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The main problems of tablet coating (including solutions)

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The main problems that occur when wrapping sugar coating

1. Peeling phenomenon

In the process of coating, the phenomenon of peeling sometimes occurs, mainly due to the following reasons.
(1) low monosaccharide syrup content, easy to cause incomplete drying, skin off. The treatment method is to control the content of monosaccharide syrup within 65%-75% (mass fraction).

(2) The drying of layers in the coating process is not achieved, and the storage amount of water in the coating layer is larger. At this time, the temperature in the pot is rising, resulting in moisture due to heat from the original adhesion in the coating layer to vaporization and expansion, resulting in crowding forcing the coating layer to shed its own skin without external force. Treatment is in the process of coating each layer should reach the requirements of dry, and then wrap the next layer.

(3) In order to save time during operation, the amount of monosaccharide syrup is larger and cannot be used up at one time so that it is stored for too long and excessively exposed, and the sucrose partly forms transforming sugar, which has strong moisture-attracting property and is prone to peeling off when coating. The treatment method is to use the monosaccharide syrup now and use it up at once.

2. Sticky pot phenomenon

When wrapping powder coating layer, sometimes there will be tablets sticky pot phenomenon. The main reasons are as follows.

(1) Adding too much syrup, the concentration of syrup is too high and the viscosity is large. The treatment method is to reduce the concentration of syrup and reduce the amount of syrup. General syrup mass fraction and syrup dosage should be controlled at 73% and 20ml-22ml of syrup per 10kg tablet respectively.

(2) Uneven stirring, especially when the pot temperature is low, is easy to occur. The treatment method is to stir the tablets evenly with proper strength, and then pass hot air to make the tablets dry.

(3) The temperature of the pot is too low. If the temperature of the pot is too low, the temperature difference between the sugar coating pot and the syrup is large and cannot be coordinated within a short period of time, resulting in the phenomenon of sticky pot. The treatment method is to control the temperature in the pot at 35℃-40℃, and to stir well with proper strength during operation.

3. Discoloration and spots

Syrup, talc does not stick to the pot phenomenon resulting in the coating process sometimes the pot wall local no syrup and talc, the formation of regional sticky, if the exposed surface is too large, can lead to tablet friction discoloration and spots. The main reasons are as follows.

(1) The white wax on the wall of the pot is not washed. Treatment is to wash the wall of the pot with 100 ℃ water, or a layer of syrup on the wall of the pot, and then sprinkle a layer of talcum powder dry before use.

(2) The electric furnace is used too early. In the package of the first layer of coating, the pot wall and the temperature of the tablets are cold, when heated with electric care, the temperature of the pot wall rises rapidly, so that the syrup stuck on the pot wall due to heat viscosity becomes small, liquidity becomes large, the lower temperature of the tablets completely away, so that the talcum powder is not adhered. The way to deal with this is to only blow hot air when wrapping the first layer of coating, without using electric furnace or making the furnace temperature lower, so that the temperature of the tablets and the wall of the pot rises evenly, and so on after full drying, the wall of the pot will wither on the syrup and talcum powder, and the surface becomes rough. Only use electric furnace to heat from the 2nd layer of coating.

(3) The angle of the coating pot is too small. Because the tablets are moving in a solitary line in the pot, the angle of the pot is too small, the descent of the tablets is accelerated, and the impact on the central part of the pot is increased, resulting in this part not sticking to the syrup and talcum powder. The treatment method is to enlarge the angle of the pot appropriately, so that the falling speed of the tablet becomes slower, so that the heart part of the pot will stick to the syrup and talcum powder.

4. Dark edge and uneven coloring

Sometimes there are dark edges and uneven coloring when the tablets are coated, which means that the talc powder does not cover the corners of the tablets, which will affect the storage, validity and beauty of the tablets. The main reasons are as follows.

(1) The powder coating layer is too thin. Talc powder does not cover the corners of the tablets, so the treatment method is to continue to wrap the powder coating layer until it completely covers the core of the tablets.

(2) The angle of the coating pot is too small. The tablet is moving in an arc in the coating pot, and the rotation of the pot brings the tablet to a certain height, and then descends slowly along the center part of the pot in a frictional rolling manner. When the angle of the coating pot is small, the angular force of the tablet becomes smaller, the speed of descent is accelerated, and the friction rolling becomes collision rolling, the angular part of the tablet collides the most, the distribution of syrup in the angular part is reduced, and the thickness of talcum powder also varies due to the reduction of syrup, resulting in dark edges and uneven coloring in the angular part of the tablet where the powder layer is too thin. The treatment method is to adjust the coating pot to the best angle, the angle is generally 35°-40°.

(3) The core of the tablet is too thick. If the pressed core is too thick, it will be difficult for the powder coating layer to cover it completely.

5. Discoloration of sugar coating

Some sugar-coated tablets will produce spots and lose their luster after storage for a period of time. The main reasons are as follows.

(1) The amount of the immersion paste is too large. Dip paste has a strong moisture attraction, in all aspects of production may absorb water, so that the water content of the core increases, and then penetrate into the coating layer, so that the sugar coating discoloration or destruction. The treatment methods are: ① from the beginning of granulation, pressing, coating, packaging each link should be moisture-proof and dry; ② in the coating layer, first two layers of corn starch can greatly reduce the moisture-attracting properties of the core, and then 20% of gum Arabic syrup or 15% of gelatin syrup wrapped several layers of isolation, which can receive better results.

(2) The core contains a lot of oily components or volatile components. Oily ingredients or volatile ingredients have strong permeability or volatility, which can easily penetrate into the coating layer and discolor the sugar coating, thus affecting the quality of the drug. Treatment methods are: ① reduce the coating temperature to reduce the volatile components volatilization; ② when wrapping powder coating layer, first 2 layers with corn starch, can absorb a lot of oily components in the core to prevent its penetration, and then use 20% gum Arabic syrup to wrap several layers of isolation layer, can receive better results.

