Phosphate-free detergent composition

DETAILED DESCRIPTION OF THE INVENTION The imido-bis-sulfates (salt of imido-bis-sulfuric acid) used in the present detergent composition are the compounds represented by the general formula (M.
sup.
1 SO.
sub.
3).
sub.
2 NM.
sup.
2, wherein M.
sup.
1 stands for sodium, potassium, lithium or ammonium and M.
sup.
2 stands for hydrogen, sodium, potassium, lithium or ammonium and the mixtures thereof; among these compounds, trisodium imido-bis-sulfate wherein both M.
sup.
1 and M.
sup.
2 are sodium (hereinafter referred to as TSIS) is preferred.
The imido-bis-sulfate, when it is formulated with a surfactant together with an N,N-bis(carboxymethyl)glutamate and/or a salt of N,N-bis(carboxymethyl)phenylalanine, enhances the cleaning performance due to a synergistic effect of the formulated components as shown in FIGS.
1 and 2.
The palmitate salts (salts of palmitic acid) used in the present invention are sodium or potassium salt of palmitic acid and mixtures thereof, and sodium palmitate is generally preferred.
The zeta-potential value of sodium palmitate determined by means of a electrophoretic method is -52 mV, which is a larger negative value than those of other fatty acid salts; e.
g.
, about -38 mV of sodium stearate, about -37 mV of sodium laurate, about -34 mV of sodium myristate.
The palmitate salt having such a large zeta-potential value, when incorporated into a surfactant together with the imido-bis-sulfate and an N,N-bis(carboxymethyl)glutamate, further enhances the detergency of the resulting composition as shown in Reference Example 3 and FIG.
3.
The palmitate salt can also be used to enhance detergency in the form of its mixture with other fatty acid salts.
By these fatty acid salts are meant sodium, potassium or ammonium salts of saturated or unsaturated fatty acids preferably having 12 to 18 carbon atoms.
The saturated fatty acids include lauric acid, myristic acic, stearic acid, etc.
and the unsaturated fatty acids include oleic acid, linolic acid, linolenic acid, ricinoleic acid, etc.
The salts of N,N-bis(carboxymethyl)glutamic acid used in the present invention are normally sodium or potassium salts of N,N-bis(carboxymethyl)glutamic acid such as the mono-, di-, tri- and tetra-sodium or potassium salts thereof, and the mixtures of these salts