HEC (hydroxyethylcellulose) dissolution problem

I am working on a roll-on formulation and I am using HEC as a thickener at 0.9% in nothing but both at cold and warm water (50 'C) but I couldn't dissolve it. I mixed it with mechanical stirrer at 500 rpm sometimes even more. Is it beacause my chemicals or my methode ? I used two different HEC but ı couldn't dissolve both anyway. To conclude if you have any suggestions I would be so glad, thanks in advance.   

Comments

  • ketchitoketchito Member
    @filiz You need to slowly add the HEC directly to the vortex formed during mixing at moderate-high speed. I'd go at 1000 rpm or even more, and leave it mixing for at leat 10 min. One thing that improves mixing is adding some base (eg., Sodium hydroxide, TEA), to help dissolve the outer shell that recovers polymer particles.  
  • PerryPerry Administrator, Professional Chemist
    And cold water is preferred. 
  • filizfiliz Member
    Thank you for your advices. Increasing pH realy works with cold water, I go with 1000 rpm for a hour, nevertheless I couldn't completely dissolve HEC. If you have any other solutions I would be so glad...
  • PaprikPaprik Member
    edited August 2
    Hi,

    you can add HEC straight into cold water and either high shear it for a prolong time or neutralise (alkaline) it to pH>7. Once fully hydrated, you can bring the pH lower again. 

    Hope that helps.
  • @filiz Add first the HEC with high mixing. Mix for 5 minutes, and only then, increase the pH (Sodium hydroxide works well, but use only a little amount -don't stop mixing while adding it-). 
  • filizfiliz Member
    @Paprik
    @ketchito
    thanks for your help.. Mixing high level and adjusting to neutralise has worked but the image i get is blurry even though it was mixed for 2 hours. What do you think?
  • filizfiliz Member
    Obsevation:
    1. Aqua + Hydroxyethyl Cellulose (%2) + TEA (Opaque white, fairly solid)
    2. Monoprpylene Glycol (4,5) + Alcohol (%20) (transparet but bullry) 

  • @filiz Could you switch from TEA to Sodium Hydroxide, to see if it improves? Also, any chance the turbidity might be caused by bubbles (since you're adding high levels of HEC, viscosity might make bubbles formed during mixing, hard to be released). 
  • filizfiliz Member
    @ketchito
    What do you think the ideal amount of HEC should be? And should I keep the rpm low to avoid bubbles?
  • @filiz I used to have few issues with HEC back in the day, and I found out some literature. Perhaps this one could help you: http://doorirng.com/data/Personel care cellosize.pdf.

    There is a method in that brochure that includes heating, and that could help get rid of the bubbles. Good luck!
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