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The Different Types Of Tablet Coating Machines

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23 June 2016 No comments

Tablet Coating machines are equipment devices used to coat the tablet’s outer surface with a thin coating film. It is mostly used:

  • To hide the color, taste and smell of the drug
  • To protect the drug inside from physical or chemical harm
  • Control the release of the drug inside the tablet
  • Protect the drug from disintegrating when exposed to gastric fluids
  • Help improved pharmaceutical elegance
  • Incorporating the drugs in the coating to prevent any chemical incompatibility

Definition

The ideologies of tablet coating is in fact very simple. It is the application of coating ingredients to a group of tablets in a moving bed with concurrent heated air to help evaporate the solvent. The coating is equally distributed to the tablets through the movement of the bed whether vertically or horizontally.

Different Types of Machine

There are various tablet coating machines currently in the market today, but below are the 3 different types:

  • Traditional/standard
    • immersion sword system
    • immersion tube system
    • Pellegrini pan
  • Perforated coating
    • Glatt coater
    • Accela-cota
    • Driacoater
    • Hi-coater systems
  • Fluidized bed/Air suspension coater
    • Low pressure air atomized systems
    • High pressure airless systems

How it works

Several manufacturing companies has developed their own version of coating machine in order to accommodate their coating process. That said, most of the systems used are based on the 3 basic designs below:

Standard Coating Pan

It is made up of circular metal pan that is mounted in an angular way on a stand

The pan is about 8 – 60 inches in diameter and can be rotated on its horizontal axis with a use of a motor

The coating solution is applied to the tablet by spraying the solution to the rotating tablet bed through atomized systems which can produce a faster and more even distribution.

Drying efficiency can easily be achieved through

  • Immersion sword – the drying air is distributed through a perforated metal sword that is immersed in the bed.
  • Pellegrini – has a baffled pan and diffuser which allows the distribution of drying fair uniformly over the bed surface.
  • Immersion tube system – the tube is immersed in the bed where the tube delivers heated air through the spray nozzle.

Perforated Pan

Equipment is consist of partial or full perforated drum that rotates on its horizontal axis which is enclosed in a housing.

  • Accela-cota/Hi-coater Systems - with this equipment, the drying air is directed to the drum, passing through the tablet bed and is release through the perforations in the drum.
  • Driacoater – the drying air is introduced through the hollow area located inside the drum’s periphery. During the drying process, the coating pan rotates the dip into the tablet bed and dry air passes up through and fluidized the tablet bed exhaust outside the pan’s back.
  • Glatt coater – latest perforated coater. The drying air is directed to the drum’s inside, through the bed and out through the exhaust duct. Another way would be an optional split chamber plenum, where the drying air is directed in the reverse manner from the drum’s perforation for partial fluidization of the bed.

All of the perforated pan system’s coating solution is applied through spraying nozzles which are positioned in the inside of the drum.

Fluidized Bed/Air Suspension System

The fluidization of the mass is achieved in a columnar wherein plenty of air enters the column’s center resulting to the tablet raising to the center. The movement of the tablet is upward and through the chamber’s center. The tablet will then fall towards the chamber wall and move downwards and re-enter the air stream from the bottom part of the column.

Spray nozzles are located in the bottom and top of the chamber in order to coat the tablets with coating solution.

The tablet’s core is frail and is prone to abrasion (edge) and chipping making it difficult to fully coat the tablet even under optimum conditions. This is due to the rough tablet to tablet impact as well as the tablet chamber contact.

2 types of system used to apply a finely divided spray coating solutions to tablets:

  • High Pressure Airless System – airless spray liquid are pumped at high pressure of about 250 to 3000 lbs. / square inch gauge, through a small opening of about .009 -- .02 inch out of a nozzle which results to a finely divided spray. The atomization degree and spray rate are all controlled by fluid pressure, liquid viscosity and orifice size.
  • Low Pressurized Air Atomized Systems – the liquid is pumped through a large opening of about .02 - .06 inch at a relatively low pressure of 5 – 50 psig. The low pressure air contacts the liquid stream at the top of the atomizer and a finely divided spray is achieved. The atomization degree is controlled by the fluid cap orifice, fluid viscosity, fluid pressure, and air cap design and air pressure.

Things to Consider in a Coating Machine

Perforated coating machines are popular in the industry.

Things that should be considered during the coating process:

  • Air capacity – this is the amount of water or solvent that can be removed during the coating process. It depends on the amount of air flowing through the bed.
  • Coating composition – the coating composition includes the ingredients that are applied to the surface as well as to the solvents that acts as a carrier for the ingredients. The solvents are then removed during the coating process. As the inlet air gives off heat, it helps to evaporate the water. The exhaust air then becomes cooler and contains more water resulting to the evaporation of the solvent from the coating composition.
  • Tablet surface area – the amount of tablets that are needed to be coated have already been determined however the tablet’s size and the debossed features can affect the coating condition. The total area/weight decreases quite significantly from a smaller to a bigger tablet.
  • Efficiency of equipment – conventional sugar coating efficiency is less and 60% is deem acceptable. The efficiency depends on the coating material that can be collected on the pan walls.

Main Coatings using a Coating Machine

Coating is crucial and is the final step in the production cycle. In order for the application of the coating solution be successful, it must show a visual characteristics of the product so that they would be able to judge on the quality of the tablets.

There are 2 types of coating which is sugar coating and film coating.

Sugar coating conventional/traditional

  • Sealing
  • Subcoating
  • Smoothing
  • Finishing
  • Polishing

Film Coating/Contemporary

  • Pan pour method
  • Pan spray method

The sugar and film coating both usually use the same equipment for the coating process.

Advantages of Tablet Coating Machines

Standard Coating

Standard/Traditional

  • A continuous process
  • Decrease the drying time
  • Can be use by both
  • To improve drying efficiency, many used a Pellegrini
  • Quick process
  • Takes less time to coat the tablet

Perforated Pan System

  • Drying air directly passes to the drum
  • Configuration of the air flow is possible though Glatt coater
  • Shows increase coating capability
  • More efficient in drying of the tablet bed

Fluidized/Air Suspension System

  • Coating solution is continuously applied from spray nozzles
  • High pressure airless systems and low pressure results to finely divided spray
  • Effective
  • Airless system is mainly used in air suspension coaters