JPH06172512A - Purification of polyphenylene ether - Google Patents

Abstract

PURPOSE:To readily purify polyphenylene ether in a short time by adding a polymeric coagulant to the solution resulting from the oxidative polymerization of a phenol to separate the metallic ions of the catalyst component as a precipitate from the solution. CONSTITUTION:A method for purifying a polyphenylene ether by separating it from the solution resulting from the oxidative polymerization of a phenol, wherein a polymeric coagulant is added to the solution to separate the ions of the catalyst component as a hardly soluble precipitate therefrom to thereby effect the purification of the polyphenylene ether. As the coagulant to be used, organic polymeric coagulants are most suitable. They are classified as cationic, anionic, amphoteric or nonionic depending upon the electrical change; any one of them can be used. An example of the suitable coagulant is a dicyandiamide/ formalin condensate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for purifying polyphenylene ether obtained by oxidative polymerization of phenols. More specifically, it relates to a method for purifying polyphenylene ether, characterized in that metal ions of a catalyst component are separated from a reaction solution obtained by polymerization as a hardly soluble precipitate by adding a polymer flocculant.

[0002]

2. Description of the Related Art Polyphenylene ether obtained by oxidative polymerization of phenols has been attracting attention as a thermoplastic engineering plastic in recent years because it has excellent mechanical properties, electrical properties, heat resistance and the like and has low water absorption. Conventionally, polyphenylene ether is generally produced by oxidative polymerization of phenols in an organic solvent, but in order to recover and purify polyphenylene ether from a polymer solution, generally, after first extracting or decomposing the catalyst used, Alternatively, simultaneously with this operation, it is carried out by contacting with a poor solvent for polyphenylene ether such as methanol. That is, as the extraction or decomposition of the catalyst, a method using an inorganic acid typified by hydrochloric acid or an organic acid such as acetic acid as shown in JP-B-53-45360 and JP-B-57-37605 and JP-B-59- 3483 gazette, Japanese Patent Publication No. 60-25450, Japanese Patent Publication No. 60-3
4571, JP-B-61-8092, JP-A-51-39800, JP-A-53-86800, JP-A-53-94598, and JP-A-60-51.
As disclosed in Japanese Patent Publication No. 720, etc., a method of adding a chelating agent such as EDTA to a reaction product obtained by a solution polymerization method has been proposed.

[0003]

However, the method of adding a chelating agent such as EDTA to the reaction product obtained by the solution polymerization method requires a long extraction time in order to reduce the residual metal in the polyphenylene ether. Therefore, there is a problem that the re-equilibrium reaction of the polyphenylene ether is brought about and the molecular weight is lowered (see JP-A-52-98098). Further, JP-A-4-25528 discloses a method using a precipitation polymerization method in which polymer particles are precipitated in the latter stage of polymerization. However, in this method, a large amount of a poor solvent for polyphenylene ether is used for washing the polymer. ,
Economic improvement is desired.

Further, in the method using hydrochloric acid or acetic acid, a salt such as NaCl is formed by the reaction with a basic compound such as NaOH used for neutralization in the subsequent step, and these remain in the polymer and remain in the polyphenylene ether resin. Negatively affects the good electrical characteristics inherent in the. Further, it has a drawback that the polymer is markedly colored during the heat molding. Japanese Patent Publication No. 55-17775 discloses a method of treating wet polyphenylene ether containing an organic solvent in hot water under sealing, but wet polyphenylene ether has a poor affinity with water, and a salt contained therein is Hardly removed.
Further, US Pat. No. 4,263,426 describes a method in which a reaction solution in which polyphenylene ether is dissolved is blown into hot water and steam distillation is carried out, but a large amount of solvent must be distilled off, resulting in high energy cost for steam. In addition, there are many problems such as fusion of polymer particles.

[0005]

The inventors of the present invention have made extensive studies on a method for separating and purifying polyphenylene ether which does not have the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention, in separating and purifying the polyphenylene ether from the reaction solution obtained by the oxidative polymerization of phenols,
A method for purifying polyphenylene ether, characterized in that the metal ion of the catalyst component is separated from the reaction solution as a hardly soluble precipitate by adding a polymer coagulant, and the polymer coagulant is polyacrylamide, or a derivative thereof. A method for purifying polyphenylene ether using a dicyandiamide folimarin condensate or the like. According to this method, the purification of polyphenylene ether can be carried out very easily and in a short time.

