CA1173998A

CA1173998A - Aromatic polyester carbonates, a process for their preparation and their use for the production of injection moulded articles, films and coatings

Info

Publication number: CA1173998A
Application number: CA000371956A
Authority: CA
Inventors: Peter Tacke; Dieter Freitag; Werner Nouvertne; Ludwig Bottenbruch; Peter R. Muller
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1980-03-01
Filing date: 1981-02-27
Publication date: 1984-09-04
Also published as: JPS6340211B2; EP0036080B1; DE3167363D1; JPS56133331A; DE3007934A1; EP0036080A1

Abstract

ABSTRACT

Aromatic polyestercarbonates with an increased melt flowability are prepared based on a diphenol, terephthalic and/or isophthalic acid, phosgene and a particular chain terminator of the formula (I)

Description

:~73~38 AROMATIC ~OLYESTER CARBONATES, A PROCESS FOR THEIR PRE-PARATION AND THEIR USE FOR THE PRODUCTION OF INJECTION
MOULDED ARTICLES, FILMS AND COATINGS.
This invention relates to tileruloplastic aromatic polyester carbonates whose molecular weight has been controlled using specific chaill terminators, a method for their preparation employin r the pllase boundary surface process, and the use of these polyester carbonates for the production of injection moulded articles, films and coatings.
Aromatic polyester carbonates are 1~nown (G.S.
Kolesnikov et al., J. Polym. Science USSR, Vol. 9, 1967, P. 1705 - 1~11; U.S. Patent Nos. 3,0~0,331;
3,169,121; 3,~09,70~; German Offenlegungsschrifts Nos. 2,714,544; 2,758,030). They may be widely used where a com~ination of the e~cellent characteristics of aromatic polycarbonates (good impact strength and notch toughness, good flowability of the melt) and of pUI e aromatic polyesters (high dimensiollal stabili-ty under heat) is required.
Although the aromatic polyester carl~onates ~nown hitherto meet many requirements, e~perts are interested in further improving the characteristics of these polymers, in particular the melt flowability.
Surprisingly, it has now been foulld that this may be achieved by using specific compounds to terminate the polyester carbonate molecules.
The present invention provides thermoplastic aromatic polyester carbonates based on diphenols, terephthalic and/or isophthalic acids, phosgene, chain terminators and optionally branching agents, having an est~r group content of from 99.95 to 5 mol %, based on the total oL ester and car~onate groups, characterised in that the chain terminators are compounds of the formula:

Le A 20 203 .

73~39~3 ,, ~-X (I) in which R
~` X represents OH, OCOCl or COCl, and R represents a branched alkyl radical having 8 or 9 carbon atoms, provided that, in the alkyl radical R, the pro~ortion of methyl-hydrogen atoms, based on all the hydrogen atoms of the alkylradical, amounts to from 47 to 89~o ~ that R is i31 the o-and/or p-position, and that the upper limit of the proportion of the o-isomer is 20~o.
The invention also relates to the use of these aromatic polyester carbonates for the production of injection moulded articles, films and coatings.
The inven-tion further provides a process for the preparation of these polyester carbonates according to the two-phase boun~y surface process characterized in that the terephthalic acid ester-formlng derivative, e.g. dichloride and/or isophthalic acid ester-formlng derivative, e.g. ~ichloride (or solutions thereof), the compounds (I) (optionally in a solvent) and tlle stirred two phase mi~ture containing alkaline aqueous ~0 diphenolate solutioll, catalysts and a solvent for the aromatic polyester carbonate and phosgene are combined ~`~; together and reacted.
~ Diphenols which are preferred for the preparation ; of the polyester carbonates of the invention are compounds of the formula:

MO - Z - OE (II) in which Z represents a bifunctional, mono~ or multi-~ nuclear aromatic radical having from 6 to 30 carbon ; 30 atoms, Z being structured so that the two O~-groups are ea~h directly bonded to a carbon atom of an aromatic system.

Le A 20 203 ~;

.

