Vacuum freeze-drying technology freezes the wet material or solution to a solid state at a low temperature (-10°C to -50°C), and then sublimates the water to a gaseous state in a vacuum (1.3 to 13 Pascals) without using a liquid state. The drying technique that finally dehydrates the material. China is a big producer of APIs, so the application of this technology is very promising. However, it should be noted that in recent years vacuum freeze-drying technology has been rapidly promoted in our country. In contrast, its basic theoretical research is relatively backward and weak, and there are not many professional and technical personnel. In addition, compared with other drying technologies such as air drying and spray drying, the vacuum freeze-drying equipment has a large investment, and the energy consumption and the production cost of the pharmaceuticals are relatively high, thereby limiting the further development of the technology. Therefore, to strengthen the basic theoretical research, to ensure the quality of drugs, to achieve energy saving, reduce production costs, has become the most important issue facing the vacuum freeze-drying technology.
Outstanding technical advantages
Since vacuum freeze-drying is performed at a low temperature and a low pressure and the water is directly sublimated, many special properties are imparted to the product. For example, vacuum freeze-drying technology can also dehydrate the heat-sensitive materials thoroughly, and the dried medicines are very stable, which facilitates long-term storage. As the drying of the material is completed in the frozen state, the physical and molecular structure of the material changes little compared to other drying methods, and its structure and appearance are well preserved. In the process of vacuum freeze-drying, there is no surface hardening problem in the material, and its interior forms a porous spongy, thus having excellent rehydration, and can restore the state before drying in a short time. Since the drying process is carried out at a very low temperature and the air is substantially isolated, the occurrence of biological, chemical or physical changes in the heat-sensitive substances is effectively suppressed, and the active substances in the raw materials are well preserved, and the raw materials are maintained. Color.
Strengthening basic theoretical research
At present, China's vacuum freeze-drying equipment tends to be perfect, but compared with developed countries, the research of this technology's basic theory appears to be lagging and weak, which hinders the improvement of the level of technology application. Therefore, the focus of the study is shifting to this aspect. At present, the research focuses on the study of vacuum freeze-drying parameters and its influencing factors, process parameters, process mechanism and model, and process optimization control.
The basic parameters of vacuum freeze-drying technology include physical parameters and process parameters, which are the basis for achieving the vacuum freeze-drying process. The lack of these data will make it difficult to optimize the raw materials for the drying process, and it will not be able to make full use of the system efficiency. Physical properties refer to the thermal conductivity, transfer coefficient, etc. of the material. The research contents in this area include the determination and measurement methods of physical parameter data, and the influence of environmental conditions such as pressure, temperature, relative humidity and material particle orientation on the physical properties. Process parameters include parameters such as refrigeration, heating, and material morphology. The study of the freezing process is intended to find the optimal freezing curve for the system. The research of heating process focuses on two aspects: one is the improvement of the raw material carrier; the other is the choice of heating method (heat transfer method and heat source). Determining the proper material form is also an important research content, which includes the particle form of the raw material and the thickness of the material layer.