JP2001335632A - Production method of polyphenylene ether - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a polyphenylene ether which is excellent in drying efficiency, when drying a wet polyphenylene ether powder. SOLUTION: When drying the wet polyphenylene ether by using a rotary drum dryer in which a plurality of heating tubes are arranged inside, in the production method, the polyphenylene ether is continuously dried by making a gas flow in the reverse direction to the transfer direction of the polyphenylene ether at a rate of 3 to 15 NL/minute per 1 kg of dry polyphenylene ether into the inside of the dryer.

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 having excellent drying efficiency when drying a wet polyphenylene ether powder.

[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. Generally, the polyphenylene ether solution after the reaction is subjected to a reaction stopping operation and a catalyst removing operation,
It is poured into a non-solvent of polyphenylene ether and solidified. In the drying step, the polyphenylene ether in a wet state after the solid-liquid separation is removed into a polyphenylene ether powder by removing the good solvent and the non-solvent of the polyphenylene ether.

[0003]

However, the drying process in the polyphenylene ether production process involves technical difficulties, and when the removal of a good solvent is insufficient, particles are aggregated and enlarged in the dryer, resulting in an increase in the size of the apparatus. It can cause clogging of scales or outlets inside. Although a method of using a plurality of dryers having different drying temperatures has been proposed to suppress the enlargement of the particles, there has been a problem that the equipment cost becomes excessive. Also, when using a dryer having a rotating shaft inside represented by a paddle dryer, it is not possible to avoid the generation of thermal degradation products at the contact portion between the rotating shaft and the polyphenylene ether powder, There was a problem that the quality of the obtained polyphenylene ether deteriorated.

[0004] Japanese Patent Publication No. 55-17775 discloses that in a water dispersion system of polyphenylene ether containing an organic solvent, the particle size of polyphenylene ether is enlarged by performing a heat treatment, and by removing a good solvent, a drying process is performed. It is disclosed that the generation of scale can be suppressed, but this method requires a new heat treatment step of the aqueous dispersion slurry, and has the disadvantage that it is economically disadvantageous.

[0005]

Means for Solving the Problems In view of the above circumstances, the present inventors have conducted intensive studies, and as a result, when drying polyphenylene ether in a wet state, a rotary type in which a plurality of heating tubes are arranged inside is used. By using a cylindrical dryer and continuously drying by flowing gas in the direction opposite to the transfer direction of the polyphenylene ether inside the dryer, scale generation in the dryer is suppressed, and the dried polyphenylene ether is efficiently dried The inventors have found that particles can be obtained, and have completed the present invention. That is, the present invention uses a rotary cylindrical dryer in which a plurality of heating tubes are arranged inside when drying the polyphenylene ether in a wet state, and feeds gas inside the dryer in a direction opposite to the transfer direction of the polyphenylene ether. 3 to 1 per kg of dry polyphenylene ether
This is a method for producing polyphenylene ether in which drying is performed continuously by flowing at a flow rate of 5 NL / min.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyphenylene ether in the present invention is a homopolymer, a block copolymer or a random copolymer represented by a repeating unit of the general formula (1).

Embedded image (In the formula, 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, 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-)
Phenylene) ether, poly (2-methyl-6-chloroethyl-1,4-phenylene) ether, and poly (2
Homopolymers such as -methyl-6-hydroxyethyl-1,4-phenylene) ether and / or 2,6-dimethylphenol as a copolymer component, one or both of 2,3,6-trimethylphenol and o-cresol And a random copolymer and the like.

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 polyphenylene ether of the present invention is disclosed, for example, in JP-B-42-3195 and JP-B-45-235.
No. 55, and JP-A-64-33131, for example, a phenol compound is prepared by using a catalyst comprising a combination of a salt of a metal selected from the group consisting of copper, manganese or cobalt and various amines. And is produced by oxidative polymerization.

Examples of the polymerization solvent include aromatic hydrocarbons such as benzene, toluene and xylene, which are good solvents for polyphenylene ether, halogenated hydrocarbons such as dichloromethane, chloroform and dichlorobenzene, and nitro compounds such as nitrobenzene. Can be Also, non-solvents of polyphenylene ether include alcohols such as methanol and ethanol, aliphatic hydrocarbons such as hexane and heptane, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and dimethylformamide. Of amides and the like can be mixed in an arbitrary ratio and composition and used as a polymerization solvent. Here, toluene is most preferable as the good solvent for the polyphenylene ether used as the polymerization solvent, from the viewpoint of easy removal of the residual solvent in the drying step.

