Production process of polyphenylene ether

Details Production process of polyphenylene ether Production process of polyphenylene ether

2001-06-19

2003-07-01

Truong, Duc (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Treating polymer containing material or treating a solid...

C528S086000, C528S491000, C528S495000, C528S497000, C528S499000, C528S500000, C528S50200C, C528S503000

Reexamination Certificate

active

06586567

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a production process of a polyphenylene ether. More specifically, the invention pertains to a production process of a polyphenylene ether, wherein water used in the polymerization-solvent-recovery step is recycled to reduce the discharged amount of water.
BACKGROUND OF THE INVENTION
A polyphenylene ether is available by polymerizing a phenol compound in an aromatic solvent or a mixture of an aromatic solvent and a nonsolvent in the presence of oxygen by using an oxidative coupling polymerization catalyst containing copper, manganese or cobalt. After termination of the polymerization reaction and removal of the catalyst, the polyphenylene ether solution thus obtained is charged in a poor solvent for a polyphenylene ether and solidified. The polyphenylene ether thus solidified is, after solid-liquid separation, fed to a drying step, whereby polyphenylene ether powders are prepared. The filtrate of the mixture of the polymerization solvent and poor solvent after solid-liquid separation is, on the other hand, fed to the recovery step. When components cannot be separated easily by distillation owing to azeotropy of the poor solvent with the polymerization solvent, and at the same time the polymerization solvent is non-water-soluble but the poor solvent is water-soluble, the filtrate is brought into contact with water to extract the poor solvent in the water phase, thus separating it from the polymerization catalyst and then, the water phase is separated into the poor solvent and water by distillation.
Water thus separated however still contains a large amount of high-boiling point organic substances, particularly diphenohydroquinone or diphenoquinone so that it cannot be recycled freely because there is a danger of it causing problems such as clogging of the pipe. At present, it is therefore the common practice to drain such water after treated with active sludge or incineration. Incineration of water however requires an enormous energy, while treatment with active sludge needs cumbersome sludge management. Thus, a technique for improving the solvent recovery step by using water has not been found yet.
SUMMARY OF THE INVENTION
The present invention was made to solve the above-described problems.
Accordingly, an object of the present invention is to provide a production process of a polyphenylene ether giving a reduced amount of water to be discharged.
Other objects and effects of the present invention will become apparent from the following description.
The present inventors carried out an extensive investigation. As a result, they found a method permitting—by bringing a mixture, which has been left after the recovery of a solidified polyphenylene ether and contains a non-water-soluble polymerization solvent and a water-soluble poor solvent, into contact with water, extracting the water-soluble poor solvent in the water phase, and distilling the water phase to separate and remove the poor solvent—recycled use of a whole or part of the water phase thus obtained. The present invention is based on this finding.
In the invention, there is thus provided a production process of a polyphenylene ether wherein water used in the polymerization-solvent-recovery step is recycled to reduce the discharged amount of water. The problem of clogging of a pipe or the like which has so far prevented the recycled use of water is solved by bringing the polyphenylene ether solution into contact with an aqueous solution of a chelating agent while maintaining the temperature at 50 to 120° C. for 10 to 180 minutes.
That is, the above-described objects of the present invention have been achieved by providing the following production processes.
1) A process for producing a polyphenylene ether, which comprises:
contacting, with an aqueous solution of a chelating agent, a polyphenylene ether solution obtained by polymerization in a non-water-soluble polymerization solvent for a polyphenylene ether in the presence of a catalyst, to terminate the polymerization and deactivating the catalyst; and
adding a water-soluble poor solvent for the polyphenylene ether to precipitate the polyphenylene ether; and
recovering the thus precipitated polyphenylene ether,
wherein (a) the contact with the chelating agent aqueous solution is carried out by holding the polyphenylene ether solution and the chelating agent aqueous solution at a temperature of from 50 to 120° C. for 10 to 180 minutes,
wherein (b) a mixture remaining after the recovery of the polyphenylene ether, which contains the non-water-soluble polymerization solvent and water-soluble poor solvent, is brought into contact with water to extract the water-soluble poor solvent, and a water phase containing the thus extracted water-soluble poor solvent is recovered by separation, and
wherein (c) the water-soluble poor solvent is separated and removed from the water phase by distillation, and the whole or a part of the remaining water phase is recycled as water to be brought into contact with the mixture, the remaining water phase having a content of a high-boiling-point organic substance of 1 wt. % or less.
2) The production process of a polyphenylene ether according to item 1) above, wherein the water-soluble poor solvent forms an azeotropic mixture not with water but with the non-water-soluble polymerization solvent and has a lower boiling point than that of water.
3) The production process of a polyphenylene ether according to items 1) or 2) above, wherein the water-soluble poor solvent is methanol.
4) The production process of a polyphenylene ether according to any one of items 1) to 3) above, wherein the non-water-soluble polymerization solvent is toluene.
5) The production process of a polyphenylene ether according to any one of items 1) to 4) above, wherein the content of a high-boiling-point organic substance in the remaining water phase to be recycled is 0.5 wt. % or less.
6) The production process of a polyphenylene ether according to any one of items 1) to 5) above, wherein the total amount of the polymerization solvent and the poor solvent contained in the remaining water phase to be recycled is 0.1 wt. % or less.
DETAILED DESCRIPTION OF THE INVENTION
Polyphenylene Ether
The polyphenylene ether for use in the invention is a homopolymer, random copolymer or block copolymer having a recurring unit represented by the following formula (1):
wherein R
1
, R
2
, R
3
and R
4
each independently represents hydrogen, an alkyl group, a substituted alkyl group, a halogen atom, a phenyl group or a substituted phenyl group.
Typical examples of the polyphenylene ether include homopolymers of 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 or poly(2-methyl-6-hydroxyethyl-1,4-phenylene)ether; and also polyphenylene ether copolymers using, in combination therewith, 2,6-dimethylphenol and either one or both of 2,3,6-trimethylphenol and o-cresol as a copolymer component.
Oxidative Polymerization
As described, for example, in JP-B-42-3195 (The term “JP-B” used herein means an “examined Japanese patent publication”), JP-A-64-33131 (The term “JP-A” used herein means an “unexamined published Japanese patent application”) or JP-B-61-8092, the polyphenylene ether of the invention is produced by oxidative coupling polymerization of a phenol compound in a uniform system in the presence of a complex catalyst which is a combination of a salt of a metal selected from a group consisting of copper, manganese and cobalt and an amine and is soluble in a polymerization solvent. Specific examples of the metal salt include cuprous chloride, cupric chloride, cuprous bromide, cupric bromide, cuprous sulfate, cupric sulfate, cuprous acetate, cupric acetate, cuprous propionate, cupric laurate, cuprous palmitate and cuprous benzoate; and similar man

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