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Remove flux from IPA (need more but only have used stuff)
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Psi:
So i need more IPA for PCB cleaning but it can't be bought for love nor money due to covid19.  Well.. unless you want to pay 10x price.

However I do have 10 liters of used IPA that's full of dissolved flux, i think it's mostly rosin.

Any ideas how to remove the flux?

Can i distill the IPA off with a heat source and a condensing column leaving the flux behind?
(yes i'm aware of the flammability safety issues trying to do this)

Ian.M:
If you've got the laboratory glassware to set up to do that, it should work well enough, but odds are the used IPA has adsorbed a significant quantity of moisture from the atmosphere, so expect to only get 91% purity even if you use a fractionating column.  If you need better than that, you'll either need to separate the water by salting out then discard the aqueous phase, or add a strong desiccant like anhydrous calcium oxide, prior to distillation.

Lastly, the lower explosive limit for isopropanol vapour is only 2.2%, so for %DEITY%'s sake make sure you've got intrinsically safe forced ventilation, no naked flames, and that any electric heating devices  have intrinsically safe controllers.
Psi:
Thanks.

Yes, safety is definitely a concern.

I'm not out of IPA just yet, stocks of IPA might recover before i need more, but it's good to know there are options.
T3sl4co1l:
That. :)

In the mean time, perhaps you can settle for acetone, MEK, denatured ethanol (unless it's been wiped out too?..) or others.  Usually not too aggressive, but spot-check as always. :-+

Incidentally, vapor condensation is about the only way to responsibly work with chlorinated solvents (1,1,1-TCE most importantly).  Terrifically good for cleaning to begin with, you're basically putting the work inside a Soxhlet extractor. :D

Tim
jogri:

--- Quote from: Ian.M on March 17, 2020, 07:28:55 am ---so expect to only get 91% purity even if you use a fractionating column.

--- End quote ---

It will be worse than 91%, you can only manage a maximal purity of 87.7% as IPA forms an azeotrope with water... But that is the best case, expect maybe 60-75% purity with a DIY setup and not much experience with distillations. If you want to remove the remaining water i would advise you to use either molecular sieves (3A) and/or magnesium sulfate. Don't bother with CaO, that stuff is just too nasty. Distill it, then add enough MgSO4 until that stuff doesn't form white fluidy blobs (you'll see) and stays as a fine powder. Decant it, then add the molecular sieves (after you've put them in an oven at 200°C for some time [let them cool down before adding them]).

If you want another solvent that is still available go to a hardware store and grab some Acetone and denatured alcohol (paint supplies).

And please work with small portions (500ml-1l max), just set it up, let it run through and NEVER open it when it is still hot. If you need help with it just PM me, i've done quite a few distillations over the years.
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