Sciencemadness Discussion Board

nasty klean strip

resveratrol - 11-2-2012 at 14:16

So, I've seen a fair amount of posts touting the use of "Klean Strip" Paint Stripper as a source of DCM. I'd like to add some thoughts:

Efforts were made to obtain reasonably pure DCM from Klean Strip (KS3 Premium) via fractionation. Not wanting to fuck up any glassware, the lid to the container was modified with a copper tubing affixed with a mighty-putty-like epoxy (which surprisingly holds up very well). The copper tubing carried the vapor up (as a traditional column), and over into an ice cold graham's condenser (with coiled condensate path). The condenser terminated into a 2-neck collection flask, with an inlet adapter leading to an activated carbon filter (for smell control).

slow, gradual heat was applied (via mantle), until the stripper reached a temp of around 40. More heat was applied as DCM was yet to liberate from the disgusting messy stripper. Finally, after increasing the temp yet again to no avail, the temp was then decreased and slight vacuum was applied to the collection flask.
25mm Hg, nothing.
50mm Hg, nothing.
100mmHg, nothing
150mm Hg, nothing
a littler over 200mm Hg....disgusting messy viscous sappy liquid proceeds to seep down from the end of the copper tubing, and into the graham's. Vacuum was decreased to about half, and the clear sappy blend continued to trickle down (maybe very slightly less viscous at this point). Vacuum was ceased, and temperature again raised....attempt was made to reach a point where the DCM would come over without any of the viscous material - to no avail.

For the sake of curiousity, typical all-glass distillation was sought. Minimal DCM collection is observed, and the thick nature of the stripper appears to hinder the boiling of DCM.

ThatchemistKid - 11-2-2012 at 15:13

I have used the same clean strip goop previously, all I did was pour it into a 1000 ml Round bottom and hook it up to a distillation set up. I heated the flask via water bath keeping the water bath at about 60 degrees C, over the course of 5 or 6 hours I recovered 600+ mls of DCM, are you sure the Klean strip you bought is the DCM methanol mixture? there are a couple of clean strip mixes that use other compounds.

Though it should be noted that the DCM methanol azeotrope is what you get out of this for the most part, this mixture has to be separated. Usually washing with water a few times and drying does the trick.

[Edited on 11-2-2012 by ThatchemistKid]

resveratrol - 11-2-2012 at 15:28

just as this thread was posted, the water bath temp reached ~75 degrees centigrade and DCM started to come over at a rate which i was comfortable with. I can see how 5-6 hrs at this temp could yield ~600mL.

thank you - and yes, this is the DCM:MeOH blend I'm speaking of.

resveratrol - 11-2-2012 at 15:31

I am going to chalk-up my first failure to the copper tubing. The tubing was very thin (about as thin as a standard laboratory thermometer). I figured it would be a problem from the start.

Sedit - 11-2-2012 at 17:15

You need to add water to the mixture to lower the viscosity of it and if done the DCM will come over at a rate which is almost to much to handle. Thats all you need to do, just add water.

resveratrol - 11-2-2012 at 17:27

Quote: Originally posted by Sedit  
Thats all you need to do, just add water.

Of course...


Sedit - 11-2-2012 at 17:34

Quote: Originally posted by resveratrol  
I am going to chalk-up my first failure to the copper tubing. The tubing was very thin (about as thin as a standard laboratory thermometer). I figured it would be a problem from the start.

Possible if you where not condensing it fast enough.

Distill it into a flask filled with water placed in an ice bath as well because this will help to not only condense your DCM vapors but keep the vapor pressure at a level to prevent further loss of DCM.

I routinely distill a mixture of Toluene, DCM, MeOH and waxy gunk to recover the fractions because this is rather economical way for me to receive these solvents.

Water into the mixture is the key to good recovery and I will bet my reputation on it. It allows for a much smoother distillation then you are dealing with at the present. Also it couldn't hurt to use a few boiling chips as the mixture tends to super heat due to the viscosity and variance in boiling points.

resveratrol - 11-2-2012 at 19:40

i really don't know what the problem was with the copper setup. it seemed very practical (with exception to the thickness of the tube). problem was not condensing it too slow, though. Oh well, even though this shit is ruining my glassware, I much prefer to actually see what the hell is going on in my distillations.

really the addition of water is key, as you said. everything else was fine (with exception to residual mess). I guess it's a trade-off to distilling it out of the can.. every method has its downside i suppose.

since you do this on the regular, if you don't mind my do you set up the distillation? all glass? do you use vacuum?

thanks sedit

resveratrol - 11-2-2012 at 19:42

and what's the best way to clean this dried-up gunk from your glassware? rinsing and setting in detergent only goes so far. aqua regia?

Sedit - 11-2-2012 at 21:31

Don't use glassware, Normally its to much bulk to use glassware anyway. Better to just solder a piece of copper tubing out of the top of a paint can. This makes for a very disposable piece of solvent distiller.

But if you must use glassware then just mix some soap with minimum amount of water and some sand. Shake the shit out of it until it cleans your flask. This has proven effective for even the worst baked on shit for a few different people other then myself.

