Lime soap dispersants

Amidosulfonates. Amidosulfonates or A/-acyl-A/-alkyltaurates, are derived from taurine, H2NCH2CH2S02Na, and are effective surfactants and lime soap dispersants (Table 9). Because of high raw material cost, usage is relatively small. Technically, amidosulfonates are of interest because they are stable to hydrolysis, unaffected by hard water, and compatible with soap. They have been used in soap—surfactant toilet-bar formulations. With shorter, acyl groups, they make excellent wetting agents. 

Sulfated Acids, Amides, and Esters. Reaction with sulfuric acid may be carried out on fatty acids, alkanolamides, and short-chain esters of fatty acids. The disodium salt of sulfated oleic acid is a textile additive and an effective lime soap dispersant. A typical sulfated alkanolamide stmcture is CiiH23C0NHCH2CH20S03Na. Others include the sulfates of mono and diethanolamides of fatty acids in the detergent range. The presence of... 

A number of these stmctures are offered commercially by BASE Corporation under the trade name Tetronic polyols. The products are similar to oxygen block polymers. Although not strongly surface active per se, they are useful as detergents, emulsifiers, demulsifiers, defoamers, corrosion inhibitors, and lime-soap dispersants. They are reported to confer antistatic properties to textiles and synthetic fibers. 

However, in a 1963 lecture it was pointed out that ether soaps had special characterics [10], i.e., good biodegradability, mildness to the skin, and less corrosiveness to metals, and that we should expect these soaps to play an important role in the future. However, the real breakthrough of the ether carboxylates came in the 1980s, when environmental properties of surfactants became even more important along with other properties of ether carboxylates such as chlorine stability, anticorrosiveness, lime soap dispersibility, electrolyte stability, alkaline stability, and so on. 

Schulze [51] described an extensive study on C12-C14 ether carboxylic acid sodium salt (4.5 mol EO) in terms of surface tension, critical micelle concentration (CMC), wetting, detergency, foam, hardness stability, and lime soap dispersing properties. He found good detergent effect compared to the etho-xylated C16-C18 fatty alcohol (25 mol EO) independent of CaCl2 concentration, there was excellent soil suspending power, low surface tension, and fewer Ca deposits than with alkylbenzenesulfonate. 

The lime soap dispersing properties are, like all ethoxylated products, dependent on the fatty chain and the EO degree [61,64] a longer fatty chain and a higher EO degree improves the lime soap dispersing effect (Fig. 3). 

The COONa group in the ether carboxylate has a positive effect on the lime soap dispersing properties [61,64] (Table 4). Stroink [61] and Meijer [64] also describe the good acid, alkali, and electrolyte stability of some ether carboxy-... 

FIG. 3 Lime soap dispersing power of some alkyl ether carboxylates compared to other surfactants (DIN 53903). AEC, alkyl ether carboxylate AMEC, amidether carboxylate CAPB, cocamidoproplylbetaine OEC, oleyl ether carboxylate SLES, sodium lauryl ether sulfate. % surfactant soap = % surfactant calculated on the soap needed to disperse the lime soap. (From Refs. 61 and 64.)... 

TABLE 4 Lime Soap Dispersing Power of Some Oleyl Ether Carboxylates Compared to Oleyl Ethoxylate (DIN 53903)... 

Due to the good lime soap dispersing properties it is possible to improve the foaming properties of hard water-susceptible surfactants. Improvement of the formulation of a fatty acid soap by laureth-17 carboxylic acid, sodium salt [57,62], and an amidether carboxylate [62] has been described. 

Lime soap dispersing power Good dermatology Hard water stability... 

Because of improved mildness and lime soap dispersing properties ether carboxylates are also used in fatty acid soap-containing products like soap bars and liquid soaps [57,62] a foam improvement in hard water takes place. 

For use in soap bars, a smooth feel after washing, mildness, lime soap dispersing effect, and foaming properties are important [36,104-106]. In transparent soap bars the clarity will be improved [104], in half-syndet soaps mildness and foam are increasing [105,106] combined with a smooth feel after use [105], With lauryldiglycolamidether carboxylate a good foaming and mild syndet soap has been formulated [36]. 

Ether carboxylates are used not only in powdered detergents but in liquid laundry detergents for their hard water stability, lime soap dispersibility, and electrolyte stability they improve the suspension stability and rheology of the electrolyte builder [130,131]. Formulations based particularly on lauryl ether carboxylate + 4.5 EO combined with fatty acid salt and other anionic surfactants are described [132], sometimes in combination with quaternary compounds as softeners [133,163]. Ether carboxylates show improved cleaning properties as suds-controlling agents in formulations with ethoxylated alkylphenol or fatty alcohol, alkyl phosphate esters or alkoxylate phosphate esters, and water-soluble builders [134]. 

The lime soap dispersing properties are very important for the dispersal of Ca soap, which is used to achieve among others, lower foam [60,64,66,181]. In addition, nontoxicity as well as good dermatological properties and biodegradability have been factors in the increased use of ether carboxylates [60,66]. 

FIG. 25 Lime soap dispersing ability of linear alkylbenzenesulfonate-a-olefmsulfonate (LABS-AOS) mixed surfactant system. LSDA, lime soap dispersion ability. (From Ref. 3.)... 

The ability to disperse the calcium soap formed from a given amount of sodium oleate has been studied for a number of a-sulfo fatty acid esters with 14-22 carbon atoms [28,30]. In principle, the lime soap dispersion property increases with the number of C atoms and the dissymmetry of the molecule. Esters with 14 C atoms have no dispersion power and in the case of esters with 15-17 carbon atoms the least symmetrical are the better lime soap-dispersing agents. However this property does not only depend on the symmetry but on the chain length of the fatty acid group. For example, methyl and ethyl a-sulfomyristate have better dispersing power than dodecyl propionate and butyrate. The esters with 18 and more carbon atoms are about equal in lime soap dispersion power. Isobutyl a-sulfopalmitate is the most effective agent under the test conditions. 

The applications of a-sulfo fatty acid esters are widely spread as for other surfactants. They can be used in detergents, cleansers, and cosmetic products as well as in the building industry and for the production of synthetic materials and agrochemicals. The main properties for these applications are surface activity, wetting ability, hard water stability, lime soap dispersion power, and good human and environmental safety profiles. 

When secondary or primary amines are used in place of ammonia the corresponding dialkylaminomethylenephosphonic acids (7) or alkyliminobismethyl-enephosphonic acids (8) are formed. These are used as lime soap dispersants and solubilizers of water in organic solvents [131-135]. 

Aminopolymethylenephosphonic acids are obtained when in place of monoamine di- and polyamines are used. Best known is ethylenediiminotetra-methylenephosphonic acid, used as a lime soap dispersant [131-133] see Eqs. (78) and (79) ... 

IV. Chemical Structure of Lime Soap-Dispersing Agents 637... 

V. Detergency of Soap-Lime Soap Dispersant Combinations 638... 

II. SYNTHESIS OF LIME SOAP DISPERSANTS A. Fatty Esters of Isethionic Acid... 

Another class of compounds which show good lime soap-dispersing ability when combined with soap was the A-methyltaurides of fatty acids, first produced by the I.G. Farbenindustrie under the name of Igepon T [5],... 

Stein and Baumann [14] studied the hydrolytic stability of MES and found the hydrolysis rate to be very slow in the pH range of 3-9.5 even at a temperature of 80°C. MES possesses good washing, foaming, and lime soap dispersing properties as well as ready biodegradability and a low acute oral toxicity. 

---