Production process of polyphenylene ether

Details Production process of polyphenylene ether Production process of polyphenylene ether

2001-06-19

2002-12-03

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...

C528S492000, C528S483000, C528S086000, C528S215000, C528S217000, C502S165000

Reexamination Certificate

active

06489439

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process for actualizing efficient production of a polyphenylene ether.
BACKGROUND OF THE INVENTION
When a polyphenylene ether is obtained by reacting a phenol compound with oxygen in the presence of a catalyst, water which is the final reductant of oxygen is generated by polymerization. This water often induces hydrolysis of the catalyst and reduces its activity, which disturbs an increase in the molecular weight of the polyphenylene ether. Several proposals have been made for keeping the activity of the catalyst. The first proposal for maintaining activity while retaining water in the system is to use a quaternary ammonium salt as described in JP-B-59-22736 (The term “JP-B” as used herein means an “examined Japanese patent publication”) or U.S. Pat. No. 4,042,564. Use of such an additive increases a cost, though its amount is not so large. The second proposal is to solubilize water by using a solvent which has compatibility therewith. This process is well known in the art. As the solvent, methanol is often employed. The polyphenylene ether obtained using a solvent system composed solely of methanol has however too low molecular weight to draw attentions as an industrial product. Since the solvent, such as methanol, having compatibility with water is often a poor solvent for a polyphenylene ether, precipitation of it occurs while its molecular weight is still low. Thus, the molecular weight cannot be increased as is expected. A polyphenylene ether is therefore often produced in a mixed solvent system containing a solvent having compatibility with the polyphenylene ether. This however requires complex solvent-collecting equipment. The third proposal is to impart the catalyst itself with water resistance. A process slightly improved in water resistance of the catalyst can be found in U.S. Pat. Nos. 4,028,341, 4,092,294 or 4,788,277, but in such a process, the catalyst has not yet acquired complete water resistance. For discharging water out of the system, conventionally employed are (most of them are well known in the art) addition of a dehydrating agent such as magnesium sulfate to a polymer mixture, use of molecular sieves, and the like (JP-B-44-27831). By removing water, the activity of the catalyst can be maintained. In U.S. Pat. No. 4,477,649, described is removal of water by centrifugal separation or decantation after a desired conversion ratio is attained by continuous polymerization of a polyphenylene ether and in Example 1 of this publication, supplementation of a catalyst component after centrifugal separation of reaction water is described. Although such a process is effective for raising the molecular weight of a polyphenylene ether, it is accompanied with such a drawback that a loss of the catalyst component caused by discarding of it upon centrifugation of reaction water must be made up for and this increases the cost. Particularly in the polymerization using a solvent having no compatibility with water, induction of phase separation of water is most important, but it has not yet been fully attained.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an effective removing method of water generated upon production of a polyphenylene ether by reacting oxygen with a phenol compound in the presence of a catalyst, thereby providing a highly efficient production process of the polyphenylene ether.
Other objects and effects of the present invention will become apparent from the following description.
The present inventors carried out an extensive investigation with a view to overcoming the above-described problems. As a result, to their surprise, it was found that in the production process of a polyphenylene ether by using a specific catalyst, marked advantages are brought about by controlling the absolute pressure of the reaction system, oxygen partial pressure of the feed gas and oxygen concentration of the feed gas, thus leading to the completion of the invention.
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 by oxidative polymerization of a phenol compound using a catalyst and an oxygen-containing gas,
wherein the catalyst comprises a copper compound, a bromine compound, a diamine compound represented by the following formula (1):
(wherein, R
1
, R
2
, R
3
and R
4
each independently represents hydrogen or a C
1-6
linear or branched alkyl group with the proviso that all of them do not represent hydrogen simultaneously, and R
5
represents a linear or methyl-branched C
2-5
alkylene group), a tertiary monoamine compound and a secondary monoamine compound,
wherein the process comprises the steps of:
controlling an absolute pressure at a gaseous phase of a reaction vessel to a range of from 0.098 MPa to less than 0.392 MPa; and
feeding the oxygen-containing gas to the reaction vessel, the oxygen-containing gas having an oxygen partial pressure, in terms of an absolute pressure, of from 0.0147 MPa to 0.0883 MPa.
2) The process according to item 1) above, wherein the oxygen-containing gas has an oxygen concentration of not greater than 21 vol. %.
3) The process according to item 1) above, wherein the oxygen-containing gas has an oxygen concentration of not greater than 11.6 vol. %.
4) The process according to any one of items 1) to 3) above, wherein the phenol compound is charged, at such a rate that charging of the whole amount thereof is completed within a period of from 10 minutes to less than 110 minutes, into the reaction vessel containing the catalyst components and being fed with the oxygen-containing gas.
5) The process according to item 4) above, wherein the oxygen-containing gas is fed at a rate ranging from 0.5 Nl/min to 15 Nl/min with respect to 1 kg of the reaction mixture at which the whole amount of the phenol compound is charged completely.
With the features as described in items 2) to 4) above, further desirable results can be obtained in the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
The invention is described in more detail below.
The phenol compound to be used in the invention is a compound having a structure represented by the following formula (2):
(wherein, R
6
represents an alkyl, substituted alkyl, aralkyl, substituted aralkyl, aryl, substituted aryl, alkoxy or substituted alkoxy group, R
7
represents, in addition to those described for R
6
, a halogen atom, and R
8
represent, in addition to those described for R
7
, hydrogen). Examples of such a compound include 2,6-dimethylphenol, 2,3,6-trimethylphenol, 2-methyl-6-ethylphenol, 2,6-diethylphenol, 2-ethyl-6-n-propylphenol, 2-methyl-6-chlorophenol, 2-methyl-6-bromophenol, 2-methyl-6-isopropylphenol, 2-methyl-6-n-propylphenol, 2-ethyl-6-bromophenol, 2-methyl-6-n-butylphenol, 2,6-di-n-propylphenol, 2-ethyl-6-chlorophenol, 2-methyl-6-phenylphenol, 2,6-diphenylphenol, 2,6-bis-(4-fluorophenyl)phenol, 2-methyl-6-tolylphenol and 2,6-ditolylphenol. They may be used either singly or in combination. Incorporation thereto of a small amount of phenol, o-cresol, m-cresol, p-cresol, 2,4-dimethylphenol or 2-ethylphenol does not cause any substantial problem. Above all of these phenol compounds, 2,6-dimethylphenol is industrially important.
As a catalyst to be used upon production of a polyphenylene ether by oxidative polymerization of a phenol compound by using a catalyst and an oxygen-containing gas, a catalyst system comprising a copper compound, a bromine compound, a diamine compound represented by the following formula (1):
(wherein, R
1
, R
2
, R
3
and R
4
each independently represents hydrogen or a C
1-6
linear or branched alkyl group with the proviso that they do not represent hydrogen simultaneously, and R
5
represents a linear or methyl-branched C
2-5
alkylene group), a tertiary monoamine compound and a secondary monoamine compound must be used. It was found that in the production process using this catalyst, remarkable activity improving effects are brought about wit

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