# Key Board Mylars - just thinking



## kurtak (Nov 17, 2014)

Kevin - in no way is this a personal attack on you nor am I trying to undercut you - I have simply been thinking about it & I don't really think there is any secret to processing mylars --- haven't tried it - just thinking about it & so am opening my thoughts for discussion

What got me thinking down this road was Kevin's return & his mention of needing to sort them to estimate value by type so I went to pull my box of mylars out & start sorting them to maybe send off to him for processing (small box of around 20 lb.)

As I am sorting through the box I run across a hand full of X-ray films in the mix & this gets me to thinking - is there really any real difference between these two materials & I think hmmm - not really - they are both silver applied to a plastic substrate in the form of an emulsion 

So - why wouldn't the same process to recover silver with NaOH from X-ray film work to recover silver from mylars

Some of the mylars have a masking (like solder masking) covering the traces & some of them are glued together around the edges but NaOH should take care of those things as well

The process may take a little tweaking but I don't think much

At this point I have decided that rather then send them off to Kevin I will just hang on to them & give it a try in the spring when the weather warms up & I can play outside again 

I don't really have any interest in figuring it out so I can set up to do it - it's more a matter of seeing if I am on the right path &/or can figure it out my self :mrgreen:

Kurt


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## g_axelsson (Nov 17, 2014)

One is metallic, the other a chloride salt.
One should conduct electric current, the other making a picture after being exposed to ligt or x-rays.

Quite a big difference I would say. But it's possible that there are a common solvent that could process both but you would get a mixture of silver oxide / silver chloride / metallic silver.

/Göran


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## goldsilverpro (Nov 17, 2014)

On developed film, the silver is in the form of metal. The difference is that it's held on there by the emulsion, a form of gelatin. The emulsion is what is attacked by NaOH. On the mylars, there is no emulsion.


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## kurtak (Nov 17, 2014)

The traces on the mylar are laid down as a silver colloid bearing ink consisting of resins & solvents - the solvents & resins are a sort of emulsion that act as the carrier for the colloid silver

once the circuit (traces) are printed & the ink dries (solvent evaporates) you are left with the resin (which adheres to the mylar) bearing the silver colloid

So it's a matter of breaking the bond of the resin - I suspect NaOH will break this bond - though some degree of heat "may" also need to be applied 

I see the process going something like this - (1) shred mylars (2) ad to bucket of NaOH (3) agitate till resin bond is broke relieving silver (4) wash relieved silver from mylar shards &/or wash out NaOH (4) dry silver (5) melt &/or refine silver

If heat is required for the process the NaOH will generate it's own heat to at least start with (reaction of NaOH + water) if more heat is required the bucket could be set in a hot water bath or the bucket wrapped with heat blanket or heat tape (they make a heat type blanket for buckets for people that ferment their own beer & wine - home brew supplies) 

Again - just kinda thinking out loud here & I just don't see a lot of difference between silver ink (a sort of an emulsion) the silver applied to X-ray film 

I tried to find some data on conductive inks looking for the resin (or binder) make up but could not find any real formula data - the resin is the only nut to crack - the solvent is already dried off & the silver is the silver

Kurt


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## g_axelsson (Nov 17, 2014)

The inks I have seen have included a heat or UV curable component.
Maybe you will find something useful here http://electrapolymers.com/

Göran


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## Palladium (Nov 17, 2014)

I am so going to try this with an inkjet printer cartridge !
May be my next video!  

http://boingboing.net/2011/10/17/how-to-make-silver-ink-that-conducts-electricity.html


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## kurtak (Nov 17, 2014)

Yes - in my searching about conductive ink I saw that video as well - ink jet cartridge instead of pen would be really cool

Not sure how compatible that ink recipe is with the actual ink used I printing key board mylars

Kurt


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## rickbb (Nov 24, 2014)

As I understand it keyboard mylars are printed using the silk screen process in order to lay down a thick enough layer to be conductive enough for the job.

Inkjet ink needs to be thinner, (more liquid by volume), to squirt though the nozzles and may not print enough of a metal layer to be an effective conductor.


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## Impster (Nov 29, 2014)

Hello all,
Back 1991 and 92 I was working with the company that was developing the on battery testers for Eveready. The process of printing the silver ink involved
2 hits of ink from rotary screens. A company trying to do the same thing for Duracell was trying uv ink while trying that I couldnt get it to cure properly.
They didnt understand why until I explained that the surface would cure but then acted as a mirror and the ink underneath wouldnt cure.

The silver ink is silver plateletts surround by something else, but i cant remember what it was. I will see if I can get a hold of the guy i worked with and 
ask him.


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## samuel-a (Dec 1, 2014)

Palladium said:


> I am so going to try this with an inkjet printer cartridge !
> May be my next video!
> 
> http://boingboing.net/2011/10/17/how-to-make-silver-ink-that-conducts-electricity.html



Rejected batches rate from this process and similar is very high. I have made a good living out of these rejects.


