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Body Wash- Viscosity drop - Disodium Cocoamphodipropionate?
I have inherited a body wash formula that is based on the following surfactants
ALS (28% active) - 30%
Disodium Cocoamphodipropionate (40% active) - 15%
Cocamidopropyl betaine (CAPB) (30% active) - 9%The formula is very thick and has a pH of 6.2 - 6.5.
My goal for this formula is to replace the current Kathon CG (isothiazoline type) preservative with a preservative that is “more acceptable” to marketing.
I have successfully used Euxyl K701 in a number of other surfactant products but this preservative needs a pH below 6. When I try to reduce the pH of this formula using citric acid the viscosity decreases significantly.
I have tried reducing the Disodium Cocoamphodipropionate as this ingredient has a high pH (9.5 to 10) and this helps to recover some of the decreased viscosity but still does not bring the viscosity to the high levels I had before.
Does any one have any insight into this phenomenon or any other suggestions to save this formula. I was thinking it might be related to pKa but am not sure.
The formula also contains Dissolvine GL, Polyquaternium-7, hydrolysed wheat proteins, Euperlan PK3000AM (pearlescent), Lamesoft PO65 and citric acid.
Thanks
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3 Replies
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Yes, sure. I’m quite familiar with this type of combo except that I use sodium cocoamphoacetate.
Your problem with viscosity is simply the salt curve in action. Salt works because of electrolytes (not the same as the ones in Brawndo) and when you add citric acid, you are adding a lot of ions, or electrolytes. The Dissolvine is also an electrolyte.
CAPB has 4.5-6%; the Disodium Cocoamphodipropionate is not listed as containing salt, so you’re probably better off increasing rather than decreasing the amount, and decreasing the CAPB in proportion, so as to reduce the salt and allow for the addition of more citric acid.
In any case a pH of 6.5 is dangerously high for a combo with ALS, it is an ammonia producer at or above that pH. Most of my shampoos contain ALS and ALES so I keep the pH around 5 maximum.
Try Disodium Cocoamphodipropionate (40% active) - 20%
Cocamidopropyl betaine (CAPB) (30% active) - 4%
and then in the lab, titrate it against citric acid for pH = 6, 5.5, 5, and 4.5 using 4 samples. Check the viscosity of each sample and draw a rough salt curve. Then you will know what’s going on. -
I agree. Run a salt curve analysis.
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Thanks. I think you might be right. It is often the simplest answer.
@Belassi - Love the Brawndo reference
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