KR960004115B1 - Method for purifying a polyphenylenether ether - Google Patents

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Description

Method for Purifying Polyphenylene Ether

The present invention relates to a process for the purification of polyphenylene ethers produced by oxidative polymerization of 2,6-disubstituted phenols.

Polyphenylene ether, a polymer produced by the oxidative polymerization of 2,6-disubstituted phenol, has excellent mechanical properties, electrical properties, heat resistance, etc. and hardly absorbs moisture. Therefore, a great deal of attention has been paid to the use of polyphenylene ethers as thermoplastic industrial plastics.

Generally this polyphenylene ether is produced by oxidative polymerization of 2,6-disubstituted phenols in organic solvents. Polyphenylene ether is recovered from the polymerization solution and purified by contacting the polymerization solution with a poor solvent such as methanol. The catalyst used is decomposed before or simultaneously with extraction or performing this operation.

Several methods of extracting or cracking the catalyst are presented. U.S. Patent No. 3,630,995 discloses the use of inorganic acids such as hydrochloric acid or organic acids such as acetic acid as solvents to extract or decompose the catalyst. U.S. Pat. Presented. US Pat. No. 4,452,164 discloses washing a reaction product obtained by precipitation polymerization using a specific polymerization medium with chelating agents such as EDTA and water.

However, the method using hydrochloric acid or acetic acid has the disadvantage that the obtained polymer is markedly discolored during thermoforming. The addition of chelating agents, such as EDTA, to the reaction product obtained by solution polymerization reduces the intrinsic viscosity of the polyphenylethers during the purification step.

The present inventors have conducted extensive and in-depth studies on the method for separating and purifying polyphenylene ethers which do not have the above-mentioned problems. As a result, the present inventors have found a method for purifying polyphenylene ether to purify the polymer by adding an aminocarboxylic acid derivative to the reaction product obtained by the precipitation polymerization method and then washing with a poor solvent for polyphenylene ether. This method has the drawback that the polymer discolors during thermoforming of the polymer and the intrinsic viscosity is reduced in the purification step. This completes the present invention.

The present invention provides a process for purifying polyphenylene ether. This method uses polyphenylene from reaction products obtained by oxidative polymerization of 2,6-disubstituted phenols using precipitation polymerization, in which a polymer precipitates in the presence of a catalyst composed of copper ions, halide ions and at least one type of amine. The ether is separated, an amino carboxylic acid derivative is added to the reaction product, the polymer is washed with a poor solvent for polyphenylene ether, and the resulting polyphenylene ether is purified.

The 2,6-disubstituted phenol used in the method of the present invention is represented by the following general formula.

(Wherein R ₁ represents a hydrocarbon residue having 1 to 4 carbon atoms; R ₂ represents a halogen atom or a hydrocarbon residue having 1 to 4 carbon atoms.)

Examples of such phenolic compounds include 2,6-dimethylphenol, 2-methyl-6-ethylphenol, 2,6-diethylphenol, 2-ethyl-6-n-propylphenol, 2-methyl-6-chlorophenol , 2-ethyl-6-bromophenol, 2-methyl-6-isopropylphenol, 2-methyl-6-n-propylphenol, 2-ethyl-6-bromophenol, 2-methyl-6-n- Butylphenol, 2,6-di-n-propylphenol, 2-ethyl-6-chlorophenol and the like. These compounds can be used individually or in mixture. In practical use, the phenolic compound may contain small amounts of o-cresol, m-cresol, p-cresol, 2,4-dimethylphenol, 2-ethylphenol and the like. Among them, 2,6-disubstituted phenol and 2,6-dimethyl phenol are particularly preferable.

As a raw material of the copper ion used by this invention, a cuprous salt, a cupric salt, or a mixture thereof can be used.

Both the cuprous and cupric compounds may actually be used. The compound can be selected in terms of economics and usability. Soluble copper salts are of course preferred, but insoluble compounds (copper and cuprous) in the reaction mixture together with amines form soluble complexes and generally insoluble compounds can also be used.

