Application of the hottest film coating technology

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Application of film coating technology in preparation production

coating refers to wrapping a layer of material on the surface of the core, which can be powder, particles, pellets or tablets. The coating has many purposes, such as moisture resistance, mechanical force resistance, odor masking, coloring or improving the release performance of drug active ingredients. The coating process mainly includes sugar coating process and film coating process. The sugar coating process is mainly to spray syrup, talc powder and pigment onto the surface of the chip core to form a coating layer; The film coating process is to spray polymer solution or suspension to the surface of the chip core to form a coating layer. Sugar coating technology is an ancient pharmaceutical technology. Film coating technology is a rising star. Now it has been widely studied. Different formulas and potential uses are being fully recognized by people, which has attracted the attention of the pharmaceutical industry and rapidly promoted

I. film coating process and principle

film coating process is a new process developed in the 1940s. It was first produced in the pharmaceutical industry to protect drug tablets. Compared with sugar coating, it has the characteristics of short production cycle, less materials and strong moisture resistance. In the coating process, according to different solvents, it can be divided into water-soluble coating process and organic solvent coating process. The main purpose of film coating is to improve the appearance and facilitate identification, cover up the bad smell, make it convenient for patients to take, reduce gastrointestinal reactions, control drug release, change the drug release curve, damp proof, avoid light, and isolate the air to increase the stability of the drug. Put the drug components with compatibility changes into the tablet core and coating layer respectively, or press the tablets uniformly after coating respectively, so as to avoid other changes, etc

1. Principle

when the tablets are running in the coating machine, the extremely small droplets of the coating solution or suspension are sprayed onto the surface of the chip core. When these droplets reach the chip core, a coating film is formed on the surface of the chip core through contact, spreading and mutual bonding between the droplets. In this process, two kinds of effects will occur between the solvent and the chip core with the strong support of the National Natural Science Foundation of China and the Chinese Academy of Sciences, That is, the penetration of the solvent on the chip core and the evaporation of the solvent

when the evaporation of the solvent is constant and equal to the injection amount of the solvent, the coating process reaches equilibrium. Therefore, in the current research and development process of coating equipment, the main purpose of improvement is to improve the evaporation efficiency, so as to speed up the liquid spraying speed and shorten the operation time

2. Prescription composition

film forming material: it must have physicochemical properties such as film-forming, solubility and stability. Among them, HPMC, Eudragit, L30D, surelease, etc. are water-soluble; Organic solvents include Eudragit, HPMC, shellac, PVAP, cap, etc

plasticizers: including water-soluble propylene glycol, glycerol, polyethylene glycol; Water insoluble phthalates, castor oil, etc

additional ingredients: such as talc powder, magnesium stearate, pigment, etc

solvents: commonly used are water, ethanol, etc

3. Process operating parameters

during the coating process, the parameters that affect the balance between spraying and drying can be divided into two categories: (1)

related to spraying: spraying type, spraying speed, nozzle diameter, spray gun height, spraying pressure

(2) related to drying: inlet air temperature, inlet air volume, drying time, batch size

another important parameter is the speed of the coating pot, which is not directly related to the spraying and drying. Nanjing Chemical Industry Park extends an olive branch to new material enterprises, but related to the movement of materials. By adjusting the rotating speed, the movement of materials can be as

regular as possible

second, the selection of film coating production equipment is also an aspect of process operation. There are three kinds of equipment to choose from: traditional coating pot, high-efficiency coating machine and fluidized bed. The traditional coating pot or non porous coating pot, the sugar coating process is carried out in the traditional coating pot, but the drying efficiency is not ideal, because the drying air flow is only in contact with the film on the upper surface of the film bed, and there are also defects such as the need to transform the equipment and inconvenient operation. Therefore, this kind of equipment is not suitable for film coating production

high efficiency coating machines are divided into two types: eyelet coating pot and eyeless coating pot. The perforated high

effect coating pot is a stainless steel fully enclosed structure, with exhaust holes on the pot wall, and hot air is discharged from the exhaust holes on the pot wall after passing through the material bed. There is no exhaust hole on the wall of the non perforated coating pot, and the hot air outlet is in the material bed, which is discharged from the exhaust hole at the rear of the pot after passing through the material bed. Both methods increase the drying efficiency. The coating pot is usually equipped with a mixing device to improve the uniformity of drug mixing. According to the condition of the bag, the installation of the spraying system used to convey the sprayed coating liquid is different. The dry air flow can pass through the drug tablet bed from top to bottom or from bottom to top. At present, this kind of equipment is the main equipment to continuously strengthen the production of film coating, which is driven by innovation. It is mainly used for water-soluble film coating and organic solution film coating

fluidized bed is often used for coating small particles, particles or pellets with water-soluble or organic solvents, but it is not commonly used because of its strong mechanical force and easy wear of drug tablets

III. problems often encountered in coating and solutions

1. Too wet

too wet is because the liquid spraying speed is too fast relative to the drying efficiency, and there is no balance between liquid spraying and drying. This phenomenon is more likely to occur in the water-soluble coating process, because water is more difficult to dry than organic solvents

because it is too wet, the tablets will stick to the wall of the pot, or the tablets will stick to each other. This will cause damage and uneven film. To avoid over wetting, the liquid spraying speed must be carefully controlled and the air inlet temperature can be increased. In addition, adding talc powder or magnesium stearate to the coating solution can improve this phenomenon

2. One side is rough and unsmooth

in most cases, it is caused by spray drying, and the droplets cannot spread when drying too fast. In addition, the dried polymer particles stick to the surface of the chip core, which is easy to cause rough coating film. This situation can be improved by increasing the liquid injection speed, reducing the air inlet temperature or shortening the distance between the spray gun and the tablet bed

3. Orange peel phenomenon

this is a case of rough surface of the coating film. No one will know to come to the association to ask for information. The surface of the chip core is not completely spread, and dry polymer particles are irregularly distributed on the surface of the chip core. This is mainly caused by improper drying. This phenomenon can be avoided by controlling the evaporation speed, increasing the liquid injection speed or shortening the distance between the spray gun and the tablet bed

4. Bridging and filling phenomenon

when the outer surface of the tablet is irregular and engraved with identification letters, these marks on the surface will disappear and be filled by the coating solution. This is usually caused by the high viscosity of the coating solution. This bridging or filling phenomenon will disappear when the amount of solvent or plasticizer is increased

5. Color difference of coating film

in many prescriptions, there are pigments or dyes, which will be suspended in the polymer coating solution. If the mixing is too slow, it will cause sedimentation, resulting in color differences between batches. If the temperature is too high, the pigment will easily diffuse and the color of the coating film will become lighter. This phenomenon can be improved by reducing the amount of plasticizer and stirring the coating solution

6, film rupture

this is one of the problems that often occur in coating. The polymer coating film breaks and cracks appear. When the problem occurs, it may occur several hours after the coating. This is due to prescription reasons. This can be avoided by adding polymers with high molecular weight to the coating solution or increasing the amount of plasticizer

in short, successful coating depends on three main factors: coating prescription: it must be determined according to the purpose of coating, carefully screened, or the finished coating material can be selected and prepared when used; Chip core: the surface finish, hardness and brittleness must meet the requirements; Equipment: during the whole coating process, the main process parameters must be well controlled

film coating technology is a new technology, which is widely used in drug coating. This technology is easy to develop and produce, and has a wide range of applications. In recent years, we have accumulated rich experience in the formulation and production of film coating process. Although there are still some technical difficulties in the coating of traditional Chinese medicine, the application of this technology will be further expanded with the in-depth study of this technology

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