APPLICATIONS FOR THE WOOD INDUSTRY

Coatings on wood need to be dried quickly but with care. Wood is treated with a wide range of different coatings before it reaches the end user. Base coatings, varnishes or powder coatings need to be dried as quickly as possible, whilst ensuring that there is no damage to the wood.

This requirement is best achieved with infrared technology. Infrared heat dries much faster than conventional hot air methods, because infrared acts specifically on the coating. Radiation which is precisely matched to the absorption characteristics of the of the coating is rapidly converted into heat, so that water or other solvents are evaporated, while the coated material and the immediate surroundings remain cool.

This careful heating of the material avoids stress on the surface of the wood. In the shorter heating time, the wood is not heated enough for the wood fibers to change their alignment because of the heating effect. Moreover, because of the rapid heating, very little water can penetrate from the coating into the wood surface to soak the fibers. The infrared heating also reduces the need for intermediate grinding and allows an improved quality of coating no matter what the season as it is independent of the storage temperature of the wood. Heraeus Noblelight matches infrared heaters precisely to the requirements of the particular process, in terms of optimum wavelength of radiation and the length and power rating of heater.

• Carbon Infrared (CIR®) heaters are particularly effective for drying water-based varnishes on wood, as these heaters give out medium wave radiation. The wavelength of the infrared radiation has a significant effect on the drying. Water and many solvents evaporate especially quickly when subjected to medium wave infrared radiation. This is because the medium wave radiation is converted directly into heat in water and solvents. This is not the case with, for example, near infrared (NIR) radiation.
• Powder coatings are reliably gelled and cured in a short time with infrared radiation. Powder absorbs infrared radiation very well and the powder heats up very quickly. Compared with conventional heating methods, such as convection ovens, the gelling of the powder is significantly accelerated. Rapid melting improves the coating quality and speeds up throughput. Powder coatings can be baked into MDF and HDF plates with short wave or CIR infrared heaters, according to the absorption characteristics of the coating.
• A combination of efficient infrared radiation and a sharply defined air stream, the so-called air knife, is particularly effective for drying water-based foundation coatings on parquet flooring tiles. The UV primer on these tiles must be completely dried before any following coating stages. An airknife heats the water with infrared and the additional air stream removes the ensuing water vapor from the coating. This eliminates the need for vapor barriers and makes the coating drying even more effective.
• In the manufacture of laminated boards, there is a requirement to dry the edges of the boards. The front edges are coated with a water-based coating, which must then be dried as quickly as possible. This is best done using a short wave high power heater, which allows production speeds to be increased up to 180m per minute.

Heraeus Noblelight can carry out tests in its in-house Applications Center or on-site, to determine which infrared heaters will provide the fastest drying and curing while providing optimum care of the material to be coated. The following page features photo examples of Heraeus IR heaters in wood drying applications. For more information, please contact us.

 

 

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