FORMULATING FOR MILDNESS 107
Sodium Cocoyl Isethionate (SCI), CH2
R O C CH2 O
R SO3Na O C O Unilever, 1955, Dove R O CH2
CH CH2 OH
SO3Na Alkyl Glyceryl Ether Sulfonate (AGES) P&G, 1952, Zest Figure 3: Syndet bar chemical structures. Low TFM soaps
The main component in soap which has effect on irritancy of soap is the total fatty matter which is normally 78%-80% in normal pure soaps. 78 TFM is equivalent to about 85% of the anhydrous soap. If the TFM is reduced then the total anhydrous soap is also reduced. It helps in the increase of the mildness of the product. Normally the reduced quantity of soap is replaced by an inert material such as talc, kaolin, starch, glycerin or simply water. Normally these types of soaps have reduced foaming properties and are prone to crack if not processed properly.
Transparent soaps Normally transparent soaps are of lower TFM with a range of 35%-75%. These are known as glycerin mild soaps. People think that the mildness is due to the presence of glycerin or other polyols in the soap but in fact the main factor affecting the mildness of the soap is its TFM. In the case of transparent soap manufactured by melt cast routes the formulations can be as shown in Table 7. From the previous two formulation
routes, one can see that the TFM in both the cases is lower than the normal soap. The other major component is the polyol which is highly water soluble and gets washed away during the washing process. The lower TFM seems to have more effect on mildness than any other factor.
Table 4: Syndet bar formulation. Ingredients
Anhydrous Soap Free Fatty Acid
Non Soapy Surfactants Salt
Water
Preservative Perfume
April 2019
Table 3: Typical formulation for Combar. Ingredients
%
Anhydrous Soap Free Fatty Acid
Non Soapy Surfactants Salt
Glycerin Water
Preservative Perfume
60.0 – 80.0 0.5 – 7.0 3.0 – 20.0 0.5 – 0.8 0.0 – 0.5
10.0 – 11.0 0.02 – 0.05 0.5 – 1.5
Liquid products Liquid cleansers are milder than bar soaps mainly because they have low levels of total surfactants and the pH can be adjusted to the skin pH. In the beginning liquid soaps were formulated using coconut fatty acids neutralised with potassium or ammonium salts. After the development of non-soapy anionic, nonionic and amphoteric surfactants the formulations of liquid cleansers were developed by using 10%- 15% active with low pH and high performance. In normal bar soaps it is fatty acid salt which is as high as 85%-86% while 10%-15% of these non-soapy actives are sufficient to give good lathering properties. A major component of bar soaps is structurant as sodium stearate and lathering components are only lower chain fatty acid soaps and unsaturated soaps. Krafft Point plays a very important role for the development of liquid products:
%
15.0 – 0.25 25.0 – 35.0 30.0 – 40.0 0.5 – 0.8 4.0 – 6.0
0.02 – 0.05 0.5 – 1.5
Soap based liquid formulation The Kraft point of sodium laurate is about 40-42°C and of sodium oleate is about 27- 28°C. But a mixture of the two at equivalent ratios is as low as 3-4°C. Potassium and ammonium salts further help in the solubility of the soap in water. 15%-20% of soap of laurate or laurate oleate mixture with sodium, potassium and ammonium salts can give a liquid which has good lathering properties. Polymers are
Table 5: General formulation for Low TFM soap. Ingredients
%
Anhydrous Soap Salt
Glycerin Water
Preservative Perfume
69.0 – 71.0 0.5 – 0.8 7.0 – 8.0
20.0 – 22.0 0.02 – 0.05 0.5 – 1.5
Table 6: Typical formula for translucent soap. Ingredients
%
Anhydrous Soap Polyols Water
Perfume
70 – 75 5 – 10
18 – 20 0.5 – 1.0
used to increase the viscosity of these types of solution. The pH of the liquid cleansers created by using soap is alkaline in the range of 9.0-9.5. The viscosity is increased by using polymers because use of salt does not convert the spherical micellar solution to rod micelles which is responsible for development of viscosity. The viscosity developed by using polymers is quite stable and does not change with the increase in temperature.
Non soapy actives Most of the liquid products in the world market are based on non-soapy actives because it is easier to get good, mild and high performing formulations. These types of formulations can be developed by using different anionic, non-ionic and amphoteric surfactants at the level of 10-15% active level. The main anionic surfactants used in these products are selected from a group of surfactants such as sodium lauryl ether sulfate, ammonium lauryl ether sulfonate, sulphosuccinates, sarcocinates etc. The main amphoteric surfactant used in liquid product is cocoamido propyl betaine. Other surfactants used in liquid products
PERSONAL CARE EUROPE CH2
C CH2 OH
H
Cocomonoglyceride sulfate (CMGS), Colgate Palmolive, 1948, vel
OSO3Na
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