Patent Number: 059360070
Section: description

EXAMPLES To prepare test specimens, an additive-free, unstabilised polycarbonate with an average molecular weight of about 30,000 (Mw by GPC), solution viscosity: .eta.=1.293, was compounded at 300.degree. C. on a twin screw extruder with the stated amount of stabiliser and then granulated. Colour test platelets (thickness 4 mm) were then made from this granular material by injection moulding. The yellowness index of these platelets is determined before irradiation (Hunter Lab. equipment), then the specimens are irradiated (dose: 5 Mrad; Co bomb), stored for 10 days in the dark and the YI determined again. YI.sub.diff, used for assessment, is determined from the difference between the two measurements, before and after irradiation. a) Comparison test ______________________________________ Conc. Compound (wt. %) YI.sub.initial YI.sub.irrad YI.sub.diff ______________________________________ Polycarbonate.sub.reextr -- 6.31 48.88 42.57 -- 6.27 48.07 41.80 Polypropylene glycol 0.75 4.58 29.24 24.66 0.75 4.70 30.07 25.37 Distearyl sulphide 0.50 10.47 25.93 15.46 0.50 10.16 25.70 15.54 ______________________________________ b) According to the invention (Irradiation dose: 5 Mrad) ______________________________________ Conc. Compound (wt. %) YI.sub.initial YI.sub.irrad YI.sub.diff ______________________________________ Example 1: Compound A 0.5 3.6 9.9 6.3 Compound B 0.5 5.3 13.1 7.8 Compound C 0.5 7.6 19.5 11.9 Compound D 0.5 6.5 12.0 5.5 ______________________________________ All the examples also contained 0.75 wt. % of polypropylene glycol M.Wt. about 2000. Compound A: phenyl--SO.sub.2 --CH.sub.2 --SO.sub.2 --phenyl PA1 Compound B: phenyl--CO--CH.sub.2 --SO.sub.2 --phenyl PA1 Compound C: dibenzylsulphone PA1 Compound D: ##STR6## According to the invention (Irradiation dose: 3 Mrad) PA1 Compound B: phenyl--CO--CH.sub.2 --SO.sub.2 --phenyl PA1 Compound D: ##STR7## ______________________________________ Conc. Compound (wt. %) YI.sub.initial YI.sub.irrad YI.sub.diff ______________________________________ Example 2 Compound B 0.5 5.3 11.4 6.1 Compound D 0.5 6.5 10.3 3.8 ______________________________________ All the examples also contained 0.75 wt. % of polypropylene glycol M.Wt. about 2000.