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Mixing
- 1. For D-pharm 1styear By Six sigma institute of science and technology Presented By- Sandhya Punetha ( Assistant Professor) MIXING AND HOMOGENISATION
- 2. MIXING • Mixing isdefined as the unit operation that combines two or more components together by agitation, shear or mixers. The final product of the mixtures contains uniform mixing. • The uniform mixing depends on the degree of mixing which depends upon the purpose of product and objective of mixing. • The equipments used for mixing is called as mixers.
- 3. OBJECTIVES OF MIXING- Simplemixing of the material to form uniform mixture. Promote chemical reaction to get uniform products. Dispersion of solid in liquid to form suspension or paste.
- 4.
- 5. POSITIVE MIXTURES- • Whentwo or more than two miscible liquids or gases or soluble solid is dissolved in water, the mixtures are called positive mixtures. • Mixtures formed is irreversible. • Example- Syrup mixtures; Solution mixtures.
- 6. NEGATIVE MIXTURES - •Mixtures formed from 2 or more immsicible components like solid and liquid to form suspension or emulsion are called negative mixtures. • These mixtures require more energy and can separate out. • These are reversible mixtures. • Example- Suspension ; Emulsion.
- 7. NEUTRAL MIXTURES- • Mixturesformed from different components like solid and liquid to form static mixtures are neutral mixtures. • Such mixtures do not mixed but once they are mixed they do not separate easily. • Example- Paste, ointment.
- 8. POWDER MIXING • Powdersare the most common pharmaceutical operations used for making different types of formulations like- tablets; capsules; etc. • Mechanism of powder mixing- 1) Convection mixing 2) Shear mixing 3) Diffusion mixing
- 9. 1) • Convective mixing-Mixing of the bulk particles as a whole from one container to another. It is also known as bulk transport. 2) • Shear mixing- Mixing of particles using shear forces by agitator or stream of air. 3) • Diffusion mixing- Mixing of materials by random movement of particles along its different layers through diffusion process.
- 10. FACTORS AFFECTING POWDERMIXING- Particle size Particle shape Particle attraction Material density Proportions of materials
- 11. • Particle size-It is easy to mix particles of same size, if the size of the particles will vary the mixing will not be uniform because small particles will move towards the bottom and large particles will move upward of the container. • Particle shape- The ideal shape of the particle should be spherical if they will have irregular shape than the chances of separation will be low. • Particle attraction- Some particles exert attractive forces due to electrostatic charges on them. This can lead to separation. • Material density- When two powders having different density are mixed than the powder which is dense settle at the bottom and powder which has less density comes upwards. Therefore, uniform mixing does not occur.
- 12. EQUIPMENTS USED FORPOWDER MIXING - • Double cone mixer. • Agitated powder mixer. • Air mixer. • Tumbler mixer.
- 13. DOUBLE CONE BLENDER- •Principle- The mixing of powder in double cone blender is due to tumbling and shearing action with blade. • Construction-
- 14. • It ismade up of stainless steel and is available in different capacity ranging from 5kg to 200kg or even more. • The efficiency of blender depends on the speed of rotation. • The rate of rotation should be optimum which depends on the size and shape of the tumbler as well as the nature of material to be mixed. • The common range is 30-100 rpm.
- 15. • Working- • Thematerial to be mixed is loaded approximately 50-60% of the total capacity of the blender. • As the blender rotates the material undergo the tumbling motion and mixes the material thoroughly. • Agitator blade are used to provide shearing action. • Advantage- It is used to mix the powders of different densities and is used mainly for small quantity of powders. • Disadvantage- Handling is difficult.
- 16. AGITATED POWDER MIXER- •Principle- It works on the principle of convection and shearing action. • Construction-
- 17. • Working- • Itconsits of a stationary vessel in which an arm rotates and transmits shearing action to the particles. • The end to end movement is required by general mixing which can be achieved by fitting helical blades to the agitator. • The mixture is commonly used for mixing free flowing powdered materials having uniform particle size and density.
