Patent ID: 7323586

Claim:
A process for preparing a mixture of isomeric dialkyl phthalates having a desired viscosity, which comprises: esterifying phthalic acid or phthalic anhydride with a mixture of isomeric alkyl alcohols having a certain number of carbon atoms, wherein the molar fraction of each alkyl alcohol isomer of an isomeric alcohol mixture is determined and wherein the viscosity parameter of each alkyl alcohol isomer of the mixture, which, upon reacting with phthalic acid or phthalic anhydride, results in a mixed isomer dialkyl phthalate ester product having a specific desired viscosity, is determined in accordance with formula (I): ln(η)=Σχ i *ln(η i ) (I) where η=the calculated viscosity of a dialkyl phthalate mixture, χ i =the molar fraction of an isomerically pure alcohol (i), and η i =the calculated viscosity parameter of isomerically pure alcohol (i).