FORMULATING FOR MILDNESS 63
40 35 30 25 20 15 10 5 0
SLS
SLES (2EO) LUMOROL K 5303 LUMOROL K 5303: CAPB 1:1
Figure 6: Mean index of ocular irritation (test results: Z&S): SLS: Sodium lauryl sulfate, SLES (2 EO): Sodium laureth-2 sulfate, CAPB: Cocamido propyl betaine, indicated ratio: Related to active matter.
This is the case for all sulfoacetate molecules but only for parts of the sulfosuccinate molecules (Structure 1 in Figure 5). As a result alkyl sulfosuccinates (n = 0 in fig. 2) are not long-term stable in aqueous formulations of about pH 5 especially when the temperature is 40 °C or above. The hydrolysis stability under these conditions is enhanced when instead of a fatty alcohol, a fatty alcohol ethoxylate is used as reactant (ether sulfosuccinates).5 The combination of sulfosuccinates with other anionic surfactants provides an additional stability contribution: In these cases the hydrolysis of sulfosuccinates in acidic formulations is drastically reduced.5 Zschimmer & Schwarz took advantage of all this knowledge to develop its sulfate- free surfactant portfolio based on sulfosuccinates and sulfoacetates.
Products based on alkyl sulfosuccinates and / or alkyl sulfoacetates
The Zschimmer & Schwarz sulfate-free surfactants based on sulfonates are on the
INCI Skin irritation
Sodium Lauryl Sulfate (2% a.m.) Disodium Lauryl Sulfosuccinate (2% a.m.)
Disodium Laureth Sulfosuccinate (3E0) (2% a.m.) CAPB (2% a.m.)
LUMOROL K 5019 (2% a.m.) LUMOROL K 5303 (5% a.m.)
Figure 7: Patch test on human skin (test results: ISPE: Institute for skin and product evaluation), A. m.: Active matter
one hand sulfosuccinates. On the other hand they are sulfoacetate blends with ether sulfosuccinate or lauroyl sarcosinate. The reason for mixing sulfoacetate with other surfactants is that even low concentrated aqueous alkyl sulfoacetate solutions are difficult to handle slurries. By adding suitable surfactants like ether sulfosuccinates or lauroyl sarcosinates, long- term stable aqueous surfactant solutions containing alkyl sulfoacetates can be created.
Zschimmer & Schwarz sulfonate surfactants in detail
Setacin F Spezial Paste (INCI: Disodium Lauryl Sulfosuccinate) is a pasty product with excellent foaming properties. It is PEG-free (n = 0 in figure 2) and therefore tends to hydrolyse in low viscous acidic aqueous solutions (even at pH 5) especially at a temperature of 40 °C and above. The recommended applications for the Setacin F Spezial Paste are in emulsions (e. g. facial cleansing creams, shower creams and shampoo formulations) and for hand cleaning pastes.
Table 1 : Shampoo formulation based on Lumorol K 5019. Phase Ingredients
Lumorol K 50191 A
Amphotensid B 51 Protelan MST 351
Perfume
Oxypon 21451 Oxetal VD 921 MerquatTM Water
B 2001 N Polymer2
Sodium chloride Citric acid
Preservative
Disodium Laureth Sulfosuccinate, Sodium Lauryl Sulfoacetate
Cocamidopropyl Betaine
Sodium Myristoyl Sarcosinate, Sodium Methyl Cocoyl Taurate
Parfum (Fragrance) PEG-15 Glyceryl Isostearate
PEG-90 Glyceryl Isostearate, Laureth-2 Polyquaternium-47 Aqua (Water)
Sodium Chloride Citric Acid
W/W% 21.0
9.0 4.0
0.5 0.3
Approx. 0.2 0.6
Up to 100.0 1.0
Approx. 0.45 q.s.
Procedure: Combine A and stir to homogeneity. Add B to A and stir until homogeneous. Control the pH value and adjust if necessary to approx 4.7 (original).
Supplier: 1 Z&S 2 Lubrizol April 2018
Setacin 103 SB (INCI: Disodium Laureth Sulfosuccinate) is an ether sulfosuccinate. It is used as basic material for the formulation of bath preparations, hair shampoos and liquid soaps. Setacin 103 SB produces a fine-bubble stable lather. Lumorol K 5019 (INCI: Disodium Laureth Sulfosuccinate, Sodium Lauryl Sulfoacetate) and Lumorol K 5303 (INCI: Sodium Lauroyl Sarcosinate, Sodium Lauryl Sulfoacetate) are surfactant blends for the formulation of hair shampoos and shower and bath preparations. Both can be used as main surfactant component in rinse-off formulations. In acidic solutions they are stable up to a pH of about 4.5. Lumorol K 5303 is additionally PEG-free. The backbone of all of the surfactants mentioned above is completely based on natural components (fatty acids, fatty alcohols, acetic acid, succinic acid and the amino acid sarcosine) with one exception: PEG in ether sulfosuccinates. Test results concerning skin (patch test on human skin) and eyes (mean index of ocular irritation) are shown in Figures 6 and 7. Figure 6 shows that Lumorol K 5303 is milder than lauryl sulfate (SLS) and laureth sulfate (SLES) in an eye irritation potential test (MIOI). In combination with cocamido propyl betaine (CAPB) it gets even less irritating. Figure 7 shows patch test results on human skin: Sulfoacetate and sulfosuccinate surfactants are much milder than alkyl sulfates. Lumorol K 5303 performs best of all tested surfactants even when the active matter is 2.5-fold in comparison to the other surfactants. Figure 7 additionally shows that ether sulfosucccinates are not only more stable to ester hydrolysis in acidic formulations but also milder than alkyl sulfosuccinates.
Foam and viscosity in sulfoacetate / sulfosuccinate based surfactant systems
Customers expect that the performance of sulfate-free surfactants is equal or at least
PERSONAL CARE EUROPE
MIOI (Mean Index of Ocular Irritation)
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