What is the technological process of wet granulation and tabletting of tablets?

The technological process of wet granulation and tabletting of tablets is: main medicine → auxiliary materials → crushing → sieving → mixing (binder/disintegrant) → making soft materials → making wet granules → drying → grading → mixing → tabletting.

Wet granulation is a method of adding adhesive liquid to raw material powder for granulation. Particles made by wet method have good surface properties, beautiful appearance, strong wear resistance and good compression formability, so they are widely used in pharmaceutical industry.

Wet granulation mechanism: In any wet granulation process, the liquid evenly wetted on the surface of powder particles produces adhesion between powder particles, so the amount and state of liquid between powder particles have an impact on the strength of prepared particles.

When the liquid is added to the powder layer, the liquid first enters some gaps in the powder layer, and the powder particles (first particles) in contact with the liquid combine and aggregate into particles (second particles).

Most wet granulation methods make dispersed powder agglomerate together through the adhesion of liquid bridge to form particles with a certain shape and size, and finally consolidate in the form of solid bridge after drying. The transition from liquid bridge to solid bridge commonly used in pharmaceutical production has the following three forms:

(1) bridging of partially dissolved solution When granulating water-soluble drugs, the added liquid contacts with the powder particles, and the surface in contact with the liquid part dissolves to make the powder particles agglomerate, and in the subsequent drying process, the dissolved part solidifies to form a solid bridge.

(2) The bridging effect of the binder When the water-insoluble drug is granulated, the binder solution is added as a bridging solution to agglomerate the powder particles into particles. During the drying process, most of the solvent in the adhesive solution is removed, and the remaining adhesive becomes a solid bridge.

(3) The bridging of drug solutes in the solution is uniformly mixed, some drugs are dissolved in the liquid bridging agent for granulation, and solute precipitates among powder particles to form a solid bridge during the drying process.

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