Process for the Preparation of Carbonic Acid Aryl Esters of Polyester-Diols Lengthened via Carbonate Groups and Their Use for the Preparation of Polyester-Diol Bis-Diphenol Carbonates and Polyester/Polycarbonates

Bis-carbonic acid monoaryl esters which are derived fron aliphatic polyester-polyols can be prepared, for example, by reacting polyester-diols with diarylcarbonates in the presence of special catalysts according to German Patent Application Ser. No. P 2,651,639.2 which corresponds to U.S. Patent Application Ser. No. 845,174, filed Oct. 25, 1977, now U.S. Pat. No. 4,191,705. Products of this type are valuable starting materials for various block copolymers and are, therefore, readily transesterified, for example with bis-phenols. The compounds thus obtained can then be used for preparing, for example, polycarbonate/polyester block copolymers, as described in German Published Patent Specification No. 2,651,639.

It has now surprisingly been found that polyester-diols with molecular weights (Mn) of over about 250, preferably over 600, can be reacted with carbonic acid diaryl esters to give mixed aliphatic-aromatic carbonic acid esters at reaction temperatures up to 200.degree. C. in a manner such that bis-carbonic acid monoaryl esters of polyester-diols lengthened via --OCOO-- groups are formed. In addition, it has now surprisingly been found that these carbonic acid aryl esters can be used for the preparation of polyester-diols bis-diphenol carbonates, lengthened via carbonate groups, which can, in turn, be used for the preparation of polyester/polycarbonates.

The reaction of the polyester diols with the carbonic acid diaryl esters proceeds smoothly and without side reactions such as, for example, etherification of the terminal OH groups (for this, compare Japanese Auslegeschrift (Japanese Published Specification) No. 69-11,377). The molecular non-uniformity determined by the starting materials is insignificantly changed by the process according to the invention, i.e., the characteristic molecular weight distribution for a polyester-diol remains virtually unchanged, but is shifted towards higher molecular weights.

The transeterification of the polyester-diol bis-aryl carbonates with excess diphenols to give the corresponding polyester-diol bis-diphenol carbonates lengthened via carbonate groups also takes place surprisingly smoothly and without side reactions, even at reaction temperatures of up to 200.degree. C. Moreover, the molecular distribution given by the starting materials is not changed, and neither are the polyester-polyols re-formed nor does polycondensation to polycarbonates take place.

The polyesters, containing hydroxyl groups, in the sense of the invention are, for example, reaction products of polyhydric, preferably dihydric and optionally additionally trihydric, alcohols with polybasic, preferably dibasic, carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof can also be used for the preparation of the polyester-polyols. The polycarboxylic acids can be of an aliphatic, cycloaliphatic, aromatic and/or heterocyclic nature and can optionally be substituted, for example by halogen atoms, and/or unsaturated. Examples of these which may be mentioned are: oxalic acid, malonic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, terephthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid and dimeric and trimeric fatty acids, such as oleic acid, optionally mixed with monomeric fatty acids. Polyhydric alcohols which can be used, optionally mixed with one another, are, for example, ethylene glycol, propylene 1,2-glycol and propylene 1,3-glycol, butylene 1,4-glycol and butylene 2,3-glycol, hexane-1,6-diol, octane-1,8-diol, neopentylglycol, cyclohexanedimethanol, 1,4-bis-(hydroxymethyl)-cyclohexane, 2-methyl-propane-1,3-diol, glycerol, trimethylolpropane, hexane-1,2,6-triol, butane-1,2,4-triol, trimethylolethane, pentaerythritol and quinitol, furthermore thiodiglycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycols, dibutylene glycol and polybutylene glycols.

The content of terminal hydroxyl groups and thus the "average" molecular weight Mn is determined by choosing a defined excess of alcohol. Polyesters obtained from aliphatic starting components are preferably employed.

Polyesters containing hydroxyl groups, in the sense of the invention are, for example, also those which are prepared by the polymerization of a lactone, for example of .epsilon.-caprolactone, or by the condensation of a hydroxycarboxylic acid, for example of .omega.-hydroxycaproic acid, with a starting material containing hydroxyl groups. Mn can again be calculated as described above.

The polyester-polyols suitable for the process sccording to the invention preferably have 2 to 4 hydroxyl groups, and particularly preferably 2 hydroxyl groups.

Carbonic acid bis-aryl esters in the sense of the invention are, in particular, those of the formula (I) ##STR1## wherein Ar is a substituted or unsubstituted aryl radical with 6 to 18 carbon atoms.

Possible substituents are, in particular, C.sub.1 --C.sub.4 --alkyls as well as nitro and halogen, such as, for example, chlorine or bromine. Examples of these compounds are diphenyl carbonate, alkyl-substituted diphenyl carbonates, such as di-toluyl carbonates, halogen-substituted diphenyl carbonates, such as di-chlorophenyl carbonates, dinaphthyl carbonate and alkyl-substituted and halogen-substituted dinaphthyl carbonates; in these compounds, the nitro, alkyl or halogen substitutents on the two phenyl nuclei or, respectively, on the two naphthyl nuclei of the diaryl carbonates can be identical or different and can be symmetrical or asymmetrical to one another. Thus, for example, phenyl toluyl carbonate, phenylchlorophenyl carbonate, 2-toluyl 4-toluyl carbonate or 4-toluyl 4-chlorophenyl carbonate are also suitable for the process according to the invention.

Bis-aryl carbonates, in the sense of the invention, of polyester-diols lengthened via --OCOO-- groups are thus, in particular, those of the formula II ##STR2## wherein Ar is a substituted or unsubstituted aryl radical with 6 to 18 carbon atoms,

-(polyester)- represents the bivalent radical of one of the polyester-diols described above and n denotes an integer from 2 to 20, preferably 2 to 10.

Suitable catalysts for the process according to the invention are basic transesterification catalysts, such as, for example, alkali metal phenolates or alkaline earth metal phenolates, alkali metal alcoholates or alkaline earth metal alcoholates and tertiary amines, such as, for example, triethylenediamine, morpholine, pyrrolidine, pyridine or triethylamine, or metal compounds, such as antimony trioxide, zinc chloride, titanium tetrachloride and titanic acid tetrabutyl ester.

The catalyst is used in amounts between 20 ppm and 200 ppm, relative to the total weight of the polyester-diol and the carbonic acid bis-aryl ester employed.

