Coating

Definition Coating

Coating is defined by covering or enveloping particles with a suitable substance. The characteristics of the product are influenced in this way. Products are coated to be protected from light, humidity, oxygen or mechanical stress, to become a smooth surface or to be soluble. The coating solution must be suitable in order to properly cover the surface of the particles, i.e. the particle diameter of the coating solution must be much smaller than the granular size of the product. The effects desired by coating depend among others on the degree of accumulation to the surface. A 100 % coated surface has different effects than a partly covered one.

Lödige Coating Systems

The process technology mainly depends on the particles size. The coating of fine particles requires another process (mixing systems) than the coating of pieces of products like tablets for example (coating units).


Coating in Lödige Mixing Systems

The coating solution is added in the fluid bed of the product. The coating solution covers the surfaces of the particles whilst mixing. The rotation speed of the mixing elements and the use of choppers can support the distribution Quality.

Horizontal Ploughshare Mixer

A 100 % coating of the surfaces is rarely obtained with this process as the distribution can not be controlled. The quantity of coating solution necessary for static safety does not usually cover the entire surface. The usual coating degrees are between 70 and 95 % for this process. However, this is absolutely sufficient for most of the applications. Because of the mechanical influence of the fluid bed the product is subject to abrasion, i.e. there might be non-coated product remaining in the final product. The process time is only a few minutes.


2.2 Coating in the Lödige Coating Systems
Particles bigger than 1 mm (for example tablets) can be coated in Lodige coating units. The coating solution is sprayed onto the tablet bed and dried by warm air according to the cocurrent principle whilst the drum is slowly rotating. A slight low pressure in the drum ensures the cocurrent flow and prevents the product from leaving the drum.

The minimum process time in coating systems is typically about 1 hour. This way an absolutely homogenous distribution of the coating solution and a complete coating of the surfaces is ensured. Coating solutions like aqueous cellulose lacquer, functional lacquer like polyacrylate, suspension containing active ingredient like plant protective, etc. Organic solutions can also be used.



2.3 Coating in the Fluid Bed Processor
Particles, baby-sized tablets and other small products are fluidised, coated with coating fluid and dried during the coating process in a Lödige Fluid Bed Processor (LFP). The heated inlet air homogeneously flows through the special designed Conidur® bottom into the product vessel, fluidizes the product and keeps it in constant motion. Liquid is added, depending on the application, by top spray, bottom spray or tangential spray system. Coating in the fluid bed may occur either batchwise or with constant throughput in continuous working systems.


3. Examples

  • Coating of tablets
  • Coating of plastic material
  • Coating of sweets
  • Coating of rice crispies with chocolate
  • Coating of seeds as protection for environmental stress
  • Coating of catalysts

Coating with Lödige

Lödige has developed, manufactured and sold Coating Systems since 1980. Lödige Coaters have been supplied worldwide for a multitude of applications. The main focus of applications still remains in the pharmaceutical industry, but has progressed to other industrial applications in the meantime.

Lödige Coaters operate on the co-current, under-pressure principle and are ideal for film and sugar coat-ing of tablets, pellets, granules and other formed products. Drying air is blown into the centre of the drum by an air inlet system projecting into the drum and flows in the same direction as the spray mist of coating solution onto the tablet bed. This process is achieved in Lödige coaters in both partially perforated coating drums and totally perforated coating drums.

The unit comprises not only the coater itself, but also the inlet air system, the exhaust air system, the controls, the liquid dosing, the tanks, the feeding and discharge components and the CIP system for the coater.

Machines for Coating

The appropriate process technology for each coating application mainly depends on the particle size. Coating of fine particles requires other applications (mixing systems, fluid bed processors) than the treatment of lumpy products like tablets (coating systems). The following machines forming part of our range of machinery could be used for your coating processes.

Coating System

 

Ploughshare® Mixer

Applications

In the past decades the wide range of products as well as the high flexibility of our facilities enabled Lödige to place different types of machines and systems for all kinds of applications on the market. The range of products to be formed vary from the classic applications like tablets, capsules or sugar dragees from the pharmaceutical industry to chemical catalysts and seeds or to plastics parts with complex geometries. Examples for coating applications realised in a Lödige system are to be found below.

Coating of tablets, capsules and manufacturing of sugar dragees for pharmaceutical applications

Coating of extruded material for the foodstuffs industry

Coating of seeds

Coating of milled granulates

Coating of catalysts for the chemical industry

Brochure

Always the right mix

Always the right mix

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