The freeze dryer is a technical method for pre-freezing water-containing items, and then advancing the moisture in a vacuum condition to obtain monotonous items. However, when the freeze-dried products of the freeze-drying machine are out of the box, defects such as bubble pits, dry shrinkage, collapse, and voids sometimes appear.
So today I will tell you about the reasons for the defects of the freeze-dried products of the freeze-drying machine when they are out of the box:
First of all, it may be because the freezing temperature is too high, or the time is too short, and the product is completely frozen; or the temperature in the drying stage is too high, and the pressure is too high. Caused by melting some products.
Vacuum sublimation is performed before it is frozen, and the external pressure is rapidly reduced to cause bubbling; the melted product will be condensed by steam and will shrink; some wet products will be heated violently and melted, which will melt the dried object and form a cavity and collapse. Therefore, it must be frozen, and the sublimation cannot exceed the eutectic temperature and disintegration temperature of the product.
The color and pores of the product are uneven in the depth direction. Due to the long storage time after packaging, some substances in the solution are precipitated or the insoluble components are precipitated.
It is also possible that it is due to the concentration of the solution and the rate of degassing. The concentration of the solution is generally controlled between 10~15%, and excipients should be added if the concentration is less than 5%.
If the concentration is too high, the thickness should be controlled, generally 10~15mm. If the solution concentration is greater than 30%, the product is prone to shrinkage, collapse and incompleteness.
In addition, when the freeze dryer is drying, the frozen surface is first dehydrated to form a dry shell with a dense structure, and the sublimated water vapor below escapes from the gaps between the molecules of the dried surface layer.
At this time, if the concentration of the solution is too high, the gap between the molecules is small, the ventilation is poor, the resistance of water vapor passing through is large, and a large number of water molecules cannot escape in time, and the stagnation time in the drying layer is long, so that some of the dried drugs are gradually deliquescent, which will cause The volume of the product shrinks, and the shape is not full or collapsed.