Polycarbonate copolymers having improved hydrolytic stability

This invention belongs to the field of polycarbonates. In particular, it relates to polycarbonate copolymers having improved solvent resistance, improved hydrolytic stability, or combinations thereof. The present invention provides polycarbonate copolymers having improved hydrolytic stability, solvent resistance, or combinations thereof. In particular, certain of the copolymers of the invention have improved resistance to dilute caustic solution. Thus, the copolymers of the present invention are particularly useful as structural elements in applications where such elements routinely come in contact with caustic solutions, such as in automatic dishwashing equipment. Preferred comonomers include 4,4′-biphenol, bis-(4-hydroxyphenyl)terephthalamide ("BHPT"), and a bisimide bisphenol obtained by reacting Bisphenol A dianhydride (BPADA) with 4,4′-isopropylidene phenol aniline. The comonomers are utilized along with 2,2-bis(4-hydroxyphenyl)propane (Bisphenol A) in concentrations in a range between about 1 and about 50 weight percent of the repeating units in the polycarbonate.