Rolf Puchta

Cationic surfactants in laundry detergents and laundry aftertreatment aids

Cationic surfactants have a positively charged nitrogen atom and at least one hydrophobic, long-chain substituent in the molecule. Because of their fabric-softening and antistatic properties, they are used as active materials in fabric-softening agents. Suitable cationic surfactants are mostly quaternary ammonium salts, and to a lesser extent, imidazolinium salts with two long hydrophobic alkyl chains. Alkylated, partly ethoxylated polyamines, amine amides, ester amines and di-quaternary compounds also have recently been used or proposed. Fabric softeners generally are aqueous dispersions of distearyl dimethyl ammonium chloride or tallow alkylated imidazolinium derivatives in concentrations of 1–9%. Concentrated fabric softeners have recently been pushed into the market as double, triple or 10-fold concentrates. Fabric softeners used in the forms of acrosol sprays, pads or sheets, are not used in the washing machine but can be used in the laundry dryer. The combination of laundry detergent and fabric softener is a single product is impaired by anionic surfactants normally contained in laundry detergents because they react with the cationics to form neural salts. With the so-called soft detergents, one attempts to circumvent these difficulties by means of special formulations, e.g., with nonionics or by using definite physical-chemical mechanisms. They represent a compromise with regard to detergency performance and softening effect.