Sorbitan monolaurate

Emulsions of fatty- and petroleum-based substances, both oils and waxes, of the o/w type are made by using blends of sorbitan fatty esters and their poly(oxyethylene) derivatives. Mixtures of poly(oxyethylene(20)) sorbitan monostearate (Polysorbate 60) and sorbitan monostearate are typical examples of blends used for lotions and creams. Both sorbitan fatty acid esters and their poly(oxyethylene) derivatives are particularly advantageous in cosmetic uses because of their very low skin irritant properties. Sorbitan fatty ester emulsifiers for w/o emulsions of mineral oil are used in hair preparations of both the lotion and cream type. Poly(oxyethylene(20)) sorbitan monolaurate is useflil in shampoo formulations (see Hairpreparations). Poly(oxyethylene) sorbitan surfactants are also used for solubilization of essential oils in the preparation of colognes and after-shave lotions. 

A series of sorbitol-based nonionic surfactants are used ia foods as water-ia-oil emulsifiers and defoamers. They are produced by reaction of fatty acids with sorbitol. During reaction, cycHc dehydration as well as esterification (primary hydroxyl group) occurs so that the hydrophilic portion is not only sorbitol but also its mono- and dianhydride. The product known as sorbitan monostearate [1338-41 -6] for example, is a mixture of partial stearic and palmitic acid esters (sorbitan monopalmitate [26266-57-9]) of sorbitol, 1,5-anhydro-D-glucitol [154-58-8] 1,4-sorbitan [27299-12-3] and isosorbide [652-67-5]. Sorbitan esters, such as the foregoing and also sorbitan monolaurate [1338-39-2] and sorbitan monooleate [1338-43-8], can be further modified by reaction with ethylene oxide to produce ethoxylated sorbitan esters, also nonionic detergents FDA approved for food use. 

NOTE Water-in-oil dispersants have an HLB of between 0 to 5. Examples include sorbitan tristearate (HLB = 3.5) and sorbitan monolaurate (HLB = 4.3). 

Fatty Acid Esters. Defoamers that are more environmentally acceptable than convential products are based on fatty acid esters of hydroxy alcohols, such as sorbitan monooleate [1908] or sorbitan monolaurate in combination with diethylene glycol monobutyl ether as a cosolvent [451]. These defoamer compositions are as effective as conventional materials, for example, those based on acetylenic alcohols are less toxic, especially to marine organisms, and are readily biodegradable. The defoamer compositions are used in water-based hydrocarbon well fluids during oil/gas well drilling, completion, and workover, especially in marine conditions. 

The HLB of a relatively pure poly(oxyethylene) adduct can be calculated from theoretical data [37]. For these agents the HLB is an indication of percentage by mass of the hydrophilic portion, divided by five to give a conveniently small number. For example, if the hydrophilic portion of a purely hypothetical nonionic agent accounted for 100% of the molecule (such a product cannot, of course, exist), its HLB is 20. Similarly, a more plausible product in which 85% of the molecule is accounted for by the hydrophilic portion has an HLB of 85/5 = 17. The ICI Americas Inc. method of calculating the theoretical HLB of a sorbitan monolaurate nonionic having 20 oxyethylene units per molecule is given in... 

As explained earlier, however, the actual constitution of a surfactant rarely conforms to its nominal structure. Consequently the theoretical method of calculation is of limited utility, practical methods being more reliable. The HLB value may be determined directly by analysis or by comparison with a range of surfactants of known HLB values. An analytical method for the sorbitan monolaurate described above uses Equation 9.2 [37]. 

