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wherein 

RA represents linear or branched C$_{1 }$-C$_{34}$-alkyl, C$_{7}$-C$_{34}$- alkylaryl, CcC$_{34}$-aryl or --COO-RD, wherein RD repre› sents hydrogen, linear or branched C$_{1 }$-C$_{34}$-alkyl, C$_{7}$-C$_{34}$ - alkylaryl or CcC$_{34}$-aryl, and 

RB and Re independently of one another are identical or different and represent hydrogen, linear or branched C$_{1 }$-C$_{34}$- alkylaryl, C$_{7}$ -C$_{34}$-alkylaryl or CcC$_{34}$-aryl. 

Suchmonohydroxyaryl compounds are, for example, 1-, 2- or 3-methylphenol, 2,4-dimethylphenol, 4-ethylphenol, 4-n› propylphenol, 4-isopropylphenol, 4-n-butylphenol, 4-isobu› tylphenol, 4-tert-butylphenol, 4-n-pentylphenol, 4-n-hexy› lphenol, 4-isooctylphenol, 4-n-nonylphenol, 3-pentadecylphenol, 4-cyclohexylphenol, 4-(1-methyl-1- phenylethyl)-phenol, 4-phenylphenol, 4-phenoxyphenol, 4-(1-naphthyl)-phenol, 4-(2-naphthyl)phenol, 4-tritylphenol, methyl salicylate, ethyl salicylate, n-propyl salicylate, n-butyl salicylate, isobutyl salicylate, tert-butyl salicylate, phenyl salicylate and benzyl salicylate. 

4-tert-Butylphenol, 4-isooctylphenol and 3-pentade› cylphenol are preferred. 

The monohydroxyaryl compound(s) are to be so chosen that their boiling point is above that of the monohydroxyaryl compound employed in the preparation of the diary! carbon› ate that is used. The monohydroxyaryl compound can be added at any point in time during the reaction. It is preferably added at the beginning of the reaction. The amount of free monohydroxyaryl compound can be from 0.2 to 20 mo! %, preferably from 0.4 to 10 mo!%, based on the dihydroxyaryl compound. 

It is additionally possible to change the end groups of the resulting polycarbonates also by addition of at least one addi- tional diary! carbonate whose base monohydroxyaryl com› pound has a higher boiling point than that of the base mono› hydroxyaryl compound of the diary! carbonate mainly used. Here too, the additional diary! carbonate can be added at any point in time during the reaction. It is preferably added at the beginning of the reaction. The amount of the diary! carbonate having the higher boiling base monohydroxyaryl compound in the total amount of diary! carbonate used can be from 1 to 40 mo! %, preferably from 1 to 20 mo! % and particularly preferably from 1 to 10 mo! %. 

The basic catalysts known in the literature, such as, for example, alkali and alkaline earth hydroxides and oxides and/or onium salts, such as, for example, ammonium or phos- phonium salts, can be used as catalysts in the melt transes- terification process for the preparation of polycarbonates. Preference is given to the use of onium salts, particularly preferably phosphonium salts, in the synthesis. Such phos- phonium salts are, for example, those of the general formula (IV) 

(III) 

R 7 - $^{10 }$represent identical or different optionally substituted C$_{1 }$-C$_{10}$-alkyl, CcC$_{14}$-aryl, C$_{7}$-C$_{15}$-arylalkyl or C$_{5}$-Cccy› cloalkyl radicals, preferably methyl or C$_{6}$-C$_{14}$-aryl, particu› larly preferably methyl or phenyl, and 

X- represents an anion selected from the group hydrox- ide, sulfate, hydrogen sulfate, hydrogen carbonate, carbonate, halide, preferably chloride, and alkylate or arylate of the formula ---OR 11 , wherein R $^{11 }$represents an optionally sub› stituted CcC$_{14}$-aryl, C$_{7}$-C$_{15}$-arylalkyl or C$_{5}$ -Cccycloalkyl radical, C$_{1 }$-C$_{20}$-alkyl, preferably phenyl. 

Particularly preferred catalysts are tetraphenylphospho› nium chloride, tetraphenylphosphonium hydroxide and tet› raphenylphosphonium phenolate, tetraphenylphosphonium phenolate being very particularly preferred. 

The catalysts are preferably used in amounts of from 1 o-s to 10-$^{3 }$mo!, particularly preferably in amounts of from 1 o- 7 to 10- $^{4 }$mo!, based on one mole of dihydroxyaryl compound. 

Co-catalysts can optionally also be used in order to increase the rate of the polycondensation. 

These can be, for example, alkaline-reacting salts of alkali metals and alkaline earth metals, such as hydroxides, option› ally substituted C$_{1 }$-C$_{10}$-alkoxides and C$_{6}$-C$_{14}$-aryl oxides of lithium, sodium and potassium, preferably hydroxides, optionally substituted C$_{1 }$-C$_{10}$-alkoxides or C$_{6}$-C$_{14}$-aryl oxides of sodium. Preference is given to sodium hydroxide, sodium phenolate or the disodium salt of 2,2-bis-( 4-hydrox› ypheny !)-propane. 

If alkali or alkaline earth metal ions are supplied in the form of their salts, the amount of alkali or alkaline earth ions, determined, for example, by atom absorption spectroscopy, is from 1 to 500 part per billion ("ppb"), preferably from 5 to 300 ppb and most preferably from 5 to 200 ppb, based on polycarbonate to be formed. In preferred forms of the process according to the invention, however, no alkali salts are used. 

Within the scope of the present invention, ppb and parts per million ("ppm") are to be understood as meaning parts by weight, unless indicated otherwise. 

The alkaline-reacting salts of alkali metals and alkaline earth metals can be mixed in during the preparation of the oligocarbonates, that is to say at the beginning of the synthe› sis, or in a later process step, in order to suppress undesirable secondary reactions. The total amount of catalyst can also be added to the process in several steps. 

It is her possible to add before the polycondensation, in addition to the catalysts and catalyst amounts already men› tioned hereinbefore, supplementary amounts of onium cata› lysts. In the case where the above-mentioned catalyst is already an onium catalyst, the onium catalyst added in supplementary amounts before the polycondensation can be the same onium catalyst mentioned above or a different onium catalyst. 

The addition of the catalysts is preferably carried out in solution in order to avoid harmful overconcentrations during metering. The solvents are preferably compounds that are inherent in the system and the process, such as, for example, the dihydroxyaryl compounds, diary! carbonates or option- ally monohydroxyaryl compounds that are employed. Mono- 

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wherein 

(IV) 