The present invention will be described in detail below. The phenols used in the present invention have the general formula shown below.

[0007]

[Chemical 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,
An aryl group, a substituted aryl group, a phenyl group, and a substituted phenyl group. ) Refers to a compound such as Examples of such compounds include, for example, 2,6-dimethylphenol, 2-methyl-6-ethylphenol, 2,6
-Diethylphenol, 2-methyl-6-n-propylphenol, 2,6-di-n-propylphenol, 2
-Methyl-6-isopropylphenol, 2-methyl-
6-chlorophenol, 2-methyl-6-bromophenol, 2,3,6-trimethylphenol, 2-methyl-6-arylphenol, 2,6-diphenylphenol, 3,5-dimethylphenol and the like can be mentioned.
These compounds may be used alone or in combination of two or more kinds. In addition, p-cresol, 2,4-dimethylphenol and the like may be contained in a small amount in fact, so that there is no problem.

Among these substituted phenols,
2,6-Dimethylphenol is industrially important. The polyphenylene ether used in the present invention is produced, for example, by oxidative polymerization of phenols using various catalysts. Specifically, a method using a manganese salt-basic compound and a monoamine catalyst system, a method using a copper salt-diamine and a secondary monoamine catalyst system (JP-A-57-44625, JP-A-64-33131, etc.). Oxidative polymerization can be carried out by such a method. In the present invention, a catalyst particularly suitable as a catalyst used for oxidative polymerization is to use a catalyst composed of a combination of copper ions, halogen ions and one or more amines.

For example, as a copper ion source, cuprous chloride,
Cuprous chloride, cuprous bromide, cupric bromide, cuprous acetate, cupric acetate and other cuprous salts, cupric salts or mixtures thereof. Practically any cuprous and cupric compound can be used, but it is determined by economics and availability of the compound. Of these, preferred examples are copper halide salts.

These copper salts may be synthesized at the time of use from oxides, carbonates, hydroxides, etc. and halogens or hydrogen halides. These catalysts can be used to polymerize substituted phenols, for example by oxygen oxidation. When oxidative polymerization is carried out by using oxygen, oxygen is pure oxygen, and a mixture of oxygen and an inert gas in any proportion (air in a special case of composition) can be used under any conditions of reduced pressure, normal pressure and increased pressure. .

Oxidative polymerization of phenols is usually carried out in a solvent. The solvent is not particularly limited as long as it is not easily oxidized as compared with the oxidizable phenols and has no reactivity with various radicals that are considered to be generated in the middle of the reaction, but the phenols are not particularly limited. And a substance capable of dissolving the polymerization catalyst is preferable. Examples of such solvents include benzene, toluene, ethylbenzene, aromatic hydrocarbons such as xylene, methylene chloride, chloroform,
Halogenated hydrocarbons such as 1,2-dichloroethane, chlorobenzene and dichlorobenzene, nitro compounds such as nitrobenzene (these solvents are good solvents for the polymer produced), etc. can be used. Alcohols such as ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, ethers such as diethyl ether, esters such as ethyl acetate, Examples include amides such as dimethylformamide. These solvents can be used alone or as a mixed solvent of two or more kinds, but it is preferable to use a solvent having a composition capable of almost dissolving the polyphenylene ether produced at the temperature at which the present invention is applied at the end of the polymerization.

The method of unit operation from polymerization to purification is classified into batch method, continuous method and the like, but the present invention can be used regardless of the method of unit operation. The present invention is applied to the polymer solution after polymerization using the polymerization method as described above until the desired molecular weight (which can be simply known by the viscosity of the polymer) is obtained. .

The polymer flocculant used in the method of the present invention is most preferably an organic polymer flocculant, and is classified into cationic, anionic, amphoteric and nonionic according to its charge. Any of these can be used. Among the main polymer flocculants, the most typical examples thereof are homopolymers, copolymers of acrylic water-soluble monomers, or modified products thereof. For example,
Polyacrylamide, alkali metal salts of polyacrylic acid (sodium polyacrylate is most representative), and polyacrylamide-sodium polyacrylate copolymer obtained by hydrolyzing polyacrylamide (this is acrylic acid and acrylamide). Can also be obtained by copolymerization of polyacrylamide), sodium polyacrylamide 2-methyl-propanesulfonate, sulfomethylation reaction product of polyacrylamide, Mannich reaction product of polyacrylamide, etc., but are not limited to these examples. Not done. As an example of the structure, for example, a copolymer of polyacrylamide and sodium polyacrylate has the following structure.

