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Granulating technology: Process materials in powder, molten solution, aqueous solution forms, etc., and make them into granules of certain shapes and sizes. Application of the granulating technology: Used in solid preparation, especially in granule and tablet preparation.
1. Improve flow ability to facilitate packaging and tableting;
2. Avoid separation of components due to difference in particle size and density;
3. Adjust bulk density and improve solubility;
4. Prevent dust from raising and attaching to the walls of machines;
5. Facilitate use and carry and enhance value of products;
6. Improve uniformity of pressure transmission in the tablet preparation process;
(I) Wet granulation
Wet granulation: Add an adhesive or a wetting agent to the drug powder to form soft materials, then sieve them to form wet granules, and dry the wet granules and finally arrange them to form finished products. Granules made by this method have the advantages of good surface modification, beautiful appearance, strong abrasion resistance, good compression and forming. This technology is most widely used in the pharmaceutical industry.
Mechanism: Firstly, liquid in the adhesive wets drug powder, which generates an adhesive force among particles; and then the wet particles are made into particles of a certain shape and size under the influence of liquid and external mechanical force; and finally the formed particles is dried and consolidated into granules.
Common equipment: Oscillating granulator and high-speed mixing granulator
Four kinds of screens: nylon wire, galvanized iron wire, stainless steel wire, plate.
(II) One-step granulator
One-step granulator: Mix the raw material and auxiliary material, spray adhesive and stir the mixture to make granules, and then dry the granules. The whole processes are carried out in one equipment; this method is called one-step granulation, also known as fluidized spray granulation.
Features: The method mixes raw material with auxiliary material, makes granules, dries granules, and can even coat granules in one equipment. It is simple to operate, saves time, and has low labor intensity. The obtained granules have low density, uniform size, good fluidity and forming. Yet strength of the obtained granules is small.
(III) Spray granulation
Spray granulation: mix raw material, auxiliary materials and the adhesive, continuously stir the mixture to make a drug solution or suspension with a solid content of about 50%-60%, and then spray the solution or suspension into the drying chamber through a high-pressure sprayer with a pump, the hot airflow in the drying chamber evaporates water quickly and obtain spherical dry fine granules directly.
Features: Liquid is directly transformed into solid powder. The surface area of fogdrops is larger than that of liquid. The temperature of hot air is high. The drying speed is very fast. The duration when materials are heated is extremely short, so the temperature of the materials is relatively low. This method is suitable for treatment of thermosensitive materials.
The production of antibiotic injections, the preparation of microcapsules, the research on solid dispersion and the drying of Chinese herbal medicine extracts are all adopting the spray granulation technology.
(IV) Dry granulation
Dry granulation: Mix the drug powder well (a diluent can be added if necessary), compress the mixture into blocks directly with an appropriate equipment (by pressing method or rolling method), and break them into granules of the required size. This method generates an adhesive force among particles by relying on the compressing force.
Features: This method is often used to deal with thermosensitive materials, drugs that are unstable in water and that are easily formed by compression. It is simple, labor-saving and time-saving. However, attention should be paid to crystal transformation and activity declines that may be caused by compression.
