JPH0128766B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for producing polyphenylene ether, and more specifically, in a method for continuously precipitation polymerizing polyphenylene ether, The reaction mixture is subjected to solid-liquid separation to obtain a separated liquid containing the catalyst component, and at least
This invention relates to a method in which raw material phenols at a concentration of 1 wt/vol% are dehydrated in a separated liquid and recycled to the polymerization system.

Polyphenylene ether is widely known as a heat-resistant and flame-retardant engineering resin.
In particular, blends with high-impact polystyrene resins are used in automobiles, as resins with an excellent balance of mechanical properties, chemical properties, electrical properties, and processability.
It is used in a wide range of industrial fields, including electrical, office equipment, and precision machinery fields.

The manufacturing method of polyphenylene ether is
The solution polymerization method represented by 36-18692 and the
-28919 is a known precipitation polymerization method,
These can be manufactured batchwise or continuously. In the former case, when the raw material phenol is polymerized at a high concentration, the viscosity becomes significantly high at the end of the reaction, which reduces operability and requires a large amount of solvent per product, making it a burden to distill and recover the solvent. be. On the other hand, in the latter case, although these disadvantages are alleviated, the amount of solvent used is still large. Furthermore, in these known examples, the catalyst is generally deactivated by adding an acid (e.g., hydrochloric acid), a complexing agent (e.g., ethylenediaminetetraacetic acid), etc. to the reaction solution to purify the polymer.
It is recycled through collection and regeneration processes. This is because the catalysts generally used for polymerizing polyphenylene ether contain copper, cobalt, manganese, and other heavy metals, so they are not allowed to be mixed into wastewater. In the specification of Japanese Patent Publication No. 39-29373,
It mentions that in a continuous circulation method, the solvent is not purified and therefore the catalyst is reused without being purified, and in this case it is necessary to dehydrate the reaction solution. Methods proposed include the use of desiccant agents, azeotropic distillation, inert gas, and others. However, the use of desiccants is industrially difficult, mainly for economic reasons. The introduction of inert gas is
The principle is the same as evaporative distillation, and the economic effect is determined by temperature. Therefore, in order to dehydrate with high efficiency, it should be operated at as high a temperature as possible without deactivating the catalyst. Ru. It is economically disadvantageous to use a large amount of inert gas at low temperatures.

Catalysts used in the production of polyphenylene ether are generally unstable, and phenolic hydroxyl groups decrease, which is noticeable at the end of the reaction when a large amount of water is present. It is proposed that dehydration be performed at a polymerization rate of 50-95%, but this process is complicated to operate and may cause process instability.

As a result of intensive research in order to realize the above process, the present inventors found that the presence of raw material phenol at a concentration of at least 1 wt/vol% during the dehydration treatment made the catalyst unstable during the dehydration operation. The present invention was achieved by discovering that it is possible to effectively prevent the deactivation and deactivation. This will be explained in detail below.

The method of continuously precipitation polymerizing polyphenylene ether is described in detail in, for example, JP-A-48-21798 and other publications, and is known to those skilled in the art. The additives and polymerization method are as follows.

The raw material phenol in this invention is expressed by the following formula (1)
The compound represented by is shown below.

(In the formula, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ represent hydrogen, a hydrocarbon group, and a substituted hydrocarbon group.) Representative examples include o-cresol, m-cresol, 2,6- Dimethylphenol, 2,6-diethylphenol, 2,6-dipropylphenol, 2-ethyl-6-ethylphenol, 2,3
-dimethylphenol, 2,4-dimethylphenol, 2,3,6-trimethylphenol, 3,
Examples include 5-dimethylphenol, 2,6-diphenylphenol, 2-ethyl-6-hexylphenol, and mixtures thereof.

These phenols undergo catalytic oxidative polymerization with a catalyst and oxygen or an oxygen-containing gas in the presence of a solvent. The solvent used is appropriately selected depending on the degree of polymerization of the target polyphenylene ether, but generally benzene, toluene, xylene,
Ethylbenzene, nitrobenzene, chlorobenzene, methylene chloride, chloroform, carbon tetrachloride,
A good solvent for polyphenylene ethers such as dichloroethane, methyl chloroform, and a non-solvent for polyphenylene ethers such as methanol, ethanol, propanol, butanol, hexanol, cyclohexanol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, and a good solvent for catalysts. It is preferable to use a system in which the phenols are dissolved but the polymer is precipitated. When the degree of polymerization of the target polyphenylene ether is low, for example, a single type of dioxane can be used, and it is not essential to mix two or more types of solvents.

