• The problems that arise during mixing of
semisolids (pastes and ointments) stem from the
fact that unlike powders and liquids semisolids
will not flow easily. The materials that bind its
way to dead spots will remain there. For the
reason suitable mixers must have rotating
elements with narrow clearances between
themselves and the mixing vessel wall and they
must produce a high degree of shear mixing as
diffusion and connection can not occur.
Mixers for paste mixing:
• Planetary mixers:
• The mixing blade is set off center and is
carried on a rotating arm. It therefore travels
round the circumference of the mixing bowl
while simultaneously rotating around its
own axis. This is therefore a double rotation
similar to that of a spinning planet rotating
around the sun, hence the name.
Mixer blade
Planetary gear
Direction of drive
Direction of rotation
of planetary gear
Stationary
ring gear
Top view
• Planetary Mixers are used for dry mixing
and dough mixing. The homogenous mixing
if various lngredients of different densities
in different proportions for solid/solid,
liquid/solid, and liquld/Iiquid is achieved
effectively by the use of Planetary Mixer.
Vacuum Jacketed Planetary Mixers for the
preparation of ointment; toothpaste; creams;
suspensions. are designed to achieve the
best results. All contact parts are made from
S S 304 or SS 316 steel as per client's
requirements. Standard Mixer is available in
200, 350 and 600 Liters... capacities.
• Sigma – blade (double arm kneader
mixer):
• This robust mixer will deal with stiff pastes
and ointments and depends for its action on
the close intermeshing of the two blades
which resemble the Greek letter ∑ in shape.
The clearances between the blades and the
mixing through are kept small.
• Roller mills:
• Roll mills can provide exceedingly high
localized shear. Roller mills consisting of
one or more rollers are in common use of
these, three roll type seems to be preferred.
A
B
C
D
E
Fig: Cross section of three roll mill showing hooper (A),
Roll (B,C,D) and Scraper (E)