Best Process for Coating Calcium Carbonate

Hi,

which particle size of the CaCO3?

Which thickness of the coating?

Which intended use?

Medical purity (GMP) or else?

Allowed residuals of other material in coating?

RHABE

CaCO3 ground particle size - 250 mesh to 400 mesh
Particle size required after coating - 500 mesh(97%) and 600 mesh(97%)
If necessary can even start with ground particle size 500 mesh or 600 mesh

Coating Thickness - Approx 5% by weight

Intended Use - Filler for PVC, Rubber, and other similar industries.

Medical Purity is not required.

Allowed Residuals - Provided does not interfere with intended application.

The CaCO3 coating can not be made into the ball mill.

Existing solution coating CaCO3 fine particles are using Continuous mixer.

After mixing, the coated particules are made in a 3 mm granules for the transportation to the end users.

waiting your answer to give you more info on the detailled process.

Hi,

if you can do cryo ball-milling this would be possible but likely too expensive.

I expect that the stearic acid will let all particles stick together so you will get a stearic acid highly filled with carbonate.

But I expect that you will like to have a powder and not a (bad) solid.

First action: have a look to individual particles in a microscope at 500 to 1000x magnification to know what surface is existing, CaC03 - is crystalline is very prone to cleaving, if "solid" is very irregular in grain form and surface structure.

So if you want to put on 5% of coating, this may not be enough to fill the many surface irregularities.

I would try to do wet hot coating by immersion into molten (highest possible temperature) stearic acid, and subsequent hot centrifuging to remove excess fluid.

If the particles are to be finer and finer you will likely need some vacuum processing.

This will include condensation of evaporated stuff onto your particles.

Another approach may be to use a liquid solvent (blow up you factory?), soak and dry again and add some slight ball milling.

Is there any additional wetting agent on the CaCO3? As on glass fibers and silicon wafers?

RHABE

Hi Usman,

How much stearic acid will be used? Up to 2% or more?

To coat with this acid, you have to operate above the melting point of the acid, around 70*C, and grind together to the fineness desired.

I already used coated CaCo3, Surfex MM, as a fine particle size, around 1 to 5 micron, to manufacture paints. I am not sure the coating was stearic acid because the supplier/maker never told.

Good luck, Gil.

Hi, we are just started manufacturing this coated CaCO3. Currently we still don't know the best method to test the quality of the coated powder. At the moment, we just using a bottle filled with water and the powder. then we shake it. If the water and powder saperate well, means the coating is ok. If the solution goes dark, then the coating not good. Is there any other method or parameter to determine this coating is ok or not?

Currently, we set 1.2% coating. How to determine this value in lab?

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