ThatchemistKid - 11-2-2012 at 21:55

I just washed out the dried gunk with acetone, worked like a charm perfectly clean glassware.

resveratrol - 12-2-2012 at 07:29

I just let it set overnight in a detergent....appears to be clean.

I would much rather distill it directly from the can, but I guess I'm a little jaded after the first experience with copper.

In theory, the thickness of the copper tubing really should not have been an issue. So I don't understand where I went wrong there.

Now that you mention it, maybe it wasn't condensing fast enough - rather maybe the vertical portion of the tubing was too long such that the vapors merely recondensed back into the tin (as not enough heat was supplied to fill the length of the tube).

watson.fawkes - 12-2-2012 at 08:42

Quote: Originally posted by resveratrol  
reasonably pure DCM from Klean Strip (KS3 Premium) via fractionation
One of your problems is that the product you chose is one of the viscous formulations: From the Klean-Strip web site: "The paste formula clings to vertical surfaces without runs or drips." These formulas have viscosity modifiers and evaporation retardants, not exactly the best thing for distillation.

Since availability tends to be by brand, go to the manufacturer's web site, read the MSDS, and pick an appropriate product. Klean-Strip has an adhesive remover that might work for you.

resveratrol - 12-2-2012 at 09:52

True. I came across two brands of klean strip in my travels. The ks3 was chosen because the other formula did not contain DCM (as per label). They weren't sealed, so I had a look inside before I bought it. I knew what I was in for, but it is still preferable to select a formula with high viscosity rather than one that doesn't contain the compound of interest. Besides, addition of water solves that problem, as sedit so eloquently elucidated.

UnintentionalChaos - 12-2-2012 at 10:19

I had almost no problems purifying DCM from the KS3 Premium. using the small can as a test run, I cut a hole in the cap and soldered in some copper tubing, added a 90 degree elbow, and some more tubing. I led that through a stopper into the top of my Friedrich condenser which was being cooled with ice water. the recieving flask was sitting in an ice bath. A hot water bath caused DCM to rapidly distill over (the water bath was significantly above the b.p. of DCM, but this is necessary if you want to generate and move a lot of vapor, fast. Eventually evolution slowed. The can was cooled and opened. The thick layer of rubbery gelatinous glop was broken up with stirring and some more DCM was recovered by further distillation. This was not repeated after distillate really began to slow down. Some liquid was still obvious in the can around the rubbery chunks of viscosity modifier, but I think this was the naphtha that is also in the formula. The can was discarded.

The crude distillate was shaken with water, with the methanol being very easily extracted. From ~600ml crude product, the first 200ml water wash extracted nearly 100ml of methanol with corresponding rise in volume. The second two washes removed very little. The third was probably unnecessary. The product was dried over CaCl2, and distilled, the product being collected at ~40C. Yield was 666g, almost exactly a half liter of DCM.

I think that a significant issue here is the need to heat the entire can. Mine was immersed entirely in hot water, right up to the top edge of the can. I could pull DCM off at a very rapid rate and there was never any stripper that moved up the copper tubing. Immersing flasks up to the neck, incidentally, also reduces bumping in vac distillations. Definetly no need to use vacuum here, since DCM has such a low boiling point, and the sudden rapid generation of gas from the (now) superheated DCM would be likely to push the stripper up the copper tubing.

[Edited on 2-12-12 by UnintentionalChaos]

resveratrol - 12-2-2012 at 11:35

thanks chaos that was very thorough. i think you are also right about about the need to heat the entire can. precisely why I was more comfortable with being able to observe the distillation (through glass).

when i was distilling from can, i tried to wait sufficiently long (for all of the contents to heat), but perhaps not long enough.

and It does seem logical that a vigorous evolution of gas would carry the stripper over.

perhaps i will give it another try. the only modification being a water bath large enough to house the stripper can....corrected for buoyancy of course lol. I guess the correct protocol would be to apply a generous amount of heat such that the DCM and methanol are both obtained - and worry about the MeOH later (since there is an azeotrope anyway). and adding water to the stripper from the start couldn't hurt...

Sedit - 12-2-2012 at 12:13

That's what I always do with my Toluene/MeOH/DCM mixture. First I give it a quick run though and then worry about gathering the fractions later. My main goal is to remove the wax first then everything runs much smoother the second time.

Art&Dreams - 27-2-2012 at 13:35

* I just distill once to remove all the gunk.. (It will totally mess up your flask it took forever to get out)
*then I distilled what I had again to get the pure fraction (fractional distillation)

Dcm boils really low. The brand used also contains methanol.

The second distill wont mess up flask.

Methanol 65*c BP
DCM 39.8*c BP

Jasco stripper *red bottle* make sure its the one that says PREMIUM Paint &epoxy remover (15)

Oh yeah I use a peanut oil pan underneath a hotplate stirrer.
you can use water.

I don't but I guess you could go the boiling container copper pipe route but you would still need to put what you get in a fractional distillation setup and sep it out.
I am ocd about purity though.

[Edited on 27-2-2012 by Art&Dreams]

resveratrol - 29-2-2012 at 07:05

I found that my initial setup worked exceptionally well after slight modification. I feel it is important that the majority of the can be submersed in a hot water bath. Also, about 3 cups of stripper was removed from the can, and replaced with water. That definitely helped as well. Maybe next time I will post a picture of the setup.