Examples of cuprous compounds used in the present invention include cuprous chloride, cuprous bromide, cuprous sulfate, cuprous nitrate, cuprous azide, cuprous acetate, cuprous butyrate, toll Cuprous acid, and the like. Examples of the cupric compound include cupric chloride and cupric bromide such as cupric chloride, cupric sulfate, cupric nitrate, cupric acetate, cuprous azide, cuprous toluene, and the like. There is this. Among them, preferred cuprous and cupric compounds are cuprous chloride, cupric chloride, cuprous bromide and cupric bromide. These copper salts can be synthesized from oxides, carbides, hydroxides, or the like or from halogens or hydrogen halides. The amount of copper compound is in the range of 0.005 to 1.0, preferably 0.01 to 0.5 copper gram atoms per 100 moles of 2,6-disubstituted phenol compound.

As a raw material of the halide ions used in the present invention, inorganic halides, halogens, hydrogen halides and mixtures thereof can be used. As halide ions, chlorine ions and bromine ions are particularly preferred.

Examples of inorganic halides include alkali metal salts such as sodium chloride, sodium bromide, potassium chloride, potassium bromide, and alkaline earth metal salts such as magnesium chloride, magnesium bromide, calcium chloride, calcium bromide, and the like. As the halogen, chlorine and bromine can be used.

As the hydrogen halide, hydrochloric acid and hydrobromic acid can be used.

As an example of the amine component used in the present invention, an amine component containing at least one secondary alkylenediamine, at least one tertiary amine and at least one secondary monoamine can be preferably used.

Secondary alkylenediamines are represented by the general formula:

R ¹ HN-R ² -NHR ₃

(Wherein R ¹ and R ³ each represent an isopropyl group, a C4-8 tertiary alkyl group or a cycloalkyl group having no hydrogen atom on the α-carbon atom; R ² represents an alkylene group having 2-4 carbon atoms or Examples of these compounds include N, N'-di-t-butylethylenediamine, N, N'-di-t-acylethylenediamine, and N, N'-diiso. Propyl-ethylenediamine and the like. The amount of diamine used is generally from 0 to 4 moles per gram copper.

Examples of tertiary amines used in the present invention include trimethylamine, triethylamine, tripropylamine, tributylamine, triisopropylamine, diethylmethylamine, dimethylpropylamine, allyldiethylamine, dimethyl-n-butyl Tertiary aliphatic amines, including tertiary aliphatic cyclic amines such as amines, diethylisopropylamine and the like. In addition, tertiary aliphatic polyamines such as N, N, N ', N'-tetraalkylethylenediamine, N, N, N', N'-tetraalkylpropanediamine and the like can be used. Examples of tertiary aliphatic polyamines are N, N, N ', N'-tetramethylethylenediamine and N, N, N', N'-tetramethyl-1,3-diaminopropane.

These tertiary amines can be used in amounts of 5 to 100 moles, preferably 10 to 60 moles per gram copper.

Examples of secondary mono amines include secondary aliphatic amines such as dimethylamine, diethylamine, di-isopropylamine and di-n-butylamine; Secondary cyclic hydrocarbon amines such as dicyclohexylamine; Secondary aliphatic ring amines such as piperidine, piperazine and morpholine; Secondary alkanolamines such as diethanolamine and di-isopropanolamine; N-alkylalkanolamines such as N-methylethanolamine, N-ethylethanolamine and N-t-butylethanolamine; And N-arylalkanolamines such as N-phenylethanolamine. The amount of secondary monoamine is in the range of 0.05 to 10 moles, preferably 0.1 to 5 moles per 100 moles of 2,6-disubstituted phenol.

Quaternary ammonium salts and surfactants can be added to the reaction system to increase the reaction rate, control the particle size of the polymer and improve phase separation between solvents.

If the reaction temperature is too low, the reaction proceeds slowly. Conversely, if the reaction temperature is too high, the catalyst is inactivated. Therefore, the reaction temperature is generally in the range of 0 to 80 캜, preferably 10 to 60 캜.

As the oxygen, a mixed gas containing an inert gas such as pure oxygen gas and nitrogen gas and an oxygen gas in an arbitrary ratio, air or the like can be used. As pressure, atmospheric pressure or pressurization can be used.

