Poly(ester-carbonate) copolymers, articles formed therefrom, and methods of manufacture

A poly(ester-carbonate) copolymer, comprising

• carbonate units of the formula
• and
• ester units of the formula
• wherein:
• T is a C2-20 alkylene, a C6-20 cycloalkylene, or a C6-20 arylene;
• and
• R1 and J are each independently
• (a) a bisphenol A divalent group of the formula
• and
• (b) a C16 or higher divalent group (b) of the formula
• wherein
• Rc and Rd are each independently a C1-12 alkyl, C2-12 alkenyl, C3-8 cycloalkyl, or C1-12 alkoxy,
• each R6 is independently C1-3 alkyl or phenyl,
• Xa is a C6-12 polycyclic aryl, C3-18 mono- or polycycloalkylene, C3-18 mono- or polycycloalkylidene, a -(Q1)x-G-(Q2)y- group wherein Q1 and Q2 are each independently a C1-3 alkylene, G is a C3-10 cycloalkylene, x is 0 or 1, and y is 1, and
• m and n are each independently 0 to 4;
• provided that
• the C16 or higher divalent group (b) is present in an amount of 40 mol % to 50 mol % based on the total moles of the bisphenol A divalent groups and the C16 or higher divalent groups;
• the ester units are present in an amount of 40 mol % to 60 mol % based on the sum of the moles of the carbonate units and the ester units;
• and
• wherein
• the poly(ester-carbonate) copolymer has a weight average molecular weight of 18,000 Daltons to 24,000 Daltons, as measured by gel permeation chromatography, using a crosslinked styrene-divinylbenzene column and calibrated to bisphenol A homopolycarbonate references;
• and
• a sample of the composition has
• a glass transition temperature of 210° C. to 235° C. as determined by differential scanning calorimetry (DSC) as per ASTM D3418 with a 20° C./min heating rate;
• and
• a melt viscosity of less than 1050 Pa·s at 644 sec−1 and 350° C., determined according to ISO11443.