JP2002020481A - Process for producing polyphenylene ether - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a polyphenylene ether wherein the polymerization of a polyphenylene ether is stopped and a metal catalyst is recovered. SOLUTION: In the process for producing a polyphenylene ether by polymerizing a polyphenylene ether in a nonaqueous polymerization solvent in the presence of a catalyst to give a polyphenylene ether solution, bringing the obtained solution into contact with an aqueous solution of a chelating agent to form a chelate compound of a metal catalyst to stop the polymerization, separating the aqueous solution containing the chelate compound of the metal catalyst from the polyphenylene ether solution, and adding an alkali metal sulfide to the aqueous solution to deposit the metal catalyst as its sulfide in the form of a solid material from the aqueous solution, the sulfide of the metal catalyst is subjected to solid-liquid separation by a rotary continuous vacuum filtration system in which a filter aid layer is formed on the surface of a filter medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyphenylene ether. More specifically, the present invention relates to a method for producing polyphenylene ether in which polymerization of polyphenylene ether is stopped to stably separate and recover a metal catalyst.

[0002]

2. Description of the Related Art Polyphenylene ether is obtained by using an oxidative coupling polymerization catalyst containing a phenol compound with copper, manganese, or cobalt, and the presence of oxygen in an aromatic solvent or a mixed solvent of an aromatic solvent and a non-solvent. It is polymerized below. After the reaction, the polyphenylene ether solution is charged with an aqueous solution of a chelating agent to generate a chelate compound of the metal catalyst to stop the reaction, and then the polyphenylene solution and the aqueous solution containing the chelate compound of the metal catalyst are separated, and the polyphenylene ether from which the metal catalyst has been removed. The solution is poured into a poor solvent for polyphenylene ether to solidify the polyphenylene ether. Next, the solidified polyphenylene ether after solidification is sent to a drying step to obtain a powdery polyphenylene ether. On the other hand, in the separated aqueous solution containing the chelate compound of the metal catalyst, the sulfide of the metal catalyst precipitates as a solid by adding the sulfide of the alkali metal, and the metal catalyst is removed by using a solid-liquid separator. Is made. The chelating agent is recovered from the chelating agent aqueous solution from which the metal catalyst has been removed,
The collected chelating agent is recycled for reuse.

[0003]

However, in an actual plant, the amount of the alkali metal sulfide to be added varies with the concentration of the metal contained in the aqueous solution containing the chelate compound of the metal catalyst or the quality of the added alkali metal sulfide. Due to the fluctuation, it was difficult to stably control the addition amount of the sulfide of the alkali metal. That is, if the addition amount is small, the metal catalyst is not sufficiently solidified and separation is insufficient, while if the addition amount is too large, there is a problem that hydrogen sulfide is generated in the subsequent process step of the aqueous solution. I was

[0004] Further, the sulfide of the solidified metal catalyst obtained by the method of the present invention is in the form of fine particles and extremely difficult to handle. There were also problems such as leaks, which forced them to sacrifice poor productivity.

[0005]

Means for Solving the Problems The present inventors have made intensive studies in view of the above circumstances, and have completed the present invention. That is, the present invention provides a polyphenylene ether solution obtained by polymerization in the presence of a catalyst in a water-insoluble polymerization solvent of polyphenylene ether, and bringing the solution into contact with an aqueous solution of a chelating agent to generate a chelate compound of a metal catalyst and terminate the polymerization. Then, the aqueous solution containing the chelate compound of the metal catalyst is separated from the polyphenylene ether solution, and a sulfide of an alkali metal is added to the aqueous solution containing the chelate compound of the metal catalyst, whereby the metal catalyst is precipitated as a sulfide from the aqueous solution as a solid. In the method for producing polyphenylene ether, a sulfide of a metal catalyst is solid-liquid separated by a rotary continuous vacuum filtration method in which a filter aid layer is formed on a filtration surface.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyphenylene ether in the present invention is a homopolymer, a random copolymer or a block copolymer having a repeating unit represented by the general formula (1). (Wherein R ¹ , R ² , R ³ and R ⁴ are each independently hydrogen,
An alkyl group, a substituted alkyl group, a halogen group, a phenyl group, or a substituted phenyl group. )