The polymerization medium used in the process of the present invention is not particularly limited as long as the polymerization is carried out by precipitation polymerization. The medium is more resistant to oxidation than the oxidized 2,6-disubstituted phenol and does not react with the various radicals generated during the reaction. However, media that can dissolve not only 2,6-disubstituted phenols but also catalysts are preferred. Aromatic hydrocarbons such as, for example, benzene, toluene, ethylbenzene and xylene; Halogenated hydrocarbons such as chloroform, 1,2-dichloroethane, trichloroethane, chlorobenzene and dichlorobenzene; Aromatic hydrocarbons such as nitro compounds such as nitrobenzene are used as good solvents for polymers. Examples of poor solvents for polymers include alcohols such as methanol, ethanol, propanol, butanol, benzyl alcohol and cyclohexanol, ketones such as acetone and methylethylkenone; Esters such as ethyl acetate and ethyl formate; Ethers such as tetrahydrofuran and diethyl ether; Amides such as dimethylformamide, and the like. Such good and bad solvents are used in the present invention as good-bad solvent pairs containing one solvent in each form or two or more different solvents in one form. Precipitation polymerization is carried out by selecting the mixing ratio of the good solvent for the polymer to the poor solvent, wherein the polymer precipitates as particles in the reaction system as the reaction proceeds. The ratio of the good solvent to the bad solvent is 3: 7-9: 1 by weight, preferably 4: 6-8: 2. In the precipitation polymerization method, polymer particles having an average particle diameter of 1 to 3000 µm and a narrow particle diameter distribution are obtained. The particles are morphed into a suitable shape in a wash to remove the catalyst metal.

The present invention can be applied to both batch polymerization and continuous polymerization. It is preferable to apply the present invention to the continuous precipitation polymerization method, since a pure white polymer can be obtained which not only has high polymerization activity but also has a narrow molecular weight distribution and hardly discolors due to heat.

One example of a continuous precipitation polymerization method is described in US Pat. No. 3,789,054.

That is, in the above continuous method, a polyphenylene ether is obtained by a polymerization reaction of a phenol compound in which a polyphenylene ether is precipitated as the reaction proceeds by using a combination of two polymerization tanks of completely mixed type, each having a different action. do. This requires a first polymerization tank in which the reaction proceeds in a uniform solution state and a second polymerization tank in which stable polyphenylene ether particles are separated. In addition, if necessary, a third polymerization tank is installed to adjust the aging and final properties to perform the post-treatment step to finish the polymer particles. Each of these polymer tanks can be divided into a number of tanks for more detailed control.

Now, the tank will be described in more detail. In the first polymerization tank, the flow rate of the oxygen gas and the average residence time of the reaction mixture are controlled so that the degree of conversion of the monomer is suppressed to 90% or less in order to prevent the polymer from being separated, and at the same time, the reaction mixture increases in viscosity much. It is possible to use a tank in a form in which the heat of polymerization is sufficiently removed by using a feature of a uniform solution. In the second polymerization tank, it is possible to prevent the separated polymer particles from adhering to the tank wall, the stirring element, etc. by controlling the composition medium, that is, by adjusting their weight to good / poor blending and weight ratio, and at the same time The size and stiffness of are controlled by keeping the reaction medium agitated and supplying oxygen gas properly.

The third polymerization tank often acts as a polymerizable role as an aging tank so that polymer particles of a size and stiffness suitable for filtration and drying in the post-treatment process are obtained. In the third polymerization tank, the stirring conditions and the residence time are precisely controlled.

The most preferred range of operating conditions for such continuous polymers may be selected depending on the type of catalyst, 2,6-disubstituted phenol and the medium, in particular the concentration of monomeric 2,6-disubstituted phenol. For example, the concentration of the monomer may be 10 to 40% by weight relative to the total amount of the polymerization solution, which is different from the case of using the homogeneous solution polymerization method. In particular, the monomer concentration is preferably 20 to 35% by weight, because the characteristics of the continuous polymerization method in the precipitation forming system are well represented within this range.

The reason for using the fully mixed polymerization tank as the polymerization tank in this method is that in all reaction tanks, the tetrahedral polymerization of 2,6-disubstituted phenol needs to increase the contact efficiency of 2,6-disubstituted phenol with oxygen gas. This is because sufficient stirring must be performed. That is, no polymerization tank is suitable in which agitation of the reaction mixture does not occur in the flow direction of the mixture when the reaction mixture has a viscosity as low as that used in the present invention.

