactions, namely steps 1 to 3.

[0030] The steps will be described in detail below.

[0031] Step 1

[0032] In the method for preparing polyphenylene ether according to the present invention, step 1 is a step of preparing a mixture comprising 2,6-dimethylphenol and o-methylphenol by alkylation reaction of phenol.

[0033] In the method for preparing polyphenylene ether according to the present invention, the mixture contains o-methylphenol in a molar ratio of 0.2 to 0.8 relative to 1 mole of 2,6-dimethylphenol.

[0034] Typically, based on the total weight of the reaction products obtained from the alkylation reaction, the content of 2,6-dimethylphenol and o-methylphenol in the reaction products is 95% by weight or more, and the content of 2,4,6-trimethylphenol is 5% by weight or less. Furthermore, in a mixture of 2,6-dimethylphenol and o-methylphenol of 95% by weight or more, the content of 2,6-dimethylphenol is 60% by weight or more, and the content of o-methylphenol is 40% by weight or less; more specifically, the content of 2,6-dimethylphenol is 75% to 80% by weight, and the content of o-methylphenol is 20% to 25% by weight. Therefore, in conventional methods for preparing polyphenylene ethers, in order to prevent or minimize the influence of o-methylphenol, a process must be performed to separate and remove o-methylphenol from the reaction products obtained after the alkylation reaction, and 2,6-dimethylphenol from which o-methylphenol has been separated and removed must be used.

[0035] However, the inventors have demonstrated that o-methylphenol, within an optimal range, improves the dielectric constant of the solvent and the solubility of the catalyst during the oxidative coupling reaction for the preparation of polyphenylene ether, and they have controlled the o-methylphenol content in the mixture used in the preparation of polyphenylene ether.

[0036] Therefore, in the method for preparing polyphenylene ether according to the present invention, the process of separating and removing o-methylphenol generated together with 2,6-dimethylphenol is not performed after the alkylation reaction. Thus, in the present invention, the content of o-methylphenol in the mixture used in the subsequent oxidative coupling reaction step is higher than the content of o-methylphenol contained as a byproduct of 2,6-dimethylphenol as described in the prior art.

[0037] Specifically, the mixture contains o-methylphenol at a molar ratio of 0.2 to 0.8 relative to 1 mole of 2,6-dimethylphenol. Therefore, o-methylphenol can improve the dielectric constant of the solvent and the solubility of the catalyst used in the oxidative coupling reaction, thereby improving the yield of PPO. When the o-methylphenol content is less than 0.2 moles, the effect of improving the dielectric constant of the solvent and the solubility of the catalyst is not significant, therefore the yield of PPO may decrease, and the physical properties of the prepared PPO, especially its molecular weight distribution, may deteriorate. When the o-methylphenol content exceeds 0.8 moles, the physical properties of PPO may deteriorate due to the excessive content and coordination of o-methylphenol with the catalyst. Considering the effect of improving processability by controlling the glass transition temperature (Tg), number-average molecular weight (Mn), and molecular weight distribution (PDI) of the final PPO, the mixture may more specifically contain o-methylphenol in amounts of more than 0.2 mol, or more than 0.3 mol, or more than 0.35 mol, or more than 0.4 mol, or more than 0.45 mol, or more than 0.48 mol, and less than 0.8 mol, or less than 0.75 mol, or less than 0.6 mol, or less than 0.55 mol, or less than 0.5 mol, relative to 1 mol of 2,6-dimethylphenol.

[0038] Therefore, in the method for preparing polyphenylene ether according to the present invention, the alkylation reaction in step 1 can be carried out by appropriately controlling reaction conditions such as reactants and their amounts, catalysts or reaction temperature, so as to satisfy the content ratio of o-methylphenol in the final mixture.

[0039] Specifically, during the alkylation reaction, methanol can be used in a ratio of 2 to 8 moles relative to 1 mole of phenol. When the ratio of methanol to phenol is too small, the amount of o-methylphenol produced increases significantly. Conversely, when the ratio of methanol to phenol is large, the content of 2,6-dimethylphenol increases; however, there is a concern about side reactions due to unreacted methanol. Therefore, considering the content ratio of 2,6-dimethylphenol to o-methylphenol in the mixture containing 2,6-dimethylphenol and o-methylphenol obtained from the alkylation reaction, it is preferable that the amount of methanol added is appropriately controlled within the above range. More specifically, to achieve the above molar ratio conditions, methanol can be used in a ratio of 2 or more moles, or 3 or more moles, and 8 or less moles, or 5 or less relative to 1 mole of phenol.

[0040] Alternatively, alkylation reactions can be carried out in the presence of alkylation catalysts such as zirconium-tungsten catalysts, magnesium oxide catalysts, iron-vanadium oxide catalysts, manganese oxide catalysts, cobalt-ferrite catalysts, alumina catalysts, or γ-zeolite catalysts.

[0041] Alkylation reaction catalysts can be used in the form of supported catalysts on a support (such as silica).

[0042] More specifically, in this invention, zirconium-tungsten catalysts that exhibit excellent catalytic activity during alkylation reactions can be used, and the catalysts can be supported catalysts on silica.

[0043] Additionally, water may be optionally introduced during the alkylation reaction, in which case water may be introduced in a ratio of less than 3 moles, more specifically from 1 mole to 3 moles, relative to 1 mole of phenol.

[0044] Alternatively, alkylation reactions can be carried out at temperatures ranging from 250°C to 500°C, more specifically, above 250°C or above 300°C, below 500°C or below 450°C.

[0045] Alternatively, alkylation reactions can be carried out under pressure conditions ranging from 1 atm to 3 atm, more specifically above 1 atm or above 1.2 atm, and below 3 atm or below 1.5 atm.

[0046] Alternatively, alkylation reactions can be carried out in an inert atmosphere (such as nitrogen, argon, etc.) and, depending on the catalyst used, in a reducing atmosphere (such as hydrogen, etc.).

[0047] As a result of the alkylation reaction, o-methylphenol is generated as a byproduct along with 2,6-dimethylphenol, and the generated o-methylphenol satisfies the content ratio conditions described above. Furthermore, if necessary, 2,6-dimethylphenol or o-methylphenol can be further introduced to additionally control the content ratio of o-methylphenol to 2,6-dimethylphenol within the aforementioned range. In this case, the preparation method according to the present invention may optionally further include a process of introducing 2,6-dimethylphenol or o-methylphenol to satisfy the above-mentioned o-methylphenol content conditions in the mixture obtained after the alkylation reaction.

