TABLET COMPRESSION

BY AKASHARA

JAMBHULKARM pharm 1st sem(pharmaceutics)

ContentsINTRODUCTION

CLASSIFICATION

THEORY OF TABLET COMPRESSION

TABLETTING PROCEDURE AND TOOLING

STUDY OF TABLET MACHINES

REFERENCES

Introduction1843 a patent was granted to Thomas Brockedon (Englishman) for manufacturing pills and lozenges1874 both rotary and eccentric presses1885 glyceryl trinitrate tablets was in the BPNo other tablet monograph appeared until 19451980 nearly 300 monographs for tablets

Types of tabletsCompressed Tablets (CT)

Sugar-coated Tablets (SCT)

Film-coated Tablets (FCT)

Enteric-coated Tablets (ECT)

Multi compressed Tablets (MCT)

• Layered tablets• Press coated tablets

Controlled-release Tablets (CRT)

Tablets for Solutions

Effervescent tablets

Buccal and Sublingual Tablets

Theory of tabletcompression

Basic definitions:Compression: the reduction in the bulk volume of a material as a result of the removal of the gaseous phase (air) by applied pressure.Consolidation:Involves an increase in the mechanical strength of a material resulting from particle-particle interactions.

Compaction:The compression and consolidation of a 2 phase (solid + gas) system due to an applied force.

Stages of compaction

a. Particle rearrangement/interparticles lippageb. Deformation of particulatesc. Bonding/Cold weldingd. Deformation of the solid bodye. Elastic recovery/expansion of the mass as a whole

Particle rearrangement

1. occurs at low pressures2. reduction in the relative volume

of powder bed 3. small particles flow into voids

between larger particles leading to a closer packing arrangement

As pressure increases, relative particle movement becomes impossible, inducing deformation.

Deformation mechanisms of materials

Bonding

When the surfaces of two particles approach each other closely enough (e.g. at a separation of less than 50nm), their free surface energies result in a strong attractive force , a process known as cold welding or bonding.

A.Solid Bridges: form directly across

particles in the absence of any binding elements or additives

B. Intermolecular/Electrostatic Forces:

forces projecting beyond the particle surface as small discrete fields with very short range order

C. Mechanical Interlocking: shape dependent

As pressure increases, the bonded solid is consolidated toward a limiting density by plastic and/or elastic deformation.If on removal of the load, the deformation is to a large extent spontaneously reversible i.e., if it behaves like rubber, then the deformation is said to be elastic.

Deformation of the solid body

Some deformation processes (plastic deformation) are time-dependent and occur at various rates during the compaction sequence, so that the tablet mass is never in a state of stress/strain equilibrium during the actual tabletting event. This means that the rate at which load is applied and removed may be a critical factor in materials for which dependence on time is significant. Hence if a plastically deformed solid is loaded (or unloaded) too rapidly for this process to take place, the solid may exhibit brittle fracture.

Recovery

The compact is ejected, allowing radial and axial recovery. Elastic character tends to revert the compact to its original shape.

Role of moistureAt least some moisture is

present in all tablet formulas

Concentration well below 1% level can effect the behavior of these feed materials and finished product.

Moisture as little as 0.002% can affect the proportion of the applied force transmitted to the lower punch.

At 0.55% moisture, the behavior is actually the reverse of that for the totally dry material.

Tabletting procedure

Filling Compression Ejection

Tooling 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.

PunchHead: the largest diameter of a common punch which contacts the machines cams and accepts the pressure from the pressure rollers.Head flat: the flat portion of the head which makes contact the pressure rollers and determines the maximum dwell time for compression.Neck: located below the head and provides clearance as the punch cycles through the machine cams.Barrel: the vertical bearing surface of a punch which contact with the punch guides in the machine turret for vertical guidance.Stem: the area from the barrel to the edge of the punch tip.

Punch type B TYPE BB TYPE D TYPE

PUNCH BARREL DIAMETER

0.750 in. (19mm) 0.750 in. (19mm) 1 in. (25.4mm)

DIES DIAMETER 1.1875 in. (30.16mm)

0.945 in. (24mm)

1.500 in. (38.10mm)

PUNCH LENGTH Lower punch is 3 9/16 in. long than BB

5.25 in. 5.25 in.

TOOLING TYPE

DiesDie: A component used in conjunction with the upper and lower punches.It accepts the product for compaction and is responsible for the tablets’s perimeter size and configuration.Die height: The entire height of a die.Die bore: the cavity of the die that accepts the product for compaction and determines the tablets size and shape configuration.

Die groove: the radial groove around the die outer diameter which accepts die lock to secure the die in position in the die table.Die chamber: the angled area between the top of the die and the die bore; it assists in guiding the upper punch into the die bore.

Round shape punches and die

Different shapes of punchesAnd die set

Oval shape punches and die

Capsule shape punch and die

Geometric shaped punch and die

Core rod tooling

Irregular punch and die

Multiple tip punches

Feed frame

The upper punch rise to allow the hopper shoe to move over the die.

The lower punch drops and the granules feed into the die.

The upper punch drops, thus compressing the granules into the tablet.

Single punch machine

Upper andLower Collar

Collar locker

Single Punch Machine (Tablets)

The upper punch rises upword and the lower punch rise upto the surface of the die to eject the tablet.

The lower punch drops and the cycle is restarted.

Multi-station rotary pressesThe 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 an lower turrets.

The portion holding the dies is called the die table.The pull down cam (C) guides the lower punches to the bottom, allowing the dies to overfillThe punches then pass over a weight-control cam (E), which reduces the fill in the dies to the desired amount.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.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.

Recent innovationsIn 1997, Ima introduced a line of unique tablet presses called Ima comprima.Unlike traditional presses Ima comprima feeds the granules through the die table taking advantage of the centrifugal force created by the rotating turret for a rapid and uniform die fill.The Ima comprima ejects the compressed tablet through the bottom of the die and uses gravity to eject the tablet from the press.Traditional tablet presses eject the tablet at the top of the die, requiring a mechanical stop or a take-off bar to physically contact and knock the tablet from the lower punch face.

In 2005 Fette GmbH Germany introduced new tablet press and tooling technology.Fette developed die segments. It provides an advantage over traditional dies by combining the tablet press turret die table and dies into 3 or 5 integral segments.Die segments are much easier and quicker to install.The concept does not require the use of dies, more space is available around the turret circumference to increase the no. of punches, resulting more no. of tablets per revolution.

References1.Remington- the science and

practice of pharmacy, 21st edition, volume I Lippincott Williams and Wilkins.

2.The theory and practice of industrial pharmacy by Leon Lachman and Herbert A. Lieberman, 2009 edition, CBS Publishers.

3.Pharmaceutical dosage form Tablet by Stephen Hogg et al. volume III

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