The low-temperature drying of the freeze dryer is to freeze the material containing a lot of water in advance to lower the temperature and freeze it into a solid state, and then immediately sublimate the water vapor under the standard of the vacuum pump, and the material itself remains on the ice shelf during freezing and cleaning.
Its volume does not change after freeze-drying, and the loose porous structure needs to digest and absorb heat during the sublimation process. The temperature of the product itself will reduce and the rate of sublimation will reduce, resulting in an increased rate of sublimation and reduced drying time, and all drying is at lower temperatures.
The moisture of product, the performance of lyophilizer freeze dryer, the control time and the temperature of analytical drying are the main factors affecting moisture level. For freeze-dried products, the moisture content is required to be ≤3%. The high moisture content of freeze-dried products will cause the product to break down and shrink.
Main causes of high moisture content:
1. Too much liquid medicine. If the filling volume is large, replace the container with a larger one to reduce the thickness of liquid medicine. Excessive thickness of liquid medicine will make the heat transfer effect worse during drying process, which is not conducive to the removal of moisture, resulting in excessive moisture in products processed by vacuum freeze dryer.
2. Dried products absorb moisture again. For varieties that are easy to absorb moisture, if they are not properly handled after freeze-drying, the products will absorb moisture again, which will increase the moisture content. If gas enters the freeze-drying box when venting, the gas causing high moisture should be sterilized, filtered and dried.
3. The temperature of products out of the box will also affect moisture content. Therefore, the product temperature when it is out of the box should be higher than the temperature of clean room to prevent moisture in the air from condensing on products.
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