Prepic
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Adipic acid and hexamethylenediamine from Nylon 6,6 cable ties
Hi guys,
I attempted preform the hydrolysis of Nylon 6,6 cable ties in order to obtain both adipic acid and hexamethylenediamine. Here is the procedure I
followed:
22.56 g (0.1 mol) of cut-up Nylon 6,6 cable ties was added into a 250 ml flask. I then added 100 ml H2O along with 15 ml of 98% H2SO4. The solution
was then brought to a very light boil for 6 hours.
A lot of nylon remained unreacted so i added 30ml 98% H2SO4 along with 35 ml H2O into the solution and reheated for 3 hours. The solution was clear.
Upon cooling, a precipated formed and i filtere this out to obtain crude adipic acid. I recrystallised from boiling water to obtain 8.02 g (55% yeild)
of adipic acid. Using an improvised melting point set up, I measure the melting point around 160 °C.
I tried to recover the hexamethylenediamine by treated the post reaction liquid with excess calcium carbonate and then some sodium hydroxide. I did
not observe any fishy/ammonical smell.
Is there a way to isolate the diamine and how should I go about this?
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Pumukli
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Are you sure the ties were made of 6.6-nylon?
I was tempted to do this experiment but postponed it because I felt I can't be sure that the starting materials were exactly what I thought. If they
weren't then the isolation/purification/identification procedure would have became too tedious.
Maybe the ties were originally made from hexamethylenediammine, but who knows, later they may modified the process, switched to another supplier who
knew a better/cheaper alternative. They may not changed the description but actually are using something else.
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Prepic
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I would say yes. According to the manufacturers website, the material used is "Polyamide 6.6 (PA66)", I used the "natural" colour which should be free
of addition additives such as colorant and potential UV stabilisers which are noted in other cable tie varients etc. Furthermore, the packaging
explicitly stated that this product is moisture sensitive which is expected. Althought my melting point is a little off the literature value of 152
°C ( vs. ~160 °C) I believe I isolated adipic acid.
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Dr.Bob
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hexametyhylenediamine is very water soluble, and likely quite polar, as a diamine, so less smell than simple amines. Also, much harder to extract
from water, might try ether extraction and see if you can get any out, or take the acidic solution and try to concentrate it to collect the salt, but
it will be very hygroscopic still, so hard to get to a dry solid, but if concentrated, may be easier to basify it and extract the amine. But a nice
experiment.
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Pumukli
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I found it strange that you couldn't smell any amine stench. I expect the 6,6-diammine to be something very "noticeable".  Maybe it is smelly only when hot? Maybe the solution was not basic enough? What if
you added more NaOH pellets? I expect the solution phase-separate at one point if you keep adding NaOH (with external cooling).
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DraconicAcid
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We use hexanediamine in the lab to make nylon- it doesn't have a very strong smell.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Prepic
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Okay so I get the feeling I've simply stopped work on the extracting the hexamethylenediamine a bit too early and that it should still be present in
my post reaction liquid.
I think the isolation of salt, liquid liquid extraction and possible phase separation are all do-able so I'll try it out. Thank you for the ideas.
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