Less than these amounts of catalyst can also optionally be employed if the starting materials contain no basic impurities when acid catalysts are used and contain no acid impurities when basic catalysts are used. Moreover, to minimize the intrinsic color in the carbonic acid esters, of the polyester-diols, minimal amounts of catalysts are preferred.

The process according to the invention is preferably carried out in bulk, that is to say in the absence of a solvent. However, solvents which are inert under the reaction conditions, such as aliphatic hydrocarbons or aromatic hydrocarbons, which can contain, for example, nitro groups, can also optionally be used.

The reaction time ranges from about 1 to 20 hours depending upon the reaction temperature and the nature and amount of catalyst used.

During the reaction or after the reaction has ended, in the case of a discontinuous procedure, the hydroxyaryl compounds formed in the process according to the invention can be removed by distillation. If the transesterification reaction is carried out by a continuous procedure, the hydroxylaryl compounds are separated off from the reaction mixture by fractional distillation.

According to a particularly preferred embodiment of the process according to the invention, the reaction is carried out using sodium phenolate, as the catalyst, in a mixture of polyester-diol and carbonic acid bis-aryl ester at about 110.degree. C. to 150.degree. C., with less than one mol of carbonic acid bis-aryl ester being employed per OH group of the polyester-diol.

Thus, bis-carbonic acid monoaryl esters of polyester-diols lengthened via --OCOO-- bridges can be prepared by the process according to the invention; in this process, it has been shown, surprisingly, that the lengthening proceeds smoothly, a quantitative esterification of the terminal hydroxyl groups taking place simultaneously. In addition, it has surprisingly been found that the molecular non-uniformity of the starting polyester-diols remains virtually unchanged during the lengthening with simultaneous esterification.

In the process according to the invention, the desired molecular weight Mn of a lengthened and esterified polyester-diol (II) is determined by the amount of the diaryl carbonate (I) reacted with the polyester-diol; it is generally applicable that n mols of polyester-diol must be reacted with (n+1) mols of (I) in order to obtain an n-fold (ranging from 2 to 20) polyester-diol, lengthened via --OCOO-- groups, with terminal aryl carbonate groups.

Unless otherwise indicated, the average molecular weights given in the examples which follow are number-average Mn, which were determined by osmometry.

The Staudinger index [.eta.].sub.THF indicated was measured in tetrahydrofurane at 25.degree. C. and is given in the formula (d1/g). For the definition of the Staudinger index, reference is made to H. G. Elias: "Makromolekule" ("Macromolecules"), Huthig & Wepf-Verlag, Basel, page 265.

800 parts by weight of a polyester-diol, obtained from n-hexane-1,6-diol and adipic acid, of average molecular weight Mn=800 (determined by measuring the OH number), 321 parts by weight of diphenyl carbonate and 0.1 part by weight of sodium phenolate are heated, while stirring and under nitrogen and a vacuum of 6 mm Hg, for 2 hours at 110.degree. C., 2.5 hours at 130.degree. C. and 3 hours at 150.degree. C.; during this time, phenol is distilled off from the reaction mixture. If desired, residual traces of phenol can subsequently be separated off in a thin film evaporator at 190.degree. C./0.1 mm Hg. A colorless, viscous oil with an average molecular weight Mn of 1,820 is obtained. The OH number is zero; the Staudinger index [.eta.].sub.THF is 0.078.

2,000 parts by weight of a polyester-diol, obtained from adipic acid and equimolar amounts of ethylene glycol an butane-1,4-diol, of average molecular weight Mn=2,000 (determined by measuring the OH number), 321 parts by weight of diphenyl carbonate and 0.12 part by weight of sodium phenolate are heated, while stirring and under nitrogen and a vacuum of 3 mm Hg, for 2.5 hours at 110.degree. C., 2 hours at 130.degree. C. and 2.5 hours at 160.degree. C. During this time, phenol is distilled off from the reaction mixture. If desired, residual traces of phenol can subsequently be separated off in a thin film evaporator at 110.degree. C./0.1 mm Hg. A colorless, viscous oil with an average molecular weight Mn of 4,240 and a Staudinger index [.eta.].sub.THF of 0.114 is obtained. The OH number is zero.

2,000 parts by weight of a polyester-diol, obtained from adipic acid and a mixture of n-hexane-1,6-diol/neopentyl-glycol in the molar ratio 65/35, of average molecular weight Mn 2,000 (determined by measuring the OH number), 321 parts by weight of diphenyl carbonate and 0.12 part by weight of sodium phenolate are heated, while stirring and under nitrogen and a vacuum of 2 mm Hg, for 2.5 hours at 110.degree. C., 3 hours at 140.degree. C. and 3 hours at 150.degree. C. During this time, phenol is distilled-off from the reaction mixture. If desired, residual traces of phenol can subsequently be separated off in a thin film evaporator at 190.degree. C./0.1 mm Hg. A colorless, viscous oil, which solidifies to a wax after some time and which has an average molecular weight Mn of 4,240, is obtained. The Staudinger index [.eta.].sub.THF is 0.25 and the OH number is zero.

2,000 parts by weight of a polyester-diol, obtained from adipic acid and a mixture of n-hexane-1,6-diol/neopentyl-glycol in the molar ratio 65/35, of average molecular weight Mn 2,000 (determined by measuring the OH number), 285 parts by weight of diphenyl carbonate and 0.12 part by weight of sodium phenolate are heated, while stirring and under nitrogen and a vacuum of 2 mm Hg, for 4 hours at 110.degree. C., 3 hours at 140.degree. C. and 5 hours at 155.degree. C. During this time, phenol is distilled off from the reaction mixture. If desired, residual traces of phenol can subsequently be separated off in a tin film evaporator at 190.degree. C./0.1 mm Hg. A colorless wax with an average molecular weight Mn of 6,270 is obtained. The Staudinger index [.eta.].sub.THF is 0.32 and the OH number is zero.