:, .
:. ' ~'73~98 . - 3 ~

Dipllenols which are particularly ~)referred are compounds of the formula:

~ ~ - Y _~ ~ 0~ (III) in which Y represen-ts a single bond, an alkylene or alkylidene radical having from 1 to 7 carbon atoms, a cycloall~ylene or cycloalkylidene radical having from 5 to 12 carbon atoms, -O-, -S-~ -S-, - S ~ or -C-, O O
as well as the nuclear-alkylated and nuclear-halogenated.
. derivatives thereof, e.g.:
` hydroquinone, resorcinol, dihydroxydiphenyls, bis-(hydroxyphenyl)-alkanes, bis-(hydro~Yyphenyl)-cycloalkanes -~ bis-(hydrox~phenyl)-sulphides, ~ bis-(hydroxyphenyl)-ethers, ;.~ bis-(hydroxyphenyl)-ketones, bis-(hydroxyphenyl)-sulphoxides, bis-(hydroxyphenyl)-sulphones and ~, ~, bis (hydroxyphenyl)-diisopropylbenzeIles, and also the nuclear-alkylated and nuclear-halogenated compounds thereof. These and other suitable diphenols are described, for e~ample, in U.S. Patents Nos.
3,028,365; 3,275,601; 3,148,172; 3,062,781; 2,991,273;
3,271,367; 2,999,835; 2,970,131 and 2,999,846, in German ~ Offenlegungsschrifts Nos. 1,570~703; 2,G63,050;

2,063,052; 2,211,956; 2,211,957; in French Patent No.
Le A 20 203 . , - :

`.` ` ~7~398 1 1,5~1,51~ and in monogra~h "H. Schnell, Chemistry and Physics of Polycarbonates, Interscience Publishers, New York, 196~".
I'he ~ost important diphenols are listed by name in the follow ng:
bisphenol A=2,2-bis-(4,4-dihydroxydiphenyl)-propane, - tetramethylbisphenol A, 1,1-bis-(4-hy~ro~yphenyl)-iso-butane, 1,1-bis-(4-hydroxyphenyl)-cycloh~e, 4,4-dihydro~diphenyl, 4,4~hydroxydiphenylsulphide, 4,4'-dihydroxydiphenylsulphone and the di- and tetra- halogenated derivatives thereo~.
Bisphenol A is particularly preferred. Any mixtures of the mentioned diphenols may also be used.
The compounds of formula (I), to be used as the ` chain terminator and thereby to control the molecular ~.
. 15 weight, are known (e.g. see J. Amer. Chem. Soc. 56, 1583-1586 (1934)) or they may be prepared in a simple - malmer.
Compounds o~ formula (I) which are preferled according to the invention are for e~ample:
~, ~0 CH3 ~CH3 \=/-- CH2- CH2-CH--CH2-C~I--CH2_C~3 .~ .
and ~5 X ~ CH3 C~3 ., \~ C-CH2-C--CH3 C~3 C~3 For the preparation of the aromatic polyester carbonates of the invention,a single compound as well as mi~tures of compounds (I) may be used.
They are generally used m quantities of from G.1 to 10 mol ~0, preferably from 0.3 to 7 mol ~0 (in the case of phenols, based on diphenols, in the case of acid Le A 20 203

3~91 1 chlorides an~ cllloloc~r~ollic acid estc~s, I)ased o acid dichlol-ides).
The following may be used, for example, as branching agellts: 3- or multifunctional carbo~Yylic acid chlorides, s~ch as trimesic acid trichloride, cyanuric acid trichloride, 3,3',4,4'-benzophenone-tetracarboxylic acid te-trachloride, 1,4,5,8-naphthalene tetracarboxylic acid tetrachloride or pyromellitic acid tetrachloride, in qualltities of from . 10 0.01 to 1 0 mol ~0 (based on the dicarboxylic acid . dichlorides used) or 3- or multifunctional phenols, such as phloroglucine~

4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene-2, 4~6-dimethyl-2~4,6-tri-(4-hydroxypheIlyl)-heptane, 15 1,3,5-tri-(4-hydroxyphenyl)-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane, tri-(4-hydroxyphenyl)-phenylmethane, 2,~-bis[4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-propaIle, ~ 2,4-bis-(4-hydroxyphenyl-isopropyl)-phenol, .` 20 tetra-(4-hydroxyphenyl)-methane, -. 2,6-bis-(2-hydro~Yy-5-methylben~yl)-4-metllyl- phenol, 2~(4-hydroxyphenyl)~2-(2,~ dihydroxyphellyl)-propane, .' tetra-(4[4-hydro~Yyphenyl-isopropyl]-pheno~y)-methane~
1,4-bis[(4,41'-dihydroxytriphenyl)-metllyl]-benzene, 25 in quantities of from 0.01 to 1.0 mol ~0 (based on the diphenols used). Phenolic branching agents may be introduced with the diphenols, and acid chloride branching agents may be introduced together with the acid dichlorides.
The aromatic polyester carbonates of the invention ~o are preferably prepared according to the two-phase bo~mdary surface process, which is described, for example, by V.V. Korshak and S.V. Vinogradova in "Polyesters", Pergamon Press, 1965, P. 448. Polycondensation may also be effected in a solvent in the presence of at least stoichiometric quantities of tertiary amines to bind Le A 20 203 3~

