sents, for example, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, neopentyl, 1-ethylpropyl, cyclohexyl, cyclo› pentyl, n-hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-me› thylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethyl› butyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethyl› butyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2- trimethylpropyl, 1,2,2-trimethylpropyl, l-ethyl-1- methylpropyl, l-ethyl-2-methylpropyl or l-ethyl-2- methylpropyl; C$_{1 }$-C$_{10}$ -alkyl additionally represents, for example, n-heptyl and n-octyl, pinacyl, adamantyl the iso› meric menthyls, n-nonyl or n-decyl; C$_{1}$-C$_{34}$-alkyl addition› ally represents, for example, n-dodecyl, n-tridecyl, n-tetrade› cyl, n-hexadecyl or n-octadecyl. The same applies to the corresponding alkyl radical, for example, in aralkyl or alky› laryl, alkylphenyl or alkylcarbonyl radicals. Alkylene radi› cals in the corresponding hydroxyalkyl or aralkyl or alkylaryl radical represent for example, the alkylene radicals corre› sponding to the preceding alkyl radicals. 

[0142] Ary! represents a carbocyclic aromatic radical hav› ing 6 to 34 skeletal carbon atoms. The same applies to the aromatic moiety of an arylalkyl radical, also referred to as aralkyl radical, and to aryl constituents of more complex groups, such as, for example, arylcarbonyl radicals. 

[0143] Examples of CcC$_{34}$ -aryl are phenyl, o-, p- and m-tolyl, naphthyl, phenanthrenyl, anthracenyl or fluorenyl. 

[0144] Arylalkyl or aralkyl denotes, in each case indepen› dently, a straight-chain, cyclic, branched orunbranched alkyl radical according to the above definition, which may be monosubstituted, polysubstituted or completely substituted by aryl radicals according to the above definition. 

[0145] The preceding lists are to be understood as being by way of example and not as limiting. 

[0146] There is in principle no limitation and restriction with regard to the manner and plant in which and the proce› dure according to which the process is carried out. The pro› cess can preferably be carried out as described below. 

[0147] Furthermore, there is no special limitation and restriction with regard to the temperatures and the pressures for the process according to the invention. Any condition is possible as long as the chosen temperatures, pressures and catalysts permit a melt transesterification with appropriately rapid removal of the monohydroxyaryl compound elimi› nated. 

[0148] The temperatures over the entire process are in gen› eral between 180 and 330° C. and the pressures between 15 bar absolute and 0.01 mbar absolute. 

[0149] A continuous procedure is preferably chosen because this may be advantageous for the product quality. 

[0150] Such a continuous process according to the inven› tion is preferably carried out in such a way that one or more dihydroxyaryl compounds are subjected to precondensation with one or more diary! carbonate(s) and optionally further reactants with the use of at least one catalyst and the molecu› lar weight of the end product is increased to the desired level after this precondensation without separating off the resulting monohydroxyaryl compound(s) in a plurality of subsequent reaction-evaporator stages with temperatures increasing step› wise and pressures decreasing stepwise. 

[0151] The devices, apparatuses and reactors suitable for the individual reaction-evaporator stages are, corresponding to the course of the process, heat exchangers, flash appara› tuses, separators, colunms, evaporators, stirred containers and reactors and other commercial apparatuses which pro- 

vide the required residence time at selected temperatures and pressures. The chosen devices must permit the necessary introduction of heat and be designed so that they are suitable for the continuously increasing melt viscosities. 

[0152] All devices are connected to one another via pumps, pipelines and valves. The pipelines between all facilities should of course be as short as possible and the number of bends in the pipes should be kept as small as possible in order to avoid unnecessarily lengthened residence times. The exter› nal, i.e. technical boundary conditions and requirements for assemblies of chemical plants should be taken into account. 

[0153] For carrying out the process according to a preferred continuous procedure, the reactants can be melted together or the solid dihydroxyaryl compound(s) in the diarylcarbonate melt or the solid diary! carbonate or carbonates in the melt of the dihydroxyaryl compound(s) can be dissolved or both raw materials are combined as a melt, preferably directly from the preparation. The residence times of the separate melts of the raw materials, in particular those of the melt of the dihy› droxyaryl compound, are set as short as possible. The melt mixture can on the other hand have a longer residence time without losses of quality owing to the lower melting point of the raw material mixture in comparison with the individual raw materials at correspondingly lower temperatures. 

[0154] The catalyst or catalysts, preferably dissolved in a suitable solvent, such as, for example, phenol, is or are then admixed and the melt is heated to the reaction temperature. 

[0155] In preferred embodiments of the process according to the invention, a part-stream, into which at least one inhibi› tor is metered, is taken off from the melt stream between the penultimate reactor and the finish reactor by means of a gear pump. Directly thereafter, the mixture is pumped back into the main stream for thorough mixing via a static mixer. Fol› lowing the entry point in the direction of flow is a further static mixer which ensures the homogeneous distribution in the main melt stream, which is then passed into the final reactor. In the final reactor, which is used for reducing residual mono› mers, the residual monomers are then reduced at temperatures of260to 310° C. preferably at 265 to 300° C. and particularly preferably at 270 to 290° C. and at pressures of0.01 to 3 mbar, preferably of 0.2 to 2.5 mbar and particularly preferably of 0 .4 to 2 mbar. The levels of fill are set in the final reactor so as to be as low as permitted by the process engineering. The residence time in the final reactor-also referred to as finish reactor-is of the order of magnitude of a few minutes to hours, preferably 5 to 180 minutes, particularly preferably 10 to 150 minutes and very particularly preferably 15 to 120 minutes. A possible slight increase in molecular weight in the final reactor, in which predominantly the expulsion of the residual monomers in vapour form is to take place, can be compensated by reducing the entry molecular weight to such an extent that, after the expulsion of the residual monomers in vapour form, the desired final molecular weight is exactly achieved. The finished polycarbonate is discharged from the final reactor by means of the pump device, if required pro› vided with additives for improving the properties by known methods, extruded, cooled and granulated. The pump device used is as a rule a gear pump. Alternatively, screws having a very wide range of designs or positive displacement pumps of special design can also be used. 

[0156] The particularly preferred embodiment of the pro› cess according to the invention in which, for example, 2,2- bis( 4-hydroxyphenyl)propane (bispheno!A, BPA) and diphe- 

