Patent ID: 7659359

Claim:
A method of forming an isosorbide-containing polycarbonate composition, the method comprising the steps of: (I) combining a polycarbonate comprising repeat units derived from isosorbide with a polycarbonate-property-modifying additive to form a polycarbonate composition, (II) dissolving a sample from the polycarbonate composition in a non-aqueous solvent to form a polycarbonate composition solution, (III) determining the non-aqueous pH of the polycarbonate composition solution and determining the non-aqueous pH of the solvent, (IV) comparing the pH of the solvent with the pH of the polycarbonate composition solution, and if the pH of the polycarbonate composition solution is more than 0.8 below or more than 0.5 above the pH of the solvent then taking an action selected from the group consisting of: (a) if the polycarbonate composition solution has a pH that is more than 0.5 above the pH of the solvent, adding an acid stabilizer to the polycarbonate composition to form an acid stabilized polycarbonate composition, wherein the acid stabilizer is added to the polycarbonate composition in an amount such that a sample of the acid stabilized polycarbonate composition dissolved in the solvent has a non-aqueous pH that is in a range of equal to or between 0.8 below and 0.5 above the pH of the solvent, and (b) if the polycarbonate composition solution has a pH that is more than 0.8 below the pH of the solvent, adding a base stabilizer to the polycarbonate composition to form a base stabilized polycarbonate composition, wherein the base stabilizer is added to the polycarbonate composition in an amount such that a sample of the base stabilized polycarbonate composition dissolved in the solvent has a non-aqueous pH that is in a range of equal to or between 0.8 below and 0.5 above the pH of the solvent, thereby forming an isosorbide-containing polycarbonate composition.