Polyvynyl alcohol

[zeocrash]

i was up at manchester uni open day and i was watching them do a polymer demonstartion with polyvynyl alcohol and borax.
now i saw the lable on the bottle and thought, "hey i can use that to make PVN". anyway the demonstrator refered to it as PVA. this got me thinking that PVA glue was polyvynyl alcohol, anyway after looking it up i found out that pva glue really was poly vynyl acrylate, like i orininally thought. anyway, i researched more and found out that PVA glue could be hydrolised into PValcohol.
i came up with a method of refluxing it with NaOH to hydrolise it
doing this leaves me with sodium acetate, polyvynyl alcohol, water, and excess NaOH
i was wondering if anyone knew how i could separate the PValcohol from the unwanted crap.
or if anyone knew a beter method of producing PValcohol

[yt2095]

Difficult, but not imposible, the PVA being macro covalent and the remainder being ionic and covalent with ionic properties.
i sugest a 2 step procedure, 1`stly the NaOH when dry will crystalise, as will the sodium acetate (same stuff they use in the pocket warmer pack)
there`s 2 ways i THINK you may be able to get away with making your product a little purer, 1`stly, can you distil the PVA out, it may indeed make an azeotrpe with the water, but you`ll be a step closer and have less crap to deal with.
secondly try and find a reaction that will make sodium salts less soluable (tho most sodium salts are quite soluable) maybe a sulphate or a carbonate perhaps?
the other idea would be a reagent that "fixed" the PVA into a solid but ignored the ionic chems in your mish mash, so that you could extract the reacted PVA and then start with a less complex and mixed molecule, and merely remove it with a simple solvent.

an EXACT answer i DON`T have, ideas plenty! and if any of this helps you think of further ideas as a thought provoker, glad to have helped, if not, sorry to have wasted a post guys.

Good luck anyway :)

[zeocrash]

i just had a thought,
how about i use calcuim hydroxide to hydrolise the PVA glue
this way when hydrolosys is complete i can blow carbon dioxide through the mix, converting the Ca(OH)2 into CaCO3, like limewater. i then filter the mixture to remove the CaCO3. then i boil the water off, and continue to heat the mixture to 160-170°C this causes the breakdown of the calcium acetate into calcium carbonate and acetone. the acetone evapourates off.
the calcium carbonate and the PValcohol stay in the flask.
the mixture is then mixed with water to disolve the PValcohol. the solution is then filtered to remove the CaCO3, and crystalised to obtain the PValcohol

this is all i have come up with and i thint it'd probably be horribly inneficient give a terribly low yield and would take hours, any ideas

[yt2095]

not a bad call actualy! tho the CO2 bit would be painfully slow, but a sulphate of calcium would be equaly as insoluable, as long as you could garauntee the sulphuric acid didn`t reverese your hydrolysis.
remember tho, as i`ve no experience with this procedure your embarking on, and only chatting basic chemistry 101 (no organic stuff) that all my posts on this particular link are meant as Thought provoking ideas only! :)

Calcium at face value seems like a good option tho, certainly easier to clear up than sodium salts. tho i stongly suspect you`ll need more refluxing time, as CaOH isn`t as PK base as NaOH.
tho it was good enought to strip the flesh off people in shallow graves during WW2!

besides, there`s no such thing as a failed experiment, only more data :)

[frogfot]

It could be extracted by Et2O but maby acetone could do it too.. Since all byproducts are salts, there will form a layer of acetone with PVOH.

[yt2095]

frogfot,

i`m not sure what Et2O is, but based on that thought it just made me think, perhaps it`s possible to lockup the sodium with EDTA. tho i`m sure that`s what you meant frogfot.
Ethylene diamime tetra acetic acid?

either way, if it IS seperate things, you`ve now got some more data to work with :)

altough i`ve only ever known EDTA used to lock up heavy or toxic metals, so maybe it won`t work with sodium? i have no data to either confirm or deny this.