[0048] Furthermore, as a result of the alkylation reaction, isomers such as 2,4,6-trimethylphenol may be generated as byproducts. Therefore, the mixture of the present invention, while containing 2,6-dimethylphenol and o-methylphenol satisfying the above-mentioned content ratio conditions, may further contain 2,4,6-trimethylphenol. When the mixture further contains 2,4,6-trimethylphenol, the content of 2,4,6-trimethylphenol relative to the total weight of the mixture may further be greater than 0% by weight, or greater than 0.0001% by weight, less than 2% by weight, or less than 1% by weight, or less than 0.1% by weight, or less than 0.01% by weight.

[0049] Step 2

[0050] Step 2 is a step of performing an oxidative coupling reaction on the mixture prepared in Step 1.

[0051] Specifically, oxidative coupling reactions can be carried out in the presence of copper catalysts and amine additives.

[0052] The copper-based catalyst may include copper (I) compounds such as copper oxide (I), copper halide (I), copper sulfate (I), or copper nitrate (I); copper (II) compounds such as copper oxide (II), copper halide (II), copper sulfate (II), or copper nitrate (II); or salts thereof, and any one or a mixture of two or more thereof may be used.

[0053] Copper catalysts can be used at a ratio of 0.001 mol to 0.1 mol relative to 1 mole of 2,6-dimethylphenol. When copper catalysts are used within this range, the yield of polyphenylene ether (PPE) can be improved with sufficient catalytic activity, and catalyst-induced color development can be prevented. When the amount of copper catalyst used is less than 0.001 mol, the yield of PPE is low; when its content is higher than 0.1 mol, a large amount of acid treatment is required for subsequent catalyst removal, and there is a concern about color development if the catalyst remains. Considering the improvement in the above effects, based on 1 mole of 2,6-dimethylphenol, the amount of copper catalyst used can be more than 0.001 mol, or more than 0.003 mol, or more than 0.005 mol, or more than 0.0075 mol, or more than 0.008 mol, or more than 0.01 mol, and less than 0.1 mol, or less than 0.05 mol, or less than 0.03 mol.

[0054] Meanwhile, amine additives act as ligands for copper catalysts.

[0055] Specifically, amine additives include secondary amines, pyridine compounds, or mixtures thereof.

[0056] Specifically, the secondary amine has two carbon atoms in its molecule. 1～20 Aliphatic alkyl groups. More specifically, the secondary amine has two linear or branched alkyl groups. Due to this structure, it readily coordinates with copper-based catalysts, thus improving catalytic reactivity. Consequently, the yield of polyphenylene ether can be significantly increased compared to the use of primary amines, tertiary amines, diamines containing two amino groups in the molecule, or secondary amines containing cycloalkyl or aromatic ring structures. Specific examples of secondary amines may include dimethylamine, diethylamine, di-n-propylamine, di-n-butylamine (or dibutylamine), diisobutylamine, di-tert-butylamine, dipentylamine, dihexylamine, dioctylamine, didecylamine, methylethylamine, methylpropylamine, or methylbutylamine, and any one or a mixture of two or more of them may be used.

[0057] Furthermore, pyridine compounds may specifically include aminopyridine compounds, such as 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 4-dimethylaminopyridine, 2,3-diaminopyridine, 2,5-diaminopyridine, 2,6-diaminopyridine, 2-amino-6-methylpyridine, 3-amino-6-isopropylpyridine, or 4-pyrrolidinylpyridine; monoalkylpyridine compounds, such as 2-methylpyridine, 3-methylpyridine, or 4-methylpyridine; or dialkylpyridine compounds, such as 2,3-dimethylpyridine (or 2,3-lutidine), 2,4-dimethylpyridine, 2,5-dimethylpyridine, 2,6-dimethylpyridine, 3,4-dimethylpyridine, or 3,5-dimethylpyridine, and any one or a mixture of two or more of these compounds may be used. Additionally, the alkyl group may be C10. 1～20 Alkyl, or C 1～10 Alkyl, or C 1～4 alkyl.

[0058] Amine additives can be appropriately selected and used based on the type of copper catalyst mentioned above. When copper catalysts and amine additives are used in the optimal combination, the yield of polyphenylene ether is further improved, and the physical properties of the prepared polyphenylene ether can be further enhanced.

[0059] Specifically, when copper (I) compounds, such as copper oxide (I), copper halide (I), copper sulfate (I), copper nitrate (I), or their salts, are used as copper-based catalysts and pyridine compounds are used as amine additives, the yield of polyphenylene ether (PPE) can be further improved, and the processability of the prepared PPE can be enhanced. The copper (I) compounds can be more specifically copper halide (I) compounds such as copper chloride (I) or copper bromide (I), and even more specifically copper chloride (I). Furthermore, the pyridine compounds can be aminopyridine compounds, such as 2-aminopyridine, 3-methylpyridine, or 4-methylpyridine. Due to their structural characteristics of readily coordinating with catalysts, aminopyridine compounds exhibit better effects in improving PPE yield and processability.

[0060] When copper(II) compounds, specifically copper(II) oxide, copper(II) halide, copper(II) sulfate, copper(II) nitrate, or their salts, are used as copper catalysts and secondary amines are used as amine additives, the yield of polyphenylene ethers (PPEs) can be increased, and the processability of the prepared PPEs can be improved. Copper(II) compounds can be more specifically copper(II) halide compounds such as copper(II) chloride or copper(II) bromide, and even more specifically copper(II) chloride. Furthermore, the secondary amine can have two carbon atoms. 1～8 Or C 2～6The alkyl chain is more specifically di-n-butylamine, diethylamine, di-n-hexylamine, or di-n-propylamine. Secondary amines can readily coordinate with catalysts, and the coordination complexes can exhibit high reactivity, thereby further improving the yield of polyphenylene ethers (PPEs), increasing the molecular weight of the prepared PPEs, and improving their thermal properties.

[0061] Based on 1 mole of 2,6-dimethylphenol, amine additives can be used in proportions from 0.1 moles to 1 mole. When amine additives are used in proportions meeting the above requirements, polyphenylene ethers can be prepared in excellent yields without concern about side reactions caused by excess amine compounds. More specifically, based on 1 mole of 2,6-dimethylphenol, amine additives can be used in proportions of more than 0.1 moles, or more than 0.2 moles, or more than 0.3 moles, or more than 0.34 moles, or more than 0.4 moles, and less than 1 mole, or less than 0.8 moles, or less than 0.7 moles, or less than 0.68 moles, or less than 0.5 moles.

