The pharmaceutical manufacturing facilities use powder classification system for size reduction. Size reduction is the most extensively used operation or process for reducing large solid unit masses into small unit masses, fine particles or coarse particles. Sometimes this process is recalled as commutation or diminution or pulverization. Manufacturers of size reduction units generally provide several types of size reducing equipment, which are usually designed to handle specific materials and later used in different situations.
When the particle size of solids is reduced with mechanical technology, it is known as milling. Medicinal powders used by pharmaceutical industry are polydisperse- which means it has particles of various sizes and this makes harder to produce dosage forms. Equal size particles – mono-size, are ideal for making medicines. Size reduction along with size separation plays significant role in production of mono-size powder.
Factors that affect the size reduction results –
- Hardness – how much hard the material is and how many hammers are needed to break it into pieces is what the facility staff look to determine hardness of the material before processing.
- Toughness – The toughness of the material is determined by its strength. How much force and tools are required to break the material can help judge the toughness of the material.
- Slipperiness – Before taking the material to processing unit, it is important to check if the material is slippery.
- Stickiness- Prior starting milling process, ensuring that material is viscose or sticky will help in the next step.
- Moisture content – It is important to check for moisture content in the material before processing it through powder classification systems.
- Abrasiveness – Often minerals are abrasive. You must find out how much time will it take to shape or rub the work piece for final results.
- Material structure- How the material response to an applied force, its hardness and strength comes under structure.
- Material size- what size of material is being used for milling.
- Material shape – The shape of material matters when you are using and processing it into milling unit.
- Melting or softening point and more- how much time does it take to melt the steel scrap you will use, or what will be its softening point should be determined well.
Critical techniques in size reduction
- Sono crystallization
- Spray drying
- Supercritical fluid process
Sono crystallization involves ultra sound of frequency range 20-100 KHZ for initiating crystallization. Experts find it ideal and effective method of size reduction that also controls size distribution of active pharma ingredients.
Spray drying is a common method of drying a liquid feed using a hot gas technology. The hot air is used for sensitive materials such as ethanol that requires oxygen free drying process and nitrogen gas.
Supercritical fluid process is a dense non-considerable fluid having greater temperature and pressure when compared to its critical temperature and pressure.
