Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-06-27
2003-10-28
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
C502S105000, C528S198000
Reexamination Certificate
active
06639043
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to azonaphthalene sulfonates useful as transesterification catalysts in melt polymerization reactions of dihydroxy aromatic compounds with diaryl carbonates. Suitable azonaphthalene sulfonates are those that comprise alkali metal counterions. The invention further relates to a method for the preparation of polycarbonates using these azonaphthalene sulfonates. The method provides a product polycarbonate comprising a lower level of Fres product than is provided by other known methods employing conventional melt transestenfication catalysts.
Increasingly, polycarbonate is being prepared by the melt reaction of a diaryl carbonate with a dihydroxy aromatic compound in the presence of a transesterification catalyst, such as sodium hydroxide. In this “melt” process, reactants are introduced into a reactor capable of stirring a viscous polycarbonate melt at temperatures in excess of 300° C. Typically, the reaction is run at reduced pressure to facilitate the removal of by-product hydroxy aromatic compound formed as the diaryl carbonate reacts with the dihydroxy aromatic compound and growing polymer chains.
The Fries rearrangement is a ubiquitous side reaction taking place during the preparation of polycarbonate using the melt process. The resultant “Fries product” serves as a site for branching of the polycarbonate chains thereby affecting flow and other properties of the polycarbonate. Although, a low level of Fries product may be tolerated in the product polycarbonate produced by the melt process, the presence of higher levels of Fries product may negatively impact performance characteristics of the polycarbonate, such as moldability and toughness. Currently, alkali metal hydroxides, such as sodium hydroxide, are employed as catalysts in the preparation of polycarbonate using the melt process. Alkali metal hydroxides, although effective catalysts in terms of rates of conversion of starting materials to product polycarbonate, tend to produce relatively high levels of Fries rearrangement product. Thus, melt polymerization methodology useful for the preparation of polycarbonate in which the formation of Fries product has been minimized represents a long sought goal among those wishing to practice such methodology.
It would be a significant advantage to prepare polycarbonate by a melt polymerization method that provides high rates of polymerization while minimizing the amount of Fries product formation.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a method for the preparation of polycarbonate, said method comprising contacting under melt polymerization conditions at least one diaryl carbonate with at least one dihydroxy aromatic compound in the presence of a transesterification catalyst to afford a polycarbonate, said transesterification catalyst comprising at least one azonaphthalene sulfonate catalyst and at least one co-catalyst.
In one aspect the method of the present invention affords a product polycarbonate having a lower level of Fries rearrangement product than polycarbonate prepared using a conventional melt transesterification catalyst.
The present invention further relates to a method of preparing polycarbonate by the melt reaction of at least one dihydroxy aromatic compound with at least one diaryl carbonate in the presence of at least one transesterification catalyst comprising an azonaphthalene sulfonate. Azonaphthalene sulfonates are a well-known class of dyestuffs, whose catalytic properties in the melt polycarbonate arena remained undiscovered until the present invention. In its broadest sense, the term azonaphthalene sulfonate includes organic molecules comprising the following elements; an azo group (—N═N—), a naphthalene ring, and a sulfonate group (SO
3
Y
+
) wherein Y
+
is a charge-balancing counterion. In one embodiment of the present invention the azonaphthalene catalyst has structure I
wherein Ar
1
is a C
4
-C
60
aromatic radical having a valence of at least one, said aromatic radical being optionally substituted by one or more hydroxy groups, amino groups, C
1
-C
10
alkylamino groups, C
2
-C
20
dialkylamino groups, C
1
-C
20
aliphatic radicals, C
4
-C
20
cycloaliphatic radicals, C
4
-C
10
aromatic radicals, C
1
-C
10
alkoxy groups, halogen atoms, and alkali metal sulfonate groups;
M is independently at each occurrence a lithium, sodium, potassium, or cesium ion;
n and m are integers independently having values of from 0 to 2 wherein the sum of n and m is always greater than or equal to 1;
R
1
is independently at each occurrence a hydroxy group, amino group, C
1
-C
10
alkylamino group, C
2
-C
20
dialkylamino group, C
1
-C
20
aliphatic radical, C
4
-C
20
cycloaliphatic radical, C
4
-C
10
aromatic radical, C
1
-C
10
alkoxy group, halogen atom, nitro group, or a cyano group;
q is an integer having a value of from 0 to 3;
p is an integer having a value of from 0-4; and
r is an integer having a value of from 1-4.
DETAILED DESCRIPTION OF THE INVENTION
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included therein. In the following specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:
The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
As used herein the term “polycarbonate” refers to polycarbonates incorporating structural units derived from at least one dihydroxy aromatic compound and includes copolycarbonates and polyester carbonates.
As used herein, the term “melt polycarbonate” refers to a polycarbonate made by a process comprising the transesterification of a diaryl carbonate with a dihydroxy aromatic compound in the presence of a transesterification catalyst.
“BPA” is herein defined as bisphenol A or 2,2-bis(4-hydroxyphenyl)propane.
As used herein when describing the instant invention, the term “transesterification catalyst” refers to a catalyst system comprising at least one “principal catalyst” and at least one co-catalyst. For Example, in one embodiment of the instant invention diphenyl carbonate and bisphenol A are melt polymerized in the presence of a transesterification catalyst comprising an azonaphthalene sulfonate and tetramethylammonium hydroxide, the azonaphthalene sulfonate being the principal catalyst and tetramethylammonium hydroxide being the co-catalyst.
“Catalyst system” as used herein refers to the catalyst or catalysts that catalyze the transesterification of the dihydroxy aromatic compound with the diaryl carbonate in the preparation of melt polycarbonate.
“Catalytically effective amount” refers to the amount of the catalyst at which catalytic performance is exhibited.
As used herein the term “Fries product” is defined as a structural unit of the product polycarbonate which upon hydrolysis of the product polycarbonate affords a carboxy-substituted dihydroxy aromatic compound bearing a carboxy group adjacent to one or both of the hydroxy groups of said carboxy-substituted dihydroxy aromatic compound. For example, in bisphenol A polycarbonate prepared by a melt reaction method in which Fries reaction occurs, the Fries product affords carboxy bisphenol A, II, upon complete hydrolysis of the product polycarbonate.
The terms “Fries product” and “Fries group” are used interchangeably herein.
The terms “Fries reaction” and “Fries rearrangement” are used interchangeably herein.
As used herein the term “hydroxy aromatic compound” means a phenol, such as phenol, p-cresol or methyl salicylate, comprising a single reactive hydroxy group and is used interchangeably with the term “phenolic by-product”.
As used herein the term “aromatic radical” refers to a radical having a valence of at least
Lemmon John Patrick
Wroczynski Ronald James
Boykin Terressa M.
Caruso Andrew J.
General Electric Company
Patnode Patrick K.
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