[0062] Furthermore, in the preparation method according to the present invention, the oxidative coupling reaction can be carried out under oxygen or air conditions. In particular, compared with conventional oxidative coupling reactions carried out under oxygen supply conditions, the preparation process can be carried out under mild reaction conditions because the oxidative coupling reaction can even be carried out under air conditions. More specifically, the oxidative coupling reaction can be carried out by supplying air by bubbling at a rate of 80 cc / min to 350 cc / min.

[0063] Furthermore, the oxygen content in the air can specifically be below 30%, more specifically below 21% and above 10%. Oxygen in the air is used to promote the oxidative coupling reaction, but when the oxidative coupling reaction is carried out under oxygen-supply conditions as in the prior art, the yield decreases and problems such as explosions occur. Conversely, in the present invention, by carrying out the oxidative coupling reaction under air conditions with low oxygen content as described above, process safety and yield can be improved.

[0064] Alternatively, air can be supplied at a rate of 80 cc / min to 350 cc / min as described above. When the supply rate is too slow, it is difficult to uniformly mix oxygen in the reaction system, which may reduce the yield of polyphenylene ether and limit chain extension, thereby reducing physical properties. Furthermore, when the supply rate is too fast, the oxygen concentration in the solvent increases, which may lead to copolymerization of o-methylphenol or coupling reaction of 2,6-dimethylphenol, thus raising concerns about the formation of byproducts. In this invention, by supplying air within the above-mentioned supply rate range, the yield of polyphenylene ether and the improvement in physical properties can be further improved. More specifically, air can be supplied by bubbling at a rate of 80 cc / min or more, or 90 cc / min or more, or 100 cc / min or more, and at a rate of 350 cc / min or less, or 330 cc / min or less, or 300 cc / min or less.

[0065] In addition, air can be supplied by bubbling air under the conditions of the above-mentioned supply rate, so that the air can be uniformly mixed in the reaction system.

[0066] Oxidative coupling reactions can be carried out in aromatic solvents such as benzene, toluene, or xylene. These aromatic solvents may be more advantageous in the preparation of polyphenylene ethers due to their high solubility for both the catalyst and the polyphenylene ether.

[0067] Step 3

[0068] Step 3 is the step of separating o-methylphenol from the reaction product obtained in step 2 and obtaining polyphenylene ether.

[0069] In this regard, there are no particular restrictions on the order in which the process of separating o-methylphenol and the process of obtaining polyphenylene ether are carried out. Specifically, the process of separating o-methylphenol can be carried out after obtaining polyphenylene ether. Alternatively, the process of obtaining polyphenylene ether can be carried out after separating o-methylphenol. Or, polyphenylene ether can be obtained through the process of separating o-methylphenol.

[0070] For example, when separating o-methylphenol after obtaining polyphenylene ether, an alcohol is introduced into the reaction product obtained by oxidative coupling to precipitate the polyphenylene ether, followed by filtration and drying, and then fractionation of the filtrate obtained by filtration in a temperature range of 180°C to 220°C or 190°C to 200°C to separate o-methylphenol.

[0071] As the alcohol introduced to precipitate polyphenylene ether, specifically, lower alcohols having 1 to 3 carbon atoms, such as methanol, ethanol, isopropanol, etc., can be used. Among these, the introduction of methanol can precipitate polyphenylene ether in a better yield and is more advantageous in subsequent fractionation removal.

[0072] There is no particular limit to the amount of alcohol introduced, and the introduction of alcohol can allow polyphenylene ether to undergo a sufficient precipitation reaction.

[0073] Furthermore, to promote the precipitation reaction of polyphenylene ether and thus improve the yield, an acid, such as hydrochloric acid, may be optionally added when the alcohol is introduced. In this case, based on 100 parts by weight of alcohol, the amount of acid introduced can be from 0.01 parts by weight to 0.5 parts by weight, more specifically from 0.1 parts by weight to 0.3 parts by weight.

[0074] When polyphenylene ether is precipitated by introducing alcohol, it can be obtained by filtration and drying of the separated polyphenylene ether.

[0075] In this regard, filtration and drying processes can be carried out using conventional methods. For example, filtration can be performed using filters, and drying can be performed by heating and drying in an oven. Furthermore, drying is preferably carried out under a vacuum or inert gas atmosphere.

[0076] In addition, the precipitation, filtration and drying processes used to obtain polyphenylene ether can be repeated more than twice.

[0077] After obtaining polyphenylene ether through precipitation, filtration and drying, the filtrate obtained by the filtration process is subjected to a fractionation process in a temperature range of 180°C to 220°C or 190°C to 200°C to separate o-methylphenol.

[0078] The fractionation process for separating o-methylphenol can be carried out using conventional methods, the difference being that the fractionation process is carried out under the above temperature conditions.

[0079] In addition to o-methylphenol, the filtrate also contains isomers such as 2,4,6-trimethylphenol generated through side reactions during the oxidative coupling reaction, aromatic solvents such as toluene used in the oxidative coupling reaction, and ethanol introduced during the precipitation reaction of polyphenylene ether. These compounds can also be separated and removed by fractional distillation. For example, when heated within the above temperature range, low-boiling alcohols are first separated and removed by evaporation within a temperature range of 50°C to 80°C or 60°C to 80°C, followed by aromatic solvents such as toluene by evaporation within a temperature range of 100°C to 150°C or 110°C to 130°C, and then o-methylphenol can be separated and removed within a temperature range of 180°C to 220°C or 190°C to 200°C.

[0080] In another example, when a process for obtaining polyphenylene ether is carried out after separating o-methylphenol from the reaction product obtained in step 2, the reaction product obtained in step 2 is fractionated to separate o-methylphenol in a temperature range of 180°C to 220°C or 190°C to 200°C, and then an alcohol is introduced into the resulting reaction product to precipitate polyphenylene ether, followed by filtration and drying.

