Drying with Hot Air
Content of this page
Drying of water based coatings
The process to speed up the dry time of water based coatings
To dry water based coatings such as acrylic-, dispersion and watertank coatings, it is necessary to use hot air dryers (airknives). These coatings normally contain about 60% water.
By blowing hot air with high speed against and over the passing coated material (paper. board etc.) the water will be evaporated out of the coating and the drying time will be much shorter. During this process it is of great importance that the with water saturated air is extracted by an exhaust system.
Before the airknives an IR dryer is placed by which the ink below the coating has a better setting and the temperature of the sheets increases. The power of the IR can be controlled stepless. The value of the temperature in the pile depends on the power setting of the IR dryer.
Adjustble dry capacity
The mounting position of the airknives depends of the type of the sheet offset press. The can be placed in the upsweep or in the extension before the delivery.
The dry capacity is adjustable by:
- The setvalue of the air temperature that comes out of the airknives. The power of the airheater is adjusted to what is needed.
- The speed of the air coming out of the knives. The capacity of the airblower is controlled by a frequence controller and also optimum tuned to what is needed.
By this the dry process and the use of energy can be controled in the best way for every kind of paper.
Interstation drying
Hot air dryers (airknives) can be used also very well for interstation drying for example between two coating units or between a printing- and a coating unit. By this the setting of the ink will be better before a water based coating is applied in-line. Also is it possible to apply two types of coating in-line, for example gold/silver coating and protective coating or water based blister coating that has to be built up in two layers.
Summary
Air drying by the use of Jac. de Vries airknives gives you the following advantages:
- Better ink setting
- Higher gloss values (also due to vapour removal)
- Improved coating viscosity
- Improved point resolution
- More than one coating can be apllied in-line
Total Drysystem
To dry the water based coatings applied on-line over the ink Jac. de Vries Infraroodtechniek has developed a so called total dry system. This system is an optimum combination of IR, airknives and exhaust. Everything is brought together in one controlpanel and is controlled by a PLC in combination with a touch screen. This makes it very easy to setup the dry system because all the relevent information is displayed by the touch screen. Also when something might go wrong you will be immediately informed about this and what to do to solve this so the stand still time will be reduced to a minimum.
Contact
If you want more information about hot air drying from Jac. de Vries, please look on our downloadpages for leaflets or ask your question by our contactform.