Granulation is a term given to a number of processes used to produce materials in the form of coarse particles.
GRANULATION
Granulation
is a term given to a number of processes used to produce materials in the form
of coarse particles. In pharmacy, it is closely associated with the preparation
of compressed tablets. Here discussion is limited to a general account of the
process.
Ideally,
granulation yields coarse isodiametric particles with a very nar-row size
distribution. The several advantages of this form can be inferred from the
discussion above. Granules flow well. They will feed evenly from chutes and
hoppers and will pack into small volumes without great variation of weight.
Segregation in a mixture of powders is prevented if the mixture of powders is
granulated. Each granule contains the correct proportions of the components so
that segregation of granules cannot cause inhomogeneity in the mixture. The
hazards of dust are eliminated, and granules are less susceptible to lumping
and caking. Finally, granular materials fluidize well and a material may be
granu-lated to gain the advantages of this process.
The
starting materials for granulation vary from fine powders to solutions. Methods
can be classified as either wet or dry granulation. In the latter, a very
coarse material is comminuted and classified. If the basic material is a fine
powder, it is first aggregated by pressure with punches and dies to give
tablets or briquettes, or by passage through rollers to give a sheet that is
then broken.
In
wet methods, a liquid binder is added to a fine powder. If the pro-portion
added converts the powder to a crumbly, adhesive mass, it can be granulated by
forcing it through a screen with an impeller. The wet granules are then dried
and classified. If a wetter mass is made, it can be granulated by extrusion.
Alternatively, the powder can be rotated in a pan and granulating fluid is
added until agglomeration occurs. Granule growth depends critically on the
amount of fluid added, and other variables, such as particle size, pan speed,
and the surface tension of the granulating fluid, must be closely controlled.
Granular
materials are also prepared by spray drying and by crystallization.
TH 2019 - 2023 pharmacy180.com; Developed by Therithal info.