Colloid mill is a machine used in the disintegration of solid particles or droplet size of a liquid present in suspension or emulsion. The machine consists of an inlet (which is subjected to a tremendous shearing action that effects a time dispersion of uniform size) and an outlet. Colloid mill works on the rotor-stator principle. The equipment breaks down materials by forming dispersion of material in a liquid. Shearing takes place in a narrow gap between a static cone (the stator) and a rapidly rotating cone (the rotor). To reduce wear, the rotor and stator are constructed using toughened steel or corundum. The rotor of a colloid mill can differ from one machine to another but the operating principle is the same for all. Each manufacturer incorporates specific features that results in changes in operating efficiency.
The final size of product obtained after comminution is a function of the followings;
- Homogenization intensity and duration
- Viscosity of the continuous phase.
- Shear force within the gap between the spinning rotor and the stationary stator.
- Clearance rate between the rotor and the stator.
The energy consumption of colloid mill depends on;
- The viscosity of the product
- Feed rate
- The temperature during processing.
Pharmaceutical uses of colloid mill
- Colloid mill is most often used for the comminution of solids and for the preparation of suspensions especially suspensions containing solids that are not wetted by the dispersion medium.
- It is also used to increase the stability of suspension and emulsion.
- It is used in the formulation of colloidal dispersions, suspensions, emulsions and ointment.
- Colloid mill is used for grinding, dispersing and homogenizing of ointment, cream, gets and high viscous fluids in one operation.
Advantages of Colloid Mills
- It has a wide range of use including comminution of slurry- fluid materials.
- No pressure is required for ionization.
- The machine is simply constructed.
- It can be easily adjusted.
- Colloid mill is easy to clean after use
- The machine is self draining.
- High capacity and minimal requirements.
- Reduced wear as a result of the construction of the rotor-stator with toughened steel/corundum.
- Low machine noise level.
Disadvantages of Colloid Mill
- It has no wide application in solids
- Wear of the rotating plates
- No fine grinding
- Consumes energy though still dependent on some factors.
- David, B. Troy and Paul, Beringer (2006). Remington: The Science and of Pharmacy. 21st edition. Lippincott Williams and Wilkins, USA.
- George D. Saravacos, and Athanasios E. Kostaropoulos (2002). Handbook of Food Processing Equipment. Kluwer Academic/Plenum Publishers, New York.