Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-08-20
2001-04-24
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06222002
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the preparation of polycarbonates, and more particularly their preparation by oxidative carbonylation followed by solid state polymerization.
Solid state polymerization (SSP) as a method for preparing polycarbonates is disclosed, for example, in U.S. Pat. Nos. 4,948,871, 5,204,377 and 5,717,056. Use of this method is of increasing interest by reason of its effectiveness and environmental benefits. It is typically described as involving three steps, of which the first step is the formation of a precursor polycarbonate, often an oligomer, typically by a reaction such as melt polymerization (i.e., transesterification) of a dihydroxyaromatic compound such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A) with a diaryl carbonate such as diphenyl carbonate. The second step is enhancement of the crystallinity of the precursor polycarbonate, and the third step is the building of molecular weight by heating the enhanced crystallinity precursor polycarbonate to a temperature between its glass transition temperature and its melting temperature.
Other methods of polycarbonate oligomer preparation are known. They include the oxidative carbonylation (hereinafter sometimes simply “carbonylation” for brevity) of a dihydroxyaromatic compound; i.e., its reaction with carbon monoxide and oxygen in the presence of a compound of a Group VIII element with an atomic number of at least 44, preferably palladium.
The carbonylation of both mono- and dihydroxyaromatic compounds by this method is disclosed, for example, in U.S. Pat. Nos. 4,096,168, 4,096,169 and 4,201,721. Further developments, of particular applicability to monohydroxyaromatic compounds, are the use of co-catalysts which may include an inorganic co-catalyst which is a cobalt compound, especially a complex with a pentadentate ligand, as illustrated by the cobalt(II) salt of bis[3-(salicylalamino)-propyl]methylamine, said complex hereinafter being designated “CoSMDPT”; and an organic co-catalyst, most often a terpyridine such as 2,2′:6′,2″-terpyridine. Reference is made, for example, to U.S. Pat. Nos. 5,231,210 and 5,284,964.
A still further catalyst constituent which is advantageously present for carbonylation of hydroxyaromatic compounds is a bromide (preferably) or chloride source, most often quaternary ammonium, quaternary phosphonium or hexaalkylguanidinium salt such as tetra-n-butylammonium bromide or hexaethylguanidinium chloride or bromide. The aforementioned U.S. Pat. Nos. 5,231,210 and 5,284,964 disclose the use of quater nary ammonium and phosphonium halides, and the similar use of cuanidinium halides is disclosed, for example, in copending, commonly owned application Ser. No. 08/929,000. The disclosures of all of the aforementioned patents and application are incorporated by reference herein.
Polycarbonate oligomers prepared by carbonylation are characterized by hydroxy end groups. Such oligomers are not generally suitable as such for SSP since their molecular weights are, for t he most part, too low, as exemplified by intrinsic viscosities (IV, in chloroform at 25° C.) below about 0.10 and glass transition temperatures (Tg) below 100° C.
They also have other disadvantages. In the first place, an essentially stoichiometric proportion of the expensive palladium compound is usually required for their preparation. In the second place, oligomer production is often low even when a stoichiometric proportion of palladium is employed, whether calculated in terms of percent yield based on dihydroxyaromatic compound or on “turnover number”, the number of moles of carbonate units formed per gram-atom of palladium. In the third place, excessive reaction times on the order of 15 hours are frequently necessary.
The conventional second step of the SSP process, crystallinity enhancement, is considered essential in accordance with the aforementioned prior art. As taught, for example, in the aforementioned U.S. Pat. No. 4,948,871, the crystallinity of the precursor polycarbonate should be in the range of about 5-55% as determined, for example, from powder X-ray diffraction patterns. If it is below 5%, the melting point of the precursor polycarbonate is so low that melting rather than SSP may occur. On the other hand, at crystallinity levels greater than 55% the rate of the molecular weight building step is too low to be practical.
Crystallinity enhancement may be performed by several methods. These include heat treatment, solvent or non-solvent treatment, contact with crystallization promoters and treatment with swelling agents. Each of these methods requires time input and/or treatment with extraneous chemicals which must be kept in inventory and stored. It would be desirable, therefore, to develop an overall polymerization method, including a final SSP step, in which the precursor polycarbonate is inherently of sufficient crystallinity to make a separate crystallinity enhancement step unnecessary.
SUMMARY OF THE INVENTION
The present invention includes an improved method for carbonylation of dihydroxyaromatic compounds, wherein the reactant containing a metal such as palladium is employed in essentially catalytic rather than stoichiometric proportions in the presence of a specifically defined solvent system. Also included is a polymerization method for the oligomeric carbonylation product which includes as a final step either melt polymerization or SSP, in the latter of which the polycarbonate oligomers initially prepared may have a sufficient degree of inherent crystallinity so that no crystallinity enhancement step is required before SSP can be conducted. On the other hand, if there is not a sufficient degree of crystallinity, then the crystallinity needs to be induced by methods know to one skilled in the art.
A first aspect of the invention is a method for preparing a polycarbonate oligomer composition which comprises contacting at least one dihydroxyaromatic compound with oxygen and carbon monoxide in the presence of an amount effective for carbonylation of at least one catalyst composition comprising:
a Group VIII metal having an atomic number of at least 44, or a compound thereof;
at least one organic or inorganic co-catalyst;
at least one halide source; and
an alcohol-free solvent comprising at least one liquid aromatic hydrocarbon.
A second aspect is a catalyst composition comprising a Group VIII metal, co-catalyst, halide source and alcohol-free solvent as defined above.
A third aspect is a method for preparing a high molecular weight aromatic polycarbonate which comprises:
(A) preparing at least one carbonylation oligomer by oxidative carbonylation of at least one dihydroxyaromatic compound,
(B) converting said carbonylation oligomer to a precursor polycarbonate oligomer by melt polymerization in the presence of at least one diaryl carbonate, and
(C) polymerizing said precursor polycarbonate oligomer to a high molecular weight polycarbonate by melt polymerization or solid state polymerization.
In particular, the invention includes such a method wherein step C is an SSP step and steps B and C follow step A without an intervening step of crystallinity enhancement, provided there is a sufficient degree of inherent crystallinity.
DETAILED DESCRIPTION; PREFERRED EMBODIMENTS
Polycarbonates which may be prepared by the method of the first aspect of this invention typically comprise structural units of the formula
wherein each A
1
is independently an aromatic organic radical. Preferably, each A
1
is a radical of the formula
—A
2
—Y—A
3
— (II)
wherein each A
2
and A
3
is a monocyclic divalent aryl radical and Y is a bridging radical in which one or two carbonate atoms separate A
2
and A
3
. Such radicals are derived from dihydroxyaromatic compounds of the formula HO—R—OH and bisphenols of the formula HO—A
2
—Y—A
3
—OH, respectively. For example, A
2
and A
3
generally represent unsubstituted phenylene, especially p-phenylene which is preferred, or substituted derivatives thereof. The bridging radical Y is most often a hydrocarbon group and pa
Avadhani Chilukuri Ver
Bhanage Bhalchandra Mahadeo
Chaudhari Raghunath Vitthal
Gupte Sunil Purushottam
Kanagasabapathy Subbareddiar
Boykin Terressa M.
General Electric Company
Johnson Noreen C.
Stoner Douglas E.
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