Main description
Sub-packed ampoules or cylinder → prefreeze → sublimate and dry → re-dry.
precool
Prefreezing is a process of constant pressure cooling.
Sublimation drying
The main process of freeze-drying, sublimation conditions: 1, to ensure that the ice does not melt 2, the water vapor around the ice is reduced to the saturation vapor pressure (there are two methods: primary sublimation method and repeated freezing sublimation method).
Dry again
After the sublimation is completed, many holes are left in the material. In the mechanism of a single material, about 10% of the unfrozen water remains. The temperature continues to rise to 0℃ or room temperature, and it is kept there for a period of time. In drying can ensure the water content of freeze-dried products < 1%, and prevent the role of moisture.
Notes
1. High water content
Excessive thickness of the liquid in the container, insufficient heat supply in excess sublimation drying, high condenser temperature or insufficient vacuum may lead to high water content. Can use rotating freezer and other corresponding methods to solve.
2. spray bottle
If the heating is too fast, the heating is not uniform or the pre-freezing is not complete, it is easy to liquefy part of the product in the sublimation process and produce spray bottle under the vacuum decompression condition. In order to prevent the spray bottle, it is necessary to control the pre-freezing temperature below the melting point of 10~20℃, while heating sublimation, temperature should not exceed the melting point.
3. The product shape is not full or atrophic Because the structure of some viscous liquid is too dense, in the process of freeze-drying internal water escape is not complete, after the end of freeze-drying, products will shrink due to deliquescence. Encounter this kind of circumstance to be able to add right amount in the prescription normally the filling agent such as mannitol, sodium chloride, and adopt repeatedly prefreeze method, in order to improve the product's aeration, the product appearance can be improved.