- 18. LIQUID MIXING • Liquidmixing is done to prepare true solution or emulsion. • True solution are formed when one miscible liquid is mixed into another miscible liquid. • Emulsions are prepared by mixing two immiscible liquid by shear forces.
- 19. MECHANISM OF LIQUIDMIXING- 1) 2) • Bulk transport • Molecular diffusion 3) 4) • Turbulent transport • Laminar transport
- 20. • Bulk transport-It is the movement of large amount of liquid from one position to another. This mechanisms tends to produce a large degree of mixing but leaves the liquid within the moving bulk unmixed. For proper mixing other devices may also be used such as blade, paddle etc. • It is the primary mixing of molecules due to diffusion. This type of mixing occurs whenever there is a concentration gradient.
- 21. • Turbulent Mixing-The paddles and turbines exert pressure on the liquid adjacent to them. Turbulent mixing result in random fluctuation of fluid velocity and force to move the liquid molecules in various directions. • Laminar Mixing- In this type of mixing the fluid moves immediately in the agitator which moves in streamlines parallel to the direction of flow. This type of mixing mainly occur in viscous fluids.
- 22. EQUIPMENT'S USED FORLIQUID MIXING- • Propeller Mixers. • Turbine Mixers. • Paddle Mixers. • Shaker Mixers.
- 23. PROPELLER MIXERS- • Itconsists of number of blades, generally three bladed design in most common for liquids. • Blades may be right or left handed depending upon the slant of their blades. • Size of the propeller is small and may increased upto 0.5m depending upon the size of the tank. • Small size propeller can rotate upto 8000 rpm and produce longitudinal movement.
- 24. • Advantage- Used whenhigh capacity mixing is required. Effective for liquid mixing. • Disadvantage- Not suitable for those liquids which have greater viscosity more than 5 cp.
- 25. SEMI-SOLIDS MIXING- • Semi-solidinvolves dispersion of liquid or solid materials in the semi-solid base. • They are neutral mixtures that does not separate out easily. • Miscible liquid and soluble solid are easily mixed with low force and short time. • Immiscible liquids and insoluble solids are mixed with the help of emulsifying agent or wetting agent.
- 26. EQUIPMENT'S USED FORSEMI-SOLIDS MIXING • Triple roller mill. • Agitator mixer. • Planetary mixer.
- 27. TRIPLE ROLLER MIXER- •Principle- It works on high shear, which causes crushing of aggregates particles and also distributes the drug uniformly throughout the semi-solid base. • Construction- Hopper Scraper
- 28. • Three parallelrollers of equal diameters are made up of stainless steel. • They are mounted on rigid framework horizontally. • The gap between the first two rollers is more than of the gap between the last two. • A hopper is placed between the first two rollers. • A scrapper is attached to the last roller.
- 29. • Working- • Thefeed is introduced in the machine by a hopper. • Rolls rotate and materials are abraded by the rubbing action of the rolls turning at different speed. • Between 1st and 2nd roll , due to large space, the materials produce a thick film and aggregates are crushed here. • Between the 2nd and 3rd roll the space is smaller. Thickness of the materials passing gets thinner and fine crushing takes place. • Finally, scraper knife is used to discharge the mixed material.
- 30. • Advantages- Low materialloss. Avoid contamination. Useful for small to large batch mixing. Excellent temperature control. Easy cleaning. • Disadvantages- Not suitable for liquid mixing. Expensive.
- 31. PLANETARY MIXER • Principle-It is also called change-can mixer. It works on the principle of shearing and convective action. • Construction-
- 32. • It consistsof vertical cylinder shell which can be removed. • The blade is mounted from the top of the bowl. • Mixing shaft is driven by planetary gear and it is normally built with variable speed drive. Working- The blade is moved slowly at the initial stage for premixing of the material and finally at increased speed for active mixing. In this way high shear can be applied for thorough mixing. The blade and stationary vessel provide kneading action and shear. This is due to narrow clearance between the blade and the wall of the vessel.
- 33. • Advantages- Speed ofrotation can be varired . • Disadvantage- It requires high power. It has limited size. Useful for batch work only.