In situ TEA-Stearate Cream Scale Up

I did a search through the forum and haven't had a ton of luck thus far, but I was hoping for some help on this issue. 

We have a stearic acid - triethanolamine in situ emulsion which usually has no issues when scaled to 160 kg. 

However, we used a much larger Silverson to produce this batch and have a super thick, almost curdled looking cream which normally would be thinner, almost lotion-thin. This is body butter level thick. It was mixed for a very long time and still was retaining heat the next day. 

I would assume too much heat and too much mixing would thin this out?? Thank you for any help!


  • in situ.... meaning in place of...

    in place of what?  

    Stearic acid : TEA  2:1
  • lewhitaklewhitak Member
    edited July 2020
    @chickenskin ;
    in situ as in "in place"--like this:
    "In situ is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in many different contexts."

    So, we don't react the TEA and stearic acid to form TEA-stearate and then proceed with an O/W emulsion.

  • I did a bit more experimenting and right now the pH is about 6.7. I am assuming we just have too much stearic acid present versus the TEA-stearate at this pH. 

    I guess the next move would be adding more TEA, but previously it passed QC at this pH and never looked this thick. 

    I wonder why we didn't get the same TEA-stearate formation as previous batches, even with no formula changes?

    The only process change was maybe an increase in shear and possibly heat. We usually homogenize using a Silverson during the initial combining of the oil and water phase, then switch to cool-down mixing with a propeller blade. 

    This time, they mixed continuously with a Silverson head too large for the vessel, generated more continuous heat, and allowed to cool by standing not propeller mixing.  
  • @lewhitak

    Is it possible that the additional heat caused a significant amount of your water phase to evaporate? That would explain it being thicker - it's surprising what a few percent less water can do to the viscosity. It'll be tricky to gauge the right amount to add back in though

  • @LincsChemist

    That is really helpful, I didn't think of it from that point of view. Thank you!
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