In the pharmaceutical process, ultrafine powder medicine is generally obtained by fine powder crystallization and ultrafine pulverization. The micro-powder crystallization is obtained by controlling the crystallization process conditions to obtain ultra-fine particle crystals, which are obtained by filtration, washing, drying, and drying; ultra-fine pulverization is obtained by subjecting crystal particles obtained by crystallization of large particles to ultrafine pulverization treatment. The disadvantage of micronized crystallization is that it is difficult to filter, wash, drain, and dry. It is easy to cause crystal leakage during the filtration and washing process, resulting in low yield and daily output, and the final product has low purity, impurities, and adverse drug reactions. It is aggravated and therefore generally less used in production. At present, most of the manufacturers use ultra-fine pulverization process.

In view of the fine particle size and high quality of ultrafine drugs, the machines suitable for superfine pulverization of drugs mainly include: mechanical impact pulverizer, ball mill, vibration mill, agitator mill, two-way rotary ball mill, jet mill, etc. Mainly introduces the jet mill.

First, the working principle of jet mill in the preparation of pharmaceutical powder

The jet mill is a device that accelerates compressed air or inert gas through a nozzle and uses high-speed elastic fluid (300~500m/s) or superheated steam (300~400°C) to make particles, between gas and particles, The particles and the wall and other components have strong impact, shear, collision, friction, etc., and at the same time, under the action of the centrifugal force of the airflow or combined with the classifier, the coarse and fine particles are classified to achieve ultrafine pulverization. device. As a common preparation method of pharmaceutical powder, jet mill is suitable for crushing antibiotics, enzymes, low melting point and other heat sensitive drugs .

Second, air jet mill classification

The types of jet mills used for the preparation of pharmaceutical powders mainly include: disc jet mill, circulating tube jet mill , target jet mill, punching jet mill, collision jet mill, fluidization . Bed collision type jet mill .

Third, the characteristics of jet mill for drug crushing

Since the jet mill is pulverized by gas as kinetic energy, its pulverization mechanism is different from other mechanical equipment. Specifically in:

In the pulverization process, due to the centrifugal force of the high-precision classifier rotating the air, the coarse and fine particles are automatically classified, so that the obtained product has a narrow particle size distribution range and a fine average particle size, and the D _{50 is} generally between 5 and 10 μm.

The powder obtained by the airflow pulverization mechanism tends to be "spherical", the particle surface is smooth, the shape is regular, the dispersibility is good, and the mechanical wear during the pulverization process is small, and the obtained product has high purity.

The airflow pulverizer is powered by compressed air. The high-speed jet airflow produces a Joule-Thomson effect. The airflow collides with the adiabatic at the nozzle, which reduces the temperature of the pulverizing system and offsets the heat generated by the collision and friction of the drug. The ambient temperature in the pulverizing chamber can reach It is tens of degrees Celsius below zero, so it is suitable for the preparation of low melting point, heat sensitive drugs.

Because the air pulverizer has good airtightness, the product yield is high; the whole pulverization process is carried out under the negative pressure state, and the pulverization does not leak, so the environment is not polluted and can be operated under aseptic conditions.

The pulverization process is continuous, using closed loop system technology and automatic control technology, and the operation is simple.

The jet mill can realize the pulverization, mixing and drying on-line operation, and can also simultaneously modify the drug powder. For example, some drugs are sprayed into the liquid while being pulverized, and the particles are coated and surface-modified.

Of course, the jet mill also has disadvantages. For example, the airflow crushing has lower energy utilization rate than the ball mill and other mechanical crushing machines, high energy consumption, and high production cost. The energy of the pulverization process is pulverized by the potential energy of electric energy→compressed air→kinetic energy of the jet stream→kinetic energy of the particle motion to the particles. As this process progresses, the particles become smaller and smaller, the kinetic energy generated is gradually reduced, and the pulverization process is more difficult to perform, so low value-added products are not suitable for use. 2 During the pulverization process, the high-speed airflow easily takes away the volatile components, resulting in the loss of the active ingredient of the drug. 3 Due to the nature of the jet mill, the output of the jet mill is generally small.