Representative polyphenylene ethers are poly (2,6-dimethyl-1,4-phenylene) ether,
Poly (2-methyl-6-ethyl-1,4-phenylene)
Ether, poly (2,6-diethyl-1,4-phenylene) ether, poly (2-ethyl-6-n-propyl-)
1,4-phenylene) ether, poly (2,6-di-n)
-Propyl-1,4-phenylene) ether, poly (2
-Methyl-6-n-butyl-1,4-phenylene) ether, poly (2-ethyl-6-isopropyl-1,4-)
Examples include homopolymers such as phenylene) ether, poly (2-methyl-6-chloroethyl-1,4-phenylene) ether, and poly (2-methyl-6-hydroxyethyl-1,4-phenylene) ether. Also, 2,6-
2,3,6- as a copolymer component in dimethylphenol
A random copolymer or a block copolymer obtained by combining one or both of trimethylphenol and o-cresol is exemplified.

The polyphenylene ether of the present invention contains, as a partial structure, various other phenylene ether units which have been proposed to be allowed to exist in the polyphenylene ether so far as they do not contradict the gist of the present invention. You may go out. For example, Japanese Patent Application Laid-Open Nos. 1-297428 and 63-301222 disclose 2-
(Dialkylaminomethyl) -6-methylphenylene ether unit, 2- (N-alkyl-N-phenylaminomethyl) -6-methylphenylene ether unit, and a small amount of diphenoquinone or the like bonded in the main chain of polyphenylene ether resin What was done. further,
Polyphenylene ether modified with a compound having a carbon-carbon double structure (for example, JP-A-2-276823, JP-A-63-108059, JP-A-59-1984)
59724).

The method for polymerizing polyphenylene ether in the present invention is described in, for example, Japanese Patent Publication No. 42-3195, Japanese Patent Publication No. 45-23555, Japanese Patent Publication No. 61-8092, and the like. Oxidative polymerization using a catalyst comprising a combination of a salt of a metal selected from the group consisting of manganese and cobalt and various amines. Among these, preferred metal salts include, specifically, cuprous chloride, cupric chloride, cuprous bromide, and copper bromide.
Copper, cuprous sulfate, cupric sulfate, cuprous acetate, acetic acid second
Copper salts such as copper, cuprous propionate, cupric laurate, cuprous palmitate, cuprous benzoate and the like can be mentioned. Instead of directly adding the metal salt as a combination component, a metal or metal oxide and an inorganic acid, an organic acid or an aqueous solution of these acids are added, and the metal salt or the hydration thereof is added in the reaction system. An object can be formed and used.

The polymerization solvent for the polyphenylene ether in the present invention is a solvent which is not substantially homogeneously mixed with water and is a good solvent for the polyphenylene ether. Examples thereof include aromatic hydrocarbons such as benzene, toluene and xylene, and nitrobenzene and the like. And the like. In addition, the good solvent is a poor solvent for polyphenylene ether, such as alcohols such as methanol and ethanol; aliphatic hydrocarbons such as hexane and heptane; ketones such as acetone and methyl ethyl ketone; and esters such as ethyl acetate. They can be mixed in proportions and compositions and used as a polymerization solvent. If the proportion of the poor solvent in the polymerization solvent increases, polyphenylene ether precipitates during the polymerization, resulting in precipitation polymerization.However, in the present invention, solution polymerization in which the polyphenylene ether does not precipitate after the polymerization is performed by transferring the solution, stopping the reaction, or separating the catalyst. It is preferable in terms of handling in the process and the like. As the good solvent for the polyphenylene ether used as the polymerization solvent, toluene is most preferable from the viewpoint of easy removal of the residual solvent in the drying step.

When the reaction proceeds to the desired viscosity, the polyphenylene ether reaction solution of the present invention is brought into contact with and mixed with an aqueous solution containing a chelating agent, and the chelate compound of the metal catalyst is extracted into the aqueous phase to terminate the reaction. Here, the chelating agent is not particularly limited as long as it is a compound which forms a water-soluble complex with the metal catalyst, and examples thereof include an alkali metal salt of ethylenediaminetetraacetic acid and an alkali metal salt of nitrilotriacetic acid.

