Troubleshooting aerosol stability discolouration separation damage to cans

I have recently moved to a company that manufacture aerosols, which as a cosmetic chemist, is not something I am knowledgeable about at all. 

The product in question is a multi surface polish and the formulation before my arrival (current) is:
Fragrance 0.4%
Benzalkonium chloride 0.2%
Ethanol 10.0%
Carnuba Wax 1.0%
Sodium Nitrite 0.1%
Sodium Benzoate 0.4%
Water 87.9%

Problems - unstable emulsion, visible splitting, sprays white and turns brown within 24 hours (sometimes staining the surface it is sprayed on to, rusting the can and splitting the can across the middle almost like a tide mark (this is seen after 12 months at 20'c). 

My proposed new formulation is: 

Water 43.95
Sodium Benzoate (Premix 1) 0.4
Water (Premix 1)  1
Sodium Nitrite (Premix 2) 0.4
Water (Premix 2)  1
Benzalkonium Chloride 0.2
Carnuba Wax 1
Fragrance (Premix 3) 0.4
Uvinul A Plus B (Premix 3) 0.4
Ethanol 10
Sorbitan Oleate (S80) 0.75
Water  41.95

My thoughts were - sorbitan oleate would help emulsification, Uvinul would help solubilise fragrance (if fragrance is potentially causing discolouration although it happens across a variety of fragrances). This formulation was a homogenous, white liquid. I gassed it in a can, sprayed and it was orange coming out of the can. 

I know the sensible next steps are to formulate and remove one material at a time to see if there are any reactions I am not thinking of.

I wanted to come here to see if anybody had any thoughts/ideas/solutions or something obvious that I am missing. Surfactants are my jam and I feel a little out out of my depth here. Is anybody able to offer some advice please? 

Comments

  • ariepfadliariepfadli Member
    edited October 2021
    Combination between quat ( benzalkonium chloride) with nitrite it not wise, since trace ammount of amine compound with nitrite will lead to formation nitrosamine compound

    For aerosol, since you use butane/propane gas for propelant, just make system solution or micible with hydrocarbon

    Do not make system emulsion or suspension, or your system will breakdown after hydrocarbon incjection

    For preservative, i will skip if my alcoholic compound more than 10%, because it already suficient for self preservation

  • Thank you so much for your feedback. So i'll remove benzoate and sodium nitrite. How would I make a system solution if wax isn't emulsified? Do you think nitrosamine would be responsible for discolouration? 

  • use another hydrocarbon or oxygenated solvent for solubilized wax, for carnauba i can used isopropanol or butanol, since this for industrial, there alot choices solvent that you can use

    you can see your mixture can be micible or into solution by try add hydrocarbon (paraffin oil) in to your mixture same volume with your propelant, if they stabile , thats good, if they separate, that also will happen in the can after you inject propelant
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