High heat copolycarbonate compositions having enhanced optical properties, articles formed therefrom, and methods of manufacture

A thermoplastic composition comprising:

• a copolycarbonate comprising 60 to 85 mol % of bisphenol A carbonate units and 15 to 40 mol % of second carbonate units each based on the total number of carbonate units in the copolycarbonate, the second carbonate units having the formula
• wherein
• Ra and Rb are each independently a C1-12 alkyl, C2-12 alkenyl, C3-8 cycloalkyl, or C1-12 alkoxy,
• each R3 is independently a C1-6 alkyl,
• R4 is hydrogen, C2-6 alkyl or phenyl optionally substituted with 1 to 5 C1-6 alkyl groups,
• p, q, and j are each independently 0 to 4;
• and
• 10 to 60 wt % of a bisphenol A homopolycarbonate based on the total weight of the thermoplastic composition;
• wherein
• the second carbonate units are present in an amount of 10 to 49 mol %, based on the sum of the moles of the copolycarbonate and the bisphenol A homopolycarbonate,
• the copolycarbonate comprises less than 2 ppm by weight of each of an ion of lithium, sodium, potassium, calcium, magnesium, ammonium, chlorine, bromine, fluorine, nitrite, nitrate, phosphite, phosphate, sulfate, formate, acetate, citrate, oxalate, trimethylammonium, and triethylammonium, as measured by ion chromatography, and
• the thermoplastic composition has a bisphenol A purity of at least 99.6% as determined by high performance liquid chromatography;
• and
• wherein
• the thermoplastic composition has:
• a Vicat B120 of 155° C. or higher as measured according to ISO 306;
• and
• a yellowness index which is at least 20% lower compared to the same composition having a Bisphenol A purity below 99.6%, as measured by ASTM D1925 on a 2.5 mm thick molded plaque with a melt temperature of 355° C. and a residence time of 10 min.

A thermoplastic composition comprising:

• 90 to 99.8 wt % of a copolycarbonate based on the total weight of the thermoplastic composition, the copolycarbonate comprising 60 to 85 mol % of bisphenol A carbonate units and 15 to 40 mol % of second carbonate units each based on the total number of carbonate units in the copolycarbonate, the second carbonate units having the formula
• wherein
• Ra and Rb are each independently a C1-12 alkyl, C2-12 alkenyl, C3-8 cycloalkyl, or C1-12 alkoxy,
• each R3 is independently a C1-6 alkyl,
• R4 is hydrogen, C2-6 alkyl or phenyl optionally substituted with 1 to 5 C1-6 alkyl groups,
• p, q, and j are each independently 0 to 4;
• and
• optionally a bisphenol A homopolycarbonate based on the total weight of the thermoplastic composition;
• wherein
• the second carbonate units are present in an amount of 10 to 49 mol % based on the sum of the moles of the copolycarbonate and the bisphenol A homopolycarbonate,
• the copolycarbonate comprises less than 2 ppm by weight of each of an ion of lithium, sodium, potassium, calcium, magnesium, ammonium, chlorine, bromine, fluorine, nitrite, nitrate, phosphite, phosphate, sulfate, formate, acetate, citrate, oxalate, trimethylammonium, and triethylammonium, as measured by ion chromatography, and
• the thermoplastic composition has a bisphenol A purity of at least 99.6%, as determined by high performance liquid chromatography;
• and
• wherein the thermoplastic composition has:
• a Vicat B120 softening temperature of 155° C. or higher as measured according to ISO 306;
• and
• an increase in yellowness index of less than 10 during 1000 hours of heat aging at 155° C., as measured by ASTM D1925 on a 1 mm thick molded plaque.