Robust process for the synthesis of polyestercarbonates

Details Robust process for the synthesis of polyestercarbonates Robust process for the synthesis of polyestercarbonates

1999-10-29

2001-10-23

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

C528S198000

Reexamination Certificate

active

06307005

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a process for preparing polyestercarbonates by the interfacial process, polyestercarbonates prepared by this process, and articles made from these 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 (BPA), for instance, is a well known 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. Known methods also include the addition of diacid residues into the polycarbonate to produce polyestercarbonate.
U.S. Pat. No. 5,510,448 discloses a copolyestercarbonate composition derived from a dihydric phenol, a carbonate precursor, and an aliphatic alpha omega dicarboxylic acid or ester precursor.
U.S. Pat. No. 5,025,081 discloses a process of preparing a coplyestercarbonate in which an aliphatic alpha omega diacid is incorporated into aromatic polycarbonate backbones. The process involved a method in which the pH is adjusted in a stepwise manner.
U.S. Pat. No. 4,983,706 discloses a process for preparing a polyestercarbonate which comprises reacting interfacially a dihydric phenol, a carbonate precursor, and the salt of an aliphatic alpha omega dicarboxylic acid having from 8 to about 20 carbon atoms.
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.
Typically, the preparation of polycarbonate, for example BPA polycarbonate, by the interfacial method is performed at a pH of from about 9 to about 11, more typically from about 9.5 to about 11. Performing the reaction at the higher pH has the advantages of better pH control, reduced build-up of phosgene in the reactor and no hydrolysis of carbonate salts to produce carbon dioxide and subsequent pressure build-up in the reactor. It would be very advantageous, therefore to be able to perform the interfacial polymerization reaction at the highest pH possible.
In order to obtain incorporation of the diacid into the polycarbonate to produce a polyestercarbonate, however, a pH profile is used. By “pH profile” it is meant that the reaction is conducted at different pHs for different periods of time during the reaction. Typically, the pH of the reaction mixture is maintained at about pH 8 to about 8.5 as long as the diacid is present in the reaction mixture. Then the pH of reaction mixture is raised to about pH 10 to about 11. If the pH is held higher than about 8.5 during the initial part of the reaction, not all of the diacid will be incorporated into the polyestercarbonate. If the pH is not raised to above about pH 10 during the latter period of the reaction, some of the diacid may be incorporated as a thermally unstable anhydride.
It would be desirable to develop a process whereby the pH of the interfacial process for the production of polyestercarbonates could be performed at higher pHs.
BRIEF SUMMARY OF THE INVENTION
In one aspect the invention relates to a method for preparing a polyestercarbonate, the method comprising:
a) reacting a dihydric phenol and a diacid having from 12 to 30 carbon atoms in the presence of an effective amount of carbonate precursor, thereby forming a reaction mixture, wherein the pH of the reaction mixture is maintained at from about 8.0 to about 9.5 for about 50 to about 95% of the total carbonate precursor addition, and from about 10 to about 12 for the remainder of the carbonate precursor addition.
The invention further relates to polyestercarbonates prepared by this method, and articles prepared from these polyestercarbonates.
DETAILED DESCRIPTION OF THE INVENTION
The present invention solves these problems, and provides further surprising properties. These and further objects of the invention will be more readily appreciated when considering the following disclosure and appended claims.
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 specification and 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.
The term “polyestercarbonate” includes polyesters and copolyestercarbonates.
The term “alkyl” as used herein refers to a branched or unbranched, saturated or unsaturated hydrocarbon group of 2 to 24 carbon atoms, with preferred groups within this class containing 2 to 8 carbon atoms.
“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-I” is herein defined as 6-hydroxy-1(4′-hydroxyphenyl)-1,3,3-trimethylindane.
“BPI” is herein defined as 1,1 bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane.
Unless otherwise stated, “mole %” in reference to the composition of a polyestercarbonate in this specification is based upon 100 mole % of residues of the total dihydric phenol (diol) units and dicarboxylic acid units of the polycarbonate.
As mentioned, the present invention relates to a process for preparing polyestercarbonates by the interfacial method. The reaction involves the reaction of a diacid and a diphenol in the presence of a carbonate precursor in a solvent.
It has been unexpectedly found that the processing window for the incorporation of diacids into polyestercarbonate becomes broader and is shifted to more favorable, i.e. higher, pHs as the methylene chainlength of the diacid chain increases above C
10
until the methylene chainlength reaches about C
30
Consequently, the interfacial reaction may be conducted at higher pHs with the incorporation of the diacids and little or no formation of anhydrides. As mentioned, this is highly desirable, as running at the higher pHs provides better pH control, little or no chance of phosgene build-up in the reactor, and no hydrolysis of carbonate salts to give carbon dioxide and subsequent pressure build-up in the reactor. In particular, it is desirable to run the initial period of the reaction at an initial pH range of from about 8.5 to about 9.5. At pHs above 9.5, the product polyestercarbonate was found to contain unacceptable levels of anhydride.
The term “anhydride”, as used herein, means the diacid moiety of the polymer which has an anhydride linkage between it and a second acid moiety as illustrated below with dodecanedioc acid:
These anhydride bonds are f

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