Troubleshooting in Film Coating

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Troubleshootingin Film Coating

MD. ESHRAK -E- ALAHI

TECHNICAL MANAGER

COLORCON BANGLADESHEMAIL: [email protected]

MOBILE: +880-171-3451832

DATE: SEPTEMBER 24,2011
mailto:[email protected]:[email protected]


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Copyright 2006 Colorcon Inc.

The information contained in this presentation is proprietary to Colorcon and may not be used or disseminated inappropriately.

Troubleshooting

Coating Process and Equipment

Critical components of film coating


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Examples of tablet breakage


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Cause

Tablets are too soft

Tablets are too brittle

Tablets cap/laminate

Poor tablet shape for coating

Excessive pan speed

Poor baffle design

Solution

Change core formulation

Change core compression

parameters

Change tablet shape

Reduce pan speed

Change baffle design

Tablet breakage


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Example of tablet twinning


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Cause

Inappropriate tablet shape

Pan speed too low

Spray droplet size too large

Spray rate too high

Insufficient drying

Solution

Chose tablet design that

eliminates flat areas

refer tablet core section

Increase pan speed

Increase atomising air pressure

Reduce spray rate

Increase drying higher inlet air temperature

higher drying air flow rate

Twinning


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Examples of tablet surface erosion


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Cause

Hygroscopic tablet core

Application rate too low/high

Pan speed too fast

Friable tablet core

Low coating film strength

Punch design

Punch wearLogo placement or design

Low coating suspension solids

Solution

Reduce hygroscopic core materials

(e.g. superdisintegrant)

Select appropriate spray rate

Decrease pan speed

Use tablet punches with deeper

concave or double radius shape

Check punches for damage

Select Opadry formulation to solve

problem

Tablet surface erosion

Opadry is a trademark of Colorcon Inc.


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Examples of edge erosion


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Edge erosion

Cause

Worn tablet tooling

Sharp edges on tablets

High core attrition

Low spray application rates

Solids content of the coating

solution is too low

Excessive pan speed

Low film strength coating

Incorrect coating pan fill

Solution

Replace tablet tooling

Change tablet shape/design

Change core formulationSelect correct application rate

Raise suspension solids level

Select correct pan speed

Select high film strength Opadry

Fill pan to correct volume


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Examples of splitting & peeling


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Cause

Low film mechanical strength

Poor adhesion of coating to core

Poorly plasticised film

Core tablet erosion

Over heating of tablet cores

Solution

Select optimised coating:

film strength

adhesion

plasticisation

Improve tablet core

Avoid overheating tablet cores

Splitting & peeling


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Examples of core expansion


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CauseCore and coating have different

thermal expansion properties

Inadequate coating formulation

Expansion of core due to

overheating

Lack of relaxation time followingtabletting

SolutionAvoid mineral-type fillers, calciumcarbonate, calcium sulfate,magnesium carbonate,Encompress etc

Extend time between tabletting &coating

Select coating formula with correctmechanical properties

Do not over heat tablet cores

Cracking of the coating


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Examples of within-tablet colourvariation


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Examples of within-tablet colourvariation


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Within-tablet colour variation

Cause

Pigments are poorly dispersed

Core ingredients (usually moisture

sensitive) bleed through thecoating

Core ingredients interact with

coating to cause colour instability

Liquid plasticiser migration

Low opacity coating system

Solution

Use Opadry

Use an isolating subcoat

Change coating formulation

Choose a solid plasticiser system

Choose high opacity coating


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Example of logo bridging


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Uncoated tablet with break-line

Initial stage -

thin coating

Later stage - thickcoating traps residual

solvent

Stress develops due to

eventual evaporationof residual solvent

Stress relieved by film

bridging over break line

Logo bridging - mechanism


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CausePoorly plasticised coating system

Low adhesion coating system

Low adhesion core ingredients

Spray rate too high

Product temperature too low

Organic to aqueous conversion

Poor logo design

SolutionUse optimally plasticised coating

Use high adhesion coating

Use high adhesion core materials

Reduce spray rate

Increase product (bed) temperature

Improve logo design

Logo bridging


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Example of spray drying/logo filling


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Spray drying/logo fillingCause

High atomising air pressure

High drying air temperature

High solids coating suspension

Gun-to bed distance too high

Poor spray gun design (air cap)

Turbulent air-flow

Aeration of coating suspension

Solution

Use lower atomisation pressure

Reduce drying air temperature

Use low viscosity coating system

Optimise gun-to-bed distance

Reduce solids level

if longer coating time acceptable

Minimise pan depression

Optimise suspension preparation

to avoid aeration


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Examples of picking


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Cause

Application rate too high

Drying air volume too low

Drying air temperature too low

Pan speed too low

Low atomisation pressure

Poor spray gun set-up

Surface solubility

Surface porosity high

Low pan load

Solution

Reduce spray rate

Increase airflow

Increase the drying temperature

Increase pan speed

Increase atomising air pressure

Increase number of spray guns

or fan width

Increase gun to bed distanceImprove core characteristics

Optimise pan loading

Picking and sticking


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Example of Orange Peel- Surface roughness


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CauseAtomising air pressure too low

Coating suspension viscosity too

high

High spray rate

Poor spray gun performance

SolutionIncrease the atomising / fan air

pressure

Reduce coating suspension solids

Choose a low viscosity coatingsystem

Decrease the spray rate

Use a better spray gun

Orange Peel roughness


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Example of poor tablet-to-tabletcolour uniformity


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Cause

Insufficient number of spray guns

Poor spray gun set-up

High coating suspension solids

Poor opacity of suspension

Inadequate mixing of tablets

Low pan speed

High core friability (needing low pan

speed)

Poor baffle design

Poor tablet shape

Low film coat weight gain

Low/high pan load

Solution

Increase number of spray guns

Correct gun set-up

Spacing

Gun-to-bed distance

Fan width

Reduce suspension solids level

Increase opacity of suspension

Increase pan speed

Improve baffle design

Improve core friability/shape

Increase quantity of film coat

Load the correct quantity of tablets

Tablet-to-tablet colour variation


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Release or disintegration issues


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Release or disintegration issues

Cause

Interaction between the core and

the coating ingredients

Coating adheres to testequipment

Coating formulation contains

ingredients that hinder the

solubility of the coating

Core ingredients are sensitive to

heat or moisture in the coating

process

Solution

Select alternative core and/or coat

ingredients

Use a subcoat

Select parameters to minimise

effect on core


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THANKS!

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Troubleshooting in Film Coating