Introduction to the hottest film coating technolog

2022-08-06
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Introduction to film coating technology (II)

problems and Countermeasures of film coating technology in the early 1950s, the first real film coated tablets were born in the United States. Since then, film coating technology has experienced half a century of development. However, China started late. In the late 1970s, various coating solutions and film coating processes developed by a small number of pharmaceutical research institutions and pharmaceutical factories appeared in succession, and were gradually popularized and applied. In the mid-1990s, the "hot" film coating technology gradually appeared in China. But on the whole, the development of this technology in China is still relatively slow. Many pharmaceutical enterprises still have many problems in application due to technical reasons

 evenly spray a layer of relatively stable high molecular polymer coating material on the surface of the core by spray to form a plastic film layer several microns thick to achieve a certain expected effect. This process is called film coating. The application of film coating technology is the demand and development trend of pharmaceutical industry. Some people think that film coated tablets are not as bright as sugar coated tablets. In fact, compared with traditional sugar coated technologies, film coated tablets have many advantages, such as shorter coating time, better moisture and light resistance, and stronger drug stability

film coating must change the concept of sugar coating in the past, which is very important. For a long time, some pharmaceutical enterprises have simply regarded film coating technology as an independent link in tablet production, and film coating is just a simple coating like sugar coating. In fact, it is not as simple as the previous work has been limited to experiments. As a new technology, film coating is much more strict on the chip core than sugar coating, and the hardness of the chip is higher. Moreover, it requires the mutual cooperation between various processes, the adjustment and mutual support of a series of technical indicators and requirements in the production process. Therefore, the introduction and application of film coating technology must be treated with a scientific and realistic attitude. Only in this way can the coated film achieve the desired effect

good core quality plays a decisive role in film coating. Sometimes the mechanical quality of the chip core is too poor, so the film coating cannot be carried out at all. Even if it is reluctantly carried out, the film coating quality is difficult to be guaranteed. Among all the factors that affect the mechanical properties of the chip core, the hardness and brittleness of the chip are the most important, and the brittleness is more prominent than the hardness. Generally speaking, the hardness of traditional Chinese medicine tablets suitable for film coating should be 5kg/cm3, and that of Western medicine tablets should be about 4kg/cm3. How to check? The simplest method is hardness tester test; Or throw a plain piece vertically upward for 2 meters to make it fall freely, and the hardness is qualified if it is continuously cracked for more than two times. The simple method to check the fragility is to scrape the edge or surface of the blade with your fingers, and it is better if there is no flake powder falling off; Another method is to place about 30 plain tablets in a 250ml glass and shake them vigorously for about two minutes, preferably if the surface and edges of the tablets are not worn. For the plain tablets with high hygroscopicity, the hardness requirements are higher

for your reference: when applying film coating technology for coating, whether it is high-efficiency coating machine, fluidized bed coating machine or sugar coating pot issued, the following principles should be followed: first, the hardness of the core should be hard enough, otherwise, when starting coating, the core and the pot wall will rub repeatedly, resulting in loose pieces, pitted surfaces and other phenomena; Second, the temperature of the tablet bed should be kept constant; Third, the solvent evaporation capacity in the equipment shall be balanced with the solvent volume brought in during the liquid injection process, that is, the solvent evaporation and liquid injection rate shall be in dynamic balance

 the key to one-sided smoothness and fineness lies in mastering the relationship among the pot temperature, spray volume and rotating speed in the whole process, which is the top priority in the film coating operation. During operation, the atomization degree of the coating liquid directly affects the appearance quality of the coating film, and the atomization effect of the spraying liquid is directly determined by the atomization pressure and the atomization system. At the beginning of spray, the principle of mastering the spray speed and the temperature of hot air blowing is to make one side slightly wet and prevent one side adhesion. The temperature should not be too low. If the temperature is too high, the drying is too fast, the film is easy to be rough, and the film color is uneven; If the temperature is too low or the spraying speed is too fast, the humidity in the pot will be too high, and the adhesion of the slices will soon occur. The relationship between the rotating speed of the pot and the coating operation is: the rotating speed is low, and the coating film adhesion is strong; High speed, poor adhesion of coating film, easy to peel off. During the coating process, if the temperature is too low, the spraying amount is too large, and the film flows and stays, the film sticking phenomenon may occur. At this time, the rotating speed can be increased to improve it. If necessary, the temperature, spray volume and spray range can be properly adjusted to overcome it

 under the condition that the quality of the coating powder remains unchanged, the common problems and solutions in the coating operation are as follows:

 1. Sticking tablets: it is mainly because the spraying amount is too fast, which violates the principle of solvent evaporation balance and makes the tablets adhere to each other. In this case, the spraying amount of coating liquid should be properly reduced, the hot air temperature should be increased, and the rotating speed of the pot should be accelerated

 2. Appearance of "orange peel" film: mainly due to improper drying and low spray pressure of coating solution, the sprayed droplets are heated and concentrated unevenly, resulting in ripple of coating film. In this case, the evaporation rate should be controlled immediately to increase the spray pressure

 3. "Bridging": refers to the blurring of marks caused by the coating film on the lettering piece. The solution is to slow down the coating spraying speed, reduce the drying temperature, and pay attention to the control of the hot air temperature

 4. Color spots: this situation is caused by uneven mixing or insufficient fineness of solid properties when preparing coating solution. The solution is to mix the coating solution well

 5. The coating film on the surface or edge of the tablet is cracked, cracked, peeled off or the edge of the tablet is worn: if the commencement of the technical renovation project of Zhangjiagang Huachang new material technology Co., Ltd. with an annual output of 30000 tons of Neopentyl 2 alcohol and other products and supporting facilities undertaken by China Chemical Engineering No. 4 Construction Co., Ltd. is caused by improper selection of coating liquid and solid content, too fast speed of the coating machine and too small spraying volume, appropriate coating liquid and solid content shall be selected, Properly adjust the speed and spray amount; If the hardness of the core is too poor, the formula and process of the core should be improved

 6. The coating film shows "frost spraying": this situation is caused by high hot air humidity, long spraying range and poor atomization effect. At this time, the temperature should be properly reduced to shorten the spray range and improve the atomization effect

 7. Color difference between tablets: this situation is caused by uneven fan surface or excessive solid content of coating liquid or slow speed of coating machine. At this time, the spray angle of the spray gun should be adjusted to reduce the solid content of the coating solution. The early signatures include refined steel, gold, platinum and platinum versions, and the speed of the coating machine should be appropriately increased

 8. There are pinholes on the surface of the coating film: This is caused by too much air involved in the preparation of the coating solution. Therefore, excessive air should be avoided during liquid preparation

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