Granulation Good

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Tablet Granulation



Introduction Granulation is the process in which primary

powder particles are made to adhere to

form larger, multi particle entities called

granules.

Pharmaceutical granules typically have a

size range between 0.2 and 4.0 mm.

Granules are used in the production of

tablets or capsules.

Granules in such cases are made as an

intermediate product and have a typical size

range between 0.2 and 0.5 mm.



Reasons for Granulation

To prevent segregation of the constituents of the

powder mix.

Segregation (or demixing) is due primarily to differences inthe size or density of the components of the mix.

The smaller and/or denser particles concentrating at the base

of a container

The larger and/or less dense ones above them.

An ideal granulation will contain all the constituents of the mix

in the correct proportion in each granule and segregation of

the ingredients will not occur



Granulation prevent segregation




To improve the flow properties of the mix Many powders, because of their small size,

irregular shape or surface characteristics, arecohesive and donot flow well.

Poor flow will often result in a wide weight

variation within the final product owing to variable

fill of tablet dies etc.




To improve the compaction characteristics of themix Some powders are difficult to compact even if a readily

compactable adhesive is included in the mix and some arecompacted easily. This is associated with the distribution of the adhesive within the

granule and is a function of the method employed to producethe granule.

Solute migration occurring during the postgranulation dryingstage results in a binder-rich outer layer to the granules. This in turn leads to direct binder–binder bonding, which assists

the consolidation of weakly bonding materials.



Other Reasons

The granulation of toxic materials will reduce thehazard associated with the generation of toxic dustthat may arise when handling powders.

Materials which are slightly hygroscopic mayadhere and form a cake if stored as a powder.Granulation may reduce this hazard, as thegranules will be able to absorb some moisture andretain their flow ability because of their size.

Granules, being denser than the parent powder mix, occupy less volume per unit weight. They aretherefore more convenient for storage or shipment.



Methods of Preparation

Wet Granulation Method



Wet Granulation

Wet granulation is widely employed method for theproduction of compressed tablets.

The steps required for the wet granulation can be

divided into following stages: Weighing and blending the ingredients. Preparing the wet granulation. Screening the dam mass in to pellets or granules.

Drying the granules. Dry screening. Lubricating and blending. Tablet by compression.



WEIGHING AND BLENDING

The active ingredients and any diluents and

disintegrating agent required in the tablet

formulation are weighed in the amount required

for the number of the tablet to be produced.

This mixture is mixed thoroughly .

The diluents used for this purpose are Lactose,

kaolin, mannitol.

Disintegrating agent used include corn and

potato starch, cellulose derivatives.



PREPARING THE WET GRANULATION

Granulation is accomplished by adding liquid binder or adhesive to the powder.

The wet mass is then passed through the screen of desiredmesh size.

The granules so obtained are dried. Then again they are passed though a second screen of

smaller mesh size to further reduce the size of the granules. The binding agent used are

10-20% aqueous preparations of corn starch. 25-50% solution of glucose. Natural gums (acacia) Cellulose derivatives ( methylcellulose, carboxy methylcellulsoe)



SCREEING THE DAMP MASS

INTO PELLETS OR GANULES The wet granulation is pressed through a

No. 6 or 8 mesh size.

This may be done with hand or specialmachines.



DRYING THE GRANULATION

The granules are dried in spl drying

cabinets the have circulating air systems

and are thermostatically controlled. Among the newer methods employed for

the drying is fluidization conducted in

fluid bed drier.



DRY SCREEING

The degree to which the granules are reduced

depends upon the size of the punch and tablet to

be produced.

The smaller tablet size, smaller the granules

used.

Sizing of the granules is important so that die

cavity of die is fully filled with granules.

The voids are air spaces could result in tablet of

varying evenness.



LUBRICATION

After dry screening, dry lubricant Is

generally added.

The more commonly used lubricants aretalc, magnesium stearate and calcium

stearate.

Range at which it is added is from as low

as 0.1% to 5%.



UTILITY OF LUBRICANTS

The improve the flow property of thegranules from hopper to the die.

Prevent the adhesion of the tabletformulation to the punches and dieduring compression.

They reduce the friction between the die

and the punch. They provide a sheen to the finished

product.



FLOW CHART FOR THE WET

GRANULATION

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