The formation of ethylcellulose nanoemulsions by a low-energy method for nanoparticle preparation was reported recently. The nanoemulsions were obtained in a water-polyoxyethylene 4 sorbitan monolaurate-ethylcellulose solution system by the PIC method at 25 °C [54]. The solvent chosen for the preparation of the ethylcellulose solution was ethyl acetate, which is classed as a solvent with low toxic potential (Class 3) by ICH Guidelines [78]. Oil/water (O/W) nanoemulsions were formed at oil/ surfactant (O/S) ratios between 30 70 and 70 30 and water contents above 40 wt% (Figure 6.1). Compared with other nanoemulsions prepared by the same method, the O/S ratios at which they are formed are high, that is, the amount of surfactant needed for nanoemulsion preparation is rather low [14]. For further studies, compositions with volatile organic compound (VOC) contents below 7 wt% and surfactant concentrations between 3 and 5 wt% were chosen, that is, nanoemulsions with a constant water content of 90% and O/S ratios from 50 50 to 70 30. 

Figure 6.1 O/W nanoemulsion region in the water/polyoxyethylene 4 sorbitan monolaurate/ [10%ethylcellulose (EC10) in ethyl acetate] system at 25 °C. Reproduced with permission from [54].

Figure 6.3 Cryo-TEM image of the nanoemulsions of the water/polyoxyethylene 4 sorbitan monolaurate/[10% EClOin ethyl acetate] system with an O/S ratio of70 30and a water content of 90 wt%.

Sorbitan monolaurate, 4 710 Sorbitan monooleate, 4 710 Sorbitan monopalmitate, 4 710 Sorbitan monostearate, 4 709 Sorbitan sequioleate... 

D Polyoxyethylene carbohydrate-20 Fatty alkylester D1 Polyoxyethylene sorbitan monolaurate, TWEEN... 

Sorbitan monolaureate Sorbitan monooleate Sorbitan monopalmitate Sorbitan monostearate Sorbitan tristearate Stannous chloride Stearyl tartrate Succinic acid Sucroglycerides... 

Surfactants (nonionic)— polyethylene sorbitan monolaurate (Tween 20, Tween 80), pluronic, Triton, sodium dodecyl sulfate (SDS)... 

Slow release rates and remarkable long shelf-life (months) were obtained compared to typical multiple emulsions stabilized by two short surfactants (SMO and polyoxyethylene (20) sorbitan monolaurate). Finally, the long lifetime of the emulsions allowed study via diffusing wave spectroscopy (DWS) of the interactions between the droplets and the globule surface [37],... 

Figure 7 indicates the phase behavior of SOW systems containing ternary nonionic surfactant mixtures that in turn contain a very hydrophilic surfactant (Tween 60 Sorbitan -i- 20 EO stearate), a very hpophihc surfactant (Span 20 Sorbitan monolaurate), and an intermediate (Tween 85 Sorbitan 20 EO trioleate or Nonylphenol with an average of 5 EO groups). The two intermediate surfactants correspond exactly to an optimum formulation in the physicochemical conditions, i.e., they exhibit three-phase behavior with the system 1 wt. % NaCl brine-heptane-2-butanol. As the intermediate hy-drophihcity surfactant is replaced by an equivalent mixture of the extreme ... 

Sorbitan monolaurate, deriv. of sorbitol/carboh. ester and stabilizer in... 

Tween 20 (polyoxyethylene (20) Sorbitan Monolaurate, Wako Pure Chemical Industries, Ltd, Osaka, Japan). 

The phase map shown in Figure IB represents the skin permeation enhancement activity of the formulations containing binary mixtures of lauryl sarcosinate and sorbitan monolaurate at different concentrations and compositions. The region of maximum activity lies in a very narrow range of compositions. For such a nonlinear activity-composition behavior, it is very important to probe the binary phase map at as fine a resolution as possible, thus increasing the experimentation volume. 

Figure 4 (A) Schematic of in vitro skin impedance guided high-throughput screening tool, INSIGHT. (B) Skin permeability skin impedance correlation for 1.5%wt/vol. menthol (open squares), 1.5%wt/vol. lauric acid (filled triangles), 1.5%wt/vol. Brij 35 (open circles), 1.0%wt/vol. Lauryl sarcosinate (filled circles), 1.0%wt/vol. sorbitan monolaurate (open triangles), and 1.5%wt/vol. benzyldodecyldimethyl ammonium chloride (filled squares) in 1 1 PBS EtOH. Abbreviation PBS EtOH, phosphate buffered saline ethanol.

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