Tablet Compression, Compression machins DMS 2012

Views:
 
     
 

Presentation Description

tablet compression machines.. and physics of tablet compression..

Comments

Presentation Transcript

PowerPoint Presentation:

Tablet Compaction and Consolidation Prof. D. M. Shinkar Assistant Professor, Department of Pharmaceutics, KCT’S R.G.S.College of Pharmacy, Anjaneri, Nashik, Maharashtra .

Contents:

Contents Definition & Concept of tablet compaction Physics of tablet compression Process of tablet compression Tablet compression machines Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

Compression - It is defined as the formation of solid specimen of defined geometry by powder compression. It is defined as the reduction in bulk volume of a powder owing to the application of a forces. Because of the increased proximity of particle surfaces accomplished during compression, bonds are formed between particles which provide coherence to the powder i.e. compact is formed. The compression takes place in a die by the action of two punches, the lower and the upper by which compression force is applied. COMPRESIBILITY: - It is the ability of powder to decrease in volume under pressure. COMPACTIBILITY:- It is the ability of a powder to be compressed into a tablet of a certain strength or hardness. Consolidation It is in increase in mechanical strength of material from particle - particle interactions. Prof. D.M.Shinkar,RGSCOP.Nashik

Physics of compression :

Physics of compression A tablet is formed by reducing the volume of a set of autonomous particles until they are consolidated into a solid body. Tablet consolidation occurs when the punches and die go between two compression rollers. The complete tablet manufacturing cycle occurs in four steps: (I) the die is filled, (II ) the fill weight is adjusted , (III) the tablet is compacted and (IV) the tablet ejected from the die . From a material point of view, a compaction process is normally described by a series of sequential phases… 4 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

5 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

Initially as the volume is reduced, the particles rearrange into a closer packing structure. At a certain point, the packing characteristics of the particles and inter particulate friction between particles will prevent any further particle rearrangement. At this point the further reduction in compact volume results in the elastic, viscoelastic and plastic deformation of the particles. Elastic deformation is reversible, whereas the plastic deformation is irreversible. 6 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

As a consequence of these processes, particle surfaces are brought into close proximity to each other which can lead to the formation of inter particulate bonds. These bonds may later break, which facilitates further compression. In addition, particle fragmentation or breakage results in smaller particles, which further decreases in compact volume. As the volume is further reduced, the smaller particles formed by fragmentation can undergo deformation. 8 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

To summarize the physics of tablet compression, the following processes are involved in the compaction of a powder, 1. Transitional repacking 2. Deformation at the point of contact 3. Fragmentation 4. Bonding 5. Deformation of solid body 6. Decompression 7. Ejection During tablet formation the following types of bond mechanisms are hypothesized to occur between particles… 1. Mechanical interlocking (between irregularly shaped particles) 2. Inter particulate attraction forces (e.g., intermolecular forces, such as Van der Waal forces, Electrostatic forces and Hydrogen bonding) 3. Solid bridges (due to melting) 9 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

In tableting, compact formation occurs due to inter particulate attraction that arises from intermolecular bonding forces that act over very short As the powder bed is consolidated and the particles start to deform around each other this leads to a mechanical interlocking of the particles and this also increases the number of contact points between the particles. The dominant interaction force between solid surfaces is the Van der Waals force of attraction and hydrogen bonding may occur intra and intermolecularly. In addition, the applied load gets transmitted from particle to particle through contact points, the pressure at these points can be very high. This may cause heating with a possibility of localized melting, especially of low-melting point solids. Upon unloading, the reduction of local stress at the point of contact could lead to reso1idification, forming a solid bridge between the particles. Hence solid bridges that contribute to the overall compact strength can be defined as areas of real contact, i.e., contact at an atomic level between adjacent surfaces in the compact. 10 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik 1. Transitional repacking or particle rearrangement. Granules to be placed in the hopper of the tablet press . Formulation and processing are designed to ensure that at a fast production rate the weight variation of the final tablet is minimal. The particle size distribution of granulation and the shape of the granules determine the initial packing as the granules is delivered in to the die cavity. In the initial event the punch and particle movement occur at low pressure. The granule flow with respect to each other, with the finer particle entering the void between the larger particle, and the bulk density of the granulation is increased. Spherical particle undergo less particle rearrangement than irregular particle as the spherical particle tend to assume a close packing rearrangement initially. To achieve a fast flow rate required for high-speed presses the granulation is generally processed to produce spherical or oval particles . Thus, particle rearrangement and the energy expended in rearrangement are minor consideration in the total process of compression.