6. Lightening difficulties

After the tablets are wrapped with color layer, they can be lightened. In the case of suitable dryness and humidity of the tablet, add the right amount of wax powder, about 5 minutes, the tablet will start to brighten and make a “rustling” sound, indicating that the lighting is smooth. However, sometimes after adding wax powder for 10 minutes, the brightness of the tablet does not change much, and even becomes rough, even if the time is extended, or the tablet always slips in the pot, the main reasons are as follows.

(1) the surface of the tablet coarse grains, sugar crystals are too coarse, resulting in the brightness of the tablet is difficult to pass. The main reasons are as follows: (1) The surface of the tablet is coarse and the sugar crystals are too coarse, which makes it difficult to pass the brightness of the tablet. The treatment method is as follows: when wrapping colored sugar coating, make the temperature in the pot lower to the same as the room temperature, so that the water on the surface of the tablet can evaporate slowly and the sucrose can precipitate small and uniform crystals on the surface of the tablet.

(2) The humidity of the tablet is too large. When adding wax powder, because the tablet is too wet, the wax powder is easy to stick to the tablet surface to form small particles, resulting in a rough and shiny tablet surface, the more wax powder the more serious this phenomenon. The more wax powder there is, the more serious this phenomenon is. The treatment method is: stop lightening, wipe away the small amount of wax powder adhering to the surface of the tablet, continue drying, and then lighten the tablet after it is qualified in dryness and humidity.

(3) The tablet is too dry or the wax powder is damp, causing the tablet to slip. The treatment method is: put a wet towel (wrung out) into the pot to increase the humidity of the tablets, or wipe the wall of the pot with a wet towel (wrung out) and beat the light with dry wax powder.

7. Moisture absorption of sugar-coated tablets

Although one of the purposes of sugar-coated tablets is to isolate air and moisture, sometimes the effect is not good, especially for sugar-coated tablets of herbal infusions, which often deteriorate due to moisture absorption. The isolation effect of sugar coating on moisture can be measured by test. A simple method is to place the sugar-coated tablets in a certain temperature and relative humidity environment for a certain period of time and measure the weight of the tablets to calculate the amount of moisture absorption.

8. Cracking of sugar coating

If the coating process is not appropriate, the coating layer will crack due to the change of temperature and humidity. The reason may be related to the moisture permeability of the coating layer, after penetrating into the water, the tablet volume becomes larger and expands and cracks; it may also be related to the lack of toughness of the coating layer is too brittle. The solution is to adjust the formulation of the coating material, for example, adding suitable plasticizer, which may improve it. It may also be related to the expansion coefficient, such as the expansion coefficient of the coating layer is different from that of the tablet, and the lobe occurs due to temperature change.

9. Sugar-coated tablets with color spots

Colored sugar-coated tablets often appear color spots, that is, uneven distribution of pigments on the surface of the tablets and inconsistent color shades. The important reason for the occurrence of discoloration is that the soluble pigment “migrates” during the drying process, and the insoluble pigment is used to prevent pigment migration. Commonly used color deposits are made of aluminum oxide, talc or calcium sulfate adsorbed pigment. Coloring tablets of inconsistent shades of color, but also may be related to the surface of the tablet is not smooth.

the main problems that occur when wrapping film coating

1. Fragment adhesion and flaking

This situation is caused by the tablets adhering to each other, re-separation from the surface of a tablet peeled off the coating film fragments stuck on the surface of another tablet. In mild cases, it is called fragment adhesion, while in severe cases, it is called flaking. Both of them are caused by adding syrup too fast and the coating film is not dried in time. When individual adhesions are found, they are corrected in time, and the adhesions are removed and recoated, otherwise they need to be washed, peeled off and recoated after drying.

2. wrinkled and “orange peel” film

This situation is mainly caused by improper drying, the film has not yet spread evenly, has been dried. Rolling package when there are wrinkles, that is, the phenomenon of wrinkling, when the spray is uneven, such as “orange peel” like rough surface. These phenomena or aura should immediately control the evaporation rate, and in the previous layer of the coating layer completely dry before adding the appropriate amount of coating solution, in order to eliminate this phenomenon. If it is caused by the nature of the film-forming materials, it is necessary to change the film-forming materials.

3. Blistering and bridging

The bubble on the surface or the engraved tablet coating makes the logo blurred, indicating that the adhesion between the coating material and the surface of the tablet core is reduced, leaving space, the former is called blistering and the latter is called bridging. To correct this phenomenon, it is necessary to improve the coating syrup formula, increase the roughness of the surface of the core or add some substances that can form hydrogen bonds with certain components within the coating film, such as microcrystalline cellulose, to improve the adhesion between the coating film and the surface of the core. Adding certain plasticizers to the coating film can improve the plasticity of the coating film. In the operation, reduce the drying temperature and extend the drying time, also conducive to overcome the blistering and bridging phenomenon.

4. Color spot and frosting

Color spot refers to the soluble coloring agent in the drying process “migration” to the surface so that it can not be uniformly distributed caused by the spots. Frosting refers to some plasticizers or colored substances in the composition of the drying process “migration” to the surface of the coating, so that it is gray and uneven phenomenon. In addition, the uneven distribution of colored materials in the coating pulp, will also show the phenomenon of color spots. Therefore, in the ingredients, we must pay attention to the affinity between these coloring agents or plasticizers and film-forming materials and the mutual solubility in the solvent, and slow drying.

5. Sweating

Sweating is mainly due to improper formulation of coating solution, the solution is to adjust the formulation of coating solution.

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