Granulation Flashcards
What are granules?
Aggregates of powder particles
What are granules for?
Oral administration
What are the different types?
Effervescent, coated + gastro-resistant
What is the size of granules?
200-4000 μm
What are the pros?
Better handling
Less likely to segregate
Better compaction characteristics
Reduced fines
Higher bulk density
Why is segregation less likely?
Particle size more uniform
What are the cons?
Addition processing = increases cost
Instability during granulation
What does particle aggregation result in?
Particle size enlargement
What does particle aggregation require?
Powder ingredients
Binder
Equipment
Wet granulation
Shear granulation
Fluidised-bed granulation
Dr granulation
Slugging
Roller compaction
What is the process?
Mix
Aggregate using suitable binder
Dry granules
Sieve to select particle size
What type of binder is used for wet granulation?
Solution
What type of binder is used for dry granulation?
Solid
What is example of wet binder?
Amorphous polymers
What do solubility of granules depend on?
Type, amount + solubility of binder
What are examples of amorphous polymers?
Starch (5-15% w/w)
Gelatin (1-3% w/w)
PVP (3-3% w/w)
Cellulose ethers (1-5%)
What is intragranular bonding?
Attractive forces between particles
Attractive forces between immobile films
Liquid bridges
Solid bridges
Mechanical interlocking
What is the classification for intragranular bonding?
Rumpf
When is there liquid bridges?
Wet granulation
When is there solid bridges?
Dry granulation
= sintering of solid binder OR re-crystallisation of liquid binder
When is there mechanical interlocking?
Shape-related bonding
= rough angular particles
What are the stages of granulation by wet granulation?
Wetting + nucleation
Consolidation + coalescence = particles grow
Attrition + breakage = particles too large = broken down
Describe wetting + nucleation
Wetted by binder solution = nuclei formed
Sprayed = uniform wetting
What are important factors for wetting + nucleation?
Droplet size, wetting properties + particle flux in wetting zone
Describe consolidation + coalescence
Other particles collide with nuclei, deform + adhere
What are important factors in consolidation + coalescence?
Particle surface moisture, particle hardness + particle velocity
Describe attrition + breakage
Fine particles shed from dry granule surface (attrition)
Dry granules break up
What are important factors in attrition + breakage?
Particle velocity + granule porosity
Describe shear granulator
(Wet granulation)
Perform low-shear granulation from wet mass
Vessel with impeller + chopper (rotate at right angle to each other)
Binder solution injected
