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Bentonite

Protocol number:	M072023
Industry:	Construction materials, Ceramics / glass industry, Foodstuffs
Feed Size:	<25µm
Desired Fineness:	d50< 600nm
Quantity:	~ 5g
Recommendation:	To be save, we performed a grinding in two steps (5mm Ø balls for pre grinding and 0,5mm balls for fine grinding). Probably it might be possible to grind such a sample directly with e.g. 1mm Ø zirconium oxide balls to the desired endfineness. We recommend using the Planetary Micro Mill PULVERISETTE 7 premium line for grinding such sample amounts. For a grinding of up to 5g, we recommend using two 80ml grinding bowls.

Result 1

	Planetary Micro Mill PULVERISETTE 7 premium line
Equipment:	80 ml grinding bowl made of zirconium oxide (ZrO2) + 100g x 5 mm grinding balls made of ZrO2 (for 60min) + 100g 0,5 mm grinding balls made of ZrO2 (60-120min)
Feed quantity:	3 g
Feed Size:	<25 µm
Additive:	+ 35ml Isopropanol
Grinding time:	∑: 2 h
Final fineness:	d50< 600 nm
Comments:	With a start size of ~ 25µm, we recommend a pre grinding step with 1-5mm Ø balls. 5mm use to have advantages by separation of sample from grinding balls. Smaller balls might speed up the grinding process and use to be able to grind into desired range of particle size. To avoid overpressure, we ground the sample in steps of 3 minutes, followed by a programmed pausing time of 10 minutes. After several cycles, the outside temperature of the bowl should be checked (remain below 70°C); grinding time or programmed pausing time might be readjusted afterwards. This counts for all further grinding trials too. After 60 minutes of grinding, a d50 < 2,1µm has been detected. A change of ball diameter to 0,5mm Ø has been performed. After totally 2 hours of grinding, the desired endfineness of < 600nm has been achieved. Probably a direct grinding with 1-1,5mm Ø balls might be able to grind the sample to the desired range in one step.
Download:	bentonite_03.pdf