Granulation Flashcards
What is granulation?
Size enlargement of powders, powders will adhere to make granule. Often used as an intermediate in tablets and capsules.
Why granulate?
- Segregation; better uniformity
- Flow; same shape, size helps flow
- Compressibility; better for tabs formation
- Densification; take up less volume
- Dust hazard; no powder everywhere
- Wettability of poorly soluble drugs; mixing with hydrophilic excipients
What are the requirements for granules?
- Similar shape and colour
- Mechanical strength
- Moisture content 3-5% w/w
- Disintegrate into original powder
- Flow
- Particle size is uniform
- No more than 10% w/w
What are the 2 types of granulation?
Wet granulation
Dry granulation
Describe wet granulation
Powder + liquid mix
Granules formed
Dried
Sieved
Describe dry granulation
Slugs or compacts formed from dry powder
Coarse grinding
Sieved
What are the mechanisms for dry granulation formation?
- Particles adhere to each other when pressure is applied.
- Held together using Van de Waals forces because of small size.
- Think of a snow ball - push together hold shape
What are the mechanisms of wet granulation formation?
- Mix liquid and powder together
- Nucleation; small number of particles combine to form pendular state
- Add more liquid = capillary state
- Continue - ball growth - too large
What are the possible mechanisms of ball growth?
- Layering; layer powder added to the granule
- Coalescence; join to make larger one
- Breakage; broken parts adhere to granule
- Abrasion; granule hit each other and break , then can be attache to other granules
What are the types of wet granulation?
Low shear mixer
High shear mixer granulation
Fluidized bed granulator
Describe the low shear mixer
- Powder and binder solution mixed in planetary mixer
- After mixing, mass is out into a granulator
- Then sieved into desired size
- Dried in try oven
Describe shear mixer granulation
- Mixer bowl with impeller and chopper
- All in one machine
- Dry powder mixed by impeller
- Add liquid and mix impeller
- Chopper will form granules from the wet mass
- Granules are formed and pushed through sieve to be dried in fluidised bed
- Easy and quick
Describe the fluidized bed granulator
- Air blown through powder bed to fluidize and mix
- Spray nozzle sprays the binder onto the powder
- Temp - to solidify the granules
What are the things that affect granules in fluiddized bed?
Air pressure
binder conc and type
particle size
granulation, drying and temp time
What are the 2 types of dry granulation?
Roller compaction
Slugging