After the polymerization, the polyphenylene ether solidified with a polyphenylene ether non-solvent such as methanol is solid-liquid separated continuously or batchwise by a centrifuge or vacuum filtration.

After the solid-liquid separation, the wet polyphenylene ether is sent to a drying step. However, the polyphenylene ether after the solid-liquid separation is generally obtained as agglomerates of particles. It is preferred to grind the mass before introduction. In particular,
It is preferable that the mass of the polyphenylene ether particles in a wet state that does not pass through a 10-mesh sieve be 10% or less of the total weight. As the pulverizing equipment, ordinary pulverizing equipment can be used, and a lump of particles can be pulverized to 10 mesh or less by using a screen at the pulverizer outlet.

The molybdenum polyphenylene ether is sent to a rotary cylindrical dryer in which a plurality of heating tubes are arranged, and continuously flows by flowing gas inside the dryer in a direction opposite to the polyphenylene ether transfer direction. Drying is performed. The heating tube is heated to 100 ° C. to 200 ° C. by filling the inside of the heating tube with steam. Further, the rotary cylindrical dryer may be provided with a heating jacket on an outer portion as necessary. By providing the heating jacket, the drying speed of the polyphenylene ether can be increased by the heat transfer effect from the outside.

As the gas used here, an inert gas represented by air or nitrogen is used alone or as a mixture. Although the temperature of the gas is not particularly limited, it is preferably in the range of 80 to 200 ° C. at the gas inlet and higher than the boiling point of the dry solvent at the gas outlet from the viewpoint of drying efficiency and prevention of dew condensation at the outlet.

The discharged gas containing polyphenylene ether powder and / or solvents may be used alone or in combination with a solid collecting equipment such as a cyclone or a bag filter or a solvent collecting equipment such as a cooler. By removing the powder and / or the solvent by the combination, the temperature can be raised again as a gas containing a small amount of the solvent and introduced into the dryer. The gas temperature in the solid collecting equipment is preferably higher than the boiling point of the gas-entrained solvent, and is usually preferably maintained at 10 ° C. or more, which is the boiling point.

The flow rate of the gas flowing through the inside of the dryer is preferably 3 to 15 NL / min per 1 kg of dry polyphenylene ether. When the flow rate of the gas is less than the above range, the drying speed is significantly reduced, and as a result, the size of the dryer is increased. When the flow rate of the gas exceeds the above range, the amount of the polyphenylene ether powder entrained in the discharged gas increases, and the size of a bag filter for trapping the powder increases.

When the polyphenylene ether in a wet state is continuously dried, the polyphenylene ether temperature is set to 1 in a drying zone in which a good solvent for the polyphenylene ether is present in an amount of 10% by weight or more per dry polyphenylene ether.
It is necessary to control the flow rate of the polyphenylene ether so as to keep the temperature at 30 ° C. or lower, preferably 100 ° C. or lower. Usually, the polyphenylene ether in a wet state before drying contains 100% by weight or less of a good solvent of polyphenylene ether per dry polyphenylene ether. As the temperature inside the dryer increases, the drying efficiency increases. However, in a drying zone in which a good solvent of polyphenylene ether is present in an amount of 10% by weight or more per dry polyphenylene ether, when the temperature of polyphenylene ether exceeds 130 ° C., the heating in the dryer is stopped The polyphenylene ether particles are fused to the tube and cause a reduction in heating efficiency.

The filling rate of the polyphenylene ether with respect to the space volume inside the cylindrical dryer must be generally 45% by volume or less, preferably 35% by volume or less. 45% by volume
If the filling rate is higher than that, the drying efficiency is remarkably reduced, and an excessively large dryer is inevitably required.

In the present invention, the rotary cylindrical dryer is used alone, but a plurality of rotary cylindrical dryers may be connected in series to dry the polyphenylene ether powder. Furthermore, as long as the effects of the present invention are not hindered, it is also possible to combine with a dryer having another structure such as a paddle dryer.