In other words, as mentioned above, at least two fully mixed reaction tanks must be combined to carry out this polymerization method, which has an average residence time and agitation to show its function as a reaction tank.

As used herein, "aminocarboxylic acid derivatives" are polyalkylene polyamine polycarboxylic acids, cycloalkylenepolyamine polycarboxylic acids, polyalkylene ether polyamine polycarboxylic acids, aminopolycarboxylic acids, aminocarboxyl Acid, alkali metal salts of these acids, alkaline earth metal salts of these acids, mixtures of alkali metal salts and earth metal salts of these acids, and the like. These aminocarboxylic acid derivatives can be used individually or in mixture. Among the above-mentioned compounds belonging to the aminocarboxylic acid derivatives, preferred examples are ethylene diamine tetraacetic acid, nitfeltriacetic acid, imino diacetic acid, glycine, diethylene triamine pentaacetic acid, triethylene tetraimine hexaacetic acid, 1,2- Diaminocyclohexane tetraacetic acid, N-hydroxyethyleneethylenediamine, -N, N ', N'-triacetic acid, ethylene glycol diethylether diamine tetraacetic acid, ethylene diamine tetrapropionic acid and salts thereof. In particular, ethylene diamine tetraacetic acid (hereinafter referred to as "EDTA") and salts thereof, nitrilotriacetic acid and salts thereof, diethylene triamine pentaacetic acid and salts thereof, and the like are more preferable. As the EDTA salt, di-, tri- and tetra-sodium salts of EDTA and di-, tri- and tetra-potassium salts of EDTA are preferable. These aminocarboxylic acid derivatives are generally used as aqueous solutions having a concentration in the range of 5-50% by weight. As the amount of the aminocarboxylic acid derivative, the molar ratio of the aminocarboxylic acid derivative to the metal ions contained in the reaction product as a catalyst is in the range of from 1: 1 to 10: 1, preferably from 1: 1 to 5: 1.

In the present invention, there are two preferred methods for removing the catalytic metal by adding an aminocarboxylic acid derivative to the reaction product obtained by the precipitation polymerization method. In one method, only the aqueous solution of the aminocarboxylic acid derivative is added to the reaction product and the catalyst metal is removed by filtering the mixture of the aqueous solution of the aminocarboxylic acid derivative and the reaction product without phase separation of the organic and aqueous phases. In another method, the catalyst metal is removed by separating the organic phase in which the polyphenylene ether is suspended from the aqueous phase by adding an aminocarboxylic acid derivative solution and an appropriate amount of water to the reaction product. In the present invention, any method can be used. However, in a method with phase separation, the purification of the polymer is insufficient because it is difficult to separate the organic phase in which the polyphenylene ether is suspended from the aqueous phase when the polyphenylene ether in the reaction product is at a high concentration of 20% by weight or more. Thus, methods involving phase separation are industrially disadvantageous because they must lower the concentration of polyphenylene ether in the reaction product. In addition, methods involving phase separation are economically disadvantageous as the separated aqueous phase needs to be purified or heat treated. Therefore, a method without phase separation is preferred.

