Semi-Solid Mixers

Industrial Pharmacy Department

Dr. Rowan Mohamed Ahmed

4th Year Pharmacy – Fall 2010

Mixing: An Introduction

Definition:

• It’s the most widely used operation in

which two or more substances are

combined together.

• Perfect Mixing is that in which each

particle of one material lies as nearly

adjacent as possible to a particle of the

other material.

• Mixing depends on the purpose of the

product and the objective of mixing.

• This process may involve the mixing of

gases, liquids or solids in any possible

combination.

Mixing: An Introduction

• Objectives of Mixing:

1. Simple Physical mixing of

materials to form uniform

mixture.

2. To promote the chemical

reaction to get uniform products.

3. Dispersion of solid in liquid to

form suspension or paste.

4. Dispersion of two immiscible

liquids to form an emulsion.

Mixing: An Introduction

• Simple Mixing Processes include:

1. Mixing of a gas with another gas.

2. Mixing of miscible low viscosity liquid.

3. Mixing of a highly soluble solid with a low viscosity

liquid to effect dissolution.

Mixing: An Introduction

• Mixing Operations Needing Specialized

equipments:

1. Mixing of gases with liquids

2. Mixing of liquids of high viscosity though miscible

3. Mixing of two immiscible liquids such as aqueous and

oily solutions to form emulsions

4. Mixing of solids with liquids when the proportion of

solids is high

5. Mixing of solids with solids

Mixing: An Introduction

• Some of the examples of large

scale mixing practiced in

pharmacy:

• Mixing of powders prior to granulation or

tableting.

• Dry mixing for direct compression in

tablets.

• Dry blending of powders in capsules.

• Dissolution of soluble solids in viscous

liquids for dispensing in soft capsules and

in the preparation of syrups.

• Mixing of two immiscible liquids for

preparation of emulsions.

Mixing of Semi-Solids:

• The mechanisms involved in mixing semi solids

depend on the character of the material which may

show considerable variation.

• Many semi solids form neutral mixtures having no

tendency to segregate although sedimentation may

occur.

• Factors to be taken into consideration while

selecting a mixing equipment include:

(1) Physical properties of materials to be mixed

such as density, viscosity and miscibility.

(2) Economic considerations: operating efficiency,

cost and maintenance.

Semi-Solid Mixers:

The most commonly used semi solid mixers

are:

1. Sigma blade mixer (Double arm mixer)

2. Triple-roller mill (Three roll mill)

1) Sigma Blade Mixer

• Engineered for mixing and homogenizing wet, pasty

and highly viscous products.

• The two Double Arm Sigma shaped blades, which

sit horizontally and parallel at the bottom of the

mixing trough, provide thorough mixing.

• The blades rotate at different speeds in opposite

directions causing the product to be transferred from

blade to blade and from end to end.

• Valves can be located in the bottom of the unit,

allowing the product to discharge

through plug, ball, or "bomb bay"

type valves.

1) Sigma Blade Mixer

1) Sigma Blade Mixer

Options of the mixer:

• Mechanical or hydraulic drive system

• Jacketed mixing troughs or heating and cooling

• Designed for pressure, vacuum, or inert gas operation

• Remote operator control.

• Specialized die heads / special extrusion spouts.

• Automated operation of cover via hydraulic piston.

• Cored blades of various design.

1) Sigma Blade Mixer:

• Laboratory Mixers are available in sizes ranging

from 1/4 gallon to 3 gallon working capacity.

• Variable speed drive on the blades standard.

Stainless steel construction standard, jacketed is

standard.

1) Sigma Blade Mixer:

Applications:

• Ideal for mixing, kneading of highly viscous mass,

sticky and dough like products.

• Mixing of pastes, rubber, and heavy plastic masses.

• Applications in Food, Pharmaceutical and Chemical

industries.

• Dry powder to wet phase mixing

• Used for products like granulation masses and

ointments.

2) Triple Roller Mill

• A Triple Roll Mill is a machine that uses the shear

force created by three horizontally positioned rolls

rotating at opposite directions and different speeds

relative to each other to mix, refine, disperse, or

homogenize viscous materials fed into it.

• The pasty substance is fed into the hoper, where it is

drawn between the feed and center rollers.

2) Triple Roller Mill

• When pre-dispersed, the substance sticks to the

bottom of the center roller, which transports it into

the second gap.

• In this gap the paste is dispersed to the desired

degree of fineness.

• The scraper system removes the finished product

from the apron roller.

2) Triple Roller Mill

Applications:

• Used to mix electronic thick film inks, high performance

ceramic, cosmetics, carbon/graphite, paints, printing

inks, chemicals, glass coatings, dental composites,

pigment, coatings, adhesives, and foods.

• Utilized in the production of cable cover, electronics,

soap and artificial plastics.

• The roller mills are generally used to grind and

complete the homogeneity of ointments.

References

• http://www.pharmatutor.org/pharmaceutics/mixing-

of-pharmaceuticals-mechanism.html

• http://www.jaygoinc.com/extruders.htm

• http://shaktipharmatech.com/triple-roller-mill.html

• http://www.microlambda.com.my/triple.htm

• http://www.brighthub.com/engineering/mechanical/a

rticles/57247.aspx#ixzz125KqFJnu

ThanQ !!