Coating is an integral part of pharma tablet and pellet production. Nevertheless, there are some problem areas that have not been adequately solved so far, although they have an impact on almost every coating process and entail economic losses. To a certain extent, this is due to a presumed lack of possible solutions– but they do exist. In particular, a new generation of tablet coaters is addressing these challenges in an innovative way.
When talking about challenges in coating, there are basically three areas involved: the quality of the coating result, the productivity of the coating process and the flexibility of the tablet coater.
Among the first things that come to mind when thinking about product quality is the prevention of defects. While the purely aesthetic defects can sometimes be tolerated, the entire batch is at risk if a functional coating is compromised. Preventing such losses is always a matter of stabilising the coating process by regularly checking parameters and adjusting them if necessary. The common method for increasing and simplifying this process control is currently to improve the technical feedback. After that, it is the operator’s responsibility to react accordingly. This is definitely a solution that works, but is it enough to achieve real process stability?
Reality is that this approach leaves a relatively large risk for errors and inaccuracies, because the regulation and optimisation of the coating process is absolutely dependent on the operator. What if there is no suitably skilled operator available due to the shortage of trained workers in the labour market or for other reasons? And even if a fitting operator is available, it is not always easy for him either to get the ideal coating settings and keep track of all the parameters, especially with batch size changes, complex coating processes or demanding products that are, for example, very sensitive to humidity or temperature.
The solution to this systemic uncertainty is to automate the coating process to a larger extent, including the fully automatic adjustment of the relevant parameters where required. The TP R Optima perforated coating pan from Romaco Tecpharm is capable of doing so. It monitors parameters such as temperature, humidity, flow rate and batch quantity, obtains the predefined optimal coating conditions for the specific product and thus minimises the risk of losing parts of or entire batches. One could say the TP R Optima tablet coater creates the absolutely reproducible coating process – irrespective of the complexity. The possibility of almost complete automation ensures that you no longer have to be an expert to achieve consistently high product quality with this technology. But what does this automatic self-regulation look like? This can be exemplified very well in the context of the second main problem area, where automation is also the means of choice for optimisation.
The deficiencies in the productivity of the coating process are partly accepted as a given. As an example, it is currently common to plan for 50 per cent more suspension than is theoretically needed to coat a product, because a loss of up to 40 per cent is considered normal. With functional coatings, like coatings with API or controlled release coatings, this can result in major financial losses. But even with standard coatings there are hidden costs in the form of cleaning and disposal expenses, not to mention logistical expenses, because if more suspension is needed, more must be transported and stored.
Here, especially the automatic adjustment of the suspension application and drying is the answer. Technically, this is implemented in the TP R Optima as follows: Using sonar technology, acoustic wave sensors continuously measure the distance between the spray nozzles and the tablet bed, which may vary depending on the process that is conducted. If modifications are required regarding the ideal spray distance or the set spray angle, the intelligent system carries them out by means of a nozzle arm with a three-point extension mechanism during the ongoing process – the machine does not have to be paused for this purpose. Drying is regulated automatically via a vacuum generated inside the drum, which can vary depending on the batch size, and via automatic air exhaust flaps, which can be opened individually and continuously. This permits absolutely precise regulation of the path taken by the air flow through the tablet bed, ensuring that the coating does not simply run over the product before being discharged again unused. With these new possibilities of the coating technology from Romaco Tecpharm only 10 to 15 per cent more coating medium is needed instead of 40 per cent. And that makes a significant difference. The associated more efficient drying and the possibility to make adjustments without interrupting the coating process also reduce process times by hours. And prior to the actual coating, time is additionally saved in the fine-tuning and preparation of a new batch, as the TP R Optima virtually adjusts itself to the recipe and the associated parameters. All this combined results in substantially lower energy usage.
Another special feature of this technological adaptability is immense batch size variability within a single machine, which not only increases productivity, but above all brings flexibility– and that leads to the third main problem area.
Almost everyone who realises coatings has to deal with scale-up and scale-down procedures in some form or another sooner or later – for example:
– When producing for various countries and batch sizes have to be adapted to the different market requirements
– When validations have to be carried out and about 10 per cent of the subsequent batch sizes have to be manufactured for this purpose
– When producing under contract, where a wide range of batch sizes must be processed
– Or when the switch from laboratory to production scale is pending.
But why is scaling up and down a challenge? Firstly, it means that companies currently need at least two machines, one for producing smaller batch sizes and one for larger batch sizes, as most coaters do not have a large enough batch size variability. Usually, they can only go down to 40 per cent of the maximum batch size at the most. This need for several machines is associated with very high investment costs, energy expenditure and space requirements. In addition, the parameters cannot simply be transferred from one machine to another – not even if they are the same type and brand. Consequently, a relatively large number of manual adjustments have to be made, and here again the problem of ensuring high quality and uniformity across all products arises. Not to forget, of course, the time and work that goes hand in hand with manual adjustments.
With the ability to monitor and adjust to batch sizes, the TP R Optima achieves a batch size range from true 10 to 100 per cent filling volume with one and the same drum. This eliminates the need for multiple machines just because of different volume requirements, the time and manpower it takes to set up the right parameters for different systems and the risk of errors and imprecisions. What is more, this not only applies to validations and batches of different sizes, but also to volume changes within a single coating process, such as coatings with multiple layers. It could be argued that coaters with this range have been around for a while, and that is true, but the batch size variability of these technological solutions necessitated drum changes and manual adjustments, which removed the problem of purchasing multiple machines, but not the risks of manual intervention. Moreover, the drum changes created extra labor and cleaning efforts. This also becomes largely obsolete with the use of only one drum.
A final aspect of flexibility in coating is the possibility to change the coating medium itself without major technical alterations. There are several reasons why this could be required. For example, a reformulation may be a necessity due to imminent and acute bans on formulation components. Trends towards more natural ingredients such as the departure from alcohol in favour of water-based suspensions may also call for recipe modifications.
Again, automated parameter adjustment provides advantages. In the demanding search for new recipes, the experts can concentrate on the formulation and leave the rest to the machine. Apart from that, process times are shorter, which further facilitates R&D activities as more formulation trials can be implemented in a given period of time. Saving time is also the big issue with water-based suspensions, which have longer drying phases. Due to more efficient drying with the “full” automation of the TP R Optima, this does not have the same impact as with previous technologies.
There is significant optimisation potential in coating that can be exploited through a higher degree of automation. Shorter process times, continuously high product quality, time and cost savings and resource conservation are just some of the gains. Tablet coaters like the TP R Optima with these technological capabilities will certainly represent the future of coating and are already supporting innovation.
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