[0081] Although polyphenylene ether is produced as a result of the oxidative coupling reaction in step 2, o-methylphenol is present in the mixture added during the oxidative coupling reaction in the reaction system. Because there is a significant difference between the boiling point (or decomposition temperature) of polyphenylene ether and the boiling point of o-methylphenol, o-methylphenol can be separated and removed by fractional distillation in this invention. Specifically, since the boiling point of o-methylphenol is 191°C and the decomposition temperature of polyphenylene ether is above 400°C, o-methylphenol can be separated by fractional distillation within a temperature range of 180°C to 220°C or 190°C to 200°C.

[0082] The fractionation process for separating o-methylphenol can be carried out using conventional methods, the difference being that the fractionation process is carried out under the above temperature conditions.

[0083] In addition to o-methylphenol, isomers such as 2,4,6-trimethylphenol may also be present in the reaction product obtained from step 2. Because these isomers have significantly different boiling points from polyphenylene ether, they can be separated simultaneously by fractionation, thus yielding polyphenylene ether with higher purity.

[0084] After separating o-methylphenol, an alcohol is introduced into the resulting reaction product, and then polyphenylene ether is obtained by precipitation, filtration and separation.

[0085] At this point, the precipitation, filtration, and separation of polyphenylene ether can be carried out in the same manner as described above. However, when the resulting product is obtained in a solid phase, the reaction product is dissolved in a solvent, and then an alcohol is introduced to carry out the precipitation reaction of polyphenylene ether.

[0086] Simultaneously, the o-methylphenol separated by fractionation can be reused as an intermediate in the synthesis of 2,6-dimethylphenol during the alkylation reaction. Therefore, after separating o-methylphenol, the preparation method according to the present invention can further include a step of introducing the separated o-methylphenol during the alkylation reaction.

[0087] The above precipitation method allows for the preparation of PPO in excellent yields under mild oxidative coupling reaction conditions. Specifically, PPO can be prepared in high yields of 70% by weight or more, or 80% by weight or more, or 90% by weight or more, or 95% by weight or more, or 99% by weight or more using the above method.

[0088] Here, the yield can be calculated from the amount of 2,6-dimethylphenol introduced during the preparation of PPO and the amount of PPO finally obtained, according to Equation 1 below.

[0089] [Equation 1]

[0090] Yield (wt%) = [Weight of PPO obtained / Weight of 2,6-dimethylphenol introduced] × 100

[0091] Furthermore, the PPO prepared according to the above method is a linear homopolymer composed only of repeating units represented by chemical formula 1:

[0092] [Chemical Formula 1]

[0093]

[0094] In chemical formula 1, n can be an integer greater than or equal to 1, more specifically from 10 to 100.

[0095] In the preparation of polyphenylene ether according to conventional methods, the repeating units of the polymer include structures derived from o-methylphenol, a byproduct of 2,6-dimethylphenol. Conversely, in the preparation method according to the present invention, even with a high content of o-methylphenol as a reactant, high selectivity for 2,6-dimethylphenol is still exhibited, thus enabling the preparation of the aforementioned homopolymer.

[0096] Therefore, in 1 In H NMR analysis, the PPO prepared according to the above method did not show a peak of o-methylphenol in the range of 6.8 ppm to 7.4 ppm.

[0097] PPO can be performed using the methods and conditions described in the test examples below. 1 H NMR analysis.

[0098] Furthermore, the PPO prepared by the above method is an oligomeric PPO with a number average molecular weight of 1600 g / mol to 3500 g / mol, and a molecular weight distribution (PDI, Mw / Mn) of 1.7 to 3 and a glass transition temperature (Tg) of 140 °C to 180 °C, thus exhibiting excellent processability.

[0099] Specifically, the number-average molecular weight of PPO is above 1600 g / mol, below 3500 g / mol, or below 3000 g / mol, thus exhibiting higher Mn content compared to oligomeric PPO prepared by conventional methods. More specifically, the number-average molecular weight of PPO is above 1600 g / mol, above 1750 g / mol, or above 1900 g / mol, or above 2000 g / mol, or above 2100 g / mol, or above 2200 g / mol, or above 2300 g / mol, or above 2400 g / mol, and below 3500 g / mol, below 3300 g / mol, or below 3200 g / mol, or below 3000 g / mol, or below 2800 g / mol, or below 2700 g / mol.

[0100] Furthermore, the molecular weight distribution (PDI, Mw / Mn) of PPO is from 1.7 to 3, thus exhibiting a wide molecular weight distribution compared to oligomeric PPO prepared by conventional methods. Therefore, PPO can exhibit excellent processability. More specifically, the molecular weight distribution of PPO is 1.7 or higher, or 1.8 or higher, or 1.9 or higher, or 2.0 or higher, or 2.1 or higher, or 2.2 or higher, or 2.3 or higher, or 2.45 or higher, and is 3 or lower, or 2.8 or lower, or 2.7 or lower, or 2.5 or lower.

[0101] Furthermore, the glass transition temperature of PPO is between 140°C and 180°C. When the glass transition temperature is high, the processing temperature increases and processability decreases; when the glass transition temperature is low, thermal stability decreases. Because its glass transition temperature is within the above range, the PPO according to the present invention can exhibit excellent processability without causing a deterioration in thermal stability. More specifically, the glass transition temperature of PPO is above 140°C, or above 145°C, or above 148°C, or above 150°C, or above 152°C, or above 155°C, or above 156°C, and below 180°C, or below 175°C, or below 170°C, or below 169°C, or below 165°C, or below 162°C, or below 160°C, or below 159°C.

[0102] Simultaneously, gel permeation chromatography can be used to measure the number-average molecular weight and molecular weight distribution (PDI, Mw / Mn) of PPO, and differential scanning calorimetry can be used to measure the glass transition temperature. Specific measurement methods and conditions will be described in detail in the following test examples.

[0103] Furthermore, when the oligomeric PPO obtained by the above preparation method is subjected to an additional oxidative coupling reaction in the presence of a copper catalyst and an amine additive, a high molecular weight PPO (or polymeric PPO) can be prepared, specifically, a high molecular weight PPO with a high number-average molecular weight of 4000 g / mol or more. Therefore, the preparation method according to the present invention can further include a step of performing a secondary oxidative coupling reaction on the obtained polyphenylene ether, specifically, on the oligomeric PPO after the separation of o-methylphenol in the presence of a copper catalyst and an amine additive.

[0104] The copper catalysts, amine additives, and oxidative coupling reaction conditions that can be used in the preparation of high molecular weight PPO are as described above.

