JP2002003594A - Method of producing polyphenylene ether - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing polyphenylene ether in which the distillating column for recovering a polymerization solvent for the polyphenylene ether is stably operated. SOLUTION: This method comprises, after polymerization of polyphenylene ether, separating the polymerization solvent by extraction, and distilling the solvent to separate a higher boiling compound from the polymerization solvent, where viscosity of the liquid from the distillation still is monitored.

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 stably recovering a polyphenylene ether polymerization solvent.

[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 obtained by polymerization below. After the reaction is stopped and the catalyst is removed, the polyphenylene ether solution after the reaction is introduced into a poor solvent for polyphenylene ether and solidified. Thereafter, the solid-liquid separated polyphenylene ether is sent to a drying step to obtain a powdery polyphenylene ether.
On the other hand, the filtrate, which has been subjected to solid-liquid separation, and solvents typified by the volatile solvent in the drying step are sent to a solvent recovery step, separated into a polymerization solvent and a poor solvent, and reused. Also,
In the solvent recovery step, recovery of an organic catalyst such as amines is also performed.

[0003]

However, when the polymerization solvent is distilled and recovered in the solvent recovery step, high boiling compounds derived from the polyphenylene ether polymer are present in the filtrate. It has been difficult to stably operate the distillation column and recover the polymerization solvent due to problems such as precipitation in the bottoms transfer pipe or blockage of the pipe due to an increase in viscosity.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above circumstances, and as a result, when the liquid viscosity of the bottoms of the polymerization solvent recovery distillation column exceeds a certain value, the risk of clogging of the piping becomes remarkable. Increase, and furthermore, the fact that the fluctuation of the bottom liquid viscosity due to temperature fluctuation becomes intense and it becomes difficult to secure a stable flow rate during transfer, and the above problem is solved by monitoring the liquid viscosity of the bottom liquid, The distillation column can be operated stably, and a method for recovering the polymerization solvent has been completed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyphenylene ether in the present invention is a homopolymer, a random copolymer and 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,
It is a substituted phenyl group. )

Typical 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 thereof 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-dimethylphenol as a copolymer component,
Examples thereof include a random copolymer and a block copolymer of polyphenylene ether in which one or both of 3,6-trimethylphenol and o-cresol are combined.

Further, the polyphenylene ether of the present invention contains, as a partial structure, various other phenylene ether units which have been proposed to be present 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 polyphenylene ether of the present invention is disclosed, for example, in JP-B-42-3195 and JP-B-45-235.
No. 55, JP-B-61-8092, etc., a phenolic compound is prepared by combining a salt of a metal selected from the group consisting of copper, manganese or cobalt with various amines and a catalyst comprising a cocatalyst. It is manufactured by oxidative polymerization.

The polyphenylene ether polymerization solvent used in the present invention includes aromatic hydrocarbons such as benzene, toluene and xylene, which are water-insoluble solvents and good solvents for polyphenylene ether, and nitro compounds such as nitrobenzene. Also, a good solvent for polyphenylene ether,
Alcohols such as methanol and ethanol, which are poor solvents for polyphenylene ether, can be mixed at any ratio and composition 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. The polymerization solvent for polyphenylene ether used as the polymerization solvent is most preferably toluene from the viewpoint of easy removal of the residual solvent in the drying step.

After the reaction, the polyphenylene ether of the present invention is brought into contact with an aqueous solution containing a chelating agent to extract the metal catalyst into the aqueous phase, thereby terminating the reaction. The chelating agent used here is not particularly limited as long as it is a compound that 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 aqueous solution containing the 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.

After the reaction solution is subjected to liquid-liquid separation from water containing a chelating agent, it is brought into contact with a water-soluble poor solvent to precipitate polyphenylene ether as a solid. Water-soluble poor solvent used for solidification of polyphenylene ether in the present invention,
For example, alcohols such as methanol and ethanol are preferable, and among them, methanol having the best poor solvent property is most preferable. The water-soluble poor solvent may contain an impurity component such as a polymerization solvent, an amine used for a polymerization catalyst, or water as long as the solidification is not hindered.

The solidified polyphenylene ether is separated into a wet polyphenylene ether and a filtrate by solid-liquid separation. The wet polyphenylene ether is sent to a drying step to be converted into a powdery polyphenylene ether. On the other hand, the main components of the filtrate are a polymerization solvent and a solidification poor solvent, which include amine added during polymerization, a chelating agent residue used for terminating polymerization, water, and / or polyphenylene ether fine powder, polyphenylene as a high boiling point compound. Ether oligomers, polymerization by-products, and the like.

The filtrate is separated into a polymerization solvent and a poor solvent by itself or by mixing with a solvent mixture generated from other steps such as a polymerization step, a drying step and a solvent recovery step. As the separation method, extraction separation with water is preferably used, and 0.5 to 2.0 times water with respect to the weight of the poor solvent, and at a temperature in the range of 0 ° C to 100 ° C for 1 minute to 60 minutes. During that time, it is performed by contact mixing. The aqueous phase containing the poor solvent thus extracted is subjected to liquid-liquid separation from the polymerization solvent by a known suitable means.