1 the hydrogen halide which is released. This process is described, for example, in German Offenlegungsschrift o 2,714,544.
When applying the p~lase boun~ary surface process, the diphenols are dissolved in an aqueous alkaline phase Into this solution, small quantities sucll as, ~; for e~ample, from 0.1 to l.O/o by weight (based on the diphenols used) of reducing alkaline substances, such as sodium borohydride or sodium sulphite 9 may be introduced to prevent the polyester carbonates from becoming discoloured.
As catalysts for the polycondensation reaction, from O.Ol to 5 mol ~O (based on the dipllellols used) of one or more tertiary amines and~or quaternary a~monium-and/or phosphonium compounds may be introduced into thcaqueous-alkaline phase.
Ammonium or phosphonium compounds which are `;; preferred as catalysts correspond to the formula:

~O Rl-A ~ -R3 X
-. 4 ~ R
` in which ~5 A represents a nitrogen atom or phosphorus atom, X represents chlorine or bromine, a1ld Rl, R2, R3 and R4 represent Cl-C20-alkyl, C6-C10- cycloalkyl, C7-C30-alkaryl or -aralkyl groups, and two substituents may together 3~ ` raprasent a C4-C12-alkylene group.
Tertiary amines which are preferred corraspond to the formula:
Rb R - N - R

Le A 20 203 ~1~73 1 in which R5, R6 and R7 represent C1-C20-alkyl or C~-C10-cycloall~yl groups, and two substituents may also together represent an alkylene group with frGm 4 to 12 carbon atoms.
~he following may be used as a sol~Tent *or compounds (I), the terephthalic or isophthalic acid dichlorides and the aromatic polyester carbonates:
the organic solvents known from the preparation of polycarbonates, such as dichloromethane, chloroform, . tri- ancl tetrachloroethylene, tetrachloroethanes, chlorobenzenes, di-chlorobenzenes and mi~tures of these compo~mds The polyester carbonates of the invention are u 15 preferably prepared with intensive stirring at temperatures of from 0 to 40C, in particular from 15 to 30C.
The aromatic polyester carbonates according to ~-~ the invention may be isolated according to the methods ~0 kno~l from polycarbonate synthesis according to the two-phase boundary surface process.
In this process, the organic phase containing the dissolved polyester carbonate is separated, washed and the polyester carbonate is then isolated by ~5 evaporating the solution, an evaporation e~truder preferably being used as the final stage of the working up process.
The ester and the carbonate proportions of the aromatic polyester carbonates of the invention may be in the ~orm of blocks or statistically distributed in the polymer.
When applying the phase boundary surface process, for e~ample, for the production of polyester carbonates with polyester blocks, an alkaline aqueous solution of one or more diphenols may be initially reacted with a Le A 20 203 ~ .
.

73~3~8 ~ 1 solution of one or more aromatic dical~o.Yylic acid ; dichlorides to form a pre-condensate having phenolic OH-terminal groups, and the pre-condensate may be ,.
further condensed into a polyester carbonate by

- 5 subsequently introducing phosgene. The length o~ the polyester blocks may be set by a suita~le choice of -the mole ratio of diphenol and acid chloride.
In an analogous manner, polyester carbonates with polycarbonate blocl{s are obtained wllell oligomeric carbonates having phenolic OE-terminal groups are reacted with the aromatic dicarboxylic acid dichlorides.
Polyester carbonates with a statistical distribution of the ester and carbonate groups may be obtained by simultaneously metering acid chloride and phosgene into the diphenolate solution.
~ The chain terminators which are to be used, according to the invention, i~ they are phenolic compounds, may be added to the reaction mixture before the reaction starts or during the reaction. However, sufficien-t O acid chloride and/or phosgene must be available so that they can react and restrict the chain; e.g. the chain terminator may be used together with the diphenol, may be contained in the solution of the chlorides of the aromatic dicarbo~ylic acids or may be added to the reaction mixture after a pre-condensate has been prepared.
If acid chlorides and chlorocarbonic acid esters are used as the chain terminator, they are preferably used together with the aromatic dicarboxylic acid dichlorides and/or the phosgene~
These chain terminators may also be added to the reaction mixture at the stage when the chlorides of the dicarboxylic acids and the phosgene have extensively or completely reacted.
In contrast to the aromatic polyester carbonates usùally prepared using phenol, o-phenyl-phenol, p-phenyl-Le A 20 203 .'^ ~' . .

