Case Study: More flexibility in tablet coating

Oct. 25, 2021
Syntegon's new state-of-the-art drum coater combines decades of experience in tablet coating and process technology to offer customers an ideal fusion of experience and innovation.

Tablet coating is a demanding and important process step in tablet production. Only a precise and tailor-made coating meets both the coloring and taste masking, as well as the more demanding requirements such as enteric coatings, slow release coatings or an active ingredient application. For Syntegon (formerly Bosch Packaging Technology) it was an obvious decision to complement the technologically leading high-shear mixer-granulators and fluid bed systems of the Hüttlin product brand by adding a state-of-the-art drum coater: the new Sepion series. Syntegon has combined decades of experience of the former Manesty product brand with the expertise of the Hüttlin product brand in tablet coating and process technology to offer customers an ideal fusion of experience and innovation.

Key requirements

What do pharmaceutical manufacturers expect from a new coater series that is designed to offer them decisive added value? The analysis of market requirements showed that the focus should not be on a single aspect. Rather, the goal was to develop a state-of-the-art drum coater that meets all customer needs. The development team consisting of engineers and pharmacists had to fulfil the following five requirements:

Closed material handling

The entire process sequence should be closed from filling to emptying and cleaning. The new Sepion series eliminates the need to open doors during the ongoing process, since it is filled and emptied via tubes with clamp connections integrated into the front door, which can be equipped with split valves.

Uncoated tablets are extremely sensitive to breakage. In the Sepion coater, they slide into the mixing drum smoothly and gently. Sampling is just as easy and uncomplicated thanks to the sampling cylinder. The mixing drum is emptied by means of reverse rotation via a closed system: specially shaped discharge baffles guide the tablets quickly and gently to the discharge opening in a continuous tablet stream, allowing a 500-liter drum to be emptied in just a few minutes.


Safe containment is especially important to protect machine operators, products and the environment. When developing a new system, the containment concept should be considered right from the start — as is the case with the Sepion coater. For example, the basic version can be upgraded to a containment coater with user-specific options. These essentially consist of split valves, safe-change filters and extended cleaning.

Flexible batch sizes

The Sepion coater is extremely flexible when it comes to batch sizes: the drum can be filled with product from a minimum of 10% up to a maximum of 100% of the working volume, thus offering wide application possibilities. The design of the mixing baffles ensures gentle and thorough mixing at any fill level. The mixing quality was examined in extensive tests, where tablets with three coatings were mixed. At 100% filling, the specified relative standard deviation (RSD) of the mixture of less than 3% was undercut during the tests after 8 minutes.

Automatic spray arm

The automatic spray arm ensures the correct distance of the spray nozzles to the tablet bed, and the correct inclination of the spray nozzles can be set automatically for all filling heights. The alignment is done either recipe-controlled or via an optional distance sensor. Depending on requirements, two variants of the spray arm are available: the standard and the pro spray arm. With the standard spray arm, each spray nozzle is supplied with a separate liquid line. The pneumatic connection of the nozzles partly takes place via hose connections.

The pro spray arm with its mechanical connection of the spray nozzles ensures all pneumatic connections and enables the connection of a common liquid supply and return, which greatly simplifies installation and cleaning. The spray nozzles are positioned along the spray arm by a tool-free quick-connect system without hose connection. This avoids misalignments, while greatly reducing setup and cleaning times.

Process optimization for best coating results

During development, the focus was also on significantly reduced process times while maintaining high yields. Hence, the drum was lengthened in relation to its diameter. On the one hand, this allows a higher number of spray nozzles. On the other hand, the longer drum results in a flatter tablet bed, allowing the individual tablet to pass through the spray zone more frequently. The combination of both features facilitates higher spray rates and more uniform coating with shorter process times. Extensive tests with different tablets and filling quantities in comparison with an established coater have shown: the Sepion coater achieves significant improvements in process times while minimizing the RSD of the coating.

The results presented here refer to a coating series with Opadry II. The objective was to achieve the required mass increase of 13% by a maximum spray rate and a high solid content of the spray solution of 20% in the shortest possible time. The average weight of an uncoated tablet was 304 mg; the measured standard deviation within a sample of 500 tablets was 3.045 mg or 1% RSD (left side of diagram). After a process time of only 155 minutes, 345 kg tablets were coated. The average weight of a coated tablet is 344 mg, with a standard deviation of 3.76 mg or 1.09% RSD.

Accordingly, the new Sepion coater is suited for all applications — from cosmetic, non-functional coatings to enteric coatings, slow release tablets and active ingredient coatings. The Sepion coater also achieves very good values in terms of yield (i.e. 98%). The effective use of the coating suspension saves process time, minimizes product use and reduces cleaning efforts.

Optimized cleaning process

The new Sepion coater has also been optimized in terms of cleaning. The WIP rack is located in the technical area. The cleaning nozzles in the drum coater are arranged in a way to safely reach all product-contact surfaces. In addition, the 360-degree high-pressure cleaning nozzle provides for even more intensive cleaning. All cleaning operations follow a validated, reproducible recipe and minimize manual intervention. Finally, the new multi-touch panel with integrated, intuitive operator guidance and optional process visualization ensures safe operations.

The new, highly flexible Sepion coater is available in six sizes: from 175 and 250 through 350 and 500 to 750 and 1,000 liter capacities. The thorough comparative tests have already convinced customers: the first new Sepion coaters are currently being installed in greenfield projects in Europe and Asia. In addition to its flexible batch size, the closed material handling and the high spray rates with a very low RSD of the Sepion coater were the main factors to clinch this decision.

Fritz-Martin Scholz is a Product Manager for Syntegon Technology. Syntegon Technology is a leading global process and packaging technology provider. Formerly the packaging division of the Bosch Group, the company, headquartered in Waiblingen (Germany), has been offering complete solutions for the pharmaceutical and food industries for over 50 years.

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