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik 2. Deformation at point of contact When the stress is applied to a material, deformation (change of forms) occurs. If the deformation disappears completely (return to the original shape) upon release of stress , it is an Elastic deformation. A deformation that dose not completely recover after release of the stress is known as a Plastic deformation. The force required to initiate plastic deformation is known as the yield stress. When the particles of a granulation are so closely packed that no further filing of the void can occur, a further increases of compressional force cause deformation at he point of contact . Both plastic and elastic deformation may occur although one type predominates for a given material. Deformation increase the area of true contact and the formation of potential bonding areas .

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

3 . Fragmentation and Deformation At higher pressure , fracture occur when the stresses within the particles become great enough to propagate cracks. Fragmentation further densification , with the infiltration of the smaller fragment in to the void space Fragmentation increase the number of particle and form new , clean surface that are potential bonding areas. 4. Bonding Several mechanism of bonding in the compression process have been conceived, but they have not been useful in the prediction of the compressional properties of material. Three theories are - 1 Mechanical theory 2 The intermolecular theory 3 The liquid surface film theory Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

Mechanical theory:- This theory proposes that under pressure the individual particle undergo elastic, plastic or brittle deformation and that the edges of the particle intermesh, forming a mechanical bond. If only the mechanical bond exists, the total energy of compression is equal to the sum of the energy of deformation, heat and energy adsorb for each constituent. Mechanical inter locking is not a major mechanism of bonding in pharmaceutical tablets. Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik The inter molecular theory:- The molecule (or ions) at the surface of the solid have unsatisfied intermolecular force, which interacts with other particles in true contact. According to the intermolecular forces theory, under pressure the molecules at the point of true contact between new , clean surface of the granules are close enough so that van der Waals forces interact to consolidate the particle. A microcrystalline cellulose tablet has been described as a cellulose fibril in which the crystals are compressed close enough together so that hydrogen bonding between them occurs . It appear that very little deformation or fusion occur in the compression of microcrystalline cellulose. Aspirin crystals under go slight deformation and fragmentation at low pressure , it appear that hydrogen bonding has strongly bonded the tablet , because the granules retain their integrity with further increase in pressure .

PowerPoint Presentation:

The liquid surface film theory:- The liquid surface film theory attributes bonding to the presence of a thin liquid film , at the surface of the particle induced by the energy of compression. During the compression an applied force is exerted on the granules; however, locally the force applied to a small area of true contact so that a very high pressure exists at the true contact surface. The local effect of the high pressure on the melting point and solubility of a material is essential to bonding . By analogous reasoning , the pressure distribution in compression is such that the solubility is increased with increasing pressure. Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

With an increase in solubility at the point of true contact, solution usually occur in the film of adsorb moisture on the surface of the granule. When the applied pressure is released and the solubility decrease, the solute dissolve in the adsorbed water crystallizes in small crystals between the particles. The strength of the bridge depend on the amount of material deposited and rate of crystallization. At higher rates of crystallization, a finer crystalline structure and a greater strength are obtained. The poor compressibility of most water insoluble material and the relative ease of compression of water soluble materials suggest that pressure induced solubility is important in tableting. The moisture may be present as that retain from the granulating solution after drying or that adsorb from the atmosphere. Granulation that are absolutely dry have poor compressional characteristics. Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik 5. Decompression:- After the compression and consolidation of the powder in the die, the formed compact must be capable of withstanding the stresses encountered during decompression and tablet ejection. The rate at which the force is removed (dependent on the compression roller diameter and the machine speed ) can have a significant effect on tablet quality. The same deformation characteristics that come into play during compression, play a role during decompression. After application of the maximum compression force, the tablet undergoes elastic recovery . While the tablet is constrained in the die, elastic recovery occurs only in the axial direction. If the rate and degree of elastic recovery are high , the tablet may cap or laminate in the die due to rapid expansion in the radial direction only. Tablets that do not cap or laminate are able to relieve the developed stresses by plastic deformation. Since plastic deformation is time-dependent , stress relaxation is also time-dependent.

PowerPoint Presentation:

The rate of decompression can also have an effect on the ability of the compacts to consolidate (form bonds). Based on the liquid-surface film theory, the rate of crystallization or solidification should have an effect on the strength of the bonded surfaces. The rate of crystallization is affected by the pressure (and the rate at which the pressure is removed). High decompression rates should result in high rates of crystallization . Typically, slower crystallization rates result in stronger crystals. Therefore, if bonding occurs by these mechanisms, lower machine speeds should result in stronger tablets . The rate of stress relieve is slow for acetaminophen so cracking occurs while the tablet is within the die. with microcrystalline cellulose the rare of stress relieve is rapid , and intact tablets result. Formulations which contain significant concentrations of microcrystalline cellulose typically form good compacts due to its plastic deformation properties. However, if the machine speed and the rate of tablet compression are significantly increased, these formulations exhibit capping and lamination tendencies. Prof. D.M.Shinkar,RGSCOP.Nashik