The amount of the chelating agent and the amount of the chelating agent aqueous solution are sufficient to form a chelating compound with the metal catalyst contained in the reaction solution, and when the metal catalyst forms the chelating agent compound, the amount of the metal catalyst is reduced from the aqueous solution. The chelating agent is not particularly limited as long as the chelating compound does not precipitate, but the amount of the chelating agent is usually 1 to 10 times, preferably 1.1 to 5 times the amount of the metal catalyst. The amount of the chelating agent aqueous solution is usually 0.01 to 0.01% based on the weight of the reaction solution.
The amount is 1 time, preferably 0.05 to 0.25 times.

[0013] The contact time or contact temperature between the polyphenylene ether reaction solution and the aqueous solution of the chelating agent may be a time or temperature sufficient for extracting the metal catalyst. The contact is performed at a contact temperature range of 50 ° C. to 80 ° C. with a contact time of 30 minutes to 180 minutes.

The aqueous solution containing a chelating agent may be mixed with a known water-soluble reducing agent. Here, examples of the water-soluble reducing agent include dithionite, thiosulfate, and phosphite.

Next, the polyphenylene ether reaction solution is subjected to liquid-liquid separation from the aqueous solution by an industrially used method such as static separation or centrifugation. The separated aqueous solution contained a chelating compound of a metal catalyst, a polymerization solvent in addition to the chelating compound, amines and cocatalysts added during polymerization, a water-soluble reducing agent, and an oxide of a water-soluble reducing agent. It is an aqueous solution. The temperature of the liquid-liquid separation is not particularly limited as long as it is a temperature of 30C to 100C. When the aqueous solution contains a chelating agent in an excessive amount relative to the chelating compound of the metal catalyst, a part of the separated aqueous solution of the chelating agent can be recycled to the reaction stopping step again.

The liquid-liquid separated polyphenylene ether reaction solution can be sent to a polyphenylene ether recovery step. However, after adding water again and contacting and mixing, the reaction solution and the aqueous phase are separated by liquid-liquid separation. It is preferable to remove the chelate compound residue of the metal catalyst remaining in the reaction solution by the following method. After the reaction solution and water are mixed, liquid-liquid separation is performed by an industrially used method such as standing separation or centrifugation. The contact time between the polyphenylene ether reaction solution and water is usually 1 to 60 minutes, preferably 2 to 10 minutes. The mixing temperature is usually 30 to 100 ° C, preferably 50 to 80 ° C. Although there is no particular limitation on the amount of water added, it is usually 0.01 to 1 times the weight of the reaction solution,
Preferably, it is 0.05 to 0.25 times the amount. The water separated by this operation can be mixed with the chelating agent aqueous solution and used in the reaction stopping step, or can be mixed with the chelating agent aqueous solution separated in the reaction stopping step and recovered.

[0017] Alternatively, the chelating agent residue of the metal catalyst remaining in the reaction solution can be removed by contact-mixing with the reaction solution again using an aqueous solution of the chelating agent instead of water. In this case, the separated aqueous solution of the chelating agent is stopped. It is preferable to use it again in the process.

The polyphenylene ether reaction solution after the liquid-liquid separation is brought into contact with a poor solvent to precipitate polyphenylene ether as a solid. Examples of the poor solvent for polyphenylene ether in the present invention include alcohols such as methanol and ethanol, and aliphatic ketones such as acetone. Of these, methanol is most preferred, which has the best poor solvent properties. In some cases, the above-mentioned polymerization solvent for polyphenylene ether or water may be present in the poor solvent within a range that does not hinder the precipitation of polyphenylene ether.

The precipitated polyphenylene ether is solid-liquid separated from the mixture containing the polymerization solvent and the poor solvent continuously or batchwise by a centrifuge or vacuum filtration. The recovered polyphenylene ether is sent to a drying step for commercialization.

