A SEMINAR

ON

Particle coating Technology

PREPARED BY:- ATIK VAHORA 09PCT02M.PHARM(SEM-II)

GUIDED BY:-Mr D.M MODIDEPT.OF PHARMACEUTICS

A.R. COLLEGE OF PHARMACY, V V NAGAR

Contents

IntroductionApplicationTypes of coatingCoating techniqueReference

Introduction

Coating is a very commonly applied technology to modify/improve the properties of materials.  Recently, there has been increased interest in the use of dry particle coating technology due to its reduced negative environmental impact and potential cost effectiveness.

Properties improved by coating

Taste masking with modified release Separation of incompatibilities Conversion of liquids to solids Sustained release FlowabilityDispersibilityHydrophilic/Hydrophobic Properties Particle Size DistributionShape/Sphericity

Application of particle coatingParticle coating are widely used in are widely used in industryindustry

CosmeticsCosmeticsDyestuffDyestuffTonerTonerPharmaceuticalsPharmaceuticalsFoodFoodCeramicsCeramicsPowderPowderBiochemicalBiochemicalElectromaterialsElectromaterialsFertilizerFertilizer

Type of coating

Mainly 2 typesWet coatingDry coating

Types of coating techniqueMicroencapsulationSpray Drying And PrillingFluidized Bed Coating TechniquesExtrusion And SpheronizationThin Precision Coating TechniqueRotating Fluidized Bed CoaterSupercritical Fluid TechniqueMagnetically Assisted Impact CoatingRotating Fluidized Bed GranulatorHybridizerDry Particle Coating

MicroencapsulationVersatile for individual particles coatingThe type and level of membrane applied is determined by release rate requirements, organoleptic features and the dosage form application. Microcaps particles can be incorporated into different dosage forms including fast melt tablets, sachets, sprinkles and reconstitutable and temporary suspensions.

Inexpensive methods for coating particles.In both of these processes, the particle to be coated is added to the melt or solution and during atomization the coating is done. Smaller coating materials are separated in a subsequent step.The Wurster process was developed for particle coating.In this process, the particles to be coated are suspended in a fluid bed and a coating solution of dissolved polymer, sugar, inorganic salts, sol gels, or other dissolved materials is sprayed onto the fluidized particles and then dried.

Spray Drying And Prilling

Spray drying systems

Open spray drying system

Closed spray drying system

Semi-closed spray drying system

Fluid bed coating techniquesFluid bed processing involves drying, cooling, agglomeration, granulation and coating of particulate material.A fluidized bed is a bed of solid particles with a stream of air or gas passing upward through the particles at a rate great enough to set them in motion.It is possible to propagate wave motion, which creates the potential for improved mixing. The fluid bed can be used to dry the wet product, agglomerate particles, improve flow properties, instantize the product, or produce coated particles for controlled release or taste masking. There are 3 typesTop Spray CoaterBottom spray coaterWuster coater

Top Spray Coater

Coating liquid is sprayed down onto a bed of fluidized particles. This design of coater is ideal for coating large quantities of powders, crystals and pellets.

Bottom spray coater

Bottom spray coating of products such as powders, seeds, crystals and other small particulates takes place in a central column as the product is airborne upwards in the presence of a fine spray of coating liquid.

Thin Precision Coating Technique for Fine Powders

A high velocity jet (30 to 60 ft/sec) is established by accelerating a stream of air or inert gas with Swirl Accelerator. Control of the accelerator geometry one can establish a laminar flow pattern at Reynolds numbers where turbulent flow would normally occur.A gap between the inlet fluidizing plate and the bottom of the coating tube allows powder to be exposed to the high velocity gas stream. Particles of powder are picked up at this interface and accelerated by the gas stream.A fine spray (of the coating) is introduced into the bottom of the high velocity gas stream. The coating spray is moving faster than the solid particles so contact occurs and a coating is deposited.The coating can be virtually any liquid material that will pass through the atomizing nozzle.

Dry Particle coating Equipments HIGH INTENSITY MACHINES :

Hybridizer Mechanofusion Theta Composer FLUIDIZATION BASED DEVICES :

Magnetically Assisted Impaction Coating ( MAIC)

Rotating Fluidized Bed coater ( RFBC)

DRY PARTICLE COATING

Mechanical ForcesDiscrete coating

Continuous coatingHost particle

Guest particle

Mechanical ForcesDiscrete coating

Continuous coatingHost particle

Guest particle

Disadvantages of wet coating

Coating is a very commonly applied technology to modify/improve the properties of materials and generally done with use of different solvents. The solution used in the process may be hazardous and requires post-treatment (which increases the cost).  The solvent used may also be volatile and toxic to human health.

