64 FORMULATING FOR MILDNESS
nearly equal to the one of sulfate surfactants. There are two main application properties where sulfate surfactants are the benchmark: At first, the easy creation of viscosity via simple means like salt addition. Secondly, the excellent foaming behaviour wanted in most cosmetic applications.
Disodium Laureth Sulfosuccinate, Sodium Lauryl Sulfoacetate A typical formulation with Lumorol K 5019 (Disodium Laureth Sulfosuccinate, Sodium Lauryl Sulfoacetate) as main component is shown in Table 1. In formulations with this ingredient small amounts of a thickener (here: Oxetal VD 92) are needed. The final adjustment of the viscosity can be done by adding salt (sodium chloride). The formulation of Table 1 has a viscosity of about 1.000 mPa*s at pH 4.7 when salt is omitted. By adding salt the viscosity can gradually be increased. When 1% salt is added (complete formulation of Table 1) the viscosity is about 15.000 mPa*s.
The foam behaviour of formulations containing Lumorol K 5019 can be enhanced by adding surfactants of the Zschimmer & Schwarz Protelan-Series.1
In
the formulation shown in Table 1 Protelan MST 35 is used for this purpose. Protelan- Types are surfactants based on amino acids which improve the foam formation, the creaminess of the foam and are able to provide a smooth skin feeling.
Sodium Lauroyl Sarcosinate, Sodium Lauryl Sulfoacetate Lumorol K 5303 (Sodium Lauroyl Sarcosinate, Sodium Lauryl Sulfoacetate) can easily be thickened in combinations with cocamido propyl betaine. We recently found out that by using a surfactant blend of cocamido propyl betaine, lauroyl
4500 4000 3500 3000 2500 2000 1500 1000 500 0
5.1 5.2 5.3 5.4 pH Figure 8: Viscosity behaviour of the formulation based on Lumorol K 5601. PERSONAL CARE EUROPE 5.5 5.6 5.7 5.8
Table 2 : Body wash formulation based on Lumorol K 5601. Phase Ingredients
INCI Lumorol K 56011 A
Perfume Water
B
MerquatTM dermofeel® Preservative
2001 N Polymer2 PA-33
Cocamido Propyl Betaine, Sodium Lauroyl Sarcosinate, Sodium Lauryl Sulfoacetate Parfum (Fragrance)
Aqua (Water) Polyquaternium-47 Sodium Phytate, Aqua, Alcohol
W/W% 42.0
0.3 - 0.5 approx. 56.75 0.8
0.05 q.s.
Procedure: Combine A and stir to homogeneity. Combine B and stir to homogeneity. Add B to A and stir until homogenous. Control the pH value and adjust if necessary to approx. 5.6 (original).
Supplier: 1 Z&S 2 Lubrizol 3 Straetmans
sarcosinate and lauryl sulfoacetate in a special ratio no thickeners are needed to get viscous formulations. We introduced this surfactant mixture – Lumorol K 5601 (INCI: Cocamidopropyl Betaine, Sodium Lauroyl Sarcosinate, Sodium Lauryl Sulfoacetate) – at the in-cosmetics 2017 in London. It is a ready-to-use blend meaning no other surfactants are needed for rinse-off formulations (see Table 2). The viscosity simply can be adjusted by the pH- value (see Figure 8). Without pH- adjustment the formulation shown in Table 2 has a pH-value of about 5.6. By adding citric acid
the viscosity first rises to a maximum at a pH of about 5.4 and afterwards decreases with the pH-value. Starting from pH 5.1 the viscosity can be enhanced when sodium hydroxide solution is added: The change of the viscosity is a reversible process. Amino acid based surfactants provide rich and creamy foam. In formulations with Lumorol K 5303 and 5601 the addition of these surfactants is not needed as they are already included in the product (lauroyl sarcosinate).
Citric Acid (50%) NaOH (45%)
Special application of sulfoacetate / sulfosuccinate surfactants: Colour protection Hair fibres and skin have some structural similarities. This means cuticle and the stratum corneum of the epidermis both consist of dead cells and are protective layers. Completely analogous to the skin some surfactants like alkyl sulfates can be detrimental for hair fibres. The damaging potential of different surfactants can easily be proven by performing colour stability tests with permanent coloured hair. The ideal shade for an investigation is red. In the hair dyeing process hair fibres swell by the alkaline dyeing solution, so that the dyeing raw material and the oxidising agent can penetrate into the hair fibre. Via an oxidation process a macromolecular dyestuff is created which is distributed evenly over the whole fibre cross-section. Different surfactants have different potential to extract the dyestuff out of the hair fibre. By hair washing with different surfactants the colour of hair fibres fades to different degrees: The fading rate is a measure for the mildness of surfactants. We tested the colour fading of strands
of hair tresses via the L*a*b system expressed as ∆ E (Figure 9). ∆ E is the colour difference before and after 8 washing cycles. The lower ∆ E the better the colour protection of the shampoo, meaning the milder the surfactants used. The tested Zschimmer & Schwarz
‘Sulfate-free Colour Protection Shampoo’ (‘Z&S Shampoo’ in Figure 9) was introduced at in-cosmetics 2012 in Barcelona. It is very similar to the formulation shown in Table 1. The only difference is that another Protelan-Type was used as co-surfactant (Protelan AGL 95 (lauroyl glutamate solution) instead of Protelan MST 35). The test results (Figure 9) show indeed that a shampoo formulation based on ether sulfosuccinate and sulfoacetate (Lumorol K 5019) as major surfactants is not only mild to skin but also to hair fibres.
April 2018
Viscosity (20ºC) (mPa*s)
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