As the catalyst used in this invention, a wide variety of known catalysts can be used, examples of which include copper-amine complexes, cobalt-amine complexes, manganese-alkoxide complexes, bissalicylaldehyde ethylene diiminate-cobalt or manganese complexes, and others. A mixture of two or more of these may be used. These catalysts are used after being dissolved in the above-mentioned solvent. It is often useful to add amines, alkoxides, phenoxides, etc. as promoters. Furthermore, compounds added for the purpose of suppressing side reactions, controlling the degree of polymerization, controlling the polymerization rate, and other purposes, such as nitroaromatic compounds (nitrobenzene, picric acid, etc.), aliphatic cyclic amines (such as morpholine, piperidine, etc.), guanidinium salts. , heavy metal oxides or salts (e.g. oxides and salts of nickel, iron, cobalt), surfactants (e.g. ethylene glycol nonyl phenyl ether and others), anion exchange resins and the like are more preferably implemented. It is possible, and these are usually used in a range of 0.01 to 20 parts by weight based on the raw material phenols.

The mixture thus obtained can be used, for example, in
The polyphenylene ether product is introduced into a continuous polymerization reactor disclosed in No. 49-28919 et al., and catalytically oxidatively polymerized with oxygen or an oxygen-containing gas, resulting in the production of polyphenylene ether as precipitated particles. The reaction mixture discharged from the polymerization vessel is separately separated into a solution containing precipitated particles, a catalyst, and other additives by centrifugation or other methods. At this time, a separation method should be adopted that minimizes the amount of catalyst and other additives contained in the precipitated particles. Of course, it is also possible to wash the precipitated particles with a small amount of solvent, recover the catalyst and other additives as a solution, and mix it with the separated liquid for treatment. Usually, the separated liquid contains solvents, oligophenylene ethers, catalysts, co-catalysts, additives, etc., and water produced in the polymerization reaction. This reaction results in a non-negligible amount of catalyst deactivation. The present invention realizes a state in which this catalyst deactivation is virtually non-existent or extremely small. As a result of a detailed investigation into the conditions under which catalyst deactivation occurs, the inventors confirmed that most of the deactivation is due to the formation of metal oxides via metal hydroxides, and found that reduction It was found that the presence of raw material phenols as a chemical substance significantly stabilized the process. The step of adding phenols is effective even in the reaction mixture stage before separation, and the important thing is to perform the dehydration treatment while the phenols are present in the liquid. It is best to add it between the separation and dehydration steps. Phenols are used as part or all of the raw materials to be added in the continuous polymerization system. The amount to be added cannot be absolutely determined depending on the type of catalyst and processing conditions, but it is sufficient as long as it can maintain the metal salt in a reduced state.

As the dehydration method, distillation, distillation under reduced pressure, evaporation by introducing an inert gas, use of a water adsorbent, etc. can be applied, but the first two are particularly preferred from an industrial point of view and because the degree of deactivation of the catalyst is large. These conditions vary widely depending on the type and amount of the solvent used, the type of catalyst, and the amount of water contained, but it is generally desirable to carry out the reaction at a temperature of 80° C. or lower. The present invention is particularly effective when using azeotropy with one component of the solvent and when the azeotropic composition is separated in the condensate (for example, trichloroethane, xylene, toluene, benzene, ethylbenzene, etc. and water). The catalyst and additives are recovered as a solution of solvent and phenols. Of course, the solvent that is a good solvent for the other catalyst (e.g., alcohols, etc.) is distilled off first, and the remaining solvent and water are immiscible (e.g., the above-mentioned solvents and others) to remove the solvent/phenol. - Water can be removed by separating the catalyst phase and aqueous phase, or water can also be removed by vacuum distillation. The catalyst solution obtained in this way has virtually no deactivation and can be recycled, and ingredients (solvent, a small amount of catalyst, additives, etc.) that are insufficient for recycling can be added. Then, it is recycled again to the polymerization process.

This invention makes it possible to reuse the catalyst,
It is extremely valuable industrially because it reduces the cost of catalyst deactivation, recovery, and regeneration, and reduces the energy consumption required for solvent distillation.

This will be explained in detail below by giving an example.

