Gerteis® Concept Dry Granulation

Gerteis® Concept Dry Granulation

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Products & Services | Gerteis Maschinen + Processengineering AG

The Gerteis® Concept describes a particular approach to dry granulation that has been proven and perfected by this Swiss-based roller compaction specialist over more than three decades.

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 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.

Process Basics

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.

  • Improved Flowability: Dry granulation is used for increasing the bulk density of powders while increasing the particle size, resulting in better flowing material, which is a prerequisite for manufacturing capsules and tablets on high speed production equipment. Furthermore, adhering the particles of various substances together during the compaction process reduces the tendency for different substances to segregate, increasing homogeneity of the active ingredients (API) within the powder blend, thus improving uniformity of dosage forms.
  • Replacing Wet Granulation: Thanks to countless and ongoing innovations nearly all dry powders can be processed on a Gerteis® dry granulation system. Unlike wet granulation, dry granulation is a truly continuous process. This results in various economic advantages. Currently the throughput of common dry granulation systems can reach up to 400kg/h. Dry granulation systems also require lower capital investment in facilities or equipment. This, together with much lower maintenance requirements results in drastically reduced lifecycle costs.
  • Reduced Carbon Footprint: Roller compaction in dry granulation is a highly effective process that delivers high throughputs from compact machinery. Therefore, valuable floor space can be utilized more efficiently and an existing manufacturing plant can improve its overall production effectiveness. Furthermore, dry granulation consumes less energy than alternative granulation methods, since no heat for drying and no air conditioning is required.
  • Further Advantages: The Gerteis® Dry Granulation Concept can also deliver series of process and efficiency benefits, including:
    • 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:

  • Mini-Pactor®: The Gerteis® laboratory roller compaction solution incorporates the same high-quality engineering and granulator design of the Macro-Pactor® in a more compact package and is designed and engineered for pharma laboratory development. At the same time, this platform is also capable of handling pilot projects and small-scale production batches. The Mini-Pactor® also features constant ribbon properties, validated gap and force measurements. Low OEL levels, under 3µg/m³ are possible when the conveyor, feed and discharge interfaces support high containment applications.
  • Macro-Pactor®: The Gerteis® flagship pharma roller compactor solution, is designed and engineered for scale up from development to high speed production at up to 400kg/h. It incorporates a wide range of press force, roller speed and gap settings. The milling unit is engineered around an open star rotor or closed pocket type granulator with integrated bulk-breaking and precrushing for optimal compaction results. The Macro-Pactor® also features real-time process control, an unprecedented sealing system to reduce uncompacted fines and complies with CFR 21 Part 11 requirements. Optional interfaces are also available for pneumatic or mechanical conveyor systems, feed and discharge for high containment applications.
  • Resources

    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.

    The Gerteis® roller compaction process showing: (1) Inlet funnel with agitator, (2) Feed auger, (3) Tamp auger, (4) Small quantity inlet funnel, (5) Press rollers with ribbon, (6) Rotor with desired granules.

    The Gerteis® roller compaction process showing: (1) Inlet funnel with agitator, (2) Feed auger, (3) Tamp auger, (4) Small quantity inlet funnel, (5) Press rollers with ribbon, (6) Rotor with desired granules.

    Gerteis Mini-Pactor®: optimized for laboratory and medium production

    Gerteis Mini-Pactor®: optimized for laboratory and medium production

    Gerteis Macro-Pactor®: flagship pharma roller compactor

    Gerteis Macro-Pactor®: flagship pharma roller compactor

    Supplier Information
    Supplier: Gerteis Maschinen + Processengineering AG
    Address: Stampfstrasse 74, 8645 Jona, Switzerland
    Tel: +41 55 222 55 22
    Fax: +41 55 222 55 23

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