2,000 parts by weight of polyester-diol, obtained from adipic acid and a mixture of n-hexane-1,6-diol/neopentyl-glycol in the molar ratio 65/35, of average molecular weight Mn 2,000 (determined by measuring the OH number), 267.5 parts by weight of diphenyl carbonate and 0.12 part by weight of sodium phenolate are heated, while stirring and under nitrogen and a vacuum of 1 mm Hg, for 3 hours at 110.degree. C., 5 hours at 140.degree. C., 2 hours at 150.degree. C. and 1 hour at 165.degree. C. During this time, phenol is distilled off from the reaction mixture. If desired, residual traces of phenol can subsequently be separated off in a thin film evaporator at 190.degree. C./0.1 mm Hg. A colorless wax with an average molecular weight Mn of 8,290 is obtained. The Staudinger index [.eta.].sub.THF is 0.40 and the OH number is zero.

In particular, the polyester diol bis-carbonic acid monoaryl esters, which are obtainable from polyester-diols and carbonic acid bis-aryl esters of the formula I ##STR3## wherein Ar is a substituted or unsubstituted aryl radical with 6 to 18 C atoms, preferably phenyl,

and which are of the simplified formula II ##STR4## wherein -(polyester)- represents the bivalent radical of a polyester-diol,

n denotes an integer from 2 to 20, preferably 2 to 10, and

Ar has the meaning given for the formula I, are reacted with diphenols to produce polyester-diol bisdiphenol carbonates, lengthened via carbonate groups.

Suitable diphenols for the preparation, according to the invention, of polyester-diol bis-diphenol carbonates lengthened via carbonate groups are: hydroquinone, resorcinol, dihydroxy-diphenyls, bis-(hydroxyphenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes, bis-(hydroxyphenyl) sulphides, bis-(hydroxyphenyl) ethers, bis-(hydroxyphenyl) ketones, bis-(hydroxyphenyl) sulphoxides, bis-(hydroxyphenyl) sulphones and .alpha.,.alpha.-bis-(hydroxyphenyl)-diisopropyl-benzenes, as well as their nuclear-alkylated and nuclear-halogenated compounds. These and further suitable aromatic dihydroxy compounds are listed, for example, in U.S. Pat. Nos. 3,028,365, 2,999,835, 3,148,172, 3,271,368, 2,991,273, 3,271,367, 3,280,078, 3,014,891 and 2,999,846 and German Patent Specifications Nos. 2,063,050 and 2,211,957.

Examples of suitable diphenols are bis-(4-hydroxyphenyl)-methane, 4,4'-dihydroxydiphenyl, 2,4-bis-(4-hydroxyphenyl)-2-methylbutane, .alpha.,.alpha.-bis-(4-hydroxyphenyl)-p-diisopropylbenzene, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane and 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane.

Preferred diphenols are, for example, 2,2-bis-(4-hydroxyphenyl)-propane, 1,1-bis-(4-hydroxyphenyl)-cyclophexane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.

One or several of the diphenols, lengthened via carbonate groups, suitable according to to the invention can be employed.

Suitable catalysts for the preparation, according to the invention, of polyester-diol bis-diphenol carbonates lengthened via carbonate groups are basic transesterification catalysts, such as alkali metal phenolates or alkaline earth metal phenolates, alkali metal alcoholates or alkaline earth metal alcoholates, tertiary amines, such as, for example, triethylenediamine, morpholine, pyrrolidine, triethylamine and tributylamine, and pyridine or metal compounds, such as, for example, antimony trioxide, zinc chloride, titanium tetrachloride and titanium tetrabutyl ester.

The catalyst is used in amounts of between 10 ppm and 200 ppm, relative to the total weight of the particular polyester-diol bis-aryl carbonate, lengthened via carbonate groups, employed and of the particular diphenol employed.

Less than these amounts of catalyst can also optionally be employed if the starting materials contain no basic impurities when acid catalysts are used and contain no acid impurities when basic catalysts are used. Amounts of catalyst which are as low as possible are to be preferred, in the interest of as slight an intrinsic color as possible in the products according to the invention.

The process, according to the invention, for the preparation of polyester-diol bis-diphenol carbonates lengthened via carbonate groups is preferably carried out in the absence of solvents for the reactants, in particular in bulk. Solvents which are inert under the reaction conditions such as, for example, aliphatic hydrocarbons or aromatic hydrocarbons, which can be unsubstituted or substituted, for example, by nitro groups, can optionally be used.

The reaction time for the transesterification process for the preparation of polyester-diol bis-diphenol carbonates lengthened via carbonate groups is between about 1/2 and about 24 hours, depending on the reaction temperature and on the nature and amount of the catalyst.

Polyester-diol bis-diphenol carbonates lengthened via carbonate groups are prepared, for example, by heating a mixture of a polyester-diol bis-carbonic acid phenyl ester, lengthened via carbonate groups, a diphenol and a catalyst to temperatures between about 100.degree. C. and about 200.degree. C., preferably between about 110.degree. C. and 180.degree. C., in vacuo and distilling-off out of the reactor the phenol formed as the reaction progresses. In this procedure, the diphenol is employed in excess, more than one mol of diphenol being used per carbonic acid phenyl ester group of the polyester-diol bis-carbonic acid phenyl ester preferably between about 1.1 mols and about 2 mols of diphenol being used. According to a particularly preferred embodiment, the reaction of a polyester-diol bis-carbonic acid aryl ester, lengthened via carbonate groups, and bisphenol A in the molar ratio bis-carbonic acid monoaryl ester to bisphenol A of 1:3 is reacted, using the disodium phenolate of bisphenol A as the catalyst, at 150.degree. C. in vacuo between 25 and 0.1 mm Hg.

In particular, according to the invention, polyester-diol bis-carbonic acid aryl esters are reacted with the diphenols of the following formula III ##STR5## wherein X denotes ##STR6## O, S or SO.sub.2 and Y.sub.1 and Y.sub.4 are identical or different and denote hydrogen or halogen, such as, for example, chlorine or bromine,

to give the polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, of the simplified formula IV ##STR7## wherein -(polyester)- represents the bivalent radical of a polyester-diol,

n denotes an integer from 2 to 20, preferably 2 to 10,

X denotes ##STR8## O, S or SO.sub.2, and Y.sub.1 to Y.sub.4 are identical or different and denote hydrogen or halogen, such as, for example, chlorine or bromine.

Polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, according to the invention are thus, for example, those of the formulae IVa-IVh: ##STR9## wherein -(polyester)- is the bivalent radical in the formulae IVa - IVh of the polyester-diols described on page 4.

The polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, according to the invention can be used as starting bis-phenols in the preparation of polycarbonates by the known two-phase interface polycondensation process. Polyester/polycarbonates of a certain structure are thus obtained.

The process, according to the invention, for the preparation of these polyester/polycarbonates is characterized in that the polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, according to the invention, in particular those of the formula IV, are reacted with other diphenols, in particular with those of the formula III, and with phosgene by the two-phase interface polycondensation process, known for the preparation of polycarbonates, at pH values between about 9 and 14 and temperatures between about 0.degree. C. and 80.degree. C., preferably between about 15.degree. C. and 40.degree. C. The polyester/polycarbonates obtained according to the invention are characterized by the presence of an amorphous (elastomeric) polyester phase and a crystalline (hard) polycarbonate phase or an amorphous/crystalline (hard) polycarbonate phase.

From a morphological point of view, the polyester/polycarbonates have two different, spatially separate phases, that is to say regions which are composed of a continuous amorphous polyester phase and regions which are composed of a crystalline or amorphous/crystalline polycarbonate phase.

Compared with other polyester/polycarbonates, for example even compared with those of German Patent Application Ser. Nos. P 27 26 376.9 and P 2,651,639, priority case of U.S. Patent Application Ser. No. 845,174, filed Oct. 25, 1977, now U.S. Pat. No. 4,191,705, the high-molecular, segmented polyester/polycarbonates which can be processed as thermoplastics and which are prepared from polyester-diol bis-diphenol carbonates lengthened via carbonate groups have additional advantages, such as, for example, an even better phase separation, which leads to better technological properties of the corresponding polyester/polycarbonates. (For a discussion of phase separation, see German Published Patent Specification No. 2,636,784).

Because they are multi-phase, the polyester/polycarbonates according to the invention have a higher heat distortion point than comparable single-phase polyester/polycarbonates.

Single-phase polyester/polycarbonates are described, for example, in U.S. Pat. No. 3,151,615. They are obtainable by various processes, but preferably by the "pyridine" process known from the preparation of polycarbonates.

The preparation of two-phase polymers, for example of polycarbonate/polycaprolactones, has hitherto only been achieved by means of bis-chloroformates of polycaprolactones and polycarbonate oligomers (see French Pat. No. 2,235,965). This is also correspondingly true for the polyester/polycarbonates of German Patent Specification No. 1,162,559, although these are not identified as two-phase.

The use, according to the invention, of polyester-diol bis-diphenol carbonates, lenthened via carbonate groups, has, compared with the use of corresponding bis-chloroformates, the advantage of being insensitive towards hydrolysis and thus having a better storability, and of having clearly bifunctional reactivity.

In particular, because of their crystalline polycarbonate phase, the polyester/polycarbonates according to the invention have a higher heat distortion point.

It is possible to detect the different phases of the polyester/polycarbonates according to the invention with the aid of differential thermoanalysis, in which, for example, the polyester phase has a transformation temperature >20.degree. C., the amorphous constituent in the polycarbonate phase has a transformation temperature between about 100.degree. C. and 150.degree. C. and the crystalline constitutent of the polycarbonate phase has a crystallite melting point between about 170.degree. C. and 250.degree. C.

In addition to their particular capacity for exposure to heat, the high-molecular, segmented polyester/polycarbonates, which can be processed as thermoplastics, prepared by the process according to the invention exhibit good transparency, highly elastic properties and an outstanding elongation of break of >400%.

Diphenols which are suitable for the preparation, according to the invention, of the polyester/polycarbonates from the polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, according to the invention, are those which have already been mentioned for the preparation of polyester-diol bis-diphenol carbonates lenthened via carbonate groups, on pages 12 and 13 of this Patent Application, in particular those of the formula III on page 15 of this Patent Application; for example 4,4'-dihydroxy-diphenyl, bis-(4-hydroxyphenyl)-methane, 2,4-bis-(4-hydroxyphenyl)-2-methyl-butane, .alpha.,.alpha.-bis-(4-hydroxyphenyl)-p-diisopropylenzene, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, bis-(hydroxy-phenyl) sulphide and 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane are suitable.

2,2-Bis-(4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane and 1,1-bis-(4-hydroxyphenyl)-cyclohexane are preferably used as other diphenols for the preparation, according to the invention, of the polyester/polycarbonates. Any desired mixtures of these other diphenols can also be employed.

Branched products with better flow properties during processing are obtained by incorporating small amounts or trifunctional or more than trifunctional compounds, in particular those with three or more than three phenolic hydroxyl groups, preferably between about 0.05 and about 2 mol % (relative to the diphenols employed).

Examples of suitable trifunctional or more than trifunctional compound are: phloroglucinol, 4,6-dimethyl-2,4,6-tri-(3-hydroxyphenyl)-hept-2-ene, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane, 1,3,5-(4-hydroxyphenyl)-benzene, 1,1,1-tri-(3-hydroxyphenyl)-ethane, tri-(4-hydroxyphenyl)-phenylmethane, 2,2-bis-[4,4-(4,4'-dihydroxydiphenyl)cyclohexyl]-propane, 2,4-bis-(4-hydroxyphenyl-isopropyl)-phenol, 2,6-bis-(2'-hydroxy-5'-methylbenzyl)-4-methyl-phenol, 2,4-dihydroxybenzoic acid, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane, 1,4-bis-(4,4"-dihydroxytriphenyl-methyl)-benzene and 3,3-bis-(4-hydroxyphenyl)-2-oxo-2,3-dihydroindole as well as 3,3-bis-(3-methyl-4-hydroxyphenyl)-2-oxo-2,3-dihydroindole.

The polyester/polycarbonates according to the invention can also be branched via the polyester component, and in particular by reacting the carbonic acid aryl esters, lengthened via carbonate groups, of polyester-polyols, of the present invention, which have three or four aryl groups, with the above mentioned diphenols, triphenols and/or tetraphenols by the process of the present invention to give corresponding polyester-polyol poly-(polyphenol carbonates), and co-using the resulting polyphenols in the polyester/polycarbonate synthesis according to the present invention in molar amounts of up to about 50 mol %, relative to mols of polyester-diol bis-diphenol carbonates employed.

