Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having a halogen atom or oxygen single bonded...
Patent
1989-03-07
1990-09-04
Anderson, Harold D.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having a halogen atom or oxygen single bonded...
526 67, 526 68, 528196, 528271, 528370, C08G 6430
Patent
active
049546139
DESCRIPTION:
BRIEF SUMMARY
The present invention is an integrated process for the production of polycarbonates from bisphenol diesters.
Polycarbonates have hitherto been produced by reacting bisphenol A, phosgene and caustic soda in a phase transfer reaction. However, the known toxicity of phosgene and the problems of disposal of by-product sodium chloride from this reaction resulted in efforts being made to produce the polycarbonate by a non-phosgene route.
One such route is claimed and described in U.S. Pat. No. 4,452,968 which is an integrated process for producing polycarbonates by carbonate; the diacetate, in the presence of a catalyst to form an oligomer and an alkyl ester; and the alkanol used in (a) above; used in step (b); and the polycarbonate resin.
The above process has some disadvantages in that the amount of ketene produced from the alkyl ester by heating it as in step (c) is inadequate for operating a continuous process. Hence additional ketene has to be added to the bisphenol in step (d) in order to form commercially viable amounts of the bisphenol diester. Since ketene is not an article of commerce, it must be manufactured on-site by e.g. pyrolysis of acetic acid in the presence of a catalyst at elevated temperature e.g. 700.degree.-800.degree. C. Thereafter the ketene has to be separated from the pyrolysis products before use for reaction with bisphenol.
The additional capital costs involved in setting up a ketene manufacturing facility and the high heat energy requirements of the relevant process adversely affect the economics of the process for producing polycarbonate resin using ketene as a key reactant. Moreover, the reaction product of ketene and bisphenol is a mixture of bisphenol mono acetate and diacetate, the mono acetate having to be further acylated by reaction with acetic anhydride.
It has now been found that the use of ketene may be avoided if the integrated process is modified to convert the by-product alkyl ester to e.g. acetic anhydride by hydrocarbonylation and the acetic anhydride can be used to produce the bisphenol diester directly.
Accordingly, the present invention is an integrated process for producing polycarbonates, said process comprising: bisphenol diester in contact with a catalyst to form a carbonate oligomer and an alkyl ester, and separating the alkyl ester from the oligomer; presence of a carbonylation catalyst to form a product comprising an anhydride; bisphenol to form the bisphenol diester, and recycling the diester to step A; and polycarbonate.
The dialkyl carbonate used in step A may be derived by reacting an alkanol with carbon monoxide and oxygen or by reacting an alkylene oxide with carbon dioxide initially to form an alkylene carbonate which is subsequently reacted with methanol. Where the dialkyl carbonate is derived from an alkanol, the alkanol is preferably a primary alkanol in which the alkyl group has 1-4 carbon atoms, most preferably 1-2 carbon atoms.
The dialkyl carbonate reactant is suitably dimethyl carbonate or diethyl carbonate, most preferably dimethyl carbonate. The method of producing dialkyl carbonates used in the process described in step A is well known in the art. For instance, the reaction between an alkanol, carbon monoxide and oxygen may be carried out in the presence of a catalyst such as salts of palladium, platinum or an organometallic complex of copper, use of cupric chloride being preferred. Specifically, the process described in U.S. Pat. No. 4,360,477 may be used and is incorporated herein by reference. In the process it is preferable to use a carbon monoxide to oxygen molar ratio of 2:1, anhydrous alkanol, e.g. methanol, a temperature 175.degree.-186.degree. C., and a pressure of 600-2500 psig.
Since this reaction is exothermic adequate cooling facilities need to be provided to maintain the reaction temperature within the desired range.
The bisphenol used in steps A and C above is suitably selected from the group of bisphenol, bisphenol A, tetramethyl bisphenol A and tetrabromobisphenol A.
The transesterification reaction in step A is also well k
REFERENCES:
patent: 4452968 (1984-06-01), Bolon et al.
Anderson Harold D.
BP Chemicals Limited
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