[0105] However, based on 1 mole of oligomeric PPO, copper catalysts can be used in proportions of 0.001 moles to 0.1 moles, more specifically more than 0.001 moles, or more than 0.003 moles, or more than 0.005 moles, and less than 0.1 moles, or less than 0.05 moles, or less than 0.01 moles.

[0106] Furthermore, based on 1 mole of oligomeric PPO, amine additives can be used in proportions of 0.1 to 1 mole, more specifically more than 0.1 moles, or more than 0.3 moles, or more than 0.5 moles, and less than 1 mole, or less than 0.8 moles, or less than 0.7 moles, or less than 0.68 moles.

[0107] The number-average molecular weight of the high molecular weight PPO prepared by the above preparation process is specifically above 4000 g / mol, or above 5000 g / mol, or above 8000 g / mol, or above 10000 g / mol, or above 12000 g / mol, and below 20000 g / mol, or below 18000 g / mol, or below 16500 g / mol, or below 16200 g / mol, or below 15000 g / mol.

[0108] In addition to the number-average molecular weight mentioned above, compared with the prior art, high molecular weight PPO has a wide molecular weight distribution (PDI, Mw / Mn) of 2 to 3, more specifically above 2, or above 2.1, or above 2.2, and below 3, or below 2.8, or below 2.6, or below 2.5, thus exhibiting excellent processability.

[0109] Meanwhile, the number-average molecular weight and molecular weight distribution of polymer PPO can be measured using gel permeation chromatography, and the specific measurement methods and conditions will be described in detail in the following test examples.

[0110] Beneficial effects

[0111] According to the preparation method of the present invention, there is no need for a separate process to separate and purify the o-methylphenol generated after the alkylation reaction of phenol, thus reducing energy consumption and enabling the preparation of PPO in excellent yield under mild oxidative coupling reaction conditions. Furthermore, the obtained PPO exhibits excellent processability. Attached Figure Description

[0112] Figure 1 It is the polyphenylene ether prepared in Example 1-1 1 1H NMR analysis diagram. Detailed Implementation

[0113] In the following description, the effects and functions of the present invention will be explained in more detail with reference to specific exemplary embodiments. However, these exemplary embodiments are provided merely to illustrate the present invention, and the scope of the present invention is not defined therein.

[0114] Example 1-1

[0115] 10 g of fumed silica was added to 50 mL of methanol, followed by 1 g of ZrO2. Ammonia solution was added to the resulting mixture to bring the pH above 9. The mixture was then stirred at room temperature (25 ± 3 °C) for 3 hours, the solvent was completely removed through a glass filter, and the product was dried in an oven at 100 °C. The dried product was mixed with a solution prepared by dissolving 1.4 g of WO3 in 20 mL of water and reacted at room temperature (25 ± 3 °C) for 2 hours. The solvent was completely removed from the resulting reaction product through a glass filter, and the product was then calcined at 750 °C to obtain a zirconium-tungsten alkylation catalyst supported on a silica support.

[0116] More than 10 g of alkylation catalyst was charged into a cylindrical reactor. The alkylation catalyst was activated by raising the temperature inside the reactor to 400 °C while blowing in a mixed gas (containing 97 vol% argon and 3 vol% hydrogen). After activation, a mixture of phenol, methanol, and water (phenol:methanol:water molar ratio = 1:5:1) was injected together with the mixed gas at a rate of 10 mL / h, and the reaction was allowed to proceed until the phenol conversion reached 98%. This yielded a mixture containing 2,6-dimethylphenol and o-methylphenol.

[0117] Approximately 1.43 g of the resulting mixture (containing 1 g, 8.2 mmol of 2,6-dimethylphenol and 0.43 g, 4 mmol of o-methylphenol, based on 1 mole of 2,6-dimethylphenol, corresponding to a molar ratio of 0.49) was placed in a glass bottle with a magnetic rod, and 10 mL of toluene was added and dissolved with stirring.

[0118] Based on 1 mole of 2,6-dimethylphenol, the catalyst CuCl2 was added to the resulting solution at a molar ratio of 0.0075, and the mixture was stirred at 25°C for 5 minutes. Then, 2.8 mmol of di-n-butylamine (based on 1 mole of 2,6-dimethylphenol, corresponding to a molar ratio of 0.34) was added, and air bubbling was performed to carry out the polymerization reaction. At this time, air bubbling was performed at a rate of 100 cc / min using a flow controller.

[0119] After the reaction was complete, the resulting reaction product was slowly placed into a flask containing 100 mL of HCl / MeOH solution (HCl content: 0.1 wt%) to precipitate the synthesized polymer, i.e., polyphenylene ether. The precipitated polymer was separated by filtration and dried in a vacuum oven. The dried polymer was dissolved in dichloromethane, and the methanol precipitation process was repeated twice to obtain polyphenylene ether.

[0120] The solution remaining after the separation of polyphenylene ether contains methanol, toluene, and o-methylphenol. Therefore, while heating the solution to 190°C to 220°C, methanol, toluene, and o-methylphenol are sequentially separated by fractional distillation at approximately 65°C, 110°C, and 190°C. Furthermore, the o-methylphenol separated by fractional distillation is subsequently recycled as an intermediate during the alkylation reaction of 2,6-dimethylphenol.

[0121] Examples 1-2 to 1-10

[0122] The various polyphenylene ethers were prepared in the same manner as in Example 1, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 1 below.

[0123] Examples 1-11

[0124] 10 g of fumed silica was added to 50 mL of methanol, followed by 1 g of ZrO2. Ammonia solution was added to the resulting mixture to bring the pH above 9. The mixture was then stirred at room temperature (25 ± 3 °C) for 3 hours, the solvent was completely removed through a glass filter, and the product was dried in an oven at 100 °C. The dried product was mixed with a solution prepared by dissolving 1.4 g of WO3 in 20 mL of water and reacted at room temperature (25 ± 3 °C) for 2 hours. The solvent was completely removed from the resulting reaction product through a glass filter, and the product was then calcined at 750 °C to obtain a zirconium-tungsten alkylation catalyst supported on a silica support.

[0125] More than 10 g of alkylation catalyst was charged into a cylindrical reactor. The alkylation catalyst was activated by raising the temperature inside the reactor to 400 °C while blowing in a mixed gas (containing 97 vol% argon and 3 vol% hydrogen). After activation, a mixture of phenol, methanol, and water (phenol:methanol:water molar ratio = 1:5:1) was injected together with the mixed gas at a rate of 10 mL / h, and the reaction was allowed to proceed until the phenol conversion reached 98%. This yielded a mixture containing 2,6-dimethylphenol and o-methylphenol.

