Size reduction- Advantages, factors affecting, hammer mill, ball mill

B. Pharmacy second year
Semester Third

1. SIZE REDUCTION B. PHARMACY SECOND YEAR BY- SHALINI K. DHAWALE D. K. PATIL INSTITUTE OF PHARMACY

2. SIZE REDUCTION Size reduction is the process of reducing large solid units or substance into smaller unit mass, coarse particles or fine particles. Size reduction process is also termed as comminution or diminution or pulverisation. Process of size reduction: Size reduction may be achieved by two methods: 1. Precipitation method 2. Mechanical process 2 DKPIOP

3. Advantages of size reduction Content uniformity Uniform flow Effective extraction of drug Effective drying Improved physical stability improved dissolution rate Improved rte of absorption Disadvantages of size reduction Drug Degradation Contamination 3 DKPIOP

4. Factors Affecting Hardness Toughness Abrasiveness Stickiness Softening temperature Material structure Moisture content Physiological effects Purity required Bulk density Ratio of feed size to product ratio 4 DKPIOP

5. Principle of size reduction Cutting : Material is cut by sharp blades. e.g. Cutter mill Compression : Material is crushed between rollers by pressure . e. g. Roller mill Impact : Material is break by hummer or bars at high speed. e. g. Fluid energy mill. Attrition : Break down of material by rubbing action between two surfaces. e. g. Fluid energy mill. 5 DKPIOP

6. Mechanisms and laws The energy requirement for particle size reduction is a function of input and output of particle size, harness, strength and other properties of solids. Various theories for energy requirements are. Rittinger’s Theory: According to this theory energy E required for size reduction of unit mass is directly proportional to the new surface area produced. E = K R ( S n –S i ) Where, E = Amount of energy KR = Rittinger’s constant Si = Initial surface area Sn = New specific area 6 DKPIOP

7. Bond’s Theory According to this theory the energy used in crack propagation is proportional to the new crack length produced. E = 2K B ( 1 – 1 )  dn  di K B = Bond’s Work index di = Initial Diameter dn = New Diameter Kick’s Theory It states that energy required for deforming a set of particle of equivalent shape is proportional to the ratio of change in particle size. 7 DKPIOP

8. HAMMER MILL Principal : Material is impact between rapidly moving hammers on a rotor and the powder material. Uses : it is used for size reduction of dry materials, wet materials, ointments, slurries etc, Brittle material and fibrous material. Advantages : Rapid in Action. Easy to install and operate. Particle size of material easily controlled by changing speed of rotor, hammer type, shape and size of the screen. 8 DKPIOP

9. HAMMER MILL 9 DKPIOP

10. BALL MILL Principle: It works of the principle of impact between the rapidly moving balls and the powder material. At low speed the balls rolls over each other attrition will mode of action thus in ball mill attrition and impact both mechanisms takes place. It is also known as tumbling mill. 10 DKPIOP

11. Ball mill Uses: For fine grinding with particle size 100to 5mm For preparation of ophthalmic and parenteral product. For milling dyes, pigments and insecticides at low speed. Advantages It can produce very fine powder. Used for both wet and dry grinding. Toxic substances can be grounded, as cylinder is closed system. Disadvantages: Very noisy machine. Soft fibrous material cannot be milled. 11 DKPIOP

12. Principle: it operates on principle of impact and attrition . Uses: To reduce particle size of drugs like antibiotics and vitamins. Fluid Energy Mill/ Jet Mill/ Micronizers /Ultrafine Grinders. 12 DKPIOP

13. Construction and working of Fluid energy mill It consist of loop of pipe with diameter 20 -200mm depending on height up to 2 meter. In mill material is suspended and conveyed at high velocity by air this mill does not have any moving part. Working : the air or inert gas is introduced with very high pressure through the nozzles. Solid are introduced to air stream through inlet. Due to high degree of turbulence, impact and attrition force occurs between particles. The fine particles are collected through classifier. Fluid energy mill reduces the particles to 1 to 20micron. 13 DKPIOP

14. Fluid energy mill Advantages: Used to grind material to fine powder. The particle size of powder can be controlled due to the use of a classifier. There is no wear of the mill and hence there is no contamination of product. It is useful to grinding heat sensitive material such as vitamins, antibiotics and sulphonamides . 14 DKPIOP

15. EDGE RUNNER MILL Principle: In this mill size reduction is done by crushing due to heavy weight of stone and shearing force which is involved during movement of stones. Construction: It consist of two heavy rollers and bed made of stone or granite. The rollers have a central shaft and they revolve on its axis. The rollers are mounted on horizontal shaft and move around the bed. 15 DKPIOP

16. EDGE RUNNER MILL Working: The material to be ground is put on the bed and with the help of scrapers it is kept in the path of the stone wheels. The materials is ground for a definite period and it is then passed through the sieves to get required size. Uses: It is used for grinding tough drugs to fine powder. It is used for plant based products. It does not require more attention during operation. Disadvantages: Occupies more space, contamination of product may possible Not used for sticky materials. 16 DKPIOP

17. EDGE RUNNER MILL 17 DKPIOP

18. END RUNNER MILL Principle: The material is getting crushed due to weight of heavy pestle and shearing force which get applied during the movement of those stones. Construction and Working It can be considered as mechanical mortar pestle The mortar is shallow and bottom of pestle is flat rather than round. It consist of bed of stone, vertical cylindrical dumb bell shaped roll supported by horizontal shaft such that shaft rotated friction between bed and stone grinding of material. Uses: used to grind brittle and tough material. 18 DKPIOP

19. END RUNNER MILL 19 DKPIOP

20. Thank you … 20 DKPIOP