In the tablet production process, the purpose of coating is to improve the appearance of the tablet, prevent moisture, avoid light, cover up bitterness or unpleasant odor, and control the release location and release rate of the drug. In the past, most of the traditional oral coated tablets were sugar-coated tablets, which tested real skills, took a long time, did not save effort, and could not guarantee the quality. In recent years, with the rapid development of the pharmaceutical industry, film coating has become a trend, and the efficiency is much faster.
It is understood that the film coating process is to spray a relatively stable high molecular polymer coating uniformly on the surface of the tablet core by spraying to form a plastic film layer of several micrometers thick to achieve a certain expected effect. It is suitable for In medicine, pharmacy, food, health care products and other industries, sugar coating, film coating, polishing and rolling round pellets are applied to the appearance of Chinese and Western tablet cores.
With the widespread use of film coating machines, how to improve the success rate of coating becomes the key. Some experts pointed out that the coating success rate of the film coating machine has an important relationship with its spray gun system. Choosing a good spray gun system and optimizing the working conditions of the spray gun before coating is an important guarantee for the success of coating production. So, how should the spray gun be optimized? Some technical personnel who have accumulated rich experience in the research and use of high-efficiency coating machine spray guns have given a few opinions, which are only for industry reference.
First：
before the coating starts, check whether the connecting tube of the spray gun is leaking, whether the needle movement is flexible, whether the needle is in the center of the nozzle, etc. According to the industry, these conditions will affect coating efficiency and coating quality. Specifically, check the position of the gun needle on the nozzle. When the gun needle deviates from the center of the nozzle, the ratio of the coating liquid and the high-pressure atomizing gas at the nozzle will change, which will affect the shape and atomization effect of the spray, and sometimes the phenomenon of spray pulses will appear. In addition, the deviation of the needle from the center of the nozzle will also cause the gun to be shut down loosely, and the coating liquid will drop and cause sticking accidents.
Second：
check the position of the spray gun. Under normal circumstances, the spray gun spray position should be located at the upper 1/3 of the bed when the core is flowing, and the spray direction should be as parallel as possible to the wind direction of the incoming air and perpendicular to the flowing bed. The distance between the spray gun and the tablet bed should be determined according to the requirements of different coating systems. For example, the distance for organic solvent coating is shorter, about 20-25cm; the distance for water-based coating is longer, about 25-30cm.
Third：
the coating effect depends on the degree of atomization of the coating liquid. It is understood that the droplet size is small and the droplets can be spread better, which is beneficial to reduce the roughness of the film surface, increase the gloss and greatly reduce the probability of bridging. At the same time, the droplets have strong stretchability, which also increases the drying speed of the droplets on the surface of the tablet core, thereby reducing the adhesion of the film. When the droplet size is too large or too small, it will affect the coating effect. The industry suggests that, in fact, how to control the droplet size should be based on the specific coating equipment, the quality of the tablet core and the viscosity of the coating liquid.
In addition, when the spray fan is wider, the uniformity of coating and color can be increased, and the amount of coating materials can be relatively reduced. It is worth noting that while adjusting the width of the spray fan as much as possible, users also need to consider the overlap of spray between spray guns to improve coating efficiency, improve coating uniformity, and reduce sticky flakes.