The chain length of the polyester/polycarbonates can be adjusted by adding a chain stopper, for example a monofunctional phenol, such as phenol, 2,6-dimethylphenol, p-bromophenol or p-tert.-butylphenol, it being possible to use between about 0.1 and about 10 mol % of chain stopper per mol of diphenol employed.

The chain length of the polyester/polycarbonates can optionally be adjusted, for example, by adding polyester-monool mono-diphenol carbonates in molar amounts of up to about 50 mol %, respectively to mols of polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, employed.

The high-molecular, segmented polyester/polycarbonates which can be processed as thermoplastics are prepared by the two-phase interface polycondensation process. For this, one of the other diphenols mentioned above or mixtures of the other diphenols mentioned above are dissolved in an alkaline aqueous solution. The polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, according to the invention, in particular those of the formula IV, or their mixtures are likewise dissolved in a water-immiscible inert organic solvent and this solution is added. Phosgene is then passed into the mixture at a temperature between about 0.degree. C. and 80.degree. C., preferably between about 15.degree. C. and 40.degree. C., and at a pH value between about 9 and 14. The amount of phosgene depends on the diphenol employed, the stirring action and the reaction temperature, and is in general about 1.1-3.0 mols of phosgene per mol of diphenol. After the phosgenation, the polycondensation is carried out by adding about 0.2-10 mol % of the tertiary aliphatic amine, relative to mols of diphenol. In this procedure, phosgenation times of between about 5 minutes and 90 minutes are required and polycondensation times of between about 3 minutes and 3 hours are required.

The present invention thus relates to the preparation of polyester/polycarbonates, which is characterized in that the polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, according to the invention, in particular those of the formula IV, are reacted with other diphenols, in particular those of the formula III, and with phosgene in a liquid mixture consisting of an inert organic solvent and an alkaline aqueous solution at temperatures between about 0.degree. C. and 80.degree. C., preferably between about 15.degree. C. and 40.degree. C., at a pH value between about 9 and 14, and after the addition of phosgene, polycondensation is carried out by adding about 0.2 mol % to 10 mol % of a tertiary aliphatic amine, relative to the molar amount of diphenol, the weight ratio of polyester-diol bis-diphenol carbonate, lengthened via carbonate groups, to the other diphenol being determined by the proportion of polycarbonate and the proportion of polyester in the polyester/polycarbonates.

The present invention thus relates to polyester/polycarbonates obtained by this process according to the invention.

The resulting solutions of the polyester-polycarbonates in the organic solvents are worked up analogously to the solutions of thermoplastic polycarbonates prepared by the two-phase interface process, with the polyester/polycarbonates also being subjected to an after-treatment; in particular they are either (a) isolated by known processes, for example by precipitating with methanol or ethanol, and then either dried and tempered, or subjected to shearing forces or dissolved in organic solvents and allowed to gel, or (b) already subjected to shearing forces during isolation, for example in a devolatilization extruder, or (c) allowed to gel, before isolation, in the solvent used in the preparation of the polyester/polycarbonates by the two-phase interface process.

Suitable inert organic solvents for the preparation process, according to the invention, of the polyester/polycarbonates are water-immiscible aliphatic chlorohydrocarbons, such as methylene chloride, chloroform and 1,2-dichloroethane, or chlorinated aromatic compounds, such as chlorobenzene, dichlorobenzene and chlorotoluene, or mixtures of these solvents.

Suitable alkaline aqueous solutions for the process according to the invention are solutions of Li(OH).sub.2, NaOH, KOH, Ca(OH).sub.2 and/or Ba(OH.sub.2) in water.

Suitable tertiary aliphatic amines for the process according to the invention are those with about 3 to 15 C atoms, that is to say, for example, trimethylamine, triethylamine, n-tripropylamine and n-tributylamine, and varies between about 0.2-5 mol %, depending on the diphenol employed, and when tetramethyl substituted diphenols are employed, between about 5-10 mol %, in each case relative to the total amount of diphenols employed (=in each case to the sum of polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, and other diphenols).

The polyester/polycarbonates prepared by the process according to the invention can be isolated by the following processes:

a. By distilling off the organic solvent down to a certain concentration, a high-strength (about 30-40% by weight) polymer solution being obtained, the polyester/polycarbonate gels on subsequent slow evaporation of the remaining solvent.

b. By precipitating the polyester/polycarbonate from the organic phase using organic solvents, examples of suitable solvents for the precipitation being methanol, ethanol, isopropanol, acetone, aliphatic hydrocarbons and cycloaliphatic hydrocarbons.

c. By isolating the polyester/polycarbonates in a devolatilization extruder at temperatures of about 160.degree.-240.degree. C. under the conditions known for polycarbonate extrusion and applying shearing forces.

The polyester/polycarbonates prepared by the process according to the invenvention are gelled, either in the worked-up organic phase of the two-phase reaction mixture, without isolation, or in a separate solution of the previously isolated polyester/polycarbonates in organic solvents, by cooling the high-strength polymer solution, gelling times of between about 5 minutes and 12 hours being required at temperatures between about 0.degree. C. and 40.degree. C., depending on the proportion of polyester or polycarbonate.

The gelled product can be worked up to give a powder grain mixture, the resulting polyester/polycarbonate being dried in vacuo at 50.degree. C. for about 48 hours and at 100.degree. C. for about 24 hours.

Suitable solvents for the separate gelling of the isolated polyester/polycarbonates are organic solvents, such as, for example, methylene chloride, benzene, toluene or xylene.

The heat treatment of the isolated polyester/polycarbonates is carried out for between about 5 minutes and 24 hours at temperatures between about 40.degree. C. and 170.degree. C.

The isolated polyester/polycarbonates are subjected to the action of shearing forces for between about 0.5 and 30 minutes, at temperatures between about 130 and 240.degree. C. and applying shearing forces of between about 0.2 and 0.7 KWh per kg of polymer.

The reaction, according to the invention, of the polyester-diol bis-diphenol carbonates, lengthened via carbonate groups, according to the invention with diphenols and with phosgene by the two-phase interface process takes place quantitatively; the particular reactant ratio of polyester-diol bis-diphenol carbonate, lengthened via carbonate groups, to the other diphenol is thus determined by the polycarbonate constituent and the polyester constituent of the polyester/polycarbonates to be synthesized in each case.