The aqueous solution of the chelating agent separated from the reaction solution may give a good result by being concentrated, and the aqueous solution of the chelating agent may be concentrated before the step of recovering the metal catalyst. The amines as catalysts contained in the aqueous solution of the chelating agent are distilled off by azeotropic distillation with water, and the amine can be recovered from the distillate by liquid-liquid separation or extraction with an organic solvent such as a polymerization solvent. The water thus obtained can be recycled for use in any process where water is used in the polyphenylene ether production process.

Here, as a method for efficiently performing amine separation, a method of adding a basic compound to a chelating agent aqueous solution or distilled water can be employed. The basic compound may be any compound having a higher basicity than the amines used as a catalyst, and includes hydroxides, carbonates, or carbonates of alkali metals or alkaline earth metals such as sodium, potassium, and calcium. Hydrogen salts are preferably used. In addition, increasing the metal concentration and the concentration of the chelating agent have led to an improvement in the recovery rate in the subsequent metal catalyst and chelating agent recovery processes, and furthermore, the amount of wastewater finally drained out of the system It also has the effect of reducing

The chelate compound of the metal catalyst dissolved in the aqueous solution of the chelating agent separated from the reaction solution is precipitated as a metal sulfide by mixing with the sulfide of an alkali metal. Examples of the alkali metal sulfide include sodium sulfide, potassium sulfide, and sodium polysulfide, and sodium sulfide is preferably used. The addition form of the sulfide may be a solid or an aqueous solution, but is preferably an aqueous solution state in which the addition amount can be easily controlled by the pump flow rate. In this case, there is no particular limitation as long as the aqueous solution concentration is lower than the sulfide solubility.

The amount of the sulfide of the alkali metal to be added is more than 1 molar equivalent and less than 2 molar equivalents, preferably 1.1 to 1.5 molar equivalents to the metal catalyst. . If the addition amount is less than the stated range, the recovery rate of the metal catalyst decreases, and if the addition amount is excessive, it is economically undesirable. The precipitation temperature may be any temperature at which the aqueous solution does not freeze or boil, but is usually 20 to 70 ° C, preferably 30 to 5
Performed at 0 ° C. The precipitation time is from 1 to 120 minutes, preferably from 5 to 60, if both solutions are mixed uniformly.
Done in minutes.

However, the addition amount of the sulfide of the alkali metal can be calculated from the measurement of the oxidation-reduction potential of the aqueous solution of the chelating agent containing the chelating compound of the metal catalyst.
That is, when an alkali metal sulfide is added to an aqueous solution of a chelating agent in which a chelating compound of a metal catalyst is dissolved, when the oxidation-reduction potential exceeds an equivalent point, the chelating compound of the metal catalyst in the chelating agent aqueous solution disappears. I do. By controlling the amount of alkali metal sulfide added to the oxidation-reduction potential value, stable regardless of the fluctuation of the alkali metal sulfide concentration and / or the fluctuation of the concentration of the metal catalyst dissolved in the aqueous solution of the chelating agent. Can be added with an alkali metal sulfide.

The gas discharge destination of the tank for depositing the metal catalyst is preferably a scrubber with an aqueous alkali solution. If an alkali metal sulfide is mixed with the aqueous solution of the chelating agent, generation of hydrogen sulfide is inevitable. Therefore, in order to capture the generated hydrogen sulfide, it is preferable that the gas discharge destination be a scrubber using an aqueous alkali solution. An alkaline aqueous solution is a hydroxide of an alkali metal or an alkaline earth metal,
Carbonates and bicarbonates. Further, a method of forcibly introducing hydrogen sulfide generated into the scrubber by a blower or the like is preferably used.

The sulfide of the precipitated metal catalyst must be separated from the filtrate by a solid-liquid separator. However, the sulfide of the metal catalyst obtained by the method of the present invention is a fine particle and precipitates in an extremely difficult-to-handle property. A precoat filtration system, preferably a precoat rotary continuous vacuum filtration system is used. Precoat filtration forms an auxiliary layer on the filtration surface and removes the trapped metal catalyst sulfide together with the surface layer of the auxiliary layer, so that a new filtration surface always appears, so that the sulfide of the metal catalyst obtained by the method of the present invention is obtained. Optimum for solid-liquid separation. The auxiliaries may be appropriately selected and used, such as diatomaceous earth, pearlite, carbon, cellulose, activated carbon, and acid clay.
Preferably, diatomaceous earth is used.