[0126] Approximately 1.43 g of the resulting mixture (containing 1 g, 8.2 mmol of 2,6-dimethylphenol and 0.43 g, 4 mmol of o-methylphenol, based on 1 mole of 2,6-dimethylphenol, corresponding to a molar ratio of 0.49) was placed in a glass bottle with a magnetic rod, and 10 mL of toluene was added and dissolved with stirring.

[0127] Based on 1 mole of 2,6-dimethylphenol, the catalyst CuCl was added to the resulting solution at a molar ratio of 0.01, and the mixture was stirred at 25°C for 5 minutes. Then, 2.8 mmol of 3-aminopyridine (based on 1 mole of 2,6-dimethylphenol, corresponding to a molar ratio of 0.34) was added, and air bubbling was performed to carry out the polymerization reaction. At this time, air bubbling was performed at a rate of 100 cc / min using a flow controller.

[0128] After the reaction was complete, the resulting reaction product was slowly placed into a flask containing 100 mL of HCl / MeOH solution (HCl content: 0.1 wt%) to precipitate the synthesized polymer, i.e., polyphenylene ether. The precipitated polymer was separated by filtration and dried in a vacuum oven. The dried polymer was dissolved in dichloromethane, and the methanol precipitation process was repeated twice to obtain polyphenylene ether.

[0129] The solution remaining after the separation of polyphenylene ether contains methanol, toluene, and o-methylphenol. Therefore, while heating the solution to 190°C to 220°C, methanol, toluene, and o-methylphenol are sequentially separated by fractional distillation at approximately 65°C, 110°C, and 190°C. Furthermore, the o-methylphenol separated by fractional distillation is subsequently recycled as an intermediate during the alkylation reaction of 2,6-dimethylphenol.

[0130] Examples 1-12 to 1-19

[0131] The various polyphenylene ethers were prepared in the same manner as in Examples 1-11, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 2 below.

[0132] Meanwhile, in Examples 1-17 and 1-18, based on 1 mole of 2,6-dimethylphenol, the molar ratios of o-methylphenol content in the mixture were 0.61 and 0.73, respectively.

[0133] Comparative Example 1-1

[0134] Polyphenylene ether was prepared in the same manner as in Examples 1-1, except that no alkylation reaction was performed and 2,6-dimethylphenol (1 g, 8.2 mmol) was used instead of the mixture containing 2,6-dimethylphenol and o-methylphenol.

[0135] Comparative Examples 1-2

[0136] The various polyphenylene ethers were prepared in the same manner as in Examples 1-1, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 1 below.

[0137] Comparative Examples 1-3

[0138] Polyphenylene ether was prepared in the same manner as in Examples 1-1, except that no alkylation reaction was performed and o-methylphenol (9.2 mmol) was used instead of the mixture containing 2,6-dimethylphenol and o-methylphenol. However, polyphenylene ether could not be prepared due to lack of reactivity.

[0139] Comparative Examples 1-4 and 1-5

[0140] The various polyphenylene ethers were prepared in the same manner as in Examples 1-1, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 1 below.

[0141] Comparative Examples 1-6

[0142] Polyphenylene ether was prepared in the same manner as in Examples 1-11, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 2 below.

[0143] Comparative Examples 1-7

[0144] Polyphenylene ether was prepared in the same manner as in Examples 1-11, except that no alkylation reaction was performed and 2,6-dimethylphenol (1 g, 8.2 mmol) was used instead of the mixture containing 2,6-dimethylphenol and o-methylphenol.

[0145] Comparative Examples 1-8 and 1-9

[0146] Polyphenylene ether was prepared in the same manner as in Examples 1-11, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 2 below.

[0147] [Table 1]

[0148]

[0149] [Table 2]

[0150]

[0151] Test Example 1

[0152] The polyphenylene oxide (PPO) obtained in Examples 1-1 was subjected to NMR analysis.

[0153] In detail, the PPO prepared in Example 1-1 was dissolved in CDCl3 and then subjected to 500MHz NMR by Varian. 1 H NMR analysis. Results are in Figure 1 As shown in the image.

[0154] According to literature reports, when o-methylphenol copolymerizes with a polymer, in 1Peaks for o-methylphenol were observed in the 1H NMR spectrum in the range of 6.9 ppm to 7.4 ppm. However, as... Figure 1 As shown, no peak of o-methylphenol was observed in the PPO prepared by the preparation method of the present invention in Example 1-1.

[0155] This indicates that the PPO prepared by the method of the present invention is a homopolymer composed only of repeating units from 2,6-dimethylphenol.

[0156] Test Example 2

[0157] The yield, glass transition temperature, number-average molecular weight and molecular weight distribution of the PPO obtained in the examples and comparative examples were measured by the following methods, and the results are shown in Tables 3 and 4 below.

[0158] (1) Yield (%)

[0159] The yield is calculated according to Equation 1 below, based on the amount of 2,6-dimethylphenol introduced during the preparation of PPO according to the examples and comparative examples, and the amount of PPO finally obtained.

[0160] [Equation 1]

[0161] Yield (wt%) = [Weight of PPO obtained / Weight of 2,6-dimethylphenol introduced] × 100

[0162] (2) Glass transition temperature (Tg)

[0163] The glass transition temperature was measured using a differential scanning calorimeter (DSC) under the following conditions:

[0164] Measuring instrument: DSC 250 (TA Instruments)

[0165] Temperature measurement: 0 to 300℃

[0166] Heating rate: 10℃ / minute

[0167] Measurement environment: N2

[0168] (3) Number-average molecular weight (Mn) and molecular weight distribution (PDI)

[0169] The polymers prepared in the examples and comparative examples were dissolved in chloroform and then analyzed by gel permeation chromatography (GPC) under the following conditions. The number-average molecular weight (Mn) and molecular weight distribution (PDI) of PPO were calculated from the results.