~73~98 g ~`
phellol, dil~ethylp~lenols, cresols, halo~ell plle1lols or p-tert - butyl phenol as the molecular weight regulator, the aro~a~ic polyester carbonates according to the in~-ention e~hibit an improved colour mlmber, a substantially i~proved flowability, an increased dimensional stability under heat and on improved strength ~rith comparable mechanical characteristics.
' The aromatic polyester carbonates of the invention usually have relative solution viscosities of . 10 frcm 1.18 to 2.0, in oarticular from 1.2 to 1.5 (measured in a solution of 0.5 g polymer in 100 ml dichlororl~ethane solution at 25~.
They may contain stabilisers, such as~ for . e~aluple, antio~idants, ultraviolet stabilisers, flowing aids and mould-removal aids or other additives such as l; fillers, e.g. glass fibres, glass balls, asbestos or carbon fibres, ~ieselgur, kaolin, mineral fibres, rock flour and pigments.
The aromatic polyester carbonates o~-tained according to the preparation process of the invention are produced as a ~mitary granule after e~trusion and may be processed into moulded bodies b~ injection moulding.
They are also suitable for the production of films and coatings.
In the following Examples, the relative solution viscosity ~ rel in dichloromethane is determined at 25C
and at a concentration of 0.5 g of polymer in 100 ml of dichloromethane solution at 25~.
E~amples Description of the measuring method for determining the ~lo~ability.

Spiral-shaped strips having dimensions of 2 mm x 20 m~ are produced on an injection mouldi~g machine of the SK~I 141 type (manufacturer: "Stubbe"), at a pressure of 1050 bars and at a determined extrusion temperature, ~5 thè cross section of the strand feed beill~ lOmm2. The Le A 20 203 173~9~3 ~ - 10 -- ldia~eter of the injection moulding ~acl1ine cylinder is ~0 c~
The length of the resulting flow s~irals is a measure for the flowability of the extruded pol~ester, the length of the flow spirals being directly proportional to the ilowability of the polyester.

Description_of the metho~ for measuring the colour number Spectroscopic colour number deterulination The granule of the aromatic polyester, whose colour number is to be determined, is dissolved in dichloromethane (concentration 4 g/lO0 ml). ~he measurements are made in a layer thic~ness o~ lO cm using a spectrometer of the "Cary 2l9" type, manufactured ` by Cary, U.S.A.
In comparison with pure dichloromethane, the light transmission I at a wave length o~ 20 nm and the light transmission Io at a wave length of 700 nm is measured. ~he colour number of the granule, measured at 402 n~, is calculated according to the equation:

FZ(420 nm) = ll.5 g log Io Determination of notch tou~hness and impact stren~th The notch touchness a~ according to Charpy and the impact strength an according to Charpy were tested accordin~ to DI~ 53 45~.
;,o Comparative E~ample 1 2.736 kg of bisphenol A (BPA), l.5 l of 45~0 by weight aqueous sodium hydroxide, 8.4 g of sodium borohydride, 120 g of triethyl benzyl ammonium chloride, 36 l of water and 22 l of dichloromethane were introduced into a steel reactor wi-th intensive stirring under a nitrogen atmosphere, the mi~ture being stirred until the BPA
completely dissolved.
Le A 20 203 ' ' ' 1~7~9~