The sulfide slurry of the metal catalyst can be directly separated into a solid and a liquid by a precoat filter, but a body feed in which a filter aid is previously mixed with the sulfide slurry of the metal catalyst can also be performed.

The sulfide concentration of the metal catalyst in the slurry is usually 0.1 to 10% by weight, preferably 0.5 to 2 watts.
t%. If the concentration is lower than the above range, the required filtration area becomes large, so an excessive apparatus is required. When the surface layer of the auxiliary layer is scraped off together with the trapping metal catalyst), there is a problem that the amount of surface removal of the auxiliary layer increases. If the concentration of the sulfide slurry of the metal catalyst is higher than the above concentration before the solid-liquid separation of the sulfide of the metal catalyst, the dilution with water or the filtrate of the sulfide slurry of the metal catalyst after the solid-liquid separation is performed. By doing so, the slurry liquid concentration can be controlled within the above concentration range. The temperature of the solid-liquid separation is not particularly limited as long as it is in the same range as the metal catalyst deposition temperature.

Since the filtrate after the above-mentioned solid-liquid separation is an aqueous solution in which various compounds are dissolved in addition to the chelating agent, it is difficult to use the filtrate as it is. Therefore, the chelating agent is once precipitated by adding an inorganic acid to the filtrate, and the chelating agent is separated into a solid and a liquid. Then, the chelating agent is reused again as an aqueous solution of the chelating agent using an inorganic hydroxide. Specifically, the filtrate from which the sulfide of the metal catalyst has been removed is mixed with an inorganic acid or an aqueous solution of an inorganic acid such as hydrochloric acid, hydrobromic acid, phosphoric acid, phosphorous acid, sulfuric acid or sulfurous acid to adjust the pH to 4 or less. 0.0 or less, preferably 3.0 or less, and the chelating agent is a protonated solid. At this time, the higher the concentration of the chelating agent in the aqueous solution, the higher the concentration of the chelating agent, since the higher the concentration of the chelating agent, the higher the yield of the chelating agent. The deposition of the chelating agent can be performed by either a batch method or a continuous method. For adjusting the pH value, a method of controlling the amount of the inorganic acid added while measuring with a pH meter is preferably used. The deposition temperature of the chelating agent is usually 20 to 70 ° C, preferably 30 to 70 ° C.
To 50 ° C., and the deposition time may be any condition under which both solutions are uniformly mixed, and is usually 1 to 120 minutes, preferably 5 to 120 minutes.
It takes 60 minutes.

Once the solidified chelating agent is subjected to solid-liquid separation, it is separated from the filtrate. As the solid-liquid separation method, a usual centrifugal separation, vacuum filtration, or pressure filtration method may be appropriately selected, and any of a batch system or a continuous system may be employed. There is no particular limitation on the solid-liquid separation temperature, but it is preferable that the separation be performed within the range of the deposition temperature of the chelating agent.

The chelating agent separated from the filtrate is mixed with an aqueous solution of an inorganic hydroxide typified by sodium hydroxide, potassium hydroxide or the like to make an aqueous solution again. At this time, the amount of the inorganic hydroxide may be any amount as long as the solidified chelating agent is dissolved or more, preferably two or more coordination with the chelating agent, more preferably three or more coordination, The concentration of the aqueous solution of the chelating agent after dissolution of the chelating agent is not particularly limited as long as the concentration is not higher than the solubility of the chelating agent. The pH value of the aqueous solution of the chelating agent at that time is generally in the range of 7.1 to 14.0, preferably in the range of 7.5 to 12.0.

The dissolution of the chelating agent after the solid-liquid separation may be carried out by transferring the solid chelating agent to an independent tank and contacting and mixing it with an aqueous alkali solution, or dissolving the solid chelating agent and the aqueous alkaline solution in a solid-liquid separator. Any method of mixing and dissolving may be used. Also, when dissolving in the solid-liquid separator, if the dissolution time of the chelating agent is shorter than the introduction time of the aqueous alkali solution, adopt a method of dissolving the solid chelating agent by circulating the filtrate a plurality of times in the solid-liquid separator. Can be.

