mixing and homogenisation .

1. For D-pharm 1st year
By
Six sigma institute of science and technology
Presented By- Sandhya Punetha ( Assistant Professor)
MIXING
AND
HOMOGENISATION

2. MIXING
• Mixing is defined as the unit operation that combines
two or more components together by agitation, shear
or mixers. The final product of the mixtures contains
uniform mixing.
• The uniform mixing depends on the degree of
mixing which depends upon the purpose of product
and objective of mixing.
• The equipments used for mixing is called as mixers.

3. OBJECTIVES OF MIXING-
Simple mixing of the material to form
uniform mixture.
Promote chemical reaction to get uniform
products.
Dispersion of solid in liquid to form
suspension or paste.

4. TYPES OF MIXTURES
POSITIVE
NEGATIVE
NEUTRAL

5. POSITIVE MIXTURES-
• When two or more than two miscible liquids or
gases or soluble solid is dissolved in water, the
mixtures are called positive mixtures.
• Mixtures formed is irreversible.
• Example- Syrup mixtures; Solution mixtures.

6. NEGATIVE MIXTURES -
• Mixtures formed from 2 or more immsicible
components like solid and liquid to form
suspension or emulsion are called negative
mixtures.
• These mixtures require more energy and can
separate out.
• These are reversible mixtures.
• Example- Suspension ; Emulsion.

7. NEUTRAL MIXTURES-
• Mixtures formed from different components like
solid and liquid to form static mixtures are neutral
mixtures.
• Such mixtures do not mixed but once they are
mixed they do not separate easily.
• Example- Paste, ointment.

8. POWDER MIXING
• Powders are the most common pharmaceutical
operations used for making different types of
formulations like- tablets; capsules; etc.
• Mechanism of powder mixing-
1) Convection mixing
2) Shear mixing
3) Diffusion mixing

9. 1)
• Convective mixing- Mixing of the bulk
particles as a whole from one container to
another. It is also known as bulk transport.
2)
• Shear mixing- Mixing of particles using shear
forces by agitator or stream of air.
3)
• Diffusion mixing- Mixing of materials by
random movement of particles along its
different layers through diffusion process.

10. FACTORS AFFECTING POWDER MIXING-
Particle size
Particle
shape
Particle
attraction
Material
density
Proportions of
materials

11. • Particle size- It is easy to mix particles of same size, if the size
of the particles will vary the mixing will not be uniform because
small particles will move towards the bottom and large particles
will move upward of the container.
• Particle shape- The ideal shape of the particle should be
spherical if they will have irregular shape than the chances of
separation will be low.
• Particle attraction- Some particles exert attractive forces due to
electrostatic charges on them. This can lead to separation.
• Material density- When two powders having different density
are mixed than the powder which is dense settle at the bottom and
powder which has less density comes upwards. Therefore,
uniform mixing does not occur.

12. EQUIPMENTS USED FOR POWDER MIXING -
• Double cone mixer.
• Agitated powder mixer.
• Air mixer.
• Tumbler mixer.

13. DOUBLE CONE BLENDER-
• Principle- The mixing of powder in double cone
blender is due to tumbling and shearing action with
blade.
• Construction-

14. • It is made up of stainless steel and is available in
different capacity ranging from 5kg to 200kg or even
more.
• The efficiency of blender depends on the speed of
rotation.
• The rate of rotation should be optimum which depends
on the size and shape of the tumbler as well as the
nature of material to be mixed.
• The common range is 30-100 rpm.

15. • Working-
• The material to be mixed is loaded approximately
50-60% of the total capacity of the blender.
• As the blender rotates the material undergo the
tumbling motion and mixes the material thoroughly.
• Agitator blade are used to provide shearing action.
• Advantage- It is used to mix the powders of
different densities and is used mainly for small
quantity of powders.
• Disadvantage- Handling is difficult.

16. AGITATED POWDER MIXER-
• Principle- It works on the principle of convection and
shearing action.
• Construction-

17. • Working-
• It consits of a stationary vessel in which an arm
rotates and transmits shearing action to the particles.
• The end to end movement is required by general
mixing which can be achieved by fitting helical
blades to the agitator.
• The mixture is commonly used for mixing free
flowing powdered materials having uniform particle
size and density.

