Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-06-02
2001-05-08
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
06228973
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to a method of preparing high molecular weight polycarbonate by the melt process using a catalyst system comprising a tetraorganophosphonium carboxylic acid salt or a derivative thereof and 1) an alkali and/or alkali earth metal compound or a derivative thereof or 2) a less active alkali metal salt or a derivative thereof. The polycarbonate has a low level of branched side products and has good processing characteristics.
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.
There exists a need for a polycarbonate produced by the melt process that has less branched side reaction products. Polycarbonates having less side reaction products will have improved properties, for example better ductility and processing characteristics.
BRIEF SUMMARY OF THE INVENTION
In one aspect, the invention relates to a method of preparing polycarbonate by the melt process comprising the steps of
a) melting a dihydric phenol and a diester of carbonic acid for a time and at a temperature sufficient to form a melt; and thereafter introducing a catalyst composition comprising from about 1.0×10
−5
to about 5.0×10
−4
moles/mol dihydric phenol of a tetraorganophosphonium salt or a derivative thereof and
1) from about 1.0×10
−7
to about 1.0×10
−6
moles/mole dihydric phenol of an alkali and/or alkali earth metal compound or derivative thereof or
2) from about 0.5×10
−6
to about 5.0×10
−6
moles/mole of dihydric phenol of a less active alkali and/or alkali earth metal derivative thereof into the melt; and
b) oligomerizing the product from step a) in a two stage reaction system comprising two continuous oligomerization reactors in series, the first oligomerization reactor maintained at a temperature of from about 210° C. to about 260° C.; the second oligomerization reactor maintained at from about 250° C. to about 290° C.; and
c) polymerizing the product from step b) in a two stage polymerization system comprising two continuous polymerization reactors in series, the first polymerization reactor maintained at a temperature of from about 290° C. to about 315° C.; the second polymerization reactor maintained at from about 290° C. to about 310° C.
DETAILED 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.
The terms “diphenol” and “dihydric phenol” as used herein are synonymous.
The “melt process” as used herein refers to a method of making polycarbonates by the melt condensation of a diester of carbonic acid and a dihydric phenol.
“Less active alkali metal salt” as used herein means that the referenced compound exhibits activity towards transesterification, but is less active than NaOH under the same conditions; and exhibits more selectivity than NaOH in avoiding side product formation, in particular Fries formation, at the same conditions.
In one aspect, the present invention relates to a method of preparing polycarbonate by the melt process, comprising the addition of a catalyst composition comprising an alkali and/or alkali earth metal compound or a derivative thereof and a tetraorganophosphonium carboxylate salt or a derivative thereof. This aspect of the invention further relates to polycarbonates prepared by this method.
In a further aspect, the present invention relates to a method of preparing polycarbonate by the melt process, comprising the addition of a less active alkali metal base or a derivative thereof and a tetraorganophosphonium carboxylate salt or a derivative thereof. This aspect of the invention further relates to polycarbonate prepared by this method.
In the present invention, it was unexpectedly found that the process as defined produces a polycarbonate having reduced side reaction products, in particular Fries products, and as a result produces a product having good processing characteristics. In particular, it was unexpectedly found that the method of the present invention, comprising the addition of a catalyst composition comprising 1) a tetraorganophosphonium carboxylate salt or a derivative thereof and an alkali and/or alkali earth metal compound, or 2) a less active alkali metal salt or a
Burnell Timothy Brydon
Heuts Johan Pieter Anna
McCloskey Patrick Joseph
Smigelski, Jr. Paul Michael
Zirkzee Hendricus Franciscus
Boykin Terressa M.
General Electric Company
Johnson Noreen C.
Stoner Douglas E.
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