The dissolution temperature and the dissolution time may be set at a temperature and a time at which the chelating agent is completely dissolved, usually at 10 to 70 ° C, for 1 to 60 minutes, preferably at 30 to 50 ° C.
For 5 to 30 minutes. Further, the obtained aqueous solution of the chelating agent is recycled to the reaction stopping step again after adjusting the concentration or as it is.

It is preferable that a gas discharge destination of a device or a tank used in the chelating agent recovery step is a scrubber using an alkaline aqueous solution. By adding an inorganic acid in the chelating agent recovery step, hydrogen sulfide is generated by a reaction between the alkali metal sulfide added excessively and the inorganic acid. In order to capture the generated hydrogen sulfide, it is preferable that the gas discharge destination is a scrubber using an aqueous alkali solution. The aqueous alkali solution includes hydroxides, carbonates, and hydrogen carbonates of alkali metals or alkaline earth metals. Further, a method of forcibly introducing hydrogen sulfide generated into the scrubber by a blower or the like is preferably used. Further, a method is preferably used in which a gas discharge pipe is connected to the scrubber introduction pipe in the above-mentioned metal catalyst recovery step, and a gas is led to the scrubber as a collective pipe.

[0035]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.

Example 1 [Polymerization of polyphenylene ether] Cupric bromide 22 g,
A solution of 2350 g of 2,6-dimethylphenol dissolved in 5400 g of toluene was added dropwise to the catalyst solution of 400 g of dibutylamine and 9800 g of toluene over 10 minutes while supplying air at a rate of 10 NL / min per kg of the monomer. Polymerization was performed. After 120 minutes from the dropping of the monomer, 1800 g of an aqueous solution in which 56 g of tetrasodium ethylenediaminetetraacetate was dissolved was added to the reaction solution with stirring to stop the reaction, and the reaction solution was withdrawn from the polymerization vessel. 70
After stirring in a nitrogen atmosphere at 2 ° C. for 2 hours, the reaction solution and the aqueous solution were separated by a continuous centrifuge. Further, 1800 g of pure water was added to the reaction solution after the separation, and the mixture was stirred at 70 ° C. for 5 minutes, and then the reaction solution and the aqueous solution were separated by a continuous centrifuge. After mixing the two aqueous solutions obtained by the above operation, a metal catalyst recovery operation was performed.

[Recovery of Metal Catalyst] The aqueous solution was concentrated by simple distillation to a copper concentration of 0.60% by weight, and the oxidation-reduction potential was measured by an ORP meter.
A wt% aqueous solution was added dropwise. Black copper sulfide began to precipitate with the addition of sodium sulfide, and the aqueous solution, which had initially exhibited a blue color, gradually turned yellow. The addition of the aqueous sodium sulfide solution was stopped when the slope of the change in the ORP meter indicated value with respect to the added amount of the aqueous sodium sulfide solution changed.
At this time, the added amount of sodium sulfide was 1.
It was 15 times mol.

[Recovery of Copper Sulfide] The copper sulfide slurry solution (copper sulfide concentration: 0.9 wt%) obtained above was subjected to a suction filter in which an auxiliary layer of diatomaceous earth (Radiolite # 600) was formed on the filtration surface. (Precoat filter), immerse the filtration surface in a slurry liquid temperature-controlled to 40 ° C.
Suction filtration was performed for 40 seconds while reducing the pressure in a. The filtration surface was separated from the slurry liquid, suction was further continued for 120 seconds, and then suction was stopped. Copper sulfide was uniformly adsorbed on the filtration surface, and a smooth surface of a new diatomaceous earth auxiliary layer appeared by shaving the diatomaceous earth auxiliary layer by 1 mm, showing good precoat filter properties.

Example 2 An experiment was conducted in the same manner as in Example 1 except that the copper sulfide concentration of the copper sulfide slurry was changed to 2.5 wt%. Copper sulfide was slightly peeled off from the filtration surface, and a 2 mm thick diatomaceous earth auxiliary layer showed a smooth surface of a new diatomaceous earth auxiliary layer, showing good precoat filter properties.