The proportion of polycarbonate in the polyester/polycarbonates prepared by the process according to the invention is between about 35 and 80% by weight, depending on the desired pattern of properties, the hardness and heat distortion point increasing and the elasticity and elongation at break decreasing with an increasing proportion of polycarbonate.

The proportion of polycarbonate in the polyester/polycarbonates according to the invention is to be understood as the amount by weight of aromatic polycarbonate structural units of the following formula V ##STR10## wherein D represents the diphenolate radicals in the polyester/polycarbonate,

in particular of aromatic polycarbonate structural units of the formula IIIa ##STR11## wherein X and Y.sub.1 to Y.sub.4 have the meaning given the formula III.

The polyester proportion of the polyester/polycarbonates according to the invention is accordingly to be understood as the amount by weight of polyester/diolate block units, lengthened via carbonate groups, of one of the polyester-diols described on page 4 of the simplified formula VI ##STR12## wherein n denotes an integer from 2 to 20, preferably 2 to 10.

The present invention thus also relates to polyester/polycarbonates, which are characterized in that they consist of about 30 to 95% by weight, preferably about 35 to 80% by weight, of aromatic polycarbonate structural units of the formula V, in particular those of the formula IIIa, and of about 70 to 5% by weight, preferably of about 65 to about 20% by weight, of polyester-diolate block units lengthened via carbonate groups, of the simplified formula VI.

Polyester/polycarbonates according to the invention are, for example, those which consist of about 30 to about 95% by weight, preferably between about 35 and 80% by weight, of polycarbonate structural units of the formula IIIb ##STR13## wherein Y is H, Cl, Br or CH.sub.3,

and of about 70 to about 5% by weight, preferably about 65 to about 20% by weight, of polyester-diolate block units lengthened via carbonate groups.

The polyester/polycarbonates according to the invention should have average molecular weights Mw (weight-average) of about 25,000 to 250,000, preferably of about 40,000 to 150,000, determined by the light scattering method using a scattered light photometer. The relative solution viscosity .eta..sub.rel (measured on 0.5 g in 100 ml of CH.sub.2 Cl.sub.2 at 25.degree. C.) of the polyester/polycarbonates according to the invention is between about 1.3 and 3.0, preferably between about 1.4 and 2.6.

The high-molecular, segmented polyester/polycarbonates which are prepared by the process according to the invention and can be processed as thermoplastics are characterized in that, measured by means of differential thermoanalysis, the polyester constituent is present in the amorphous form and has a transformation temperature between about -100.degree. C. and +100.degree. C., preferably between about -80.degree. C. and +20.degree. C., and in that the polycarbonate constituent is present in the partially crystalline form, the crystalline polycarbonate portion having a crystallite melting point of at least about 160.degree. C., preferably between about 165.degree. C. and 250.degree. C., and in that the transformation temperature of the amorphous polycarbonate portion is above about 80.degree. C., preferably above about 100.degree. C.

This difference in the transformation temperature of the polyester constituent and the transformation temperature and crystallite melting point of the polycarbonate constituent is characteristic for the presence of the phase separation between the polyester constituent and the polycarbonate constituent.

The partial crystallinity of the polycarbonate constituent of the polyester/polycarbonates according to the invention, which can be detected by a measureable fusion enthalpy which is at least 1-8 cal/g of polymer, can be increased by a further 50% by stretching and by the subsequent heat treatment mentioned (5 minutes to 25 hours) at 40.degree.-170.degree. C., or by the action of shearing forces, which has been mentioned, during thermoplastic processing in a multiscrew extruder, whereupon the heat distortion point of the products rises and the appearance changes from transparent to opaque to intransparent.

The partially crystalline elastic polyester/polycarbonates can be processed as thermoplastics at temperatures from about 130.degree. C. to a maximum of 250.degree. C., in each case below or in the region of the crystallite melting point of the crystalline polycarbonate portion, whereupon a substantial proportion of the crystallinity is retained. Amorphous, transparent products are obtained at processing temperatures above the crystallite melting point of the crystalline polycarbonate portion.

The crystalline portion of the polycarbonate constituent of the polyester/polycarbonates according to the invention can thus be varied; the fusion enthalpy of the cristalline polycarbonate portion in order to give a high heat distortion point of the polyester/polycarbonates in practice, is about 1-8 cal/g of polymer, preferably about 2.5-5.5 cal/g of polymer.

If the polyester/polycarbonates are worked up and isolated according to the invention without heat treatment, without gelling and without the action of shearing forces, single-phase polyester/polycarbonates are obtained, that is to say those products which have only one transformation temperature which can be measured by means of differential thermoanalysis.

The stability of the polyester/polycarbonates according to the invention towards UV light and their stability towards hydrolysis can be improved by amounts of UV stabilizing agents customary for thermoplastic polycarbonates, such as, for example, substituted "benzophenones" or "benztriazoles" by agents which impart stability towards hydrolysis, such as, for example monocarbodiimides and, above all, polycarbodiimides (compared W. Neumann, J. Peter, H. Holtschmidt and W. Kallert, Proceeding of the 4th Rubber Technology Conference, London, 22nd-25th May 1962, pages 738-751) in amounts of 0.2-5% by weight, relative to the weight of the polyester/polycarbonates, and by anti-ageing agents known in the chemistry of thermoplastic polyesters and thermoplastic polycarbonates.

Substances such as, for example, carbon black, kieselguhr, kaolin, clays, CaF.sub.2, CaCO.sub.3, aluminum oxides and customary glass fibers can be added in amounts of about 2 to 40% by weight, in each case relative to the total weight of the molding composition, and inorganic pigments, both as fillers and as nucleating agents, in order to modify the products according to the invention.

If flame-repellant products are desired, about 5 to 15% by weight, in each case relative to the weight of the polyester/polycarbonates, of flameproofing agents known in the chemistry of thermoplastic polyesters and thermoplastic polycarbonates, such as, for example, antimony trioxide, tetrabromophthalic anhydride, hexabromocyclododecane, tetrachloro- or tetrabromo-bisphenol A or tris-(2,3-dichloro-propyl) phosphate, can be admixed, the tetrachloro- and tetrabromobisphenols statistically incorporated into the polycarbonate portions of the polycarbonates according to the invention also exhibiting flame-repellant properties.

Furthermore, processing auxilaries, such as mold release agents, known in the chemistry of thermoplastic polyesters and thermoplastic polycarbonates can be used effectively.

