Syndet bar

The solubihty characteristics of sodium acyl isethionates allow them to be used in synthetic detergent (syndet) bars. Complex blends of an isethionate and various soaps, free fatty acids, and small amounts of other surfactants reportedly are essentially nonirritant skin cleansers (66). As a rule, the more detersive surfactants, for example alkyl sulfates, a-olefin sulfonates, and alkylaryl sulfonates, are used in limited amounts in skin cleansers. Most skin cleansers are compounded to leave an emollient residue on the skin after rinsing with water. Free fatty acids, alkyl betaines, and some compatible cationic or quaternary compounds have been found to be especially useful. A mildly acidic environment on the skin helps control the growth of resident microbial species. Detergent-based skin cleansers can be formulated with abrasives to remove scaly or hard-to-remove materials from the skin. 

Syndet bar soaps were developed for sensitive skin. Their pH value usually is around 5-6, far less than that of the normal soaps (pH 9-10), which is the reason for the latter causing dermal fissures with people who need frequent washing of their hands. The manufacture of syndet bar soaps requires special attention to methodology. A typical raw material composition of a syndet bar soap is as follows ... 

Koch and Kligman s [70] assessment of syndet bar soaps will be discussed in Sec. VI. To repeat their conclusion, the syndet bar soap containing a sulfo-succinate elicited the weakest skin reaction. 

FIGURE 31.4 The amount of water soluble free amino acids (a) and cholesterol (b) removed from porcine skin after a single wash with a syndet bar versus a soap bar. Results show significantly higher removal from the soap washed site. 

Similar to water plasticizing the proteins, fluid lipids in the bilayer lipids are implicated in the elasticity of the corneum. Removal of fluid lipids can make the corneum brittle. For example, solvent treatment of the corneum to remove fluid lipids has been shown to make the SC brittle.29 It has been shown that soap treated corneum behaves somewhat similarly to the solvent treated corneum in the sense that both exhibit a brittle fracture under tension. In contrast, syndet bar treated corneum behaves more like water treated corneum exhibiting a more elastic and pliable structure. 

As cleansers moved to syndet bars to liquid detergent systems, they became more and more innocuous in the short term and required exaggerated exposure to elicit measurable dryness and damage response. However, as cleansers have begun to move toward active moisturization, methods traditionally associated with lotion-testing can be applied. 

With regular cleansers, a procedure like FCAT (Forearm Controlled Application Test) provides good sensitivity to varying discriminate products based on their drying potential. Looking at soap versus syndet bar, we can compare three clear trends in Figure 31.13 an increase in the visible appearance of dry skin over time, a concomitant decrease in the equilibrium hydration state of the skin, and an increase in the disruption to the moisture barrier evidenced as an increase in TEWL. In all the three measures, the syndet is seen as milder and less drying. 

FIGURE 31.13 FCAT study comparing soap and syndet bars shows soap induces higher visible dryness, lower hydration state, greater loss of barrier function, and increased erythema. 

Syndet bars contain no soap and, again, often rely on SCI to give mild cleansing, often in combination with sulphosuccinate and alkyl sulphates. Syndets have a small share of the cleansing bar market and are often marketed as a care product, rather than as a simple cleansing bar. 

The C12-C14 alcohol finds special application as lubricant additives and in the formulation of bearing and hydraulic oils. The C16-C18 fatty alcohol finds application as a defoamer, as a solubility retarder for syndet bars, and as a consistency giving factor in creams, lipstick, pastes, and polishes. 

Definition Sodium salt of the lauric acid ester of isethionic acid Empirical C14H28O5S Na Formula CH3(CH2)ioCOOCH2CH2S03Na Uses Antistat, surfactant in cosmetics, syndet bars, liq. skin cleansers Sodium lauroyl lactylate CAS 13557-75-0 EINECS/ELINCS 236-942-6 Synonyms Dodecanoic acid, 2-(1-carboxyethoxy)-1 -methyl-2-oxoethyl ester, sodium salt Sodium 2-(1-carboxylatoethoxy)-1-methyl-2-oxoethyl laurate Definition Sodium salt of the lauric acid ester of lactyl lactate... 

Laundry bars can be divided into two main categories—soap bars and syndet bars. In some markets, combars are available, which contain both soap and synthetic detergent Soap bars are generally more mild to the skin than syndet bars, but syndet bars are usually more efficacious, especially at high water hardness. Consumers will choose a laundry bar based on their habits and practices, desired level of efficacy, and their economic situation. 

Soap bars are more basic, and consist largely of saponified animal tallow or vegetable oils. The choice of fats and oils is often dictated by local availability. In some soap bars, other ingredients are included, such as fragrance, pigments, clays, soda ash, and silicates. The quality of the final product is a function of the oil used. Formulation examples for both soap and syndet bars are shown in Table 4.1. 

Syndet bars consist of similar ingredients as powdered detergents. Surfactants, builders, bright-eners, antiredeposition agents, and perfumes are some of the rntgor componeuts. 

Soap scum cleaners are by far the largest group of bathroom cleaners. Soap scum is a prevalent problem in almost any bathroom. Hard water deposits are more of a problem in very hard waters area such as Europe, but the precipitatiou of soap caused by hard water salts can become a problem even in areas with moderate hard water. This tends to be less of a problem in households that use shower gels or synthetic detergent (syndet) bars, because the detergents used in these products are... 

Normal soaps Filled low-TFM soaps T ransparent soaps Superfatted soaps Syndet bars... 

SCI, sulfosuccinates, AGES, and CMOS are the main synthetic detergents used in com-bars and syndet bars. The KP of surfactants plays a very important role in the selection of a particular surfactant for the product. Vel Beauty Bar, launched by Colgate in 1948, was the first syndet bar, followed by Zest and Dove in 1952 and 1955, respectively, by P G and Lever Brothers. 

Syndet bars are nonsoap-based materials and their active ingredients can be of widely different types. They can be derived from both natural oils and fats through chemical modification of their fatty acids, or the petrochemical industry. 

Syndet bars contain a high percentage of fillers, which can act as inert materials, that is, pure fillers or more often as plasticizers or binders. 

The production of syndet bars is to some extent more difficult than the manufacture of normal soaps. The difficulty is always in the area of refining and stamping. Properly formulated syndet bars can be produced with standard soap-finishing line machinery. 

Refining the syndet base and all the additives into a homogeneous uniform mixture is the most critical and difficult processing step in syndet bar manufacturing. 

To choose the best-suited refining system for a particular syndet bar production, the formula must be well established in advance and the moisture content of the syndet base and final syndet bar has to be kept within weU-defined close ranges. 

The purpose of conditioning is to harden the slug surface before stamping. Most syndet bar formulations are sticky and, at times, soft for trouble-free stamping even with the use of refrigerated (chilled) stamping dyes. 

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