[0170] As the GPC instrument, a Water PL-GPC220 instrument was used, and a Polymer Laboratorie PLgel MIX-B column with a length of 300 mm was used. The measurement temperature was 40°C, chloroform was used as the solvent, and the flow rate was 1.0 mL / min. Using the GPC analyzer (PL-GPC220), the polymers according to the examples and comparative examples were pretreated at 160°C for 10 hours by dissolving them in chloroform containing 0.0125% BHT, then prepared at a concentration of 1 mg / mL, and then supplied in 100 μL volumes. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) values ​​were obtained using calibration curves formed from polystyrene standard samples. The molecular weight distribution (PDI, Mw / Mn) was calculated by dividing the weight-average molecular weight by the number-average molecular weight. At this point, nine polystyrene standard samples with weight-average molecular weights of 2000 g / mol, 10000 g / mol, 30000 g / mol, 70000 g / mol, 200000 g / mol, 700000 g / mol, 2000000 g / mol, 4000000 g / mol, and 10000000 g / mol were used.

[0171] <Measurement Conditions>

[0172] Column: PLgel Mixed-B×2

[0173] Solvent: Chloroform (stabilized with BHT)

[0174] Flow rate: 1.0 mL / min

[0175] Sample concentration: 1 mg / mL

[0176] Supply volume: 100μL

[0177] Column temperature: 40℃

[0178] Detector: Waters RI detector

[0179] Data processing: Empower

[0180] [Table 3]

[0181] Example 1-1 88 154 2,400 2.3 Examples 1-2 97 158 2,500 2.7 Examples 1-3 99 160 2,300 3.0 Examples 1-4 99 170 3,200 3.0 Examples 1-5 96 170 3,300 2.7 Examples 1-6 99 153 2,100 2.0 Examples 1-7 99 153 2,200 2.1 Examples 1-8 96 156 2,700 2.3 Examples 1-9 97 169 3,100 2.3 Examples 1-10 99 154 2,200 2.0 Comparative Example 1-1 72 183 4,300 1.9 Comparative Examples 1-2 40 155 2,200 2.7 Comparative Examples 1-3 ND ND ND ND Comparative Examples 1-4 6 147 1,900 1.8 Comparative Examples 1-5 13 148 1,900 2.0

[0182] In Table 3, "ND" indicates undetermined.

[0183] [Table 4]

[0184] Examples 1-11 71 151 1,900 1.9 Examples 1-12 90 160 2,700 2.3 Examples 1-13 90 155 2,200 2.3 Examples 1-14 >99 154 2,400 2.3 Examples 1-15 70 151 2,100 1.8 Examples 1-16 >99 159 2,300 3.0 Examples 1-17 93 155 2,200 2.7 Examples 1-18 96 148 1,900 1.7 Examples 1-19 80 150 2100 1.9 Comparative Examples 1-6 31 149 1,800 1.5 Comparative Examples 1-7 9 137 1,700 1.6 Comparative Examples 1-8 40 149 2,000 2.1 Comparative Examples 1-9 15 147 1,800 2.0

[0185] The test results confirmed that, due to the combined use of the copper catalyst and amine additives of the present invention, the yield of PPO was significantly increased compared to the prior art, and the Tg, Mn, and PDI of the obtained PPO were within the optimal range, thus exhibiting excellent processability. It was also confirmed that oligomeric PPO could be produced even under mild air-supply conditions using the preparation method of the present invention.

[0186] Specifically, the test results from Examples 1-1 to 1-4 confirmed that when PPO is prepared by the preparation method according to the present invention, the yield increases as the amount of catalyst increases within a predetermined range, and the Tg and molecular weight or PDI of PPO increases as the amount of amine additive increases.

[0187] It was also confirmed that when aminopyridine compounds are used as amine additives, PPO with higher molecular weight, wider molecular weight distribution, optimal Tg range, and excellent processability can be obtained in significantly increased yields. On the other hand, in Examples 1-15 using alkylpyridines, the yields were considerably lower compared to Examples 1-11 using aminopyridines due to the large steric hindrance of the alkylpyridine compounds.

[0188] The results from Examples 1-11 and 1-16 also confirmed that when copper bromide (I) was used instead of copper chloride (I) as a copper catalyst, there was no significant difference in reactivity, but the molecular weight distribution of the obtained PPO increased.

[0189] The results from Examples 1-1, 1-7, and 1-8 also confirmed that, under the same conditions, the Tg, molecular weight, and molecular weight distribution of the prepared PPO increased with increasing o-methylphenol content to a certain level due to the excellent solubility of the catalyst. However, when the o-methylphenol content exceeded a certain level, specifically a molar ratio of 0.6 to 1 mole of 2,6-dimethylphenol, the Tg, molecular weight, and molecular weight distribution of the prepared PPO relatively decreased.

[0190] Conversely, in Comparative Example 1-1, which used only 2,6-dimethylphenol without o-methylphenol, compared to Examples 1-2, 1-5, and 1-6, which used 2,6-dimethylphenol and o-methylphenol in the optimal mixing ratio under the same conditions, the PPO yield decreased despite the increased catalyst supply. The Tg and Mn of PPO increased excessively, and the PDI decreased, resulting in poor processability. Furthermore, in Comparative Example 1-7, the polymerization of PPO did not proceed well compared to Examples 1-14. These results indicate that o-methylphenol plays a role in improving the dielectric constant of the solvent and the solubility of the catalyst during oxidative coupling reactions, but in Comparative Examples 1-1 and 1-7, the solubility of the catalyst was reduced because o-methylphenol was not used.

[0191] Furthermore, in Comparative Examples 1-2, which used equal amounts of a mixture containing 2,6-dimethylphenol and o-methylphenol, the yield of PPO was significantly reduced. In Comparative Examples 1-3, which used only o-methylphenol without 2,6-dimethylphenol, PPO was not obtained due to a lack of reactivity.

[0192] Furthermore, in Comparative Examples 1-4 and 1-6, which used triethylamine and n-butylamine as amine additives respectively, the yield of PPO was significantly reduced compared to Examples 1-2, 1-8 and 1-14, and the Tg, Mn and PDI of the obtained PPO were lower.

[0193] Example 2-1

[0194] The oligomeric polyphenylene oxide (PPO) prepared in Example 1-1 was placed in a glass bottle with a magnetic rod, and 10 mL of toluene was added and dissolved under stirring.

[0195] Based on 1 mole of oligomeric PPO, catalyst CuCl2 was added to the resulting solution at a molar ratio of 0.005, and the mixture was stirred at 25°C for 5 minutes. Then, based on 1 mole of oligomeric PPO, di-n-butylamine was added at a molar ratio of 0.68, and air bubbling was performed to carry out the polymerization reaction. At this time, air bubbling was performed at a rate of 300 cc / min using a flow controller.