The polyester/polycarbonates obtained by the process according to the invention can be advantageously used in all instances where a combination of hardness and elasticity, in particular of cold flexibility, is desired, for example, in the construction of vehicle bodies, for the manufacture of low-pressure tires for vehicles, for sheathing for hoses, sheets and tubes and for flexible drive pulleys.

The average molecular weights given in the Examples which follow are number-average Mn and are ascertained by determining the OH number.

The relative solution viscosity .eta..sub.rel of Examples 7(a)-(d) is defined as the viscosity of 0.5 g of polyester/polycarbonate in 100 ml of methylene chloride at 25.degree. C.

The tensile strength and the elongation at break were measured according to DIN 53,455 and 53,456 respectively; the corresponding United States ASTM Equivalent is D-638. Investigations by gel chromatography were carried out in tetrahydrofurane using Styragel columns (separation range 1.5.times.10.sup.5 A, 1.times.10.sup.5 A, 3.times.10.sup.4 A and 2.times.10.sup.3 A) at room temperature. The calibration of bisphenol A polycarbonate was used for the determination. In comparison with the Mw determination by the light-scattering method, no large deviations were found.

The differential thermoanalysis (DTA) was carried out with the "Dupont (E. I. du Pont de Nemours and Co.) Model 900" apparatus. For the interpretation of the transformation temperature, the approximate middle of the softening range, according to the tangent method, was chosen and for the crystallite melting point the approximate middle of the endothermic peak of the melting curve was chosen.

Preparation of a polyester-diol bis(bisphenol A) carbonate, lengthened via carbonate groups, which also contains 2.06% by weight of bisphenol A

313.5 parts by weight of the biscarbonic acidphenyl ester which has been prepared according to Example 4, of a polyester-diol lengthened via carbonate groups and obtained from adipic acid and a mixture of hexane-1,6-diol and neopentylglycol in the molar ratio 65/35, of average molecular weight M.sub.n 6,270, 29.7 parts by weight of 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A) and 0.03 part by weight of catalyst (sodium bisphenolate of bisphenol A to bisphenol A=1:100) are heated, while stirring and under a nitrogen atmosphere, first at 125.degree. C. for 1 hour, then at 150.degree. C. for 4 hours and under 0.05 mm Hg. During this time, 9.4 parts by weight of phenol are distilled off. A colorless wax is obtained.

Preparation of a polyester-diol bis(bisphenol A) carbonate, lengthened via carbonate groups, which also contains 2.95% by weight of bisphenol A

297 parts by weight of the biscarbonic acid-phenyl ester which has been prepared according to Example 4, of a polyester-diol, lengthened via carbonate groups and obtained from adipic acid and a mixture of hexane-1,6-diol/neopentylglycol in the molar ratio 65/35, of average molecular weight Mn 4,240, 41.5 parts by weight of 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A) and 0.1 part by weight of sodium phenolate are heated while stirring and under a nitrogen atmosphere, first at 125.degree. C. for 1 hour, then at 150.degree. C. for 4 hours and under 0.8 mm Hg.

During this time, 13.1 parts by weight of phenol are distilled off.

Preparation of a polyester-diol bis-diphenol carbonate, lengthened via carbonate groups, of the formula IV f, which also contains 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane in amounts of 3.5% by weight

297 parts by weight of the biscarbonic acid-phenyl ester carbonate, which has been prepared according to Example 4, of a polyester-diol, lengthened via carbonate groups and obtained from adipic acid and a mixture of hexane-1,6-diol/neopentylglycol in the molar ratio 65/35, of average molecular weight Mn 4,240, 51.8 parts by weight of 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane and 0.26 part by weight of catalyst (sodium bisphenolate of bisphenol A: bisphenol A=1:100) are heated, while stirring and under a nitrogen atmosphere, first at 125.degree. C. for 1 hour, then at 150.degree. C. for 5 hours and under 0.2 mm Hg. During this time, 13.1 parts by weight of phenol are distilled off.

Preparation of a polyester-diol bis-diphenol carbonate, lengthened via carbonate groups, of the formula IV f, which also contains 2,2-bis-(3,5-dimethyl-4-hydroxy-phenyl)-propane in amounts of 2.5% by weight

313.5 parts by weight of the biscarbonic acid-phenyl ester, has been prepared according to Example 4, of a polyester-diol, lengthened via carbonate groups and obtained from adipic acid and a mixture of hexane-1,6-diol/neopentylglycol in the molar ratio 65/35, of average molecular weight Mn 6,270, 37 parts by weight of 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane and 0.19 part by weight of catalyst (sodium bisphenolate of bisphenol A: bisphenol A=1:100) are heated, while stirring and under a nitrogen atmosphere, first at 125.degree. C. for 1 hour, then at 150.degree. C. for 5.5 hours and under 0.2 mm Hg. During this time, 9.4 parts by weight of phenol are distilled off.

Preparation of a polyester/polycarbonate with a polyester proportion of 50% by weight

110.6 parts by weight of the viscous oil from Example 6a, dissolved in 1,725 parts by weight of methylene chloride, are added to a solution of 80 parts by weight of bisphenol A and 1.77 parts by weight of p-tert.-butylphenol in 70 parts by weight of 45 percent strength NaOH and 1,300 parts by weight of distilled water. 58.3 parts by weight of phosgene are passed in at 20.degree.-25.degree. C. in the course of 30 minutes, while stirring and under a nitrogen atmosphere. During this introduction, 126 parts by weight of 45 percent strength NaOH are simultaneously added dropwise so that the pH value remains constant at pH 13. After passing in the phosgene, 39.8 parts by weight of a 1 percent strength triethylamine solution are added and the mixture is stirred for 1 hour. The organic phase is separated off and washed successively with 2 percent strength phosphoric acid and finally with distilled water until free from electrolytes. After separating off the water, the organic phase can be worked up by the following processes:

7a.1 A high-strength (about 30-40% by weight) polymer solution is obtained by distilling off the CH.sub.2 Cl.sub.2 down to a certain concentration or by adding chlorobenzene to the organic phase and distilling off the entire methylene chloride. The polyester/polycarbonate gels by subsequently slowly evaporating off the remaining methylene chloride or the chlorobenzene and can be further worked up to a powder grain mixture. The resulting polyester/polycarbonate is dried in vacuo at 50.degree. C. for 48 hours and 100.degree. C. for 24 hours.

