Gerteis® pharmaceutical roller presses

More than three decades of constant development and innovation has made Gerteis of Switzerland an internationally respected expert force in pharmaceutical roller compaction of powders for tableting and other applications.

Gerteis® pharma roller compactors, including POLYGRAN®, MACRO-PACTOR® and MINI-PACTOR®, are renowned for their reliability and versatility in supporting roller compaction from lab to production scale of all kinds of powders, even notoriously problematic ones.

Pharma roller compaction principles

Granulation is a process that combines compaction (‘compressing’) with milling (‘grinding) to produce uniformly sized powder particles with usable flow characteristics (‘flowability’) that allow them to be used for tableting or capsule/sachet filling.

Performing this process while adding liquid is Wet Granulation while Dry Granulation is the process of compacting a dry powder blend by applying a force to produce a spread compacted mass (briquettes, flakes or ribbons).

While wet granulation has to be done in staged batches, dry granulation can be performed as a continuous roller compaction process, delivering various efficiency benefits, principally increased throughput at up to 400 kilograms per hour (kg/h).

Dry granulation systems also require comparatively fewer investments into buildings or equipment. Coupled with lower energy requirements and maintenance costs, this results in a much higher overall profit.

Roller compaction vs. slugging  

There are two basic methods to obtain the compacts when using dry granulation: slugging and roller compaction.

• Slugging relies on flowing powder particles into the die of a tablet press, where they are compacted under vertical pressure. The main problem with this method is that small particles do not flow well into the die, meaning that individual slugs (tablets) can show considerable weight differences, significant fluctuations in the pressing force and thus inconsistent mechanical strength or breaking force. Hence slugging is becoming obsolete as a dry granulation method.
• Roller Compaction combines feeding, compaction and milling into a single and continuous process, as reflected in the three-part design of a Gerteis Pharma Roller Compactor:
  1. Feeding system to convey powder to the compaction area between the rolls
  2. Compaction unit where force is applied between two counter rotating press rollers to compact powder to a ribbon.
  3. Size reduction unit to mill the ribbons to desired particle size.

Ensuring roller compactor pharmaceutical quality

The key parameters in ensuring high process quality in pharma roller compaction are Force and Gap.

The powder is compacted between two press rolls by applying a force, which is the most important parameter in the dry granulation process. The applied force is expressed in kN/cm, being the force per cm roll width. Occasionally the press force is also indicated in bar. This, however, merely represents the pressure within the hydraulic system rather than the mechanical force applied onto the powder.

At a given force, depending on the amount of powder conveyed to the press rolls, the powder will be compacted to a predefined ribbon thickness.

A precise process control with respect to both force and gap is essential to obtain even granular properties from a homogenous ribbon.

The Gerteis Process Analytical Tool (PAT) enables its roller compactors to calibrate and validate all quality relevant parameters, including force, gap and roll speed on-line, while also measuring and recording them. These capabilities are key in fulfilling pharma industry quality and regulatory requirements of the pharmaceutical industry for a well-controlled and fully-documented manufacturing process.

Floating gap advantages

Both fixed gap and variable gap roller compactors follow the three-step process described above but differ in the way the smallest distance (gap) between the rolls is realized.

With fixed gap, the amount of powder drawn in into the compaction area between the rolls is inconsistent, which results in different forces applied to the powder bed. Like in slugging, this will cause large fluctuations in the ribbon and granulate properties.

With the floating gap used in Gerteis machines, the distance between the rolls changes according to the amount of powder provided. This ensures force applied to the powder remains constant, minimizing property fluctuations in the granules.

Floating gap technology is used on all five Gerteis’ pharma roller compactor solutions, tailored for a range of needs from proving laboratories to high containment production.

• MACRO-PACTOR®: Gerteis’ flagship pharma roller compactor solution, is designed and engineered for scale up from development to high speed production at up to 400kg/h and a very wide range of press force, roller speed and gap settings. Engineered around an open star rotor, closed pocket type granulator with integrated bulk-breaking and precrushing for optimal compaction results, Macro-Pactor also features real-time process control, perfect sealing system to reduce uncompacted fines and complies with CFR 21 Part 11 requirements.
• MINI-PACTOR®: Gerteis’ laboratory roller compaction solution incorporates the same high-quality engineering and granulator design in a more compact package designed and engineered for pharma laboratory development, while also handling pilot projects and small-scale production batches. Mini-Pactor features constant ribbon properties, validated gap and force measurement and low OEL levels, with the interfaces needed to support high containment applications.
• ULTRA-PACTOR®: a high-end pharma roller compactor engineered for ultra-high containment applications, supporting OEL levels of under 0.1µg/m³, while still offering throughputs up to 400kg/h. Ultra-Pactor guarantees optimal protection for the operator against highly active and hazardous substances with glove ports, ATEX-compliancy and the ability to purge N₂ into the process area.
• POLYGRAN®: A pharma roller compactor oriented towards production and value for money, featuring simplified handling and controls for high accessibility. Ingeniously engineered powder feeding and parts assembly. These allows POLYGRAN^® to support medium production quantities with throughputs of up to 300kg/h.
• MINI-POLYGRAN®: an ultra-compact and highly mobile pharma roller compaction solution that strikes an ideal balance between performance and flexibility. The unique POLYGRAN^® setup of individual machine parts allows ultra-rapid maintenance and changeover from batch to batch, with hassle-free scale-up to production volumes of up to 40kg/h.

Gerteis offers regular ‘master class’ workshops in pharma roller compaction techniques and has produced a White Paper guide to the basic concepts and approaches. This product bulletin summarizes the main points of the White Paper.