Comparative Example 1 The same method as in Example 1 was used except that a suction filter having a filtration surface having a felt layer having a thickness of 10 mm was used. A large amount of copper sulfide remained without being separated from the filtration surface. In addition, copper sulfide penetrated into the inside of the felt layer, indicating that the filtration characteristics were poor.

COMPARATIVE EXAMPLE 2 A 1 mm thick polypropylene cloth (air permeable 12 cm)
Example 1 except that a suction filter of ³ / cm ² · s) was used.
The same method was used. A large amount of copper sulfide remained on the filter cloth without peeling from the filtration surface. Further, a large amount of copper sulfide leaked into the filtrate, indicating that the filtration characteristics were poor.

COMPARATIVE EXAMPLE 3 When adding a 10 wt% aqueous solution of sodium sulfide, the oxidation-reduction potential was not measured by an ORP meter. The experiment was performed in the same manner as in Example 1 except that the solution was dropped. The temperature of the obtained copper sulfide slurry solution (copper sulfide concentration: 0.9 wt%) is adjusted to 40 ° C. by a suction filter (precoat filter) having an auxiliary layer of diatomaceous earth (Radiolite # 600) formed on the filtration surface. The filtration surface was immersed in the slurry liquid thus obtained, and suction-filtered for 40 seconds while reducing the pressure at -0.05 MPa. The filtration surface was separated from the slurry liquid, suction was further continued for 120 seconds, and then suction was stopped.
However, the recovered filtrate was still blue, suggesting that copper ions were dissolved in the recovered aqueous solution of the metal catalyst.

[0043]

According to the method of the present invention, a method for producing polyphenylene ether is provided in which an alkali metal sulfide is added to an aqueous solution containing a chelate compound of a metal catalyst, and the metal catalyst is precipitated as a sulfide from the aqueous solution as a solid. In order to solve the problems such as clogging of filter cloth and leakage to the filtrate side by solid-liquid separation of sulfide of metal catalyst by rotary continuous vacuum filtration method that forms a filter aid layer on the filtration surface It has the effect that it can be done.

Claims (6)

[Claims] 1. A polyphenylene ether solution obtained by polymerization in a water-insoluble polymerization solvent of polyphenylene ether in the presence of a catalyst is brought into contact with an aqueous solution of a chelating agent to form a chelate compound of a metal catalyst to terminate the polymerization. By separating an aqueous solution containing a metal catalyst chelate compound from a polyphenylene ether solution and adding an alkali metal sulfide to the aqueous solution containing a metal catalyst chelate compound, the metal catalyst is precipitated as a sulfide from the aqueous solution as a solid. A method for producing a polyphenylene ether, wherein a sulfide of a metal catalyst is subjected to solid-liquid separation by a rotary continuous vacuum filtration method in which a filter aid layer is formed on a filtration surface. 2. The method for producing polyphenylene ether according to claim 1, wherein a gas discharge destination of a tank for mixing an alkali metal sulfide with the chelate compound-containing aqueous solution is a scrubber using an alkaline aqueous solution. 3. The method for producing polyphenylene ether according to claim 1, wherein the addition amount of the sulfide of the alkali metal is 1.1 to 1.5 times the molar equivalent of the metal catalyst. 4. The method according to claim 1, wherein when the metal catalyst sulfide is subjected to solid-liquid separation by a continuous vacuum filtration method using a filter aid, the sulfide concentration of the metal catalyst is 2 wt% or less based on the total weight.
3. The method for producing a polyphenylene ether according to 1. 5. The method for producing polyphenylene ether according to claim 1, wherein the metal catalyst is a copper compound. 6. An inorganic acid is added to the filtrate obtained after solid-liquid separation of the sulfide of the metal catalyst, and the pH is adjusted to 3 or less to cause the chelating agent to precipitate from the aqueous solution. The method for producing polyphenylene ether according to claim 1, wherein an aqueous solution of a metal hydroxide is mixed to dissolve the chelating agent.