[0015]

[Chemical 2]

(Here, n and m represent the amounts of the respective units, and it is not determined that they are block copolymers.) Also, as a polymer flocculant suitable for the present invention, a dicyandiamide folimarin condensate is used. Is mentioned. It has the following structure.

[0017]

[Chemical 3]

In the present invention, these polymer flocculants may be used alone or in combination of two or more kinds. Further, in the present invention, it is desirable to add the above-mentioned polymer flocculant to the reaction mixture containing the polymer as an aqueous solution or a solution of a mixed solvent of water and an organic solvent. As water for dissolving the polymer flocculant, it is preferable to use neutral water having low hardness such as distilled water or tap water.

Although the concentration of the polymer coagulant added as a solution depends on the kind of the polymer coagulant to be used, it is possible to use up to the saturated solubility at the temperature of the aqueous solution to which the compound is to be added. Is. The amount of the polymer flocculant added may be about 2% with respect to the total amount of the reaction mixture to be added.
Basically, the addition amount is good as long as almost all the metal ions in the reaction mixture are obtained as hardly soluble precipitates, and it is meaningless to increase the addition amount too much. This addition amount depends on the type of polymer flocculant used.

When the polymer flocculant is added, it is desirable that the reaction mixture is in a stirring environment. Further, it is preferable from the viewpoint of operability that the temperature at the time of addition is the same as the temperature at which the polymerization reaction is usually performed. Generally, it is often about 10 to 100 ° C. When adding a polymer flocculant, a compound such as a surfactant added for the purpose of improving the polymerization activity such as reaction rate improvement or phase separation between solvents in the reaction mixture, or by-products Additives used for the purpose of treating what is expected to impair the properties of polyphenylene ether may be included.

Generally, it takes several tens of seconds to several tens of minutes after addition,
A precipitate containing the metal ions used as catalyst for the polymerization results. A polymer solution containing almost no metal ions can be obtained by separating this precipitate by a known method such as centrifugation or filtration. The obtained polymer solution is contacted with a poor solvent for polyphenylene ether such as methanol to precipitate polyphenylene ether, which is then separated from the solvent by a known method such as centrifugation or filtration and dried to powder the polyphenylene ether. It can be obtained as a body, or can be obtained as pellets of polyphenylene ether by flashing and then extruding with a degassing extruder or the like.

[0022]

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples of industrially important poly (2,6-dimethyl-1,4-phenylene) ether, but the present invention is limited to the following examples. It is not something that will be done. The polymerization of phenols was carried out according to JP-A-64-33131.

[0023]

Example 1 0.014 g of cupric chloride dihydrate and 36 w
0.0597 g of t% HCl was dissolved in 7.9 g of methanol. N, N, N ', N'-tetramethyl-
A solution prepared by dissolving 0.5329 g of 1,3-diaminopropane and 0.201 g of di-n-butylamine in 10 g of methanol was added. To this catalyst solution was added a solution of 20 g of 2,6-dimethylphenol dissolved in 161.3 g of toluene. The total amount of the reaction solution was 200 g, and the reaction solvent used was a mixed solvent of toluene and methanol in a weight ratio of 90:10. The concentration of 2,6-dimethylphenol is 10 wt%. Copper is adjusted to be 0.05 gram atom per 100 moles of 2,6-dimethylphenol. These mixtures were put in a 500 ml reaction vessel and polymerization was carried out at 30 ° C. for 4 hours while supplying oxygen while stirring. The reaction solution was a light orange homogeneous solution in which the polymer was dissolved.

This solution was kept at 30 ° C., and 1 g of 50 wt% aqueous solution of polyacrylamide-sodium polyacrylate copolymer was added with vigorous stirring. A greenish blue precipitate formed shortly after the addition. The stirring was continued for 10 minutes as it was. This was filtered using a glass filter, and methanol was added to the filtrate kept at 30 ° C. in an amount 5 times the weight of the filtrate to precipitate a polymer, which was then filtered with a glass filter. The resulting wet polymer was dried under vacuum at 120 ° C. The copper remaining in the obtained dry polyphenylene ether was 0.6 ppm.

