the Mark-Houwink relationship according to [ri]=KxMw a ([ri]: intrinsic viscosity; K: 11.lxl0- $^{3 }$ml/g; a: 0.82). 

Content of Phenolic Terminal OH Groups: 

[0198] The content of phenolic terminal OH groups was determined by photometric determination of the TiCl$_{4 }$ com› plex according to Harbach et. al. (Die Makromolekulare Che› mie 88 (1965) 215-231). 

Measurement of the Electric Field Strength: 

[0199] The measurements of the electric field strength were carried out on finished injection moulded parts, in the present case on discs. The following injection moulding parameters and conditions were set for the production of these optical discs: 

Machine: Netstal Discjet 

[0200] Cavity: Audio stamper Cycle time: 4.4 s Melt temperature: 310-330° C. Substrate dimensions: Audio CD Mould temperature on cavity side: 60° C. 

[0201] Before the beginning of the injection moulding pro› cess, a new audio stamper was inserted into the machine. Before insertion of the new stamper, the total injection moulding unit was cleaned to remove the preceding mate› rial so that the measured values were not falsified. Further› more, discs were injection-moulded initially for two hours with a cycle time of 4.4 seconds; this ensures that a stable and representative state of the unit or of the discs with regard to the buildup of electrostatic charge was achieved. After a preliminary run time of 2 hours, the next 100 discs were all measured as follows: 

[0202] Each of these discs was removed from the injection mould immediately after the end of the injection moulding process by means of a robot arm and placed on a turntable. The disc was held on this turntable only by means of four points in the outer region so that the load present on the disc ( electrostatic field) was practically not adversely affected. After the turntable had brought the disc to a position where the measuring probe for measurement of the electric field strength (probe 3455E from TREK Inc., 1160 Maple Ridge Road, Medina, N.Y. 14103) was present, the disc was gripped in this position in the inner hole region with the aid of a lifter and raised about 2 cm. The disc was therefore present at a distance of 5 mm from the measuring probe, which was incidentally mounted so that its measuring range aimed at the radius of35 mm of the disc. Thereafter, the disc was moved under the probe for one revolution with the aid of this lifter which was rotatable by means of a motor. The electrostatic field was recorded practically con› tinuously (200 measuring points per revolution). For this purpose, the signals delivered by the probe were first trans› ferred as an analogue signal to the measuring device (Model 3418 from TREK Inc., 11601 Maple Ridge Rd., Medina, N.Y. 14103), converted there by means of an analogue-digital converter into digital measured values, which were acquired by means of suitable software. For each disc, 200 measured values were thus recorded and evaluated per revolution. The mean electric field strength (F mean) of the 200 values was calculated by determining the mean value, and the maximum and the minimum electric field strength (F min and F max) in each case were deter- 

mined. The values for F meam F min and F max present for each of the 100 discs were now averaged again in total. The mean electric field strength and the mean maximum and mean minimum electric field strength were thus obtained for the set of 100 discs. The difference between the mean maximum and mean minimum electric field strength was likewise determined by subtraction and designated below as field strength variation. 

[0203] 7 500 kg/h of melt mixture comprising 3 7 41 kg/h of diphenyl carbonate (17.45 kmol/h) and 3759 kg/h of bisphenol A (16.47 kmol/h) were pumped from a receiver, with addition of 4.19 kg/h of a catalyst mixture, through a heat exchanger, heated to 190° C. and fed through a dwell colunm at 12 bar and 190° C. The average residence time was 50 minutes. The catalyst mixture consisted of0.52 kg of the phenol adduct oftetraphenylphosphonium phenolate (containing 65.5% by weight oftetraphenylphosphonium phenolate 0.786 mo!) dissolved in 4.5 kg of phenol. 

[0204] The melt was then passed via an expansion valve into a separator under a pressure of 200 mbar. The melt flowing away was heated again to 200° C. in a falling-film evaporator likewise under 200 mbar and was collected in a receiver. After a residence time of20 minutes, the melt was pumped into the next three, similarly designed stages. The conditions of pressure, temperature and residence time in the 2nd/3rd/4th stage were 90/70/40 mbar; 223/252/279° C. and 20/10/10 minutes. All vapours were fed with pres› sure regulations into a colunm under a vacuum and removed as condensates. 

[0205] Thereafter, the oligomer was subjected to conden› sation in a subsequent basket reactor at 280° C. and 4.7 mbar during a residence time of 45 minutes to give a higher molecular weight product, the relative viscosity of which was 1.195. The vapours were condensed. 

[0206] A part-stream of 150 kg/h of melt was branched off by means of a gear pump from the melt stream which was passed into a further basket reactor, 2.0 g/h of 1,2,3-pro› panetriol tris( 4-benzenesulphonate) were added, the mix› ture was fed via a static mixer having a length-to-diameter ratio of 20 and was recycled to the main melt stream. Directly after combination, the 1,2,3-propanetriol tris(4- benzenesulphonate) was homogeneously distributed in the total melt stream by means of a further static mixer. The melt thus treated was further subjected to the process con› ditions in a further basket reactor at 294 ° C. and 0.7 mbar and during an average residence time of 130 minutes, dis› charged and granulated. 

[0207] The production of the optical shaped articles (discs) and the measurement of the electric field strength were effected as described below. For this purpose, the granules obtained were dried for 6 hours and then processed by means of a Netstal Discjet injection moulding machine (see above) during a cycle time of 4.4 seconds under the abovementioned parameters to give discs. The cavity used was an audio stamper. For stabilizing the process, discs were initially produced for two hours and then the mean electric field strength and the field strength variation were determined in each case for the following 100 discs. 

## Example 1 

## Comparative Example 

