Tablet coaters are becoming increasingly important in pharmaceutical production: tablets are the most important oral dosage form in the pharmaceutical industry and are often coated. This involves applying a thin film of one or more polymers and other functional excipients (colorants or humectants) to the tablet, which can perform a variety of functions.
Tablets are coated to modify the release of the active ingredient, to protect the active ingredient from light or moisture or to mask a bitter taste in the tablet formulation. Tablets are also coated to improve swallowability.
Active ingredient coating is becoming increasingly important. Both combination preparations and the combination of two incompatible active ingredients in one dosage form are realized. In addition, different release profiles of the same active ingredient can be combined with each other. The core contains the slow-release component and the tablet coating contains the fast-release initial dose. The formulation approaches sometimes consist of up to four different film types. This leads to long process times. In order to successfully develop and produce such formulations, the uniformity of the tablet coating is a mandatory requirement.

Mixing, spraying and drying
In tablet coating, the interaction of mixing, spraying and drying is crucial. Mixing, spraying and drying must be carried out simultaneously and with the correct settings in order to achieve optimum coating uniformity.

Mixing:
Uniform and, above all, gentle movement of the tablet cores under the spray cones is crucial. The tablet cores must not be subjected to excessive mechanical stress in order to avoid damage.

L.B. Bohle (Ennigerloh) has been successfully using an extended coating drum (length diameter (L/D) > 1) with welded-in mixing spirals for more than 20 years. The mixing spirals ensure continuous and gentle mixing of the tablet bed. Homogeneous mixing is achieved after just a few minutes and is maintained over the entire process time. The flat tablet bed reduces the mass pressure in the tablet bed. The continuous guidance of the mixing spirals means that the tablets are not greatly accelerated. Tablet breakage and twinning do not occur.

Tablet coater: drum geometry, spray arm design and reduced coating time
The drum geometry of the BFC tablet coater from L.B. Bohle creates a large spraying surface in the moving tablet bed. This means that more spray nozzles can be used than with shorter drums, resulting in a larger spray area and higher spray throughput. In addition to the coating suspension, the nozzle type, the number of nozzles and the nozzle spacing are of particular importance.

L.B. Bohle offers various solutions for adjusting the nozzle-to-bed distance, the spray angle of the nozzles and the pressure parameters for atomization.
As a rule, the proportion of suspension mass in film-coated tablets is 5-15% of the mass of the core. Special mention should be made of the film thickness, which is not only important for active ingredient coatings, but must also be uniform for thin color (protective) coatings. An uneven film application within a batch, for example, leads to color differences that reduce product quality.
Compared to conventional tablet coaters with L/D ratios <1, systems with extended drums enable up to 40 % shorter process times due to higher spray rates. Drying
It is crucial to ensure optimum energy and mass transfer. This means that the energy must be introduced directly into the tablet bed. The air flows directly and calmly into the tablet bed and effectively ensures rapid drying of the sprayed suspension. The periphery of the coater or the housing are not heated.
The optimum air flow creates a calm spray pattern, which reduces the spray drying effect. The spray nozzles are not exposed to the supply air flow and remain cool during the spraying process. This reduces spray drying effects to a minimum and achieves a uniformity of the coating of > 97% and better.
World premiere at Interpack 2023 - Coater optimized in terms of process, technology and machine equipment
The tablet coaters from L.B. Bohle tablet coaters have been firmly established on the market for more than two decades and are recognized as technologically advanced.
Through an intensive exchange with customers and continuous cross-departmental research and process optimization, L.B. Bohle was able to further improve the BFC series. This has led to improvements in the areas of technology / machine equipment, cleaning, user-friendliness and safety, hygienic design and sustainability. The aim is to optimize the daily production process by making production not only more flexible and faster, but also more resource-efficient with optimum uniformity.
A new machine control system is used in the area of machine equipment. The iFix application enables processes to be monitored and controlled. As an HMI (Human Machine Interface), iFix provides the elements required for operation. In addition, important data such as long-term data storage of measured values, alarms and messages as well as data interfaces to external systems and recipe management are recorded.
The BFC tablet coater offers maximum flexibility, allowing batch sizes with a filling level between 10 and 100 % to be realized. With a BFC 400, this corresponds to batch sizes of 65-650 l.
L.B. Bohle has redesigned the nozzle block in the BFC. Nozzle adjustment in angle and distance is motorized and automatic. In addition, the nozzle block is now slimmer and rounded. This enables better process monitoring and makes cleaning easier.

Easier operation and greater safety
L.B. Bohle has implemented user suggestions in particular in the new system. Opening and closing the side door is now supported by pneumatic cylinders so that less force is required. The air supply shoes are separate, which means a significant reduction in weight and easier handling.
Safety aspects have also been taken into account. Inflatable seals are now used as standard. Fully automatic sampling and tablet loading with the door closed increase operator safety.
The operating panel has been redesigned in a hygienic design and a status light integrated into the front of the machine supports process monitoring.

Fast emptying and effective cleaning
Once the coating process is complete, the coater is emptied quickly, gently and completely by reversing the direction of rotation and adjusting the inclination. This is followed by fully automatic cleaning. An additional cleaning lance at the bottom of the system is now integrated as standard. Further improvements shorten the cleaning time and ensure that the cleaning medium runs off quickly and residue-free.

Focus on sustainability
For the first time, L.B. Bohle is offering optional heat recovery in the ventilation system, which significantly minimizes energy consumption.
A new energy monitoring system for the coater's energy supply provides manufacturing companies with a complete overview of their own process and consumption.