[frogfot]

Soz, i meant diethyl ether (Et2O), but this may be hard to get by anyway.. btw, hydroxide is preferrably neutrolised before extraction.
EDTA with metal would be still soluble..

[Mr Cool]

I'm wondering about an acid-catalysed hydrolysis, where the acid is simply your nitrating acid. This would be nice, as it makes it into a one-pot reaction, with fewer impurities. After the reaction, neutralise any remaining acid with NaOH. So you'd have sodium nitrate, sulphate and acrylate in solution, and insoluble PVN which could be filtered and purified as usual.
It just depends on where the equilibrium lies between PVA + HNO3 <=> PVNO3 + HA...

Edit: Tetrasodium EDTA exists, but EDTA will not form a complex/chelate with sodium because it isn't a d-block element - it has no unfilled d-orbitals to accept electrons from the EDTA in order to form the complex. Thus you can only get the sodium salt of EDTA.

[Marvin]

PVA glue is mostly polyvinyl acetate together with some unreacted alcohol, so it would indeed hydrolyse to to the alcohol and sodium acetate. Extraction with ether could work, but I dont know how soluable it is. I think its virtually insoluable in something like hexane, and probably in anything thats completely insoluable in water. I have the funny feeling salting out would work well though, say with pot carbonate. Youd have to remove anything that crystalised, which should be everything after neutralisation. I have the feeling the sodium carbonate wouldnt work. Driving out the water by heating then decanting from the insoluable solids might also work.

What would bother me, is half way through the reaction, how can you tell if its totally hydrolysed or not?

[kingspaz]

i guess you wouldn't and work on the assumption that after a given time it MUST be hydrolised. like keep the heat on for 2 hours or something as that would hydrolise most if not all.

[Mr Cool]

PVAcetate? I thought it was PVAcrylate :confused:.
I've spread some out in a thin layer to dry out, then I'll mince it up in a coffee grinder and try a direct nitration, to see if I can swap a nitrate for the acetate/acrylate/whatever.

One problem might be that it is very possible that the generic "PVA Glue" is not pure PVA and water. Other things might be present to improve its guiness.

Edit (typo): "guiness" should be "gluiness." Guiness doesn't need improving :).

[kingspaz]

i thought the A in PVA was acetate also. i'm pretty sure it is.

http://www.export911.com/ref/plasApp4.htm

in the middle of the page somewhere.

[Marvin]

Acrylate glues are of the 'superglue' class activly polymerise (and usually crosslink) when hardening.

The 'wait 2 hours and assume its all gone' would require an act of faith I wouldnt have. For example, if you have a secondary alkyl chloride and refluxed it with plain water I'd expect it to be gone pretty rapidly. The secondary chloride equivalent in this case though is polyvinyl chloride! If I refluxed that with water, or even with strong alkali I'm not convinced Id have a significant conversion after a year, though I confess I dont have the slightest real idea how long it would take. (Yes it would be a different phase than the water which slows things down, but then so is the alkyl chloride)

What bothers me slightly more is that with polymers the reaction is never actually 'done' done. Instead of a molecule with 1 OH, that goes directly to the product you have a molecule with thousands (probably) or more and its a question of getting a polyalcohol that is 50% aceylated or 10% or 5% or 0.5%.... How can you check how far along hydrolysis has progressed without purifying the product out of the reaction mixture and then measureing its density or boiling point....

Edit, Yes there will be small amounts of plasticisers too.

[zeocrash]

mr cool: i dont think that a direct nitration/hydrolosis of PVA would be a sensible idea, according to meglomania's synth while making PVn you should cool the mixture to -8 °C during the nitration. but the hydrolosis requires refluxing and therefore heat. now i have 2 queries, firstly what would happen if i were to heat this mixture as it was hydrolising / nitrating
secondly do i need to hydrolise the pva at all or would it be possible to do a direct nitration, substituting PVA for PValcohol.
also i believe industrial hydrolosis to form PValcohol uses alcohols, which would definatly be worth a try