Sciencemadness Discussion Board

making tablets

plantdoctor - 25-3-2004 at 21:42

Can anybody suggest a suitable hardening agent to help my fertilizer tablets remain intact. I am using a tablet press which forms 20g fertilizer tablets (using a mix of ibdu, potassium sulphate, monoammonium phosphate and magnesium sterate and calicum lignosulphonate). The calcium lignosulphonate was meant to be a binder keeping the tablets hardr, but is not working. Any ideas would be appreciated.

[Edited on 26-3-2004 by plantdoctor]

Mr. Wizard - 26-3-2004 at 07:32

What is "ibdu"? Lignium sulphonate (sp?) is a liquid used to spray on loose soil to consolodate it for use as a temporary road. Calcium lignosulphonate would be a dry material, right? Are all the materials to be consolodated in the dry state and at room temperatures? Magnesium Stearate is a 'soap' often used in pills. I noticed you didn't have any Magnesium Oxide in the mix. It would react with the ammonium phosphate and a trace of moisture to form a very solid plaster, used in dental casting. Maybe if you added more Magnesium Stearate, Magnesium Oxide, a trace of moisture and increased the pressure on the press, it would form a hard pill. You might try using a hydraulic jack and make yourself a reall strong press.

axehandle - 26-3-2004 at 16:25

Well, I've done it, and this is my hydraulic press. I used aluminum (Fortal alloy (MG-Al)) for the bars, and 8/8 steel for the ´tensile carrying bars.




[Edited on 2004-3-27 by axehandle]

Mr. Wizard - 26-3-2004 at 19:57

It's a nice looking press. Is the curvature of the threaded rods due to the camera lens or did the get a little bent in use? I need to make one like that. I don't have any nice chunks for the cross bars yet.

axehandle - 27-3-2004 at 05:07

The curvature is due to the camera. I calculated the maximum tensile stress on the steel to be 36 tons, the jack only gives 12... but it's enough to make BP cakes with a density of 1.8 g/cc.

Edit: Oh, btw, the steel threaded rods are M16 in diameter. I had to pay through the nose to get 8/8 quality (about 40 EUR for all 4).



[Edited on 2004-3-27 by axehandle]

[Edited on 2004-3-27 by axehandle]

making tablets

plantdoctor - 28-3-2004 at 15:44

Thanks for your comments. ibdu is isobutylidene diurea. It is produced through the condensation of urea and isobutyaldeyde. It is used in agriculture as a slow release form of nitrogen. Calcium Lignosulphonate is a powder (byproduct from paper making mills i believe). All products are combined at room temperature. I will try the Mag Oxide. Would Magnesium carbonate work also?

Quote:
Originally posted by Mr. Wizard
What is "ibdu"? Lignium sulphonate (sp?) is a liquid used to spray on loose soil to consolodate it for use as a temporary road. Calcium lignosulphonate would be a dry material, right? Are all the materials to be consolodated in the dry state and at room temperatures? Magnesium Stearate is a 'soap' often used in pills. I noticed you didn't have any Magnesium Oxide in the mix. It would react with the ammonium phosphate and a trace of moisture to form a very solid plaster, used in dental casting. Maybe if you added more Magnesium Stearate, Magnesium Oxide, a trace of moisture and increased the pressure on the press, it would form a hard pill. You might try using a hydraulic jack and make yourself a reall strong press.

Mr. Wizard - 28-3-2004 at 17:27

Is this recipe one that has worked before? The magnesium oxide is mentioned because it, when mixed with ammonium phosphate, form a dental casting plaster. I'm not sure what effect if any it would have on dry powders. How much pressure does your tablet press exert? The fertilizer spikes I've seen can be hammered into the ground, which indicates an extreme pressure in their formation. They have a glazed look on their exterior, almost like a rock.

I suspect it will take a big hydraulic jack (20 to 30 tons) , compressing a cylinder of powder 25mm in diameter or less, contained in a strong mould. This is pure guessing on my part.

You might try hammering some of the components in a narrow pipe to see if they will consolodate.

axehandle - 29-3-2004 at 07:20

About the cake diameter and the jack: No a 12 ton one is enough to press BP cakes with a diameter of 75mm to a density of 1.8g/cc.

Since I basically had to hang my full body weight on the lever to squeeze the last millimeter, I've since upgraded to a 20 ton jack. <b>Very</b> powerful.... :)

And very heavy to carry home.... oooh, I remember how my back ached...

ordenblitz - 15-8-2004 at 10:50

Magnesium stearate is used as a lubricant in tabletting. It makes the tablet easier to eject from the die and tends to keep the material from sticking to the punch faces, which causes capping. A lubricant will also aid the compression by reducing bridging in the die and promote better density with an equal pressure.