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Factors influencing the process of film coating
Nov 30, 2018

Factors influencing the process of film coating

As a common technology of tablet technology, coating has been developed from traditional icing to thin film coating. At present, the development, introduction and adoption of high-efficiency coating machine and new thin film coating materials make thin film coating become a widely used coating technology in the research and production of preparations. The film coating saves time, the process is less, the energy consumption is lower, and the effect is better. This paper focuses on the improvement of the coating effect of several technological factors.
1, the surface of the core
The appearance of the garment requires light, smooth, and beautiful. When the core of the piece is attached to fine powder, the surface after the coat appears "rising"; When there are small holes, cracks, or abrasions in the core, these phenomena also occur on the surface behind the coat. The surface of the garment core is uneven and unpolished, which will affect the coating effect. Therefore, before wrapping, should sift off the fine powder on the core, pick out the damaged core, ensure that the core meets the requirements.
2, the hardness of the core
During the coating process, the movement of the core is intense, and a greater impact force is generated between them, causing friction, shedding or cracking of the core, destroying the appearance of the tablet, and unfavorable to the coating. In order to reduce the loss of the piece and ensure that the piece core maintains a flat appearance, it is necessary for the piece core to have sufficient hardness. Hardness refers to tensile strength and represents the compressive ability of the sheet. The greater the hardness, the stronger the pressure resistance, and the more stable the surface of the sheet. The hardness requirement can be determined by the length of the sheet diameter. The hardness of the coated sheet is greater than that of the uncoated sheet. The sustained release sheet and the controlled release sheet require a large hardness and can be suitable for coating.
3, degree of atomization
The coating liquid is sprayed on the surface of the core by the atomization treatment of the spray gun. The better the atomization effect, the better the film coating effect. The experiment uses the common spray gun and the imported spray gun(German) for comparison, and compares the atomization and coating effects. The calculation of the deviation value of the dissolution data shows that the result error caused by the imported spray gun is less than that of the spray gun. Tip, choose atomization performance of the spray gun, can improve the coating effect.
4, the flow of clothing liquid
The choice of flow rate can be determined according to the size of the package pan. The sugar coating pan for experimental use, diameter 750px, covering volume 900g, the flow rate during the coating process and the speed of the package pan should be properly adjusted. In case the core is too wet to cause one-sided "wrinkles."
For hygroscopic drugs, such as tartaric acid metoprool tablets, to avoid the wet surface of the film to produce shedding or lobes, using low flow coating, coating pots to turn at low speed. After a period of time, a partial initial spray film, and then increase the flow of coating fluid, improve the speed of the garment pan. By controlling the flow rate and speed, the effect of coating can be improved.
5, spray gun and air location
The core is turned in the coating pan to form a "slope". The spray gun is placed directly above the "slope" and its height is adjusted until the coating fluid can be fully sprayed on the core between the mouth of the pot and the bottom of the pot. The coating fluid is evenly distributed on the surface of the film. Observation results: When the spray gun deviates from the top of the "slope", the color of the coated film is inconsistent and the effect is poor; When the spray gun is located directly above the "slope", the color of the coated piece is uniform and the effect is good. In addition, because the spray gun uses air pressure spray, the spray gun is placed at a suitable height to prevent the air flow from affecting the motion state of the film. Due to the use of sugar coated pots in the experiment, the wall of the pot lacks exhaust holes. When the hot wind is sent to the core, it hits the mouth of the pot through the wall of the pot and forms two types of airflow in the opposite direction, which may interfere with the spray work of the spray gun. Effect. Therefore, the right location for hot air should be chosen. From the experimental operation, it was found that the hot air delivery position should be fixed above the spray gun, facing the top of the moving piece, so that the clothe liquid is evenly arranged on the surface. When the piece turns to the top and is ready to roll down, it is just affected by the hot wind. Dry, A thin film is formed, and then the coating fluid is re-sprayed and reheated. After a long period of spray coating, a complete and tough film is formed on the surface of the core. If the air supply position is low, it will not only blow away the coating fluid, lose the amount of the coating fluid, but also premature drying of the coating fluid on the core, resulting in the coating fluid not being evenly arranged on the surface in time, the surface of the sheet appears "wrinkled skin." The location of the spray gun and the hot air should be coordinated with each other, and the reasonable placement can maximize their role.
6, coating temperature
The coating process can be understood as a process of humidity and drying, and the coating fluid is sprayed so that it is evenly distributed on the surface of the film(wet process); The hot air leads to rapid volatilisation of the solvent, thus leaving a thin film coating(drying process) on the surface of the film. Adopting suitable temperature is an important factor to improve the coating effect. The temperature is too high, and the surface of the piece appears "wrinkled skin"; The temperature is too low, and the coating sheet forms the phenomenon of "adhesion" or "stripping". The temperature is determined based on the properties of the solvent of the coating fluid.
In the course of the experiment, the temperature can be adjusted by sending hot air, and the hot air delivery device can be fast or slow. For tablets that are unstable in nature, such as tartarate metoprolol controlled release tablets, when they begin to wrap, small flow is required, and the slow speed of the air supply is sufficient to provide temperature; For tablets that are stable in drug properties, such as diclofenac sodium sustained release tablets, it is required to wrap clothes under normal flow, and air supply options are fast to increase heat to provide suitable temperatures. The surface and hardness of the core mentioned above, the degree of atomization of the spray gun, the flow of the coating liquid, the position of the spray gun and the air outlet, and the temperature of the coating are all factors that affect the effect of the film coating, although they are obtained from the experimental operation of the sugar pan., But in fact it also applies to efficient garment machines.

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