• 31 May, 2022
• By EPIC Powder
• 2 Comments

Research progress on crushing and dispersing technology of Chinese herbal medicines

Crushing is an important link in the processing of Chinese medicinal materials and the production process of Chinese medicinal preparations. Traditional Chinese medicine has had fine processing methods such as "water flying", "frustration" and "pounding" since ancient times. Its main application objects are mineral medicines, precious medicines and traditional Chinese medicines with special properties, but the processing volume is very small. my country's existing traditional Chinese medicine processing technology adopts hammer type, ball mill type, universal grinding type, flow type, cutting type, drum type and other crushing machines. Due to the different pulverization methods, there are certain limitations on the particle size of the powder, the powder extraction rate, and the preservation of the active ingredients, and the use of non-closed powder milling results in large dust leakage and low powder collection rate.

Preparation of traditional Chinese medicine powder

The traditional Chinese medicine powder system refers to the powder of traditional Chinese medicine including botanical medicine, animal medicine, mineral medicine and their extracts with a particle size of less than 2000 μm. It is generally believed that traditional Chinese medicine powders in the range of 10-200 meshes are called ordinary powders, and traditional Chinese medicine powders with a particle size of less than 75 μm prepared by ultrafine powder technology are called micron powders. The particle size prepared by nanotechnology Traditional Chinese medicine powder less than 100nm is called nano powder.

The history of traditional Chinese medicine powder can be traced back to the germination of powder in the Warring States Period. Powder is a very characteristic traditional Chinese medicine formulation. The history of powder can be regarded as the unconscious application history of powder and powder technology in the field of traditional Chinese medicine. At present, the Chinese Pharmacopoeia has clear requirements for the quality of ordinary powders. For example, general powders should pass through No. 6 sieve, be dried, loosened, mixed evenly, and have the same color and luster, and should be uniform in their uniformity, difference in loading, and microbial limit. There are clear regulations, but there is no unified regulation for micron powder and nanometer powder.

Preparation of ordinary powder

The preparation methods of ordinary powder are divided into two categories: dry pulverization and wet pulverization. Dry pulverization includes separate pulverization, mixed pulverization, etc.; wet pulverization is the traditional "water-flying method", and now large-scale production is improved to mechanical "liquid grinding method".

Preparation of Micron Powder

Micron powder is the use of mechanical or hydrodynamic methods to pulverize traditional Chinese medicine to the micron level. The principle of ultrafine pulverization is the same as that of ordinary pulverization. Due to the higher fineness requirements, it mainly uses external mechanical force to destroy the cohesion between the molecules of the material to achieve the purpose of pulverization. At present, ultrafine pulverization methods can be divided into high-frequency vibration pulverization, Bailey pulverization and jet pulverization. Its equipments include high-frequency vibrating pulverizer, Bailey pulverizer and jet pulverizer.

Preparation of Nanopowders

At present, the preparation of traditional Chinese medicine nano-powders mainly adopts ultra-fine pulverization, high-energy ball milling, supersonic jet pulverization, molecular gels, solid lipid nanoparticles, microemulsions and solid dispersions. The preparation of nano-powders by high-energy ball milling has low energy utilization, long time consumption, uneven particle size distribution, and easy introduction of impurities. Ordinary supersonic jet mill has low crushing efficiency. The grinding efficiency of the rotary collision supersonic jet mill has been further improved. Molecular gels, solid lipid nanoparticles, microemulsions and solid dispersions are suitable for preparing Chinese medicine extract nanoparticles.

The finer the particles of Chinese herbal medicines are, the better their medicinal effect is.

Chinese herbal medicine superfine grinding

The preparation methods of ultrafine traditional Chinese medicine are divided into physical method and chemical method, and the ultrafine grinding process belongs to the physical method.

The ultra-fine traditional Chinese medicine pulverization process is a processing technology formed by combining traditional industrial pulverization with the characteristics of traditional Chinese medicine. The traditional industrial pulverization mainly falls into three categories: mechanical impact pulverization, jet pulverization and ball milling. Table 2 shows the comparison of ultra-fine traditional Chinese medicine processing equipment with other traditional equipment.


mechanical crushing

The mechanical pulverization method uses a mechanical pulverizer to pulverize the Chinese medicinal materials to obtain powder. The working principle of the mechanical pulverizer is mainly by changing the pulverizing medium, adding a stirring and vibrating device, changing the structure or movement form of the machine, installing a classifier, etc., so that the external force can fully and powerfully act on the material to be processed, so as to achieve the ideal pulverization. Effect. When using this pulverizer to pulverize common materials, the D90 of the powder (the particle size at which the cumulative distribution of particles is 90%) can be less than 2 μm, and the D50 (the particle size at which the cumulative distribution of particles is 50%) can reach 0.1 to 1 μm. The newly developed MIC grinding and shearing superfine pulverizer uses multiple high-speed revolution and rotation ring-shaped pulverizing media to obtain a strong centrifugal force field, so that the raw materials are subjected to strong compressive force, shear force and grinding force, and the raw material particles are crushed. "Pulverized", the particle size of the obtained powder can reach 2 μm or less.

jet mill technology

Jet crushing technology is to use the material to obtain huge kinetic energy under the action of high-speed airflow, causing high-speed collision between material particles in the crushing chamber, severe friction, and the shearing effect of high-speed airflow on the material, so as to achieve the purpose of crushing the material. . In this way, the raw materials are processed into extremely fine powders (<10μm), so that the raw materials have a series of physical and chemical characteristics that were not previously available.