The polymerization solvent separated by extraction still contains a water-soluble poor solvent, a light-boiling compound typified by water, and a high-boiling compound typified by a polyphenylene ether polymer. Unless the boiling compounds and high boiling compounds are removed, they cannot be recycled as polymerization solvents. The method of removing the light-boiling compound and the high-boiling compound by distillation is, for example, a method of simultaneously separating the light-boiling component and the high-boiling compound by one distillation column, or a method of separating the light-boiling component and the high-boiling compound by two or more distillation columns connected in series. A method of sequentially separating high-boiling compounds can be used. There is no particular limitation on the type of distillation column, and examples thereof include a tray distillation column and a packed distillation column. These methods may be used in various combinations.
The distillation is usually carried out by a continuous distillation method, and the polymerization solvent is separated into three types: a recovered polymerization solvent, a mixture of the polymerization solvent and a low-boiling compound, and a bottom liquid which is a mixture of the polymerization solvent and a high-boiling compound.

When the amine used for the polymerization catalyst is contained in the polymerization solvent after the water extraction separation, the amines are recovered and recycled. Although it is possible to independently recover the amines using a dedicated distillation facility, it is preferable to recover the amines simultaneously with the polymerization solvent when recovering the polymerization solvent because the number of distillation columns can be reduced. Here, the amine may be a catalyst used for polyphenylene ether polymerization, and may be one kind or a mixture of two or more kinds.

In the bottoms of the polymerization solvent distillation, the high-boiling compounds are discharged out of the distillation column as a mixture with the polymerization solvent.
It is necessary that the pressure be not more than a · s, preferably not more than 3 mPa · s. If the bottoms viscosity exceeds this range, blockage in the bottoms transfer pipe becomes remarkable, and it is necessary to increase the capacity of a liquid sending pump for flowing the bottoms, which is economically disadvantageous.

Furthermore, it is preferable that the bottoms viscosity does not fluctuate with a change in temperature. Specifically, the difference between the viscosity of the distillation bottom at 120 ° C and the viscosity of the distillation bottom at 50 ° C is 10
mPa · s or less, more preferably 5 mPa · s or less. If the temperature exceeds the range, the viscosity of the bottom liquid with respect to the temperature change in the piping becomes large, which causes a problem that uniform transfer of the bottom liquid becomes difficult.

The high-boiling compounds contained in the bottoms are various and generally contain a polyphenylene ether monomer polymer as a main component, but are modified with polyphenylene ether monomer impurities and diphenoquinone and diphenoquinone, which are by-products of polyphenylene ether polymerization. Hydroquinone and the like are also included. Further, in addition to the compounds derived from the polyphenylene ether monomer, impurities such as polymerization solvent impurities, solidification solvent impurities, and catalyst impurities are also included. Also included are polyphenylene ether monomers, polymerization catalysts, polymerization solvents, poor solidification solvents, and compounds obtained by oxidizing or heat-modifying the above listed compounds alone and / or in combination of two or more kinds in the polymerization step or the distillation step. I have.

In the present invention, maintaining the bottoms viscosity at 120 ° C. at 6 mPa · s or less means that the amount of high boiling compounds in the bottoms is 60% by weight based on the total weight of the bottoms. It corresponds to the following. Also, the bottoms viscosity is 120 ° C
Holding at 3 mPa · s or less means that the amount of the high-boiling compound in the bottoms is 50% by weight or less based on the total weight of the bottoms. The method for quantifying the high-boiling compound can be determined by dividing the weight of the bottom liquid after drying at 120 ° C. for 24 hours by a vacuum dryer by the amount of the bottom liquid sample.

The operation control of the distillation column for continuously recovering the polymerization solvent is usually controlled by the discharge flow rate of the bottom liquid or the bottom temperature of the condensing tank. By measuring the effluent viscosity and setting the discharge flow rate of the bottoms or the temperature of the bottoms, the polymerization solvent recovery distillation column can be operated stably.

In order to prevent the clogging of the piping, the bottom portion is heated at a temperature of 20 to 150 ° C., preferably 30 to 150 ° C.
It is preferable to keep the temperature in the range of -120 ° C. If the bottom temperature falls below the above temperature range, the risk of pipe blockage increases. On the other hand, when the temperature is higher than the above temperature range, boiling of the polymerization solvent and precipitation of the high boiling point compound occur in the pipe, and it becomes difficult to discharge the bottom liquid stably.

