Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-02-04
2001-11-13
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
06316578
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to salts of nonvolatile acids useful in catalyst systems in melt polymerizations. Suitable salts of nonvolatile acids include phosphites of alkali metal compounds, phosphates of alkali metal compounds, and mixture thereof. The invention further relates to polycarbonates prepared using the catalyst systems of the present invention, and articles made from these polycarbonates.
BACKGROUND OF THE INVENTION
Conventional industrial plants synthesize polycarbonate by mixing together an aqueous solution of dihydric compound (e.g., bisphenol-A) with an organic solvent (e.g., dichloromethane) containing a carbonyl halide (e.g., phosgene) Upon mixing the immiscible organic and aqueous phases, the dihydric compound reacts with the carbonyl halide at the phase interface. Typically, a phase transfer catalyst, such as a tertiary amine, is added to the aqueous phase to enhance this reaction. This synthesis method is commonly known as the “interfacial” synthesis method for preparing polycarbonate.
The interfacial method for making polycarbonate has several inherent disadvantages. First it is a disadvantage to operate a process which requires phosgene as a reactant due to obvious safety concerns. Second it is a disadvantage to operate a process which requires using large amounts of an organic solvent because expensive precautions must be taken to guard against any adverse environmental impact. Third, the interfacial method requires a relatively large amount of equipment and capital investment. Fourth, the polycarbonate produced by the interfacial process is prone to having inconsistent color, higher levels of particulates, and higher chlorine content, which can cause corrosion.
Some new commercial polycarbonate plants synthesize polycarbonate by a transesterification reaction whereby a diester of carbonic acid (e.g., diphenylcarbonate) is condensed with a dihydric compound (e.g., bisphenol-A). This reaction is performed without a solvent, and is driven to completion by mixing the reactants under reduced pressure and high temperature with simultaneous distillation of the phenol produced by the reaction. This synthesis technique is commonly referred to as the “melt” technique. The melt technique is superior over the interfacial technique because it does not employ phosgene, it does not require a solvent, and it uses less equipment. Moreover, the polycarbonate produced by the melt process does not contain chlorine contamination from the reactants, has lower particulate levels, and has a more consistent color. Therefore it is highly desirable to use the melt technique in a commercial manufacturing process.
In the production of polycarbonates by the melt polymerization process, alkali metal hydroxides, in particular sodium hydroxide, are used as polymerization catalysts. While alkali metal hydroxides are useful polymerization catalysts, they also effect side reactions which results in branched side reaction products. This causes changes in the melt behavior of the polycarbonate, which can lead to difficulties in processing.
It would be desirable, therefore, to develop a catalysts system which effects melt polymerization while minimizing undesirable reaction products, such as branched side reaction products.
DESCRIPTION OF THE INVENTION
The present invention addresses these concerns and provided further surprising properties.
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.
Before the present compositions of matter and methods are disclosed and described, it is to be understood that this invention is not limited to specific synthetic methods or to particular formulations, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
In the following specification, 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 “melt polycarbonate” refers to a polycarbonate made by the transesterification of a carbonate diester with a dihydroxy compound. “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 dihydric phenol and the carbonic acid diester in the melt process.
The terms “diphenol” and “dihydric phenol” as used herein are synonymous.
“Catalytically effective amount” refers to the amount of the catalyst at which catalytic performance is exhibited.
In the present invention, it was unexpectedly found that a catalyst system comprising alkali metal salts of nonvolatile acids and a base reduces side reaction products, including “Fries” product and other branched side reaction products. The reduction of these products provides the advantage of increased ductility, and prevents the reduction of rheological properties which results when undesirable side reaction products, such as Fries product, are present. It was further unexpectedly found that for a given set of conditions the catalyst systems as described in the present invention product less Fries than alkali metal hydroxides, such as sodium hydroxide.
Specifically, the present invention provides a catalyst system for the production of polycarbonate by the melt process, wherein the polycarbonate has a reduced content of undesirable branched side reaction product, in particular Fries products. It is desirable to have Fries product of less than 1000 ppm, preferably less than 900 ppm, more preferably less than 500 ppm, even more preferably less than 200 ppm.
Polycarbonate produced by the melt process typically has higher Fries content than polycarbonates produced by the interfacial method. As used herein the term “Fries” or “fries” refers to a repeating unit in polycarbonate having the following formula (I):
where the X variable represents
Variable R
c
and R
d
each independently represent a hydrogen atom or a monovalent hydrocarbon group and may form a ring structure. Variable R
e
is a divalent hydrocarbon group.
It is very desirable to have a low Fries content in the polycarbonate product, as Fries products reduce the performance characteristics of the polycarbonate, such as the ductility. Higher Fries contents results in lower ductility. Preparing polycarbonate by the melt process results in the formation of Fries products.
The present invention relates to melt polymerization catalysts in a melt polymerization system in which a dihydric phenol and a diester of carbonic acid are reacted. Dihydric phenols which are useful in preparing the polycarbonate of the invention may be represented by the general formula
wherein:
R is independently selected from halogen, monovalent hydrocarbon, and monovalent hydrocarbonoxy radicals;
R
1
is independently selected from halogen, monovalent hydrocarbon, and monovalent hydrocarbonoxy radicals:
W is selected from divalent hydrocarbon radicals,
n and n
1
are independently selected from integers having a value of from 0 to 4 inclusive; and
b is either zero or one.
The monovalent hydrocarbon radicals represented by R and R
1
include the alkyl, cycloalkyl, aryl, aralkyl and alkaryl radicals. The preferred alkyl radicals are those containing from 1 to about 12 carbon atoms. The preferred cycloalkyl radicals are those containing from 4 to about 8 ring carbon atoms. The preferred aryl radicals are those containing from 6 to 12 ring carbon atoms, i.e., phenyl, naphthyl, and biphenyl. The preferred alkaryl and aralkyl radicals are those containing from 7 to about 14 carbon atoms.
The preferred halogen radica
Burnell Timothy Brydon
McCloskey Patrick Joseph
Smigelski, Jr. Paul Michael
Boykin Terressa M.
Brown S. Bruce
General Electric Company
Johnson Noreen C.
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