1 A solution of 852.72 g each o~ isophthalic acid chloride and terephthalic acid chloride and 39.5 g (3.5 mol d5) of phenol, dissolved in 3 1 o~ dichlorometllane, was introduced into the intensively stirred two phase mixture, with water cooling in 15 minutes 9 followed by stirring for 1 hour. Thereby, -the -temperature of the reaction mixture did not exceed 22C. Tlle plL vallle of the mixture was maintained at 12-13 by addillg sodium hydroxide.
600 g of phosgene were introduced while stirring was continued, the temperature again being main-tained at approximately 20C and the pH value at 12-13. When the phosgene had been introduced, 12 ml of a 4~0 by weight aqueous solution of triethyl amine was added, followed by stirring for 1 hour.
After the aqueo-us-alkaline phase had been separatèd, the organic phase was initially washed with dilute phosphoric acid and then washed free of salt with water and approximately 50~0 of the dichloromethalle was distilled off under normal pressure. The remaining solution was diluted with 15 1 of chlorobenzene and the dichloromethane was continuously distilled off until the sump temperature was approximately 80C, the polyester carbonate was then released from the chlorobenzene in the vacuum extruder at 320C, was drawn off as a strand and granulated. The ~ranulate had a relative solution viscosity ~ rel of 1.262.
Comparative E~ample 2 Analogous to comparative Example 1, a polyester 3o carbonate was prepared using 63 g (3.5 mol O) of ~-tert -butyl phenol (instead of phenol) as the chain terminator. The relative solution viscosity ~ rel o~
the product was 1.258.
Examples 1 and 2 (according to the invention) Analogous to comparative Exa~ple 1, polyester ` Le A 20 203 --7~998 1 car~onates were prepared using 86.7 g 0:~ p-isooctyl phenol or 92.5 g (87~o of ~-proportion, 13~o of o-proportion) of isononyl phenol (respectively 3.5 mol ~ of chain terminator!. The relative solution viscosity ~ rel was 1.265 and 1.259.
Comparative Example 3 As ~as described ~or co~lparative ~ample 1, 2.736 ky of BPA, 1.5 1 of 45 ~ by weight of aqueous sodium h~droxide~
8.4 ~ of sodium borohydride, 180 g o~ triethyl benzyl ammonium chloride, 39.5 g of phenol, 36 1 of water and ~2 1 o~ dichloromethane were stirred in the steel reactor until the BPA dissolved.
A solution of 365.46 g each of iso- and terephthalic acid chloride, dissolved in 3 1 dichloromethane, and 1450 g of phosgene were then simultaneously introduced or directed into the intensively stirred two-phase mi~Yture during 15 minutes, the temperature of the mixture not eYceeding 22C and the p~ value remaining at 12-1 (cooling, addition of sodium hydroxide).
120 ml of a 4% by weight aqueous solution of triethyl amine were added subsequent to the metering of acid chloride, whereupon the mixture was then stirred intensively for another hour.
The mixture was worked up as described in comparative ample 1. The granulate which was obtailled had a relative solution viscosity ~ rel of 1.251.
ample 3 (according to the invention) Analogous to comparative Example ~, a polyester car~onate was prapared using 86.7 g of p-isooctyl phenol (3.5 mol $) instead of phenol, The isooctyl phenol was contained in the solution of the acid chlorides. The granulate of the cocondensate had a relative solution viscosity ~ rel of 1.255.
Comparative Exanlple 4 ~5 Analogous to comparative Example 1, 2.736 kg of Le A 20 203 .i .

~7~9~3 1 BPA, 1.5 1 of 45 % by weight aqueous sodium hydroxide, 130 g of triethyl benzyl ammonium chloride, 8.4 g of sodium borohydride, 36 1 of water and 22 1 of dichloromethaIle were stirred until the BPA completely dissolved. .~ sclution of - 5 1096.38 g eacll of iso- and terephthalic acid chloride and 67.86 g of p-tert.-butyl phenol (3.77 mol ~0) in 3 1 of dichloromethane was then introduced into the mi~ture with intensive stirring in 15 minutes. After subsequently s-tirring for 1 hour, 215 ~ of phosgene were introduced in 10 minutes. During this process, the pH value was maintained at 12-13 as for the first step of the reaction using sodium hydroxide and the temperature was maintained belo~ 22C by cooling. The subsequent reaction lasted 1 hour. Also, a tertiary amine was not used as a catalyst. The granulate which was obtained after working up the miæture in conventional manner had a relative solution viscosity ~ rel of 1.248.
E~ample 4 (accordin~ to the inventioll) The reaction described in comparative Example 4 was repeated, but 43.3 g (3.77 mol %) of ~-isooctyl phenol were used instead of p-tert.-butyl phenol. The product had a relative solution viscosity ~ rel of 1.246.
Comparative E~an~ple 5 As in comparative Example 1, 2.736 kg of BPA, 1.5 1 of 45 % by weight aqueous sodium h~droxide, 44.5 g of triphenyl ethyl phosphonium bromide, 8.4 g of sodiu~ borohydride, 36 1 of water and 22 1 of dichloromethalle were stirred until the BPA completely dissolved, a solution of each 609.1 g of iso- and terephthalic acid chloride and 39.5 g (3.5 mol ~0) of phenol dissolved in 3 1 of diohloromethane were then added simultaneously, and 900 g of phosgene were introduced during 20 minutes. The subsequent condensation took place during 1 hour after the addition of 120 ml of a 4p by weight triethyl amine solution. After ~5 the conventional working up (comparative Example 1), the Le A 20 203 1~739~8 1 granulate which was obtained had a relative solution viscosity ~ rel o:E 1.258.
E~ample 5 (according -to the invention) Analogous to comparative Example 5, a cocondensate was prepared ~lsing 92.5 g (3.05 mol ~0) of isononyl phenol (87do of p-isomer, 13% of o isomer) instead of phenol.
The relative solution viscosity ~ rel of the product was 1. 256.
Com~arative EYample 6 ~nalogous to comparative Example 1, 2.736 kg of BPA, 1.5 1 of 45 ~ by weight a~ueous sodium hydroxide, 100 ~ of triethyl benzyl a~nium chloride, 8.4 g of sodium borohydride, 2~ 1 of water and 22 1 of dichloromethane were stirred until the BPA completely dissolved. A solution of 73 g f tere- and 171 g of isophthalic acid chloride and 63 g (3.5 mol ~0) of p--tert.-butyl phenol dissolved in 3 1 of dichloromethane, was simultaneously added during 20 minutes with intensive stirring, and 1600 g of phosgene were introduced. After adding 120 ml of 4~0 by weight of triethylamine solution, the reaction mixture was then reacted for 1 hour. The granulated cocondensate had a relative solution viscosity ~ rel of 1.265.
Example 6 (accordin~ to the invention) . In order to prepare a polyester carbonate according 25 to the invention, the process was carried out analogo~s '~ to comparative Example 6, but the p-tert.-butyl phenol ;~ was replaced by 86.7 g of p-isooctyl phenol. The relative solution viscosity ~ rel of the product was 1,268.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A thermoplastic aromatic polyester carbonate based on a diphenol, terephthalic and/or isophthalic acid, phosgene and a chain terminator having an ester group content of from 99.95 to 5 mol %, based on the total of ester and carbonate groups, in which the chain terminator is a compound of the formula:

(I) in which X reprepresents OH, OCOCl or COCl, and R represents a branched alkyl radical having 8 or 9 carbon atoms, provided that, in the alkyl radical R, the proportion of methyl-hydrogen atoms, based on all hydrogen atoms of alkyl radical, is from 47 to 89%, that R is in the o- and/or o-position, and that the upper limit of the proportion of o-isomer is 20%.

2. A polyester carbonate according to claim 1, which has a relative solution viscosity of from 1.18 to 2.0 measured in a solution of 0.5 g polymer in 100 ml dichloromethane solution at 25°C.

3. A polyester carbonate according to claim 1 which has a relative solution viscosity of from 1.2 to 1.5 measured in a solution of 0.5 g polymer in 100 ml dichloromethane solution at 25°C.

4. Polyester carbonates according to claim 1, which is branched.

5. A polyester carbonate according to claims 1 or 2, wherein the chain terminator is selected from the compounds:

and wherein X is as defined in claim 1.

6. A polyester carbonate according to claim 1 or 2, wherein the diphenol has the formula:

(III) in which Y represents a single bond, an alkylene or alkylidene radical having from 1 to 7 carbon atoms, a cycloalkylene or cycloalkyl-idene radical having from 5 to 12 carbon atoms, -O-, -S-, -?-, -SO2- or -C-, as well as the nuclear-alkylated and nuclear-halogenated derivatives thereof.

7. A process for the preparation of the polyester carbonate as defined in claim 1, which process comprises combining to-gether terephthalic acid dichloride and/or isophthalic acid dichloride or a solution thereof, the compound of the formula (I) or a solution thereof and a stirred two-phase mixture containing alkaline aqueous diphcnolate solution, a catalyst and a solvent for the aromatic polyester carbonate and phosgene and reacting them according to the two-phase boundary surface process.

8. A process according to claim 7, wherein the compound of the formula (I) and the terephthalic and/or isophthalic acid dichloride are introduced together into the reaction mixture.

9. A process according to claim 7, wherein the compound of the formula (I) is used in quantities of from 0.1 to 10 mol % by weight based on the diphenol or the acid dichloride.

10. A process according to claim 7 or 8, wherein the compound of the formula (I) is used in quantities of from 0.3 to 7 mol %
by weight based on the diphenol or the acid dichloride.

11. A process according to claim 7, 8 or 9, wherein the reaction is carried out at a temperature of from 0 to 40°C.

12. A method for the production of molded articles, films or coatings, which method comprises injection molding using the polyester carbonate as defined in claim 1, 2 or 3.