Process for producing polyphenylene ether

Details Process for producing polyphenylene ether Process for producing polyphenylene ether

2001-12-26

2004-07-06

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...

C528S495000, C528S496000, C528S499000, C528S501000, C528S50200C, C528S50200C

Reexamination Certificate

active

06759507

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a method for producing polyphenylene ether. More specifically, the present invention relates to a method for producing the polyether that includes recycle use of a solvent.
PRIOR ART
As a method for synthesizing the polyphenylene ether, there is a method of subjecting phenol to oxidative polymerization in the presence of a copper compound and amines such as di-n-buthylamine and the like, in an aromatic compound solvent. A non-solvent for the polyphenylene ether such as methanol, water or the like is added in the above-obtained polyphenylene ether solution to precipitate the polyphenylene ether particles. Then, dry particles of the polyphenylene ether can be prepared through steps such as solid-liquid separation, washing with methanol or the like and dryness.
It surely needs to achieve reduction of the manufacture cost that components used in the above method of preparing the polyphenylene ether, such as the aromatic compound solvent, the amines, methanol or water, are each separated and recovered for every component to reuse. However when di-n-buthylamine is used especially as the amines, it has not been established a method of separating and recovering an aromatic compound solvent, di-n-buthylamine and methanol efficiently and economically.
The present invention has been made to solve the above problems, and the object of the present invention is to provide an industrially advantageous method for producing the polyphenylene ether by separating and recovering efficiently the solvent used in polyphenylene ether production process, such as aromatic compound solvent, amines and methanol.
Other purposes and advantages of the present invention will become clear from the following explanation.
DISCLOSURE OF INVENTION
The present inventors have made extensive studies to solve the above problems, and as a result, have found that it was able to recovered methanol having the low amines content and water by adding water to a mixed solution of the aromatic compound solvent, amines and methanol, separating a phase which consists of the aromatic compound solvent and a large portion of the amines from the mixed solution by liquid-liquid separation, supplying a phase which consists mainly of methanol containing a part of the amines and water to a distillation column, and distilling the phase while carrying out side-cut of the amines. Thus, the present invention has been accomplished.
That is, the present invention is a method for preparing polyphenylene ether comprising the following steps,
(a) a step for synthesizing polyphenylene ether by subjecting phenol to oxidative polymerization in the presence of a copper compound and amines in an aromatic compound solvent,
(b) a step for precipitating the polyphenylene ether particles by adding methanol to the solution of polyphenylene ether in the aromatic compound solvent obtained by the step (a),
(c) a step for solid-liquid separating a slurry of polyphenylene ether obtained by the step (b), and washing the separated polyphenylene ether particles with methanol to obtain the polyphenylene ether,
(d) a step for adding water to a filtrate obtained by the step (c) to mix them, and then, liquid-liquid separating the mixture into phase consisting mainly of the aromatic compound and a phase consisting mainly of methanol and water, and
(e) a step for supplying the phase consisting mainly of methanol and water, obtained by the step (d), to the middle portion of the distillation column to perform distillation, and separating out a distillate liquid consisting mainly of methanol, a bottom liquid consisting mainly of water and a side-cut liquid comprising the amines by distilling, recycling the distillate liquid consisting mainly of methanol as methanol which is used at the step (b) and (c), and recycling the side-cut liquid as part of the filtrate which is used at the step (d).
EMBODIMENT FOR PRACTICING THE INVENTION
The polyphenylene ether in the present invention is derived from a compound represented by the following formula (1) by oxidative polymerization.
(wherein R
1
, R
2
, R
3
and R
4
represent independently a substituent selected from the group consisting of a hydrogen atom, an alkyl group, a substituted alkyl group, a halogen atom, an aryl group and a substituted aryl group.)
Examples of polyphenylene ether according to the present invention are a homopolymer such as
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-methyl-6-n-propyl-1,4-phenylene)ether,
poly(2-ethyl-6-isopropyl-1,4-phenylene)ether,
poly(2-methyl-6-chloroethyl-1,4-phenylene)ether,
poly(2-methyl-6-hydroxyethyl-1,4-phenylene)ether;
polyphenylene ether copolymer such as 2,6-dimethylphenol copolymerized with 2,3,6-trimethylphenol and/or o-cresol.
The step (a) of the present invention is a step for obtaining the polyphenylene ether by subjecting phenol to oxidative polymerization in the presence of the copper compound and the amines in the aromatic hydrocarbon solvent.
The aromatic hydrocarbon solvent used in the reaction of polymerization is preferably benzene, toluene and xylene, and especially toluene is preferred. The concentration of polyphenylene ether in a solution of polymerization reaction is preferably 5 to 70 wt %, more preferably 10 to 50 wt %. Further, the solution may contain substances for removing catalysts, by-products or the like, other than polyphenylene ether and catalysts for polymerization (the copper compound and the amines).
The step (b) is a step for precipitating the polyphenylene ether particles by adding methanol which is a non-solvent for polyphenylene ether, to the solution of polyphenylene ether in the aromatic compound solvent, obtained by the step (a).
The amount of methanol to be added is preferable 1 to 2 times by weight of the aromatic compound in polyphenylene ether solution. It is desirable further to let water co-exist with a mixture of the aromatic compound solvent and methanol within such a range that the mixture can maintain a single liquid phase. Moreover, when the solution of polymerization reaction is supplied, it is preferred that the polyphenylene ether solution and methanol are continuously supplied into one or more stages of a stirring vessel having a reciprocating stirrer. Further, to decrease the amount of methanol used, it is desirable to supply the polyphenylene ether solution into the stirring vessel while maintaining temperature to the extent that polyphenylene ether does not precipitate after heating and condensing the polyphenylene ether solution.
The step (c) is a step for solid-liquid separating the slurry of polyphenylene ether obtained by the step (b), and then, washing the separated polyphenylene ethers particles with methanol.
As a method of solid-liquid separating the slurry of the polyphenylene ether particles precipitated, for example, there are a method of using a centrifugal force and a vacuum filtration method under reduced pressure. Moreover, not only these but any method scan be used. The solid-liquid separated wet particles of polyphenylene ether were washed with methanol, and dried by heating or the like, to obtain dry particles. Since it is hard to remove the aromatic compound solvent and the amines by drying, if these are not removed from the wet particles by methanol-washing, these will remain in the dry particles and will become cause a stench or the like.
The step (d) is a step for adding water to the filtrate obtained by the step (c), i.e. the filtrate containing the aromatic compound, the amines and methanol, and liquid-liquid separating into a phase consisting mainly of the aromatic compound and a phase consisting mainly of methanol and water.
It is desirable to set up the amount of water to be added so that the weight ratio of water/methanol in the liquid-liquid separated raw solution may be 0.5 to 1.5. Further, as for a method of liquid-liquid separation, there are a stand separation, a centrifugation and a tower system separation or

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