Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2001-10-25
2003-06-24
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
C528S196000
Reexamination Certificate
active
06583258
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to salts of organic phosphates useful as transesterification catalysts in melt polymerization reactions of dihydroxy aromatic compounds with diaryl carbonates. The invention further relates to a method for the preparation of polycarbonates using alkali and alkaline earth metal salts of organic phosphates. The method may be used to provide 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 at least one diaryl carbonate with at least one dihydroxy aromatic compound in the presence of a transesterification catalyst and optionally a co-catalyst, under melt polymerization conditions to afford a polycarbonate, said transesterification catalyst comprising at least one alkali metal or alkaline earth metal salt of an organic phosphate.
In one aspect the method of the present invention affords a product polycarbonate having a lower level of Fries rearrangement product than polycarbonate of similar molecular weight prepared using a conventional melt transesterification catalyst.
The present invention further relates to a method of preparing polycarbonate under melt polymerization conditions by reacting at least one dihydroxy aromatic compound with at least one diaryl carbonate in the presence of at least one salt of an organic phosphate, said salt having structure I
wherein A is independently at each occurrence an alkali metal ion or an alkaline earth metal ion; p is an integer having a value of 1 or 2; q is an integer having a value in a range from 1 to about 10, and R
1
is an C
1
-C
60
aliphatic radical, a C
3
-C
60
cycloaliphatic radical or a C
4
-C
60
aromatic radical.
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 compounds 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.
“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 “aliphatic radical” refers to a radical having a valence of at least one comprising a linear or branched array of carbon atoms which is not cyclic. Examples of aliphatic radicals include methylene; ethylene; 1,2-dimethylethylene; hexamethylene; and the like.
As used herein the term “aromatic radical” refers to a radical having a valence of at least one, said radical comprising at least one aromatic group. The aromatic radical may be composed entirely of carbon and hydrogen atoms, or may comprise heteroatoms such as nitrogen, oxygen and sulfur.
As used herein the term “cycloaliphatic radical” refers to a radical having a valance of at least one comprising an array of atoms which is cyclic but which is not aromatic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen.
It should be understood that as used herein, the terms “aliphatic radical”, “aromatic radical” and “cycloaliphatic radical” include both substituted and unsubstituted embodiments of said radicals. Typical substituents according to the present invention for the substituted forms of aliphatic, aromatic and cycloaliphatic radicals include C
1
-C
20
alkyl, C
3
-C
20
cycloalkyl, C
4
-C
20
aryl, halogen, hydroxy, carbonyl, nitro, cyano, C
1
-C
20
alkoxy, C
1
-C
20
alkoxycarbonyl, and the like.
It should be understood that the terms “mmHg” and “torr” are used interchangeably herein as units of pressure.
It has been discovered that the use of salts of organic phosphates as polymerization catalysts in the melt transesterification reaction of a dihydroxy aromatic compound such as bisphenol A with a diaryl carbonate such as diphenyl carbonate, provides a product polycarbonate comprising a reduced level of Fries rearrangement product. This reduction in the amount of Fries rearr
Lemmon John Patrick
Wroczynski Ronald James
Boykin Terressa M.
Caruso Andrew J.
General Electric Company
Johnson Noreen C.
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