A method for performing a flying grade switch in an ester production process, which preferably is operated in semi-continuous mode, maximizes plant equipment productivity while minimizing product cross-contamination. Mixed ester products of the process containing a C9-C11 alkyl or isodecyl benzoate together with a higher molecular weight di-alkyl phthalate or cyclohexanoate, bring performance advantages such as improved permanence in plasticized PVC articles or improved processability in manufacturing these articles.