7a.2 A finely divided solid product is obtained by distilling off the solvent, drying the residue in a vacuum drying cabinet at about 80.degree.-110.degree. C. and under 15 mm Hg and subsequently grinding it.

7a.3 By precipitating the polyester/polycarbonate from the organic phase using, for example, methanol, ethanol, isopropanol, acetone, aliphatic hydrocarbons and cycloaliphatic hydrocarbons, and subsequently drying the precipitate in a vacuum drying cabinet at 80.degree.-110.degree. C. and under 15 mm Hg.

7a.4 By concentrating the organic phase in an evaporation extruder and subsequent extrusion at about 160.degree.-240.degree. C. under the conditions which are known for polycarbonate extrusion.

The relative viscosity of the polyester/polycarbonate obtained according to 7a.1-7a.4 .eta.rel is 1.63 (measured in CH.sub.2 Cl.sub.2 at 25.degree. C. and d=5 g/l). According to a determination by gel chromatography, the polyester/polycarbonate exhibits a maximum at 40,000. It contains 50% by weight of polyester and has a polycarbonate proportion of 50% by weight. Some mechanical properties of a film cast out of methylene chloride are: Tensile strength 26.9 (MPA) (measured according to ASTM D-638) Elongation at break 366% (measured according to ASTM D-638)

According to differential thermoanalysis of the granular polyester/polycarbonate, the polyester constituent has a glass transition temperature (transformation temperature) of -38.degree. C., the amorphous polycarbonate portion has a glass transition temperature (transformation temperature) of 120.degree. C. and the crystalline polycarbonate portion has a crystallite melting point of about 190.degree. C. The fusion enthalpy of the crystalline polycarbonate portion is between 2.5 and 5.5 cal/g of polymer.

Preparation of a polyester/polycarbonate, lengthened via carbonate groups, with a polyester proportion of 50% by weight

115.1 parts by weight of the viscous oil from Example 6b, dissolved in 1,725 parts by weight of methylene chloride, are added to a solution of 75.2 parts by weight of bisphenol A and 1.18 parts by weight of p-tert.-butylphenol in 1,300 parts by weight of distilled water and 70 parts by weight of 45 percent strength sodium hydroxide solution.

A solution of 0.52 part by weight of 1,4-bis-(4',4"-dihydroxytriphenylmethyl)-benzene and 45 parts by weight of 5 percent strength sodium hydroxide solution is added to this.

58.3 parts by weight of phosgene are passed into the mixture in the course of 40 minutes, while stirring and under a nitrogen atmosphere, 135 parts by weight of 45 percent strength sodium hydroxide solution being simultaneously added dropwise in order to keep the pH constant at 13. After passing in the phosgene, 0.4 part by weight of triethylamine is added. The mixture becomes more viscous. After 1 hour, the organic phase is separated off and the polyester/polycarbonate is isolated as described in Example 7a (working up 7a.1-7a.4).

The relative viscosity of the polyester/polycarbonate .eta..sub.rel is 1.71 (in CH.sub.2 Cl.sub.2).

According to a determination by gel chromatography, the polymer exhibits a maximum at 45,000 and an additional maximum at 200,000.

The mechanical properties of a film, cast out of methylene chloride, containing 50% by weight of polyester and having a polycarbonate proportion of 50% by weight are:

Tensile strength: 20.1 MPA

Elongation at break: 426%

According to differential thermoanalysis of the granular polyester/polycarbonate, the polyester constituent has a glass transition temperature (transformation temperature) of -34.degree. C., the amorphous polycarbonate portion has a glass transition temperature (transformation temperature) of 125.degree. C. and the crystalline polycarbonate portion has a crystallite melting point of about 185.degree. C. The fusion enthalpy of the crystalline polycarbonate portion is between 2.5 and 5.5 cal/g of polymer.

Preparation of a polyester/polycarbonate from 2,2-bis-(3,5-dimethyl-4-hdyroxyphenyl)-propane with a polyester proportion of 50% by weight

118.0 parts by weight of the viscous oil from Example 6c and 0.6 part by weight of tributylamine (=1 mol % per mol of bisphenol units), dissolved in 1,725 parts by weight of methylene chloride, are added to a solution of 73.5 parts by weight of 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane in 57.3 parts by weight of 45 percent strength sodium hydroxide solution and 1,300 parts by weight of distilled water.

95.6 parts by weight of phosgene are passed in the course of 30 minutes, while stirring and under a nitrogen atmosphere, 225 parts by weight of 45 percent strength sodium hydroxide solution being simultaneously added dropwise in order to keep the pH constant at 13. After passing in the phosgene, 5.4 parts by weight of tributylamine (=9 mol % per mol of bisphenol units) are added to bring the condensation reaction to completion. The mixture becomes more viscous. After 3 hours, the organic phase is separated off and the polyester/polycarbonate is isolated as described in Example 7a (working up 7a.1).

The relative viscosity of the polyester/polycarbonate .eta..sub.rel is 1.55 (in CH.sub.2 Cl.sub.2).

Preparation of a polyester/polycarbonate from 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane with a polyester proportion of 50% by weight.

112.5 parts by weight of the viscous oil from Example 6d and 0.6 part by weight of tributylamine (=1 mol % per mol of bisphenol units), dissolved in 1,725 parts by weight of methylene chloride, are added to a solution of 79.5 parts by weight of 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane in 57.3 parts by weight of 45 percent strength sodium hydroxide solution and 1,300 parts by weight of distilled water. 95.6 parts by weight of phosgene are passed in the course of 30 minutes, while stirring and under a nitrogen atmosphere, 235 parts by weight of 45 percent strength sodium hydroxide solution being simultaneously added dropwise in order to keep the pH constant at 13. After passing in the phosgene, 5.4 parts by weight of tributylamine (=9 mol % per mol of bisphenol units) are added in order to bring the condensation reaction to completion. The mixture becomes more viscous. After 3 hours, the organic phase is separated off and the polyester/polycarbonate is isolated as described in Example 7a (working up 7a.1).

The relative viscosity of the polyester/polycarbonate .eta..sub.rel is 1.68 (in CH.sub.2 Cl.sub.2).

Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.