Nanoparticle Applications by Dry Particle Coating Technology

In dry coating techniques, materials with relatively large particle size (1- 200 microns) form a core and these core (“host”) particles are mechanically coated with guest nanoparticles.Dry particle coating can be applied to a wide variety of situations to improve particle performance. Material properties which can be improved by dry particle coating include flowability, dispersability, wettability, coloring, flavor/taste, electrostatic, electric, magnetic and optical characteristics, and solid phase reactivity.With the expected development of an enormous variety of new guest nanoparticles, we believe that dry particle coating can be a successful coating technology for extensively industrial applications.

Rotating Fluidized Bed Coater

This newly developed coating device operates on the principle of a rotating fluidized bed. The host and guest powder mixture are placed into the rotating bed and is fluidized by the radial flow of gas through the porous wall of the cylindrical distributor.Due to the high rotating speeds, very high centrifugal and shear forces are developed within the fluidized gas-powder system leading to the break-up of the agglomerates of the guest particles. The very large flow of gas needed to fluidize the particles at high rotating speeds and the motion of bubbles when operating the bed above minimum fluidization conditions creates strong mixing and hence good coating is achieved. The RFBC also has the capability of being operated in a continuous mode, by feeding guest particles in with the fluidizing gas and operating the RFBC in a vertical position so that host particles can be continuously fed into and removed from the device by gravity

Rotating Fluidized Bed Coater

Rotating Fluidized Bed Coater

Magnetically Assisted Impact Coating

The oscillating magnetic field generated by the coil is used to accelerate and spin the large magnetic particles mixed with the host and guest particles promoting collisions between the particles and with the walls of the vessel. Since the magnetic particles ‘‘fluidize’’ the host and guest powders, ‘‘soft’’ coating occurs by powder impaction.Magnetically Assisted Impact Coating (MAIC, pronounced mace), coats particles onto particles by a peening process. By adding a small coating particle and a large core particle into an assembly of small oscillating magnets, the small particles are readily coated onto the core particles. Materials that have been used in this process include glasses, pigments, metals, metal oxides, polymers, organic and inorganic powders.

N-S S-N

AC Power supply

Guest Particle

Magnetic particle

Chamber

Collar coil

Oscillatingmagnetic fieldHost

Guest

N-S S-N

AC Power supply

Guest Particle

Magnetic particle

Chamber

Collar coil

Oscillatingmagnetic fieldHost

Guest

Magnetically Assisted Impact Coating

Rotating ( Centrifugal ) Fluidized Bed Granulator/Coater

The rotating fluidized bed consists of a chamber and a porous cylindrical air distributor made of stainless sintered mesh. The horizontal cylinder (air distributor) rotates around its axis of symmetry inside the chamber. There is a stationary concentric cylindrical metal filter inside the air distributor to retain any elutriated fine powder. Coating procedure includes following steps:(1) The powder sample was fed into the cylindrical air distributor (vessel).(2) The air distributor was rotated and fluidization air was supplied.(3) Coating liquid was sprayed onto the powder bed.

Hybridizer

The hybridizer consists of a very high-speed rotating rotor with six blades, a stator and a powder re-circulation circuit made with ceramic or stainless steel. The powder (host and guest particles) placed in the processing part of the vessel is subjected to high impaction and dispersion due to the high rotating speed of the rotor. The particles undergo many collisions, and this allows for break-up of fine agglomerates and powder coating due to the embedding or filming of the guest particles onto the surface of the host particles.  Very short processing times are required to achieve coating.The rotor of the hybridizer can rotate anywhere from 5000 rpm to 16000 rpm. Due to the strong forces applied to the materials at these high rpm, very short processing times are required to achieve coating.

Theta ComposerSlow revolution of outside vessel: Promotion of favourable bulk mixingHigh speed rotation of inside rotor: high shear stress required for coating.Elliptical Shape: Stress & relaxation

Mechanisms of the dry particle coating process

Hot air coating technique a method to produce microparticles

This technique, called hot air coating (HAC), was developed to overcome the drawbacks of the conventional spray-congealing technique.Consists of a special venturimeter, deliberately designed to prevent any hindrance along the axial path through which the powder is conveyed. In HAC technology, the raw material is a solid, generally small granules, which is aspirated through the "Venturi effect" and accelerated in a flux of hot air to soften and then to melt the excipient, especially on the particle surface. The microparticles then solidify during falling in air at room temperature.

References

Michelle Ramlakhan, C.-Y. Wu, Satoru Watano, R.N. Dave, Robert Pfeffer, Dry particle coating using magnetically assisted impaction coatings: modification of surface properties and optimization of system operating parameters, Powder Technology 112 (2000) 137–148.P. Singh, T.K.S. Solanky, R. Mudryy, R. Pfeffer, R.N. Dave, Estimation of coating time in the magnetically assisted impaction coating process, Powder Technology 121 (2–3) (2001) 159–167.Nethersole, Douglas C.; Dudley, Michael A.; Parthasarathy, Mellapalayam R.; United States Patent 4069792Powder Coater’s Manual 1/98www. biophan - nanotechwire_com - the online resource for nano technology and researchwww. ventilex.htmwww. caleva.co.ukwww. coating place, inc.htm

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