[0196] After the reaction was complete, the resulting reaction product was slowly placed into a flask containing 100 mL of HCl / MeOH solution (HCl content: 0.1 wt%) to precipitate the synthesized polymer. The precipitated polymer was separated by filtration and dried in a vacuum oven. The dried polymer was dissolved in dichloromethane, and the methanol precipitation process was repeated twice to obtain high molecular weight polyphenylene ether.

[0197] Examples 2-2 and 2-3

[0198] Polyphenylene ether was prepared in the same manner as in Example 2-1, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 5 below.

[0199] Examples 2-4

[0200] The oligomeric polyphenylene oxide (PPO) prepared in Examples 1-11 was placed in a glass bottle with a magnetic rod, and 10 mL of toluene was added and dissolved under stirring.

[0201] Based on 1 mole of oligomeric PPO, catalyst CuCl2 was added to the resulting solution at a molar ratio of 0.005, and the mixture was stirred at 25°C for 5 minutes. Then, based on 1 mole of oligomeric PPO, di-n-butylamine was added at a molar ratio of 0.28, and air bubbling was performed to carry out the polymerization reaction. At this time, air bubbling was performed at a rate of 300 cc / min using a flow controller.

[0202] After the reaction was complete, the resulting reaction product was slowly placed into a flask containing 100 mL of HCl / MeOH solution (HCl content: 0.1 wt%) to precipitate the synthesized polymer. The precipitated polymer was separated by filtration and dried in a vacuum oven. The dried polymer was dissolved in dichloromethane, and the methanol precipitation process was repeated twice to obtain high molecular weight polyphenylene ether.

[0203] Examples 2-5

[0204] Polyphenylene ether was prepared in the same manner as in Examples 2-4, except that the amount of reactants added and the polymerization conditions were changed as shown in Table 5 below.

[0205] Test Example 3

[0206] The high molecular weight polyphenylene ethers prepared in Examples 2-1 to 2-5 were subjected to GPC analysis in the same manner as in Test Example 2, and their number-average molecular weight (Mn) and molecular weight distribution (PDI, Mw / Mn) were measured. The results are shown in Table 5 below.

[0207] [Table 5]

[0208]

[0209] The test results confirmed that the catalyst can be used again to perform an oxidative coupling reaction on the oligomeric PPO prepared by the method of the present invention to prepare high molecular weight PPO.

Claims

1. A method for preparing polyphenylene ether, comprising: Step 1: Prepare a mixture containing 2,6-dimethylphenol and o-methylphenol by alkylation reaction of phenol and methanol; Step 2: The mixture undergoes an oxidative coupling reaction in the presence of a copper catalyst and an amine additive. as well as Step 3: Separate o-methylphenol from the reaction product obtained in Step 2, and obtain polyphenylene ether composed of repeating units represented by the following chemical formula 1. In this process, methanol is used in a ratio of 2 to 8 moles relative to 1 mole of phenol, and water is introduced in a ratio of 1 to 3 moles relative to 1 mole of phenol during the alkylation reaction. The mixture contains o-methylphenol in a molar ratio of 0.3 to 0.75 relative to 1 mole of 2,6-dimethylphenol. The amine additive comprises secondary amines, pyridine compounds, or mixtures thereof, wherein the secondary amine has two carbon atoms in its molecule. 1~20 Aliphatic alkyl groups, and The polyphenylene ether is an oligomeric polyphenylene ether with a number-average molecular weight of 1600 g / mol to 3500 g / mol, a molecular weight distribution of 1.7 to 3, and a glass transition temperature of 140°C to 180°C. [Chemical Formula 1] In chemical formula 1, n is an integer greater than or equal to 1.

2. The method as described in claim 1, wherein, The steps are carried out as a series of consecutive reactions.

3. The method as described in claim 1, wherein, The copper catalyst is selected from one or more of the group consisting of cuprous oxide (I), cuprous halide (I), cuprous sulfate (I), cuprous nitrate (I), copper oxide (II), copper halide (II), copper sulfate (II), and copper nitrate (II).

4. The method of claim 1, wherein, The copper catalyst is used in a ratio of 0.001 to 0.1 mol based on 1 mol of 2,6-dimethylphenol.

5. The method of claim 1, wherein, The secondary amine is dimethylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-tert-butylamine, dipentylamine, dihexylamine, dioctylamine, didecylamine, methylethylamine, methylpropylamine, or methylbutylamine.

6. The method of claim 1, wherein, The pyridine compounds are aminopyridine compounds, monoalkylpyridine compounds, or dialkylpyridine compounds.

7. The method of claim 1, wherein, The pyridine compounds are 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 4-dimethylaminopyridine, 2,3-diaminopyridine, 2,5-diaminopyridine, 2,6-diaminopyridine, 2-amino-6-methylpyridine, 3-amino-6-isopropylpyridine, 4-pyrrolylpyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,3-dimethylpyridine, 2,4-dimethylpyridine, 2,5-dimethylpyridine, 2,6-dimethylpyridine, 3,4-dimethylpyridine, or 3,5-dimethylpyridine.

8. The method of claim 1, wherein, The amine additive is used in a ratio of 0.1 to 1 mole based on 1 mole of 2,6-dimethylphenol.

9. The method of claim 1, wherein, The copper catalyst is selected from one or more of the group consisting of cuprous oxide (I), cuprous halide (I), cuprous sulfate (I), and cuprous nitrate (I), and the amine additive is a pyridine compound; or The copper catalyst is selected from one or more of the group consisting of copper(II) oxide, copper(II) halide, copper(II) sulfate and copper(II) nitrate, and the amine additive is a secondary amine.

10. The method of claim 1, wherein, The oxidative coupling reaction is carried out by supplying air via air bubbling at a rate of 80 cc / min to 350 cc / min.

11. The method of claim 1, wherein, o-methylphenol was separated by fractionation.

12. The method of claim 1, further comprising the step of performing a secondary oxidative coupling reaction on the polyphenylene ether obtained in step 3 in the presence of a copper catalyst and an amine additive.

13. The method of claim 1, further comprising the step of introducing the separated o-methylphenol into the alkylation reaction of step 1 after separating o-methylphenol in step 3.

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