In the present invention, the polyphenylene ether is further purified by adding an aminocarboxylic acid derivative to the reaction product, followed by washing with a poor solvent for the polyphenylene ether. As a poor solvent for polyphenylene ether, in the present invention, a solvent which does not dissolve the polyphenylene ether but dissolves the chelate of the aminocarboxylic acid derivative and the catalyst metal is used. The higher the solubility of the chelate of the aminocarboxylic acid derivative and the catalyst metal in the poor solvent, the higher the cleaning efficiency. Therefore, the poor solvent of the high solubility of the aminocarboxylic acid derivative and the chelate of the catalyst metal is preferable. Examples of such poor solvents include alcohols such as methanol, ethanol, n-porpanol, iso-propanol, n-butanol, sec-butanol, iso-butanol, tert-butanol, benzyl alcohol, cyclohexane and the like; Ketones such as acetone and methyl ethyl ketone; Esters such as ethyl acetone and ethyl promate; Ethers such as tetrahydrofuran and diethyl ether; And amides such as dimethylformamide. Of these poor solvents, methanol is preferred. The purpose of washing with poor solvents for polyphenylene ethers is to extract chelates of residues of aminocarboxylic acid derivatives and catalyst metals from polyphenylene ethers with poor solvents. Thus, the greater the amount of bad solvent used and the longer the wash time, the smaller the amount of catalyst metal in the polymer. However, it is economically disadvantageous to use excess bad solvent and wash for too much time. If the amount of bad solvent is the same, it is desirable to divide the amount or increase the number of washes since the amount of catalyst metal in the polymer is reduced. In the present invention, since the shape of the polymer particles is maintained when the poor solvent is added for washing, there is no limitation on the washing conditions such as the rate of addition of the bad solvent, the order of addition, etc. to control the properties of the polymer particles. The amount of poor solvent for the polyphenylene ether used is 1 to 10 times, preferably 1 to 7 times the dry weight of the polyphenylene ether in the reaction product. The number of washings of the polyphenylene ether using the poor solvent for the polyphenylene ether is 1 to 10 times, preferably 2 to 7 times.

It is preferable to carry out washing with a poor solvent after separating the polyphenylene ether from the reaction product.

Preferably, washing is performed at a temperature of 20 to 60 ° C.

In the process of the invention, a reducing agent can be used when an iminocarboxylic acid derivative is added to the reaction product obtained by oxidative polymerization of 2,6-disubstituted phenol. As the reducing agent used, any reducing agent can be used. However, examples of particularly preferred reducing agents include sodium itionate, sodium sulfite, hydrazine, hydroquinone and the like. The reducing agent is added before or after the addition of the aminocarboxylic acid derivative to the reaction product or simultaneously with addition of the aminocarboxylic acid derivative to the reaction product. The amount of reducing agent used is in the range of 0.01 to 5 mol%, preferably 0.05 to 3 mol% relative to the amount of 2,6-disubstituted phenol.

The invention will be described in more detail with reference to the following examples which do not limit the scope of the invention.

Definition of Color Index

0.5 g of the polymer subjected to compression molding at 310 ° C. is dissolved in chloroform. The resulting solution is adjusted to a total volume of 100 ml, the absorbance at 480 nm of the sample solution is measured at 25 ° C., and the color index of the polymer is calculated according to the formula shown below.

The color index value is the value measured by calculating the thermal oxidation degree of the polyphenylene ether. The lower this value, the less coloring of the polymer by heat and the more stable the polymer is to thermal oxidation.

Color index = log (Io / I) / ab × 100

In the above formula, Io: sensitivity of incident light

I: sensitivity of transmitted light

a: length of the cell (cm)

b: concentration of sample solution (g / cm 3)

Example 1

100 g (0.82 mole) of 2,6-dimethylphenol is dissolved in a mixture of 240 g xylene, 80 g butanol and 80 g methanol. Cu ₂ O-HBr-di-n-butylamine-dimethyl-n-butanamine-N, N'-di-t-butylethyldiamine type catalyst and trioctylmethylammonium chloride in the presence of trioctylmethylammonium chloride for 6 hours at An oxidative polymerization reaction is carried out to obtain a polymerization reaction solution of poly- (2,6-dimethyl-1,4-phenylene) ether. The amount of catalyst was 0.100 g (7.0 x 10 ^-4 moles) of Cu ₂ O, 0.458 g (5.7 x 10 ^-3 moles) of HBr, 0.996 g (7.7 x 10 ^-3 moles) of di-n-butylamine, 3,644 g (3.6 × 10 ⁻² moles) of dimethyl-n-butylamine and 0.155 g (9.0 × 10 ⁻⁴ moles) of N, N′-di-t-butylethyldiamine. As a 48% HBr aqueous solution of Cu ₂ O in the Cu ₂ O it is dissolved supplies. The amount of trioctylmethylammonium chloride is 0.11 g (0.022 wt% based on the amount of the polymerization solution).

The resulting polymerization mixture is a suspension in which polymer particles are precipitated.