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## Palladium (Dec 1, 2014)

If you don't mind me asking Sam, what is the chemical composition of the inks you're running? The one i referenced above is just silver ( metallic state, not chemical salt ), water, and a cellulose binder that doesn't require heating or sinstering to cure. I've been knee deep in reading about this subject for a week now. My background includes my years in the chemical coating industry and from everything i've read so far you wouldn't believe how exactly the chemistry matches that of paint!


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## samuel-a (Dec 2, 2014)

Palladium said:


> My background includes my years in the chemical coating industry and from everything i've read so far you wouldn't believe how exactly the chemistry matches that of paint!



I can imagine.


Honestly, I do not know the exact composition and the production process as these are trade secrets.
I never bothered myself with it too much as the processing, recovery-wise is quite simple and straightforward. 

I'm no expert, but I have to question the reliability of the ink shown in the video with real life applications. As you know it is one thing to print on paper and worlds apart from printing on plastic/glass/metal...


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## solar_plasma (Dec 7, 2014)

kurtak said:


> Yes - in my searching about conductive ink I saw that video as well - ink jet cartridge instead of pen would be really cool
> 
> Not sure how compatible that ink recipe is with the actual ink used I printing key board mylars
> 
> Kurt



I just found this link and remembered you guys did talk about ink jettable silver:

http://www.google.com/patents/EP2440624A1?cl=en


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## kurtak (Dec 8, 2014)

Solar 

thanks for the patent link - here is another one I found (meant to post this sometime back but got side tracked by more important projects) http://www.google.com/patents/US8158032

in this patent the bonding resin is a polyvinyl alcohol derivative resin (the common element along with the silver) were as the stabilizers & solvents are selected from a list for ink compositions 

I saw the polyvinyl alcohol derivative resin as a common element for the resin/binder in some other patents I looked at as well

another thing of interest I found in my research was that UV cured inks tend to be brittle with poor adhesion compared to heat cured inks so not really suitable for use on substrates that are flexed which leads me to believe that key board mylars are silk screen printed

Also when I lived in Northern California (very small town) there was a company that did touch (flex) pad circuit printing & all there printing was done by silk screen

palladium - you wrote - "My background includes my years in the chemical coating industry and from everything i've read so far you wouldn't believe how exactly the chemistry matches that of paint!"

this is what "in part" makes me think that NaOH may work on mylars the same as X ray film --- NaOH is used in many of the common paint stripers

Kurt


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## MarcoP (Dec 8, 2014)

kurtak, you are right. Check my reply followed by testerman' in his topic http://goldrefiningforum.com/phpBB3/viewtopic.php?f=61&t=21438&p=221247#p221247


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## Lou (Dec 8, 2014)

1.) Good job Kurt. Many, many pounds of silver paste, ink, etc have I run. Tons. It's usually PVA to adjust viscosity, a polymerization inhibitor like BHT, some sort of functionalized cellulose is also sometimes used, then a petroleum distillate solvent or a high bp glycol. Most of what we would get in was from solar cell manufacturing.
2.) Good luck melting it as-is gents; this same stuff will sit in a furnace a long time and not consolidate.

Spread it into a pan, thin, incinerate it until it crumbles--then you can pull a sample and take to a cupel and get silver with a little soda ash. If it melts no problem, it's done. Put it into a crucible, cast an anode (usually it's pure, but it'll always have too high oxygen to make into consumer bars) and off to the cell. 

Presuming one is feeling absolutely nuts (but it does work ,although with Ag losses), nitre prills milled in with the paste will do the trick in spectacular fashion. That needs a bag house and scrubber combo.

Now regarding keyboard mylars:
10% hot NaOH, concrete mixer, strainer, rinse. Re-use rinses. Frankly, those seem to be a bit of a waste of time.


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## rickbb (Dec 15, 2014)

Lou said:


> Now regarding keyboard mylars:
> 10% hot NaOH, concrete mixer, strainer, rinse. Re-use rinses. Frankly, those seem to be a bit of a waste of time.



So pretty much the same as exposed rare earth x-ray film then? 
Since I have a some of each to do, any problems with running them together?


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## g_axelsson (Dec 15, 2014)

rickbb said:


> Lou said:
> 
> 
> > Now regarding keyboard mylars:
> ...


No one of us have tested it yet, so I wouldn't do any big batches without testing first. The only "expert" on this we have was banned again.

My guess, after doing that one test is that there are many different glues used so the treatment can differ between different mylars. If you run it as one big batch you would probably get some cleaned sheets while some would still have the silver attached.

And X-ray film have an emulsion, not a heat (or UV) curable glue and would probably need different time / concentration / temperature for the optimum result. Run it in separate batches but you could probably reuse the lye.

Göran


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## rickbb (Dec 15, 2014)

Well no problems on the big batches, if I get 100 lbs. that's big to me.

After looking further at more posts it looks like the mylar gives up the silver as metal silver and film has further processing steps.

I'm going to do the mylars first then decant to retrieve the silver and use the same lye for the film.


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