[0022]

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

Example 1 In a catalyst solution of 22 g of cupric bromide, 400 g of dibutylamine and 9800 g of toluene, 2350 g of 2,6-dimethylphenol was dissolved in 5400 g of toluene while supplying air at 10 NL / min per kg of monomer. The resulting solution was added dropwise over 60 minutes, and polymerization was carried out at 40 ° C. After 120 minutes from the dropping of the monomer, an aqueous solution in which tetrasodium ethylenediaminetetraacetate was dissolved in a 1.5-fold molar amount with respect to the catalyst copper (the amount of the aqueous solution was 0.2 times the total amount of the polymerization reaction solution) was added to the reaction solution while stirring, and the reaction was performed. The operation was stopped, and the reaction solution was discharged from the polymerization vessel. The extracted reaction solution was separated into a toluene phase and an aqueous phase using a centrifugal separator, and the separated toluene phase was poured into methanol twice the weight of the toluene phase to precipitate polyphenylene ether. The solution after the filtration was contact-mixed with the same amount of water as methanol at 40 ° C. for 30 minutes to extract the methanol into an aqueous phase, and separated into a toluene phase and a water / methanol phase by centrifugation. The toluene phase was distilled off by a distillation apparatus equipped with a reflux device to remove components distilled off up to a boiling point of 70 ° C. to obtain a mixture of a high-boiling organic substance and toluene. This operation was repeated to obtain a mixture of a high boiling organic substance and toluene.

Using a continuous simple distillation apparatus, a mixture of a high-boiling organic substance and toluene was introduced at a rate of 500 g / min.
The sample was extracted at 0 ° C. so as to have a pressure of 2.1 mPa · s. The withdrawal of the can was performed well. Table 1 shows the temperature dependence of the obtained bottoms viscosity. The bottoms had low viscosity and low temperature dependence. The average concentration of high boiling compounds in the bottoms was 42% by weight.

Table 1 Temperature ° C 120 100 50 Boiler viscosity mPa · s 2.1 2.6 4.3

Example 2 The bottom concentration was increased, and the bottom liquid was 3.8 mPa at 120 ° C.
An experiment was performed in the same manner as in Example 1 except that the sample was extracted so as to obtain s. The withdrawal of the can was performed well. Table 2 shows the temperature dependence of the obtained bottoms viscosity. The bottoms had low viscosity and low temperature dependence.
The average concentration of high boiling compounds in the bottoms was 54% by weight.

Table 2 Temperature ° C 120 100 50 Canned product viscosity mPa · s 3.8 5.1 8.9

COMPARATIVE EXAMPLE 1 The bottom concentration was increased and the bottom liquid was 6.5 mPa.
An experiment was performed in the same manner as in Example 1 except that the sample was extracted so as to obtain s. During the distillation operation, a problem withdrawing the bottom liquid occurred due to blockage of the piping. Table 3 shows the temperature dependence of the obtained bottoms viscosity. The viscosity of the bottoms was high and the temperature dependence was large, suggesting the risk of pipe blockage in the actual plant. The average concentration of high boiling compounds in the bottoms is 65
% By weight.

Table 3 Temperature ° C 120 100 50 Canned product viscosity mPa · s 6.5 9.6 17.4

[0030]

According to the method of the present invention, the distillation column for recovering the polymerization solvent can be stably operated by monitoring the liquid viscosity of the bottom of the distillation column for recovery of the polymerization solvent. Therefore, the polymerization solvent recovered by distillation can be recycled as the polymerization solvent to stably produce polyphenylene ether.

Claims (7)

[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 terminate the polymerization and deactivate the catalyst. In a method for producing a polyphenylene ether, wherein a polyphenylene ether is recovered by adding a poor solvent of a polyphenylene ether which is soluble in water and has a lower boiling point than the polymerization solvent, a polyphenylene ether polymerization solvent is prepared from a mixture of the polyphenylene ether polymerization solvent and the high-boiling compound. A process for separating polybutadiene by distillation, wherein the viscosity of the distillate bottom is monitored. 2. The distillation bottoms viscosity at 120 ° C. is 6 m.
The method for producing a polyphenylene ether according to claim 1, wherein the pressure is Pa · s or less. 3. The distillate bottom viscosity at 120 ° C. and 50
The method for producing polyphenylene ether according to claim 1, wherein a difference in the viscosity of the distillation bottoms at 10 ° C is 10 mPa · s or less. 4. The distillation bottom liquid has a viscosity of 3 m at 120 ° C.
The method for producing a polyphenylene ether according to claim 1, wherein the pressure is Pa · s or less. 5. The distillation bottoms viscosity at 120 ° C. and 50
The method for producing a polyphenylene ether according to claim 1, wherein the difference in the viscosity of the distillation bottom at 5 ° C is 5 mPa · s or less. 6. The poor solvent for the polyphenylene ether,
The method for producing a polyphenylene ether according to claim 1, which is methanol. 7. The method for producing a polyphenylene ether according to claim 1, wherein the water-insoluble polymerization solvent for the polyphenylene ether is toluene.