Di-alkyl imidazoline quaternaries have been widely used as fabric softeners industrially and for home use in the rinse cycle of washing machines.1 They impart a fluffy, soft feel to fabrics by adsorbing onto them with hydrophobic groups oriented away from fiber.
The most widely used imidazolinium-type fabric softener has been the tallow alkyl derivative. The hydrogenated tallow product shows better softening performance than the nonhydrogenated material because the former contains a higher portion of saturated stearic chains. The distribution of hydrocarbon chains in nonhydrogenated tallow product is 5% myristic, 30% palmitic, 20% stearic (C18 saturated) and 45% oleic (C18 unsaturated), while the hydrogenated tallow product contains 65% saturated stearic chain. It is obvious that the improved softening performance is due to the higher amount of saturated stearic chain in the hydrogenated product.
Imidazoline quats also show the best performance in static control compared to dialkyl dimethyl quats or diamido alkylated quats having the same hydrocarbon chains. The physical form of imidazoline quats changes dramatically with an increase in the chain length and saturation degree. At 75% solids of quat in isopropyl alcohol, the oleyl product is a clear amber liquid; the tallow material is an opaque liquid; the hydrogenated tallow product is a nonpourable opaque paste; and the di-behenyl imidazoline quat is a solid.
To date, no studies on the use of behenyl imidazoline quat in personal care applications have been published. This is presumed to be due to the material’s solid form and the difficulty in its manufacturing process. Recently, we have successfully developed and manufactured a new producta whose INCI name is Quaternium-91 (and) cetrimonium methosulfate (and) cetearyl alcohol. The main component in this product is the Quaternium-91, which is di-behenyl imidazolinium methosulfate (Figure 1). Quaternium-91 is prepared by reacting a behenyl moiety with diethylenetriamine and cyclizing to produce the imidazoline. The imidazoline is then reacted with dimethyl sulfate to produce imidazolinium.