To the resulting polymerization suspension is added 2.27 g (2.8 x 10 ^-2 moles) of a 50% aqueous solution of EDTA3K. In addition, 160 g of methanol is added to the suspension to wash the polymer. The solution is stirred at 45 ° C. for 30 minutes and then the mixture is filtered to give the polymer wetted with solvent. 240 g of methanol is added to the polymer to obtain a methanol suspension. The suspension is stirred at 45 ° C. for 30 minutes and then the stirring suspension is filtered to give the polymer. Subsequently, the same method is repeated twice, and the resulting polymer wetted with solvent is dried at 150 ° C. for 1 hour.

The intrinsic viscosity of the final polymer is measured in chloroform at 30 ° C. The value was 0.57. The amount of residual copper in the polymer is 0.5 ppm. The color index of the molded article obtained by compression molding at 310 ° C. was 3.0.

After the above operation step of adding an aqueous solution at 50% EDTA, 3K to the polymerization reaction solution, some mixtures were left at 45 ° C. for 5 hours and the others were left at the same temperature for 24 hours. After that, the operation is continued. After the operation is completed, the intrinsic viscosity of the final polymer is measured. The intrinsic viscosity of the polymer left for 5 hours during the operation was 0.57. The inherent viscosity of the polymer left for 24 hours was 0.57. There was no difference between the intrinsic viscosities of these polymers.

Comparative Example 1

To the resulting polymerization reaction suspension obtained in the same manner as in Example 1 was added 11.6 g (1.1 × 10 ⁻¹ mole) of 35% hydrochloric acid and 100 g of water. The suspension is stirred at 45 ° C. for 30 minutes and then the suspension is left to remove the aqueous layer. Filtration of the resulting solution yields a polymer wetted with solvent. The suspension is stirred at 45 ° C. for 30 minutes and then the stirring suspension is filtered to give the polymer. Subsequently, the same procedure was repeated twice to dry the obtained polymer wetted with solvent at 150 ° C. for 1 hour.

The intrinsic viscosity of the final polymer is measured in chloroform solvent at 30 ° C. The value was 0.57. The amount of copper remaining in the polymer was 1.0 ppm. The color index of the molded article obtained by compression molding at 310 ° C. was 6.

After the above operation step of adding 35% hydrochloric acid and water to the resulting polymerization suspension, a portion of the mixture is left at 45 ° C. for 5 hours and the other part is left at the same temperature for 24 hours. After that, the operation continues. After the operation, the intrinsic viscosity of the final polymer is measured. The inherent viscosity of the polymer left for 5 hours during the operation was 0.57. The inherent viscosity of the polymer left for 24 hours was 0.57.

Comparative Example 2

The same operation as in Example 1 was carried out except that a polymerization solvent containing 300 g of xylene was used instead of xylene, butanol and methanol. The resulting polymerization product is a homogeneous solution containing a polymer. The intrinsic viscosity of the obtained polymer is measured in chloroform at 30 ° C. The value is 0.55. The amount of residual copper in the polymer was 1.5 ppm. The color index obtained by compression molding at 310 ° C. was 3.5.

After the above operation step of adding 50% EDTA, 3K aqueous solution to the polymerization reaction solution, part of the mixture was left at 45 ° C. for 5 hours and the rest was left at the same temperature for 24 hours. After that, the operation is continued. After the operation, the intrinsic viscosity of the final polymer is measured. The inherent viscosity of the polymer left for 5 hours during the operation was 0.48. The inherent viscosity of the polymer left for 24 hours was 0.38. A decrease in molecular weight was recognized.

Example 2

The same operation as in Example 1 was carried out except that 4.12 g (2.8 × 10 ⁻³ mol) of 25% EDTA, 3Na aqueous solution was used instead of EDTA, 3K. The intrinsic viscosity of the obtained polymer was measured at 30 ° C. in chloroform. The value was 0.57. The amount of residual copper in the polymer was 0.6 ppm. The color index of the molded article obtained by compression molding at 310 ° C. was 3.2.

After the above operation step, after the above operation step of adding 25% EDTA, 3Na aqueous solution to the polymerization reaction solution, part of the mixture was left at 45 ° C. for 5 hours and the rest was left at the same temperature for 24 hours. After that, the operation continues. After the operation, the intrinsic viscosity of the final polymer is measured. The inherent viscosity of the polymer left for 5 hours during the operation was 0.57. The inherent viscosity of the polymer left for 24 hours was 0.57. There was no difference between the intrinsic viscosities of these polymers.

