Reducing Water-borne Paint Contamination in Electrostatic Rotary Atomizers

The electrostatic rotary atomizer has the highest paint efficiency in all kind of atomizers. The usage of an electrostatic rotary atomizer, therefore, has contributed to reduce the waste of paint and volatile organic compounds (VOCs). Concurrently, water-borne painting processes which use water-soluble paint have been introduced to reduce the amount of VOCs emissions. With the water-borne painting, the atomizer body is easily contaminated by the paint mists. The contamination has been an important problem to be solved in factories. In this report, the causes of water-borne paint contamination was considered and the experimental results of the contamination proof system were presented. The atomizer is surrounded by the repelling film that is charged and repels the incoming paint droplets which otherwise contaminate the atomizer. From the experimental results, following electrical properties are found to be important for the repelling film such as low capacitance and high insulation property to keep high surface potential. These features were also checked by the space charge measurements inside the repelling film. In addition, safety against incendiary sparking was investigated. The ground electrode of sphere, needle or blush-shape was approached to contact to the charged film. Energy of the discharge was calculated from the measured discharge current and the surface potential of the film. The discharge energy of all measured electrodes was below the minimum ignition energy of 0.24 mJ used in the painting industries. At the meantime, the results indicate that shape of the electrode is an important parameter to affect the discharge energy.