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
2004-03-23
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
C502S150000, C502S208000, C528S198000
Reexamination Certificate
active
06710155
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to polyhydropolyborates useful as transesterification catalysts in melt polymerization reactions of dihydroxy aromatic compounds with diaryl carbonates. Suitable polyhydropolyborates are those which comprise alkali metal counterions. The invention further relates to a method for the preparation of polycarbonates using these polyhydropolyborates. The method provides a product polycarbonate comprising a lower level of Fries product than is provided by other known methods employing conventional melt transesterification 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 which 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 polyhydropolyborate 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 a polyhydropolyborate catalyst having structure I
(B
n
H
m
)(M)
p
I
wherein (B
n
H
m
) is a monovalent or divalent anion consisting of boron and hydrogen; n and m are positive integers n having a value greater than or equal to 3, m having a value greater than or equal to n; M is an alkali metal cation; and p is an integer having a value of 1 or 2.
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 Cs
2
B
12
H
12
and tetramethylammonium hydroxide, Cs
2
B
12
H
12
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 one and comprising at least one aromatic ring. Examples of aromatic radicals include phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene, and biphenyl. The term includes groups containing both aromatic and aliphatic components, for example a benzyl group, a phenethyl group or a naphthylmethyl group. The term also includes groups comprising both aromatic and cycloaliphatic groups for example 4-cyclopropylphenyl and 1,2,3,4-tetrahydronaphthalen-1-yl.
As used herein the term “aliphatic radical” refers to a radical having a valence of at least one and consisting of a linear or branched array of atoms which is not cyclic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of aliphatic radicals include methyl, methylene, ethyl, ethylene, hexyl, hexamethylene and the like.
As used herein the term “cycloaliphatic radical” refers to a radical having a valance of at least one and comprising an array of atoms which is cyclic but which is not aromatic, and which does not further comprise an aromatic ring. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of cycloaliphatic radicals include cyclopropyl, cyclop
Boykin Terressa M.
General Electric Company
Parker Kimberly H.
Patnode Patrick K.
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