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Flashcards in granulaiton Deck (26)
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wet agglomeration

wet massing by planetary or HSM, extrusionand pelletization


agglomerate growth through continuous agitation

balling, fluid bed



humidification and vacuum drying


types of granulation method

1) direction compression
2) wet granulation ----> sphere
3) dry granulation
4) thermoplastic granulation --> sphere


particle size of primary component
compare particle size

smaller particles requires higher amount of binding liquid than larger particles,
smaller particle usually more difficult to densify to due higher packing density and SA higher


component particle size on end product

smaller particles are favored in producing agglomerates that are more spherical, with smoother surfaces and of narrower size distributions

smaller particles also generally produce stronger agglomerates


packing properties affected by

particle shape
irregular shape cr8 interlocking among particles and thus increase agglomerate strength whereas a rounder particles reduces the strength


Direct compression
advantage and prerequisit

1) most effective and efficient method to prepare free flowing powders for tableting, mix and blend, without the additional step to increase particle size

requires material w
- suitable flow
- narrow size distribution
- minimal segregation and good compressibility


major advantage of dry granuatin by roller compaction wet granulation methods

- few unit processes ,thus lower production cost
- suitable for heat and or water sensitive material

- a feasible process for preparing controlled release product


bonding mechansim in dry granulation

1) particle rearrangement
2) particle fragmentation
3) particle bonding


adv roller compaction

1) simple direct processing
2) eliminates granulating solvent
3) less energy and manpower to operate
4) allows continuous manufacturing
5) useful for heat/moisture sensitive products

5) vacuum to suck air , air can cause breaking??


critrical operation attribution for roller compaction

1) screw feed rate
2) roll speed
3) roll pressure
4) roll gap


compaction zone

1) slip region
particle begin slipping at the roll surfaces, some plastic
deformation of solid occurs

2) nip angle region
densification occur

3) release region:
immediate after powder compaction, size depends on extend of powder's (compact's) elastive recovery


factors affecting compact strength

1) applied pressure
2) extend of air entrapment (use vacuum system)
3) roll dwell time
4) powder void fraction (space into which air is compacted)
5) particle size of component and density
6) type of binders included
7) moisture content of material


purpose of wet granulation

1) improve flow properties
2) reduce bulk volume, densification
3) improve compression properties
4) improve distribution of a minor constituent eg low dose drug binder, colorant
5) prevent components from segrating
6) reduce dust
7) minimise or mitigate adverse properties of API
eg hydrophobicity, bad taste, poor stability


disadv of wet granulation

1) additional processing steps, adds complexity, cost, extra validation work
2) additional time and space needed
3) unsuitable for moisture-sensitive or thermolabile drgs
4) material loss due to additional processing steps


types of LSM and HSM

planetary mixer



low mean particle size + wide size distribution

pack well and high strength

1) nucleation
2) coalescence


large paricle size + narrow size distributino

low strength

1) nucleation
2) layering


Main granule growth mechanism

- nucleation
- coalescence


seconfary growth mechanisms

- layering from degradation of existing particles
- ball growth


requirements for successful granulation

1) dissolution of solids by solvent, and later the solute forms crystaline bridges when dried

2) dissolved binder in the granulating liquid may also by responsible for the formation of solid bridges

3) solid bridge formed the binding structure between particles

if solid bridges are absent, granules will revert back to the original powder


Process steps of granulation by HSM

1) mixing of dry powder at high impeller speeds for 2-5min

2) additional of liquid binders, lower speeds, 1-2min
3) wet massing, high speeds, 1-5min
4) wet sieving of granules usually using cone mill
5) drying usually by fluid bed dryer
6) regranulation by cone mill


adv of HSM granulaiton

1) short process time
2) less binder needed, therefore, shorter drying time
3) suitable for cohesive materials as well dense production

4) less sensitive to raw material physical attributes than fluid bed granulation

5) closed system: GMP, possibility for vacuum, microwave drying

6) easy to clean, CIP possible


problems associated with HSM granualtors

1) mechanical degradation of weak powders and granules

2) some heat generation, unsuitable for thermolabile products

3) risk of over-wetting leading to uncontrolled growth.


process variable for HSM

1) Impeller rotation speed (tip speed)
2) chopper rotation speed
3) load
4) liquid addition method
5) liquid addition rate
6) wet massing time