The invention relates to esters of general formula (I) R1—C(═O)—O—R2, wherein (1) R1 represents a linear alkyl radical having 7 to 9 carbon atoms and R2 represents a linear alkyl radical having 9 to 10 carbon atoms or (2) R1 is a linear alk radical having 8 to 9 carbon atoms and R2 is a linear alkyl radical having 8 carbon atoms, or (3) R1 is a linear alkyl radical having 7 to 9 carbon atoms and R2 is a linear alkyl radical having 7 carbon atoms, or (4) R1 is an alkyl radical having 7 or 8 carbon atoms and R2 is an alkyl radical having 9 carbon atoms where, if R1 is a linear alkyl radical, R2 is a branched alkyl radical, or, if R1 is a branched alkyl radical, R2 is a linear alkyl radical or (5) R1 represents an alkyl radical having 8 carbon atoms and R2 is an alkyl radical having 8 carbon atoms, where, if R1 is a linear alkyl radical, R2 is a branched alkyl radical, or, if R1 is a branched alkyl radical, R2 is a linear alkyl radical, or n-octyl isooctanoate, n-decyl isooctanoate, n-decyl isononanoate, isononyl n-decanoate, n-heptyl n-dodecanoate or isononyl isooctanoate.