Abstract: The invention relates to an apparatus and a process for devolatilizing solvent-containing polycarbonate solutions. By employing the inventive apparatus, polycarbonates with low residual values of volatile constituents are produced from solvent-containing polymer melts, which improved optical properties, especially yellowness index, with the aid of an apparatus combination of a heatable tubular devolatilizer and a vented extruder.

Abstract: The invention relates to an apparatus and a process for devolatilizing solvent-containing polycarbonate solutions. By employing the inventive apparatus, polycarbonates with low residual values of volatile constituents are produced from solvent-containing polymer melts, which improved optical properties, especially yellowness index, with the aid of an apparatus combination of a heatable tubular devolatilizer and a vented extruder.

Abstract: A process for the preparation of optical data carriers made of a particualr polycarbonate is disclosed. The polycarbonate is prepared by the phase boundary process that entails reacting at least one dihydroxydiarylalkane in the form of its alkali metal salts with phosgene in the heterogeneous phase in the presence of sodium hydroxide solution and an organic solvent. The process is characterized in that the feedstock have but low content of Fe, Cr, Ni, Zn, Ca, Mg, Al metals or homologues thereof, and in that the organic solvent is separated off, and in that the polycarbonate which is obtained is worked up. The resulting polycarbonate is particularly useful in producing optical data carriers.

Abstract: Polycarbonate substrates, the preparation of which is based on 1,1-bis-(4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, and their use for producing shaped articles with particularly high purity and extremely high surface brilliance and also the shaped articles which can be produced from the polycarbonate substrate are described.

Abstract: A process for the preparation of polycarbonate by the phase boundary process is disclosed. The process entails reacting at least one dihydroxydiarylalkane in the form of its alkali metal salts with phosgene in the heterogeneous phase in the presence of sodium hydroxide solution and an organic solvent. The process is characterized in that the feedstock have but low content of Fe, Cr, Ni, Zn, Ca, Mg, Al metals or homologues thereof, and in that the organic solvent is separated off, and in that the polycarbonate which is obtained is worked up. The resulting polycarbonate is particularly useful in producing transparent shaped articles.

Abstract: Polycarbonate substrates having low concentration of defects are disclosed. The substrates are suitable for producing molded articles characterized by low cloudiness.

Abstract: Polycarbonate substrates, the preparation of which is based on 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexanone, and their use for producing shaped articles with particularly high purity and extremely high surface brilliance and also the shaped articles which can be produced from the polycarbonate substrate are described.

Abstract: Polycarbonate substrates, the preparation of which is based on 1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexanone, and their use for producing shaped articles with particularly high purity and extremely high surface brilliance and also the shaped articles which can be produced from the polycarbonate substrate are described.

Abstract: A titanium dioxide composition useful as the opacifier agent for vitreous enamels and fusion enamels comprises TiO.sub.2 predominantly in the form of isometric primary particles from 0.5 to 5.0 .mu.m in size, which are aggregated to predominantly spherolithic particles 1 to 100 .mu.m in diameter, with a BET surface of 1 to 4.5 m.sup.2 /g and an apparent density of 0.2 to 1.3 kg/1, is prepared by subjecting titanium dioxide hydrate having a BET surface of from 50 to 500 m.sup.2 /g to accelerated calcination at temperatures of 800.degree. to 1600.degree. C.

Abstract: A titanium dioxide composition useful as the opacifier agent for vitreous enamels and fusion enamels comprises TiO.sub.2 predominantly in the form of isometric primary particles from 0.5 to 5.0 .mu.m in size, which are aggregated to predominantly spherolithic particles 1 to 100 .mu.m in diameter, with a BET surface of 1 to 4.5 m.sup.2 /g and an apparent density of 0.2 to 1.3 kg/l, is prepared by subjecting titanium dioxide hydrate having a BET surface of from 50 to 500 m.sup.2 /g to accelerated calcination at temperatures of 800.degree. to 1600.degree. C.