Application of ultrafine grinding equipment in the field of traditional Chinese medicine
Ultrafine grinding technology can improve the extraction rate and bioavailability of traditional Chinese medicine, enhance the quality of traditional Chinese medicine preparations, and save resources. Traditional Chinese medicine can be further made into various dosage forms after ultrafine grinding, and has broad development prospects.
Ultrafine grinding technology is an advanced technology that uses mechanical or fluid dynamics to deagglomerate 0.5~5.0mm materials to micrometer or even nanometer levels. Compared with traditional grinding, it has the advantages of saving materials, fast grinding speed, and uniform and fine powder particle size.
Depending on the grinding media, ultrafine grinding technology is divided into dry and wet grinding. Dry grinding is to grind materials under dry conditions, which can produce ultrafine powders with good adsorption, expansion and water solubility; wet grinding is to grind (semi) fluid materials. Compared with dry grinding, it has the advantages of less dust hazard and less heat generation, and at the same time has homogenization and emulsification effects, making the product taste more delicate.
Based on the inherent properties of Chinese medicinal materials, Chinese medicinal ultrafine powder is mostly prepared by adding mechanical force. There are three common mechanical equipment.
Jet mill is also called fluid energy mill. The core components are nozzle and crushing chamber. The working principle is to use high-speed airflow or superheated steam as the impact carrier, spray it from the nozzle, provide energy for the fracture behavior of the material, cause the material crack to become unstable and open and expand under the action of external force, and the macroscopic manifestation is the change of material particle size. Jet mill with high-speed airflow as the impact carrier is often used for Chinese medicine crushing, which can be divided into the following 5 types: horizontal disc type, circulating tube type, opposite spray type, impact plate target type, fluidized bed type.
Jet mill is suitable for Chinese medicine with crisp texture, heat sensitivity and low melting point, but not for medicinal materials containing volatile components. The product after crushing has uniform particle size distribution, high classification accuracy, strong affinity, and retains the inherent properties of the particles. Therefore, this technology has become the preferred method for the development of various high-performance micropowder materials.
High-speed mechanical impact mill
The high-speed mechanical impact mill uses a rotor rotating at high speed around the axis to transfer momentum to the material, causing the material to collide violently with the liner to obtain ultrafine powder. The grinding, shearing and eddy current effects generated in this process can promote the formation of new powder surfaces.
This equipment is convenient for feeding, occupies a small area, has high crushing efficiency, and has adjustable crushing particle size. It is widely used in the crushing of medium and low hardness Chinese medicines; but it has a thermal effect during the crushing process and is not suitable for heat-sensitive and low-melting-point Chinese medicines. This equipment mainly relies on high-speed operation of parts for crushing, which will cause serious wear of parts and pollution of Chinese medicines is inevitable. Therefore, the development of high-wear-resistant materials is an important way to promote the development of such equipment.
The vibration mill includes grinding media, grinding bowl and eccentric excitation device. Its working principle is complex and multi-scale. The eccentric mechanism drives the bowl to vibrate periodically at high frequency. The grinding media moves accordingly and produces multiple forces on the material, aggravating the extension of cracks in the material, thereby breaking the external structure.
The vibration mill is suitable for crushing Chinese medicines of different hardness, and the particle size distribution of the obtained particles is narrow. If the vibration mill is equipped with a cooling device, it can also achieve low-temperature crushing of heat-sensitive, low-melting-point and volatile Chinese medicinal materials.
Ultrafine grinding technology has brought new opportunities to the field of traditional Chinese medicine, but it also has some challenges, such as the energy consumption of air jet mills and the noise of vibration mills.