PowerPoint Presentation:

6. Ejection As the lower punch rises and pushes the tablet upward there is a continued residual die wall pressure and considerable energy may be expanded due to the die wall friction. As the tablet removed from the die, the lateral pressure is relieved , and the tablet undergoes elastic recovery with an increase (2 to 10 %) in the volume of that portion of the tablet removed from the die. During ejection that portion of the tablet within the die is under strain , and if this strain exceeds the sheer strength of tablet the tablet break as elastic recovery . Prof. D.M.Shinkar,RGSCOP.Nashik

Compression :

Compression Tableting procedure Filling Compression Ejection Tablet compression machines Hopper for holding and feeding granulation to be compressed Dies that define the size and shape of the tablet Punches for compressing the granulation within the dies Cam tracks for guiding the movement of the punches Feeding mechanisms for moving granulation from the hopper into the dies 1. Single punch machine The compression is applied by the upper punch Stamping press 1/7/2013 Prof. D. M.Shinkar, KCT'S R.G.S.C.O.P.Nashik 24

PowerPoint Presentation:

Upper and Lower Collar Collar locker Single Punch Machine (Tablets) 1/7/2013 Prof. D. M.Shinkar, KCT'S R.G.S.C.O.P.Nashik 25

PowerPoint Presentation:

Common stages occurring during compression Stage 1: Top punch is withdrawn from the die by the upper cam. Bottom punch is low in the die so powder falls in through the hole and fills the die Stage 2: Bottom punch moves up to adjust the powder weight-it raises and expels some powder Stage 3: Top punch is driven into the die by upper cam. Bottom punch is raised by lower cam. Both punch heads pass between heavy rollers to compress the powder Stage 4: Top punch is withdraw by the upper cam. Lower punch is pushed up and expels the tablet. Tablet is removed from the die surface by surface plate Stage 5: Return to stage 1 1/7/2013 Prof. D. M.Shinkar, KCT'S R.G.S.C.O.P.Nashik 26

Multi-station rotary presses:

Multi-station rotary presses The head of the tablet machine that holds the upper punches, dies and lower punches in place rotates As the head rotates, the punches are guided up and down by fixed cam tracks, which control the sequence of filling, compression and ejection. The portions of the head that hold the upper and lower punches are called the upper and lower turrets The portion holding the dies is called the die table 1/7/2013 Prof. D. M.Shinkar, KCT'S R.G.S.C.O.P.Nashik 27

PowerPoint Presentation:

28 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

29 Prof. D. M.Shinkar 1/7/2013

Compression cycle:

Compression cycle Granules from hopper empty in the feed frame (A) containing several interconnected compartments. These compartments spread the granulation over a wide area to provide time for the dies (B) to fill . The pull down cam (C) guides the lower punches to the bottom, allowing the dies to overfill The punches then pass over a weight-control cam (E), which reduces the fill in the dies to the desired amount 30 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

A swipe off blade (D) at the end of the feed frame removes the excess granulation and directs it around the turret and back into the front of the feed frame The lower punches travel over the lower compression roll (F) while simultaneously the upper punches ride beneath the upper compression roll (G) The upper punches enter a fixed distance into the dies, while the lower punches are raised to squeeze and compact the granulation within the dies After the moment of compression, the upper punches are withdrawn as they follow the upper punch raising cam (H) The lower punches ride up the cam (I) which brings the tablets flush with or slightly above the surface of the dies 31 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

The tablets strike a sweep off blade affixed to the front of the feed frame (A) and slide down a chute into a receptacle At the same time, the lower punches re-enter the pull down cam (C) and the cycle is repeated 32 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

Although tablet compressing machinery has undergone numerous mechanical modifications over the years, the compaction of materials between a pair of moving punches within a stationary die has remained unchanged The principle modification from earlier equipment has been an increase in production rate which is regulated by Number of tooling sets Number of compression stations Rotational speed of the press Special adaptations of tablet machines allow for the compression of layered tablets and coated tablets A device that chills the compression components to allow for the compression of low-melting point substances such as waxes i.e. suppositories 33 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

HIGH SPEED ROTARY MACHINE MULTI ROTARY MACHINE 34 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

DOUBLE ROTARY MACHINE UPPER PUNCH AND LOWER PUNCH 35 Prof. D. M.Shinkar 1/7/2013

PowerPoint Presentation:

Prof. D.M.Shinkar,RGSCOP.Nashik Thank You If you salute your duties, No need to salute anybody , If you don’t salute your duties, You have to salute everybody….. dattashinkar@gmail.com

authorStream Live Help