Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-07-28
2002-11-19
Raymond, Richard L. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S130000, C560S190000
Reexamination Certificate
active
06482977
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for preparing diaryl esters of aliphatic acids. Diaryl esters of aliphatic diacids are used as monomers in melt polymerization processes for preparing polyestercarbonates.
BACKGROUND OF THE INVENTION
Polycarbonates are well known as tough, clear, highly impact resistant thermoplastic resins. Polycarbonates, however, possess relatively high melt viscosity. The polycarbonate of 4,4′-isopropylidenediphenol (bisphenol A polycarbonate), for instance, is a well know engineering molding plastic.
In order to prepare a molded article from polycarbonate, relatively high extrusion and molding temperatures are required. In order to reduce the melt viscosity while also maintaining the desired physical properties, methods including the addition of plasticizers, the incorporation of aliphatic chainstoppers, the reduction of molecular weight, and the preparation of blends of polycarbonate with other polymers have been practiced.
One method of reducing the melt viscosity while maintaining the desired physical properties of a polymer is the incorporation of residues of aliphatic diacids into the backbone of the polymer chain. These residues are commonly referred to as “soft blocks”. Diaryl esters of aliphatic diacids are prepared industrially by two methods: 1) Transesterification with phenyl acetate; 2) Reaction of alkanedioyl dichlorides with phenol.
Some new commercial polycarbonate plants synthesize polycarbonate by a transesterification reaction whereby a diester of carbonic acid (e.g., diarylcarbonate) 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. Diaryl esters may be used as monomers in melt polymerization processes to prepare polyestercarbonates. The incorporation of the diaryl esters provides reduced melt viscosity in the polymer, while maintaining the desirable properties of the polycarbonate.
Residual acid contaminates generated by the esterification reactions mentioned above are detrimental to a base-catalyzed melt process used to prepare polyestercarbonates in that the rate of the melt polymerization is decreased. Thus, the diaryl ester monomer must be purified. The purification involves multiple recrystallization steps in solvents. The purification steps add considerable cost to the preparation of the diaryl ester monomers.
It would be desirable to prepare diaryl esters of aliphatic diacids that do not require extensive purification before introduction into a melt process. In particular, it would be desirable to prepare diaryl esters of aliphatic di acids that have a sufficiently low level of acids impurities such that the diaryl esters may be introduced into a melt process without requiring purification steps.
BRIEF SUMMARY OF THE INVENTION
In one aspect, the invention relates to a method for preparing diaryl esters suitable for use in a melt transesterification process, comprising the step of reacting a diaryl carbonate and a dicarboxylic acid in the presence or absence of a base, wherein from 2.005 to 2.2 molar equivalents of diaryl carbonate per molar equivalent of dicarboxylic acid are provided. In one embodiment, the diaryl esters contain less than 10 ppm of residual carboxylic acids.
In a further aspect, the invention relates to a method for preparing polyestercarbonate by the melt process utilizing the diaryl esters prepared by reacting a diaryl carbonate and a dicarboxylic acid, wherein from 2.01 to 2.02 molar equivalents of diaryl carbonate per molar equivalent of dicarboxylic acid are provided.
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.
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 that 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.
“SBI” is herein defined as 6,6′-dihydroxy-3,3,3′,3′-tetramethylspirobiindane.
“CD-1” is herein defined as 6-hydroxy-1-(4′-hydroxyphenyl)-1,3,3-trimethylindane.
“BCC” is herein defined as 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane
“DPC” as used herein is defined as diphenyl carbonate.
The terms “diphenol” and “dihydric phenol” as used herein are synonymous.
I. Preparation of Diarylesters
In one aspect, the present invention relates to a method of preparing diaryl esters of aliphatic diacids. The diaryl esters are prepared by the transesterification reaction of a diarylcarbonate and an aliphatic diacid.
The diaryl carbonate is a carbonate diester of an aromatic monohydroxy compound, which is represented by formula (I):
wherein each of Ar
1
and Ar
2
each independently represents a monovalent carbocyclic or heterocyclic aromatic group; preferably having from 5 to 12 carbon atoms.
Each of the monovalent aromatic groups Ar
1
and Ar
2
may be unsubstituted or substituted with at least one substituent which does not adversely affect the reaction. Examples of such substituents include, but are not limited to, a halogen atom, a lower alkyl group, a lower alkoxy group, a phenyl group, a phenoxy group, a vinyl group, a cyano group, an ester group, an amide group and a nitro group. Representative examples of monovalent aromatic groups include a phenyl group, a napthyl group, a biphenyl group and a pyridyl group, each of which is substituted or unsubstituted with at least one substituent, as mentioned above.
Representative examples of diaryl carbonates include diphenyl carbonates represented by formula (II)
wherein each of R
1
and R
2
independently represents a hydrogen atom; a halogen atom; a lower alkyl group; a lower alkoxy group; a cycloalkyl group having from 5 to 10 ring carbon atoms or a phenyl group, and each of m an n independently represents an integer of from 1 to 5; with the proviso that when m is an integer of from 2 to 5, each R
1
may be the same or different; and when n is an integer from 2 to 5, each R
2
may be the same or different.
Of the diphenyl carbonates represented by formula (II), it is preferable that the diphenyl carbonates have a symmetrical structure; such as diphenyl carbonate; ditolyl carbonate and diphenyl carbonate substituted with a lower alkyl group having from 1 to 4 carbon atoms. In one embodiment, diphenyl carbonate, having formula (III) is used.
In the method of the present invention, a transesterification reaction between the diaryl carbonate and an aliphatic diacid, also referred to herein as a “dicarboxylic acid” is conducted to produce diaryl esters. The aliphatic diacid is represented by the general formula (IV):
wherein R
3
is a C
1
-C
40
branched or unbranched alkyl or branched or unbranched cycloalkyl.
Representative acids of structure (IV) include, but are not limited, to dodecanedioic acid, sebacic acid, adipic acid, octadecanedioic acid, octadec-9 enedioic acid, 9-carboyxoctadecanoic ac
Boven Geert
Faber Rein Mollerus
Lens Jan-Pleun
Whitney John Morgan
Caruso Andrew J.
General Electric Company
Johnson Noreen C.
Raymond Richard L.
Tucker Zachary C.
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