The development of jet mill provides a reliable guarantee for the fine processing of traditional Chinese medicine. The jet mill is also called a fluid energy mill. Its working principle is to make the material particles collide, impact and grind under the action of high-speed fluid between the material particles and between the particles and the chamber wall to produce a strong pulverization effect. . The pulverizer has good applicability for hard materials. The particle size distribution range of the powder obtained after being pulverized by the jet pulverizer is narrow. The heat and the cooling temperature cancel each other out, therefore, the equipment has a lower pulverization temperature, and is the first choice for the preparation of ultrafine powder from low melting point and heat-sensitive Chinese herbal medicines. However, due to the high airflow velocity during pulverization, part of the volatile components contained in the material will be lost. This instrument is more suitable for pulverizing raw materials with a crisp texture. However, it should be noted that the energy consumption of the pulverizer is high, which is several times that of the ordinary pulverizing method.

ball milling

The mechanism of ball milling is that the grinding ball collides, accumulates and rubs against the inner wall of the tank and other grinding balls under the action of gravity, centrifugal force, Coriolis force and friction, so that the material is gradually broken or mixed. Planetary ball mills are widely used in material mixing, fine grinding, sample preparation, nanomaterial dispersion, and high-tech material development. Planetary ball mills are generally divided into two types: vertical and horizontal. Since there is no material deposition at the bottom of the ball mill during ball milling, the ball milling effect is better than that of vertical ball mills. When working, the materials and grinding balls are mixed in a certain proportion and then loaded into the ball mill tank. In order to obtain high production efficiency and good ball milling effect, the general charging amount does not exceed two-thirds of the ball mill tank capacity.

Vibration mill

Vibration mill mainly uses high-intensity vibration to make the material and the wall collide and discuss at high speed, and can make the material mix evenly in a short period of time. The main process parameters affecting ultrafine pulverization are the pulverization time and the medium filling rate. The medium filling rate of the vibrating mill is relatively high, generally 60% to 80%, and the number of times of material impact and shearing per unit time is large. The number of impacts is usually 4 to 5 times that of ordinary ball mills, so the crushing efficiency is 10 to 20 times that of ordinary ball mills, and the energy consumption is much lower. At the same time, because the vibration mill is equipped with a water cooling device, it can achieve low temperature or normal temperature pulverization, and it is also suitable for Chinese medicinal materials containing volatile components.

In the process of ultra-fine pulverization by vibration mill, the particle size changes in four stages: "fast pulverization - slow pulverization - pulverization balance - reverse pulverization". The particle size tends to increase due to powder agglomeration, so the pulverization time should be controlled during application.

Ultrafine Chinese Medicine Grinding Method

Based on the principle and strategy of traditional ball mills and the technical characteristics of mechanical impact pulverizers, a new ultra-fine grinding method is proposed. The method can cover the grinding of various materials from ultrafine to nanometer size. On the basis of theoretical analysis and preliminary research on key equipment and technology, a technical process plan was proposed, and relevant technical parameters were obtained, forming the overall design plan and process system of the technology.

The material to be ground is the raw material of Chinese herbal medicine. Under the action of the external rotating power T and the shock force, the grinding medium (referred to as the grinding medium, that is, the rolling rod) performs an upward throwing motion that sometimes disperses and sometimes aggregates, and the rolling rod itself does the same. Rotating in the direction of rotation, the speed is ω′, the rolling rod group is revolving, and the speed is ω. Through the continuous exchange of positions between the inner and outer rolling rods, the two rolling rods continue to collide, squeeze and cut the Chinese herbal medicine material, so that the material is crushed and cut. During the crushing process, the large particles are crushed first by force, and the particles are continuously crushed from large to small. The whole crushing process is carried out in a low temperature environment of -10°C, which makes the tough Chinese medicinal materials into a wet and brittle body that is easy to crush, and improves the crushing efficiency. Oxidation to ensure no loss of medicinal properties. The device structure and schematic diagram are shown in Figure 3. P is the extrusion force and τ is the shear force.

With the progress and development of today's science and technology, more and more new technologies and new equipment have been widely used in the research of traditional Chinese medicine pulverization and ultra-fine grinding. For the preparation of raw powder as medicine, the Chinese herbal medicine must be pulverized to a certain particle size and mixed evenly before the next production. The pulverized medicinal powder is beneficial to the dissolution and absorption of the active ingredients, and can improve the bioavailability of the medicine and the stability of the preparation.