Gerteis® Concept Dry Granulation
Products & Services | Gerteis Maschinen + Processengineering AG
This is a holistic and synergistic method in which the processes are adapted to the capabilities of Gerteis® roller compactors, which are themselves optimized to comply with the process principles.
Granulation is a process in which powder particles are made to adhere to each other, resulting in larger, multi-particle entities, or ‘granules’. When this process is performed without adding liquids, it is known as dry granulation or roller compaction.
In dry granulation, the powder blend is compacted by applying a controlled force onto the powder, which in general leads to a considerable size enlargement. The compacts thus obtained are called ribbons, flakes or briquettes.
In order to obtain granules of optimum size, the compaction process must be followed by a milling step.
Principally there are two methods to obtain the compacts when using dry granulation: slugging and roller compaction.
- Slugging: This describes the compaction process when performed on a tablet press directly. However, obstructions to thw flow of small-sized particles into the die of a tablet press can result in weight differences from one ‘slug’ (tablet) to another. This in turn causes large fluctuations in the forces applied onto the individual slugs and variability in the mechanical strength of the slug. This means in turn that it becomes almost impossible to control precisely the properties of the granulates obtained by milling the slugs. These are the main reasons why slugging should not be used as a dry granulation method.
- Roller Compaction: A better way to perform dry granulation is on a roller compactor, where the powder is compacted between two counter rotating rolls by applying a force to form ribbons or flakes. A Gerteis® roller compactor consists of three main systems:
- Feeding system: a series of inlet funnels and augers that convey uncompacted powder with small particle size to the compaction unit and feed the powder between the rolls.
- Compaction system: where the powder blend is compacted between two counter rotating press rollers, applying precisely defined force and a metered gap between the rollers to produce a ribbon with defined ribbon strength or ribbon density.
- Milling system: a rotating body, called granulator, cuts the ribbon pieces against a screen for size reduction. A combination of different granulators as well as various screen sizes and types allow precise control of particle size and distribution of granules.
Product Quality Aspects
Final product quality is determined by a series of adjustable factors and process parameters:
- Force and Gap: The powder is compacted between two rolls by applying a nominal mechanical force for each centimeter of roll width, with actual forces on the powder varying depending on the gap and quantity of granulates conveyed to the rolls. Together, these will then determine the ribbon thickness. Obtaining uniform granule properties from a homogenous ribbon requires precise process control (see PAT section below).
- Variable or Fixed Gap: The gap is defined as the minimum distance between the two press rollers. Roller compactors can be divided into two categories: One is equipped with a fixed gap, the other one with a floating gap. Both consist of the three major units as explained above but differ in the way in which the gap between the rolls is achieved. When a fixed gap is installed, the amount of powder drawn in into the compaction area between the rolls is inconsistent due to the powder flow characteristics, which results in various forces applied to the powder bed. As with slugging, this leads to larger fluctuations in the ribbon and granulate properties. Gerteis® machines use a floating gap system in which the gap is formed by the amount of powder provided. Gerteis’ Gap Control Mode constantly measures the actual gap and efficiently adapts feeding to maintain ideal gap settings. Combined with constant force applied to the powder, this results in reduced property fluctuations in the granules.
- Milling: Gerteis® integrated models mill the ribbons immediately after compaction through a screen with a given mesh size, thus limiting the upper particle size. This milling process has to be performed as gently as possible to avoid creating excess fines.
- Process Analytical Technology (PAT): This is a digital control and monitoring system that allows Gerteis® roller compactors to control and measure all product quality relevant parameters online in order to fulfill pharmaceutical industry requirements for a well-controlled and documented manufacturing process. All the parameters are calibrated and validated. Additionally, in order to cope with batch-to-batch variations, Gerteis® machines are fitted with control systems to ensure consistent granule properties during manufacturing.
Applications & Benefits
Applying the Gerteis® Concept to dry granulation applications delivers several user benefits.
- Ultra-High Containment, with options available to avoid contamination of manufacturing areas and personnel from highly potent active ingredients (HPAIs).
- Lower running costs
- Customized solutions with bespoke machine designs
- MES integration
- VM solutions
Gerteis® dry granulation machines
Gerteis® offers two premium solutions for dry granulation roller compaction:
Click on Gerteis® Concept dry granulation for more information.
Click on Gerteis to contact the company directly.
Click on Mini-Pactor® for further product details.
Click on Macro-Pactor® for further product details.