18. LIQUID MIXING
• Liquid mixing is done to prepare true solution or
emulsion.
• True solution are formed when one miscible liquid
is mixed into another miscible liquid.
• Emulsions are prepared by mixing two immiscible
liquid by shear forces.

19. MECHANISM OF LIQUID MIXING-
1)
2)
• Bulk transport
• Molecular diffusion
3)
4)
• Turbulent transport
• Laminar transport

20. • Bulk transport- It is the movement of large amount of
liquid from one position to another. This mechanisms
tends to produce a large degree of mixing but leaves
the liquid within the moving bulk unmixed. For
proper mixing other devices may also be used such as
blade, paddle etc.
• It is the primary mixing of molecules due to diffusion.
This type of mixing occurs whenever there is a
concentration gradient.

21. • Turbulent Mixing- The paddles and turbines exert
pressure on the liquid adjacent to them. Turbulent
mixing result in random fluctuation of fluid velocity
and force to move the liquid molecules in various
directions.
• Laminar Mixing- In this type of mixing the fluid
moves immediately in the agitator which moves in
streamlines parallel to the direction of flow. This
type of mixing mainly occur in viscous fluids.

22. EQUIPMENT'S USED FOR LIQUID MIXING-
• Propeller Mixers.
• Turbine Mixers.
• Paddle Mixers.
• Shaker Mixers.

23. PROPELLER MIXERS-
• It consists of number of blades, generally three
bladed design in most common for liquids.
• Blades may be right or left handed depending
upon the slant of their blades.
• Size of the propeller is small and may increased
upto 0.5m depending upon the size of the tank.
• Small size propeller can rotate upto 8000 rpm and
produce longitudinal movement.

24. • Advantage-
Used when high capacity mixing is required.
Effective for liquid mixing.
• Disadvantage-
Not suitable for those liquids which have greater
viscosity more than 5 cp.

25. SEMI-SOLIDS MIXING-
• Semi-solid involves dispersion of liquid or solid
materials in the semi-solid base.
• They are neutral mixtures that does not separate
out easily.
• Miscible liquid and soluble solid are easily mixed
with low force and short time.
• Immiscible liquids and insoluble solids are mixed
with the help of emulsifying agent or wetting
agent.

26. EQUIPMENT'S USED FOR SEMI-SOLIDS MIXING
• Triple roller mill.
• Agitator mixer.
• Planetary mixer.

27. TRIPLE ROLLER MIXER-
• Principle- It works on high shear, which causes
crushing of aggregates particles and also distributes the
drug uniformly throughout the semi-solid base.
• Construction- Hopper
Scraper

28. • Three parallel rollers of equal diameters are made up of
stainless steel.
• They are mounted on rigid framework horizontally.
• The gap between the first two rollers is more than of
the gap between the last two.
• A hopper is placed between the first two rollers.
• A scrapper is attached to the last roller.

29. • Working-
• The feed is introduced in the machine by a hopper.
• Rolls rotate and materials are abraded by the rubbing
action of the rolls turning at different speed.
• Between 1st and 2nd roll , due to large space, the
materials produce a thick film and aggregates are
crushed here.
• Between the 2nd and 3rd roll the space is smaller.
Thickness of the materials passing gets thinner and fine
crushing takes place.
• Finally, scraper knife is used to discharge the mixed
material.

30. • Advantages-
Low material loss.
Avoid contamination.
Useful for small to large batch mixing.
Excellent temperature control.
Easy cleaning.
• Disadvantages-
Not suitable for liquid mixing.
Expensive.

31. PLANETARY MIXER
• Principle- It is also called change-can mixer. It works
on the principle of shearing and convective action.
• Construction-

32. • It consists of vertical cylinder shell which can be
removed.
• The blade is mounted from the top of the bowl.
• Mixing shaft is driven by planetary gear and it is normally
built with variable speed drive.
Working- The blade is moved slowly at the initial stage for
premixing of the material and finally at increased speed for
active mixing. In this way high shear can be applied for
thorough mixing. The blade and stationary vessel provide
kneading action and shear. This is due to narrow clearance
between the blade and the wall of the vessel.

33. • Advantages-
Speed of rotation can be varired .
• Disadvantage-
It requires high power.
It has limited size.
Useful for batch work only.