Dry granulation can be described as a process of powder agglomeration that is generally used within the pharmaceutical industry for improving the smoothness and flowing quality of powders by enhancing the size of the granules or the particles. The operation can be carried out with the help of a roller press machine that can come in varying equipment structures, designs, and configurations. The process of dry granulation is also called double compression or pre-compression. The size enlargement process associated with dry granulation can greatly enhance the compression of the powders. Unless dry granulation is carried out, these granules cannot be compressed at all. The powder particles are exposed to a process of compacting so that large pieces can be formed with them. These can then be subsequently made into granules so that they can be processed to create small dosages.
The process of dry granulation is usually recommended for manufacturing tablets in case the ingredients that are to be used are very fluffy or may cause hindrances to smooth flowing which can make direct compression difficult. The dry granulation mechanism can also be followed when the ingredients are highly vulnerable to degradation from moisture and heat. Dry granulation is the process of choice when it is not possible to perform wet granulation. Sometimes dry granulation is considered to be a viable alternative for the wet granulation process if it is not possible to carry out direct compression. There are also pharmaceutical firms that prefer to work with dry granulation process because they have more work experience with it or they want to bring down the processing time as far as possible. Dry granulation is also the preferred method of compaction if the pharmaceutical team wants to cut down on manufacturing costs.
There are mainly two different techniques that are used for the dry granulation process. These include the roller compaction technique and the other one is the slugging technique. Roller compaction technique or ribbon blending technique is the simpler and more efficient of the two and can be handled more or less in an inexpensive manner. In this process, the formula ingredients are passed constantly between 2 counter-rotating rollers. This helps to consolidate and increase the density of the material to produce a solid mass. The rollers that are used for this purpose can vary and the output is also determined by that. Therefore, you can get flakes or dense briquettes provided that the rollers have grooves and/or etched features in them. The compacted materials are collected and then they are lubricated, sized and finally compressed to form tablets.
In the slugging technique, primary powder particles are first compressed into big-sized flat pallets or tablets with the help of a tablet press or a powerful rotary press machine. This is milled with the help of a hammer mill or any other type of milling tool. Once this is done, the resulting milled slugs are collected and passed through a meshed system for sizing. A lubricant is combined with the pharmaceutical powder and tablets are formed out of these granules.