Example 3

The same operation as in Example 1 was carried out except that 0.18 g of hydroquinone (1.64 x 10 ^-3 mol) was added after the addition of EDTA and 3K. The intrinsic viscosity of the obtained polymer is measured in chloroform at 30 ° C. The value was 0.57. The amount of residual copper in the polymer was 0.7 ppm. The color index of the molded article obtained by compression molding at 310 ° C. was 2.6.

After the above operation step of adding 50% EDTA, 3K aqueous solution to the polymerization reaction solution, part of the mixture was left at 45 ° C. for 5 hours and the rest was left at the same temperature for 24 hours. After that, the operation is continued. After the operation, the intrinsic viscosity of the final polymer is measured. The inherent viscosity of the polymer left for 5 hours during the operation was 0.57. The inherent viscosity of the polymer left for 24 hours was 0.57. There was no difference between the intrinsic viscosities of these polymers.

Example 4

0.085 g (5.0 x 10 ^-4 moles) of cupric chloride, 0.37 (3.6 x 10 ^-3 moles) of 35% hydrochloric acid, 1.09 (8.5 x 10 ^-3 moles) of di-n-butylamine and 3.31 g ( The same operation as in Example 1 was carried out except that an oxidative polymerization catalyst containing 2.5 × 10 ⁻² mol) of N, N, N ′, N′-tetramethyl-1,3-diaminopropane was used. . The intrinsic viscosity of the obtained polymer is measured in a chloroform solvent at 30 ° C. The value was 0.55. The amount of residual copper in the polymer was 0.3 ppm. The color index of the molded article obtained by compression molding at 310 ° C. was 2.4.

After the above operation step of adding 50% EDTA, 3K aqueous solution to the polymerization reaction solution, part of the mixture was left at 45 ° C. for 5 hours and the rest was left at the same temperature for 24 hours. After that, the operation is continued. After the operation, the intrinsic viscosity of the final polymer is measured. The inherent viscosity of the polymer left for 5 hours during the operation was 0.55. The inherent viscosity of the polymer left for 24 hours was 0.55. There was no difference between the intrinsic viscosities of these polymers.

As described above, polyphenylene ethers which are hardly discolored during thermoforming and which do not reduce intrinsic viscosity during the purification step can be obtained by the present invention.

Claims (9)

In the presence of a catalyst composed of a combination of copper ions, halogen ions and one or more amines, the polymer produced in the solvent in which the ratio of the good solvent to the bad solvent is mixed in a weight ratio of 3: 7 to 9: 1 is precipitated as particles. After the oxidative polymerization of 2,6-disubstituted phenol while adding an aminocarboxylic acid derivative to the reaction mixture to form a chelate of copper, and then a polymer produced with a poor solvent of polyphenylene ether to dissolve the chelate Method for producing a polyphenylene ether, characterized in that the washing. The process according to claim 1, wherein the precipitation polymerization method is a continuous polymerization method using three completely mixed reactors. The method of claim 1, wherein the 2,6-disubstituted phenol is 2,6-dimethylphenol. The method of claim 1 wherein the aminocarboxylic acid derivative is a di-, tri- or tetra sodium salt of ethylenediaminetetraacetic acid. The method of claim 1 wherein the aminocarboxylic acid derivative is a di-, tri- or tetra potassium salt of ethylenediaminetetraacetic acid. The method of claim 1 wherein the poor solvent of the polyphenylene ether is an alcohol. The method of claim 6, wherein the alcohol is methanol. The method according to claim 1, wherein the amount of the poor solvent of the polyphenylene ether used is 1 to 10 times the dry weight of the polyphenylene ether. The method of claim 1, wherein in the case of refining the polyphenylene ether after adding the aminocarboxylic acid derivative to the reaction product obtained by the precipitation polymerization method, the aqueous solution of the aminocarboxylic acid derivative is added without phase separation, and then the reaction product and the aminocarboxylic acid. A method of filtering a mixture of aqueous derivatives.