[0020]

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

The wet polyphenylene ether powder described in the present example contained 31% by weight of toluene, 75% by weight of methanol and 4% by weight of water, based on the weight of the dry polyphenylene ether. Here, the occupied volume of polyphenylene ether in the dryer is
The bulk density of the dried polyphenylene ether powder and the weight after drying of the polyphenylene ether held up in the dryer were measured, and were determined as weight / bulk density after drying. The particle entrainment rate was determined by drying the polyphenylene ether powder collected by the cyclone, measuring the weight, and determining the weight as a percentage by weight based on the dry weight of the supplied polyphenylene ether powder. The amount of residual toluene was determined by dissolving polyphenylene ether powder sampled from a sampling port provided in each part of the dryer in chloroform, solidifying with methanol, filtering off, and analyzing the filtrate by gas chromatography. . The heating tube scale was used to observe the inside from the sampling port and visually determine the adhesion of polyphenylene ether to the heating tube.

Example 1 Polyphenylene ether moistened at 10 kg / h per dry polyphenylene ether while heating a heating tube and a jacket with steam heated to 140 ° C. in a rotary cylindrical dryer having a heating jacket on the outside. The powder was continuously introduced, and nitrogen heated to 140 ° C. in advance in the opposite direction to the flow direction of the polyphenylene ether powder was flowed at 10 NL / min per 1 kg of dry polyphenylene ether, and discharged from the polyphenylene ether inlet. Table 1 shows the results.

Example 2 Polyphenylene ether particles were obtained in the same manner as in Example 1 except that the introduction rate of polyphenylene ether was changed to 5 kg / hour. Table 1 shows the results.

Example 3 Polyphenylene ether particles were obtained in the same manner as in Example 1, except that 13 wt% of a particle mass not passing through a 10-mesh sieve was contained in the polyphenylene ether powder before drying. Table 1 shows the results.

Example 4 The filling ratio of polyphenylene ether in the dryer was 38% by volume.
Polyphenylene ether particles were obtained in the same manner as in Example 1, except that Table 1 shows the results.

[0026]

[Table 1]

Comparative Example 1 Polyphenylene ether particles were obtained in the same manner as in Example 1, except that nitrogen introduced into the dryer was 1 NL / min per 1 kg of dry polyphenylene ether. Table 2 shows the results.

Comparative Example 2 Polyphenylene ether particles were obtained in the same manner as in Example 1, except that nitrogen introduced into the dryer was set at 20 NL / min per 1 kg of dry polyphenylene ether. Table 2 shows the results.

[0029]

[Table 2]

[0030]

According to the method of the present invention, when drying polyphenylene ether in a wet state, a rotary cylindrical dryer in which a plurality of heating tubes are arranged is used, and a gas is introduced into the inside of the dryer. By continuously drying by flowing in the direction opposite to the ether transfer direction, it is possible to suppress the generation of scale in the dryer and efficiently produce dried polyphenylene ether particles.

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Claims (6)

[Claims] When drying a polyphenylene ether in a wet state, a rotary cylindrical dryer in which a plurality of heating tubes are disposed is used to introduce gas into the dryer in a direction opposite to the direction of transport of the polyphenylene ether. A method for producing polyphenylene ether, wherein drying is continuously performed by flowing at a rate of 3 to 15 NL / min per kg of dry polyphenylene ether. 2. The temperature of the polyphenylene ether in the drying zone in which a good solvent of the polyphenylene ether is present in an amount of 10% by weight or more based on the weight of the dry polyphenylene ether,
The method for producing polyphenylene ether according to claim 1, wherein the flow rate of polyphenylene ether is controlled so as to keep the temperature at 100 ° C or lower. 3. A wet mass of polyphenylene ether particles at the entrance of the dryer (polyphenylene ether particles agglomerated during solid-liquid separation and formed into a mass), the mass of which does not pass through a 10-mesh sieve is wet. The method for producing polyphenylene ether according to claim 1, which is 10% or less of the total weight of the polyphenylene ether. 4. The method for producing polyphenylene ether according to claim 1, wherein the filling rate of polyphenylene ether with respect to the space volume inside the cylindrical dryer is 35% by volume or less. 5. The method for producing a polyphenylene ether according to claim 2, wherein the good solvent for the polyphenylene ether is toluene. 6. The method for producing polyphenylene ether according to claim 1, wherein the residual ratio of the good solvent of the dried polyphenylene ether is 0.5% by weight or less based on the weight of the dried polyphenylene ether.