POLYCARBONATE FOR MAKING EXTRUDED FILMS VIRTUALLY FREE OF SURFACE DEFECTS Russian patent published in 2012 - IPC C08G64/40 C08G63/00 

FIELD: chemistry.

SUBSTANCE: present invention relates to a linear polycarbonate, as well as an improved continuous interfacial polymerisation method for obtaining a polycarbonate which is suitable for extruding articles which are virtually free of surface defects. Said polycarbonate contains fluorescent particles with size from 15 mcm to 250 mcm in amount of up to 1.8 units per gram. The amount of said particles is determined by exciting the residue remaining after filtering a solution of the polycarbonate in chloromethane at wavelength 400-440 nm, 25 times magnification and illumination time of 40 ms. Filtration is carried out through a teflon filter with pore size of 5 mcm. The improved continuous interfacial polymerisation method involves extraction of polycarbonate at three flash evaporation stages and an evaporation extruder. Temperature at the first stage is from 70 to 80°C at excess pressure 0.35-0.45 bar, at the second stage - from 125 to 135°C at excess pressure 0.75-0.85 bar and at the third stage - 175 to 185°C at excess pressure 1.85-1.95 bar.

EFFECT: obtaining a linear polycarbonate suitable for making films with improved optical properties.

4 cl, 2 tbl, 1 ex