[0025]

Example 2 Polymerization was carried out under the same conditions as in Example 1 to obtain a light orange uniform solution in which the polymer was dissolved. This solution was kept at 30 ° C. and stirred vigorously with 50 wt% of dicyandiamide formalin condensate (molecular weight about 1 × 10 5
1 g of the aqueous solution of ⁴ ) was added. A green precipitate formed shortly after the addition. The stirring was continued for 10 minutes as it was. This was filtered using a glass filter, and methanol was added to the filtrate kept at 30 ° C. in an amount 5 times the weight of the filtrate to precipitate a polymer, which was then filtered with a glass filter. The resulting wet polymer was dried under vacuum at 120 ° C. The amount of copper remaining in the obtained dry polyphenylene ether was 0.5 ppm.

[0026]

Comparative Example 1 Polymerization was performed under exactly the same conditions as in Example 1 to obtain a light orange uniform solution in which the polymer was dissolved. The solution was kept at 30 ° C. and 0.5 g of water was added with vigorous stirring. The stirring was continued for 10 minutes as it was. This was filtered using a glass filter, and methanol was added to the filtrate kept at 30 ° C. in an amount 5 times the weight of the filtrate to precipitate a polymer, which was then filtered with a glass filter. The resulting wet polymer was dried under vacuum at 120 ° C. The amount of copper remaining in the obtained dry polyphenylene ether was 29.5 ppm.

Comparative Example 1 shows that the amount of residual copper was extremely large because the treatment according to the present invention was not performed.

[0028]

Comparative Example 2 Polymerization was carried out under exactly the same conditions as in Example 1 to obtain a light orange uniform solution in which the polymer was dissolved. Keeping this solution at 30 ° C., stirring vigorously, ethylenediaminetetraacetic acid tripotassium salt dihydrate (EDTA / 3K)
A solution prepared by dissolving 0.073 g (EDTA.3K / Cu = 2 mol ratio) in 0.5 g of water was added. The stirring was continued for 10 minutes as it was. This was filtered using a glass filter, and the filtrate kept at 30 ° C. was added with 5% of the filtrate weight.
The polymer was precipitated by adding twice the weight of methanol and filtered through a glass filter. The resulting wet polymer was dried under vacuum at 120 ° C. The copper remaining in the obtained dry polyphenylene ether was 12.2 ppm.

In Comparative Example 2, since copper is extracted using EDTA.3K, the effect of reducing residual copper is somewhat recognized as compared with Example 1, but it is completely inferior to the method of the present invention.

[0030]

Comparative Example 3 Polymerization was carried out under exactly the same conditions as in Example 1 to obtain a light orange homogeneous solution in which the polymer was dissolved. Keeping this solution at 30 ° C., stirring vigorously, ethylenediaminetetraacetic acid tripotassium salt dihydrate (EDTA / 3K)
A solution prepared by dissolving 0.073 g (EDTA.3K / Cu = 2 mol ratio) in 0.5 g of water was added. The stirring was continued for 10 minutes as it was. This was filtered using a glass filter, and the filtrate kept at 30 ° C. was added with 5% of the filtrate weight.
The polymer was precipitated by adding twice the weight of methanol and filtered through a glass filter.

Further, the obtained wet polyphenylene ether was dispersed in 5 times the weight of methanol based on the weight of the wet polyphenylene ether, stirred at 30 ° C. for 10 minutes and filtered. This operation was repeated 3 times. The resulting wet polymer was dried under vacuum at 120 ° C. The amount of copper remaining in the obtained dry polyphenylene ether was 1.6 ppm.

It can be seen that in Comparative Example 3, a large amount of methanol and a large amount of processing time are required although a level equivalent to that of the residual copper of the present invention is reached by repeating washing with a large amount of methanol several times.

[0033]

INDUSTRIAL APPLICABILITY As described above, the residual metal content in the polyphenylene ether obtained by removing the metal ion used as a catalyst from the polymer solution as a sparingly soluble precipitate by using the polymer flocculant as in the present invention is controlled. It can be made extremely low and the processing time is extremely short, which is very useful in industry.

Claims (3)

[Claims] 1. When separating and purifying polyphenylene ether from a reaction solution obtained by oxidative polymerization of phenols, metal ions of a catalyst component are separated from the reaction solution as a sparingly soluble precipitate by adding a polymer flocculant. A characteristic method for purifying polyphenylene ether. 2. The method for purifying polyphenylene ether according to claim 1, wherein the polymer flocculant is polyacrylamide or a derivative thereof. 3. The method for purifying polyphenylene ether according to claim 1, wherein the polymer flocculant is a dicyandiamide forimarin condensate.