Example 1 Carbon tetrachloride 14, -butanol 6,2,6-
A solution consisting of 4 kg of xylenol, 172 g of bissalicylaldehyde ethylene diiminate manganese () ethylene diamine, and 300 g of ethylene diamine was prepared. This liquid was completely mixed by connecting two jacketed reactors with oxygen blowing pipes in series with overflow pipes and controlling the temperature of the first tank to 35°C, the second tank to 20°C, and the third tank to 10°C. The polymerization was carried out by supplying the polymer to a three-tank continuous polymerization apparatus using a metering pump and setting the average residence time to 45 minutes. The liquid discharged from the third tank was continuously subjected to solid-liquid separation using a centrifuge, and the precipitated particles were washed three times with 10 methanol containing hydrochloric acid and dried. Polyphenylene ether with [η]=0.44 (in chloroform at 25°C) was obtained with a yield of 96%. On the other hand, 4 kg of 2,6-xylenol was added to the separated liquid, and after stirring well under a nitrogen stream, the separated aqueous phase was removed using a centrifuge.
The catalyst was recovered with a recovery rate of 85%.

The insufficient carbon tetrachloride, n-butanol, catalyst, and ethylenediamine were added to this solution and polymerization was carried out again. As a result, polyphenylene ether with [η]=0.44 was obtained with a yield of 97%. The catalyst recovered in this polymerization was 86%, and the polyphenylene ether obtained in the third polymerization had the same yield as before.
It had viscosity.

Example 2 In Example 1, as a result of treating the separated liquid without adding 2,6-xylenol, the recovery rate of the catalyst was 60%.
It was hot.

Example 3 Xylene 13, n-propanol 7,2,6
- A solution consisting of 2 kg of xylenol, 172 g of bissalicylaldehyde ethylene diiminate manganese () ethylene diamine, and 300 g of piperidine was heated in the first tank of Example 1 at 20°C, the second tank at 15°C, and the third tank at 20°C.
Polymerization was carried out at 10°C with an average residence time of 2 hours. The reaction mixture was continuously centrifuged to separate the precipitated polyphenylene ether and the catalyst solution. The polyphenylene ether was purified by the method of Example 1 to obtain a colorless polyphenylene ether with a yield of 98% and [η]=0.46.

90% of the catalyst was recovered in the separated liquid. After adding 2 kg of 2,6-xylenol to this liquid and stirring well, the mixture was distilled under reduced pressure at 60°C to remove water together with n-propanol. The remaining liquid contained xylene and 2,6-xylenol as main components, and the catalyst and additives were recovered as a solution. A second polymerization was carried out by adding insufficient n-propanol, xylene, a catalyst, and additives to this solution. As a result, a colorless polyphenylene ether with [η]=0.46 was obtained with a yield of 98%.

After the same treatment, a third polymerization was carried out to obtain a colorless polyphenylene ether with a yield of 98% and [η]=0.47.

Example 4 12 xylene, 8 methanol, 2 kg of 2,6-xylenol, bissalicylaldehyde ethylene diiminate manganese () ethylene diamine
A liquid consisting of 172 g of ethylenediamine and 300 g of ethylenediamine was polymerized by the method of Example 3. Thereafter, the same operation was carried out to obtain colorless polyphenylene ether with [η]=0.50 in a yield of 98%.

Add 2 kg of 2,6-xylenol to the separated liquid and
Distillation was carried out under reduced pressure at ℃ to remove most of the methanol. After the remaining liquid was allowed to cool, the separated aqueous phase was removed using a centrifuge. 95% of the catalyst was recovered in the xylene phase. Manganese in the water phase was 20 ppm. Recycle polymerization was performed five times with the addition of missing solvent, catalyst, and additives to the xylene phase with identical results.

[Brief explanation of drawings]

The drawings are process diagrams of the present invention.

Claims (1)

[Claims] 1 In a method in which phenols are catalytically oxidized and polymerized with oxygen or oxygen-containing gas in the presence of a catalyst and a solvent to continuously precipitate and polymerize polyphenylene ether, the reaction mixture discharged from the polymerization vessel is converted into solid-liquid. The precipitated polyphenylene ether is separated and added to the separated liquid containing the remaining catalyst and water produced in the polymerization reaction at least 1 wt/
A method for producing polyphenylene ether, which comprises transferring a solution containing a catalyst to a dehydration step in a state in which phenols are present at a concentration of vol%, and then recycling a solution containing a catalyst to a polymerization step.