Apparatus for heating polymeric powders by means of radiation in powder coating methods
An apparatus for heating powder particles, contains a radiation source ( 1 ), a housing ( 2 ) and a screen ( 4 ). The radiation source ( 1 ) has its maximum radiative power in the wavelength range of 0.78-2.5 μm. The screen ( 4 ) has an absorbance of at least 0.8 in the wavelength range of 0.78-2.5 μm.
1. An apparatus for heating polymer powder particles, comprising:
a radiation source,
a housing, and
a screen,
wherein the radiation source has its maximum radiation power within the wavelength range of 0.78-2.5 μm and the screen has an absorbance of at least 0.8 within the wavelength range of 0.78-2.5 μm.
2. The apparatus according to claim 1 , wherein the surfaces of the housing facing the radiation source have an absorbance of less than 0.4 within the wavelength range of 0.78-2.5 μm.
3. The apparatus according to claim 1 , wherein the screen is arranged between the radiation source and a guard plate.
4. The apparatus according to claim 3 , wherein the guard plate has a transmittance of at least 0.9 within the wavelength range of 2.5 μm-10 μm.
5. The apparatus according to claim 3 , wherein housing, screen and guard plate are thermally decoupled.
6. The apparatus according to claim 1 , wherein the screen consists of anodized and coloured aluminum.
7. The apparatus according to claim 1 , wherein the screen has a thickness of not more than 1 mm.
8. A method of heating polymer powder particles, said method comprising:
heating the polymer powder particles with an apparatus according to claim 1 , wherein the polymer powder particles are exposed to the radiation from the apparatus.
9. The method according to claim 8 , wherein the polymer powder particles are heated at a heating rate of at least 2 K/s.
10. A method of coating a powder, said method comprising: heating of polymer powder particles with an apparatus according to claim 1 .