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Alternative base to sodium hydroxide
Due to the HazMat shipping on sodium hydroxide, I find that buying sodium carbonate is about 3 times cheaper. Also, I find that sodium carbonate would possibly be much safer to handle. Are there any downsides to making emulsions using Arlacel 165 without the use of acrylate polymers with sodium carbonate (not the bicarbonate) as the pH adjusting compound? What about Arlacel 165 combined with 0.5% of Ultrez 30?
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22 Replies
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You could use carbonates as base but they form CO2 once fully reacted. Hence, if you don’t mind a bubbly product and a workspace full of slimy foam…Depending on the used acid (e.g. acrylate), full reaction is slow and in order to avoid formation of gas, you could add twice the amount needed and end up with one part neutralised acid/polymer, one part sodium bicarbonate, and no bubbles. This means, given you did the maths right, that sodium carbonate is now only 1.5 times cheaper, you might run into difficulties due to an increased amount of dissolved electrolytes, might have to spend more money on preservatives since your product will be pH >8, and, if you’re unlucky or opt for a slightly lower pH than 8, overpressure builds up during storage because of a small excess in acids.Me, I wouldn’t use it. -
Many thanks for the reply. Is sodium hydroxide best (avoiding TEA)?
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You could also use potassium hydroxide. Some emulsions behave quite differently with different bases, others not so much. Similar to sodium soap usually being solid whilst potassium soap being liquid.
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Is getting sodium carbomer financially feasible for you? If yes, just get it, because you don’t need to neutralize it.
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I think I’ll just stick with the sodium hydroxide due to Pharma’s first comment. I can look into sodium carbomer too as an alternative. I would need to look into a supplier for it.
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Some companies will allow you to pick up NaOH and avoid the shipping hassle.
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That’s a good idea Cafe. I think I found a supplier who may not be charging the expensive shipping price after much searching.
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From the Neutralizing Carbopol and Pemulen in Aqueous and Hydroalcoholic Systems pdf. I use Arginine.
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Thank you for the chart Jemolian.
So neutralizing 1.00g of Carbopol with 4.50 g of l-Arginine… Is that what the neutralization ratio means?
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@Cafe33 I don’t really follow the ratio actually. I just add the arginine slowly and observe the neutralization which normally happens at around pH 4.2, and then add a little more to get to the pH i want, which is around pH 4.8 to pH 5 or so.
I tried the 4.5:1.0 in the very beginning when testing with Ultrez once to see what will happen, i believe it ended at about pH 9 to pH 10. -
Thanks for the clarification. I was always terrible at titration in school. Always lost patience near the end and added slightly too much.
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I can test some sodium bicarbonate I have versus l-arginine to see which one has a higher pH as I am not so certain from the chart. I am very surprised that an amino acid could do this. Then again, I am only a beginner-learner of chemistry.
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Upon re-inspecting the chart, I think that l-arginine is the weakest pH base since I recall reading that KOH is a weaker base than NAOH in o/w emulsions. Either way, l-arginine would be much safer to use and offer moistursing properties too. The downside will probably be cost as I have recently found a supplier selling NAOH extremely cheap comparing to what I’ve previously seen.
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Choose the one you want based on your formulation requirements, cost or marketing requirements.
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NAOH seems best for now, it just seems like it will be a bit of a hassle to work with (wearing a dust mask-should be wearing one anyway). Many thanks
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You can get a prilled version of Sodium Hydroxide. And you can also work with an aqueous solution of it instead of a solid.
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@Cafe33 So neutralizing 1.00g of Carbopol with 4.50 g of l-Arginine… Is that what the neutralization ratio means?
actually yes just becarfull of the concentration of initial product , so returning to table you will find NaoH has 18 % concentration same for KoH , TEA 99 % , Tris amino 40 % so if concentration change you should make the adequat amount knowing c1*m1 = c2*m2 wich gives m2= m1 * (c1/c2) . -
Thanks Perry, I had forgotten about prilled versions.
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What is a good starting solution dilution of sodium hydroxide? 10%/20%/25%?
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@LuisJavier i think from 10 % to 50 % will be good if you have not problem to intrduce more water 10 % will be better cause the amount of NaOH will be more precise .
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Thank you
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I wouldn’t advise a 50% solution unless you make it pretty slowly. The reaction of NAOH dissolving is very exothermic so if you dump all the required base in at once you’ll get some steaming hot and strongly caustic solution.
We make 20 or 25% typically and it doesn’t contribute much water if the only acid is a carbomer.
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