Mazda Motor Corporation’s new paint system—the Aqua-tech Paint System—has received the Prime Minister’s Award (Manufacturing and Production Process Category) at the 6th Monodzukuri Nippon Grand Award ceremony. The Aqua-tech Paint System reduces emissions of volatile organic compounds (VOCs) compared to Mazda’s previous oil-based paint systems without increasing energy consumption (and associated CO2 emissions).
Mazda had already achieved world-class low CO2 emission levels with the implementation of the Three Layer Wet Paint System. The company’s follow-on goal was to further reduce volatile organic compound (VOC) emissions to world-class levels.
|Source: Mazda. Click to enlarge.|
Water-based paints tend to produce lower VOC emissions than solvent-based paints due to their low VOC content. However, the water, used as a diluent, must be evaporated through a drying process which consumes large amounts of energy. CO2 emissions associated with the production of this energy mean the water-based paint systems tend to produce higher levels of CO2 emissions than solvent-based paint systems.
The key issue facing the development team was how to keep using water-based paints that greatly reduce VOC emissions while curbing the CO2 emissions that result from producing the required energy. To solve this challenge, Mazda pursued two tracks:
Consolidate the paint process by developing a highly functional new paint. Mazda developed two new types of top coat paint for the Aqua-tech Paint System: a water-based color basecoat and the first urethane clear coat to be fully implemented by any company in Japan. By switching to these paints, VOC emissions are among the lowest in the world—57% lower than the Three Layer Wet Paint System and 50% lower than common water-based paint systems.
In addition, these highly functional top coat paints exhibit additional properties that are usually provided by the primer paint, thereby enabling Mazda to consolidate the coating processes. As a result, energy consumption is substantially curtailed, and the issue of high CO2 emissions is addressed. The highly functional quality of the paint also ensures that the paint reliability and durability are as high as ever, while other properties including smoothness, gloss and resistance to chipping are even better.
Increase the efficiency of the paint process by developing two new energy-saving technologies: paint booth air conditioning and an energy saving flash-off process. By changing the approach to air-conditioning the paint booth, Mazda achieved a 34% reduction in CO2 emission volume compared to conventional water-based paint booths.
In order for the paint to stabilize on the surface of the car body, water content must be precisely controlled from the moment the paint is applied and it is important that it has reached the ideal viscosity before application of the next coat. Therefore it is important to maintain a constant drying rate.
For this reason, in regular paint booths for water-based paint systems it is necessary to constantly maintain the temperature and humidity level via air conditioning. Because the paint booth is a large space big enough to hold an entire vehicle body, this requires a large-scale air conditioning system and a large amount of energy—especially in summer and winter.
Mazda’s newly developed system constantly controls the maximum water vapor absorption volume by monitoring external conditions and making the minimum necessary adjustments to temperature and humidity inside the paint booth. The result is a significant reduction in energy consumed during the paint process.
With water-based paint systems, a preheating (flash off) drying process is applied between the base and clear top coats. By evaporating the water contained in the base coat paint before applying the clear coat, the process is intended to improve the finished paint quality.
Usually the process involves raising the temperature to 80 °C until the paint is sufficiently dry. However, before the clear coat can be applied, the temperature must be reduced back down to 40°C. If the vehicle body is too hot, the clear coat paint will dry before it has time to spread out, and the final smoothness will be impaired.
Conventional heating systems blow hot air into the paint booth. However, this method heats the steel vehicle body as well as the paint. Cooling the steel afterwards also consumes large amounts of energy.
In order to overcome this problem, the Aqua-tech Paint System flash off process utilizes an infra-red heater. This heats only the paint surface, enabling the water solvent to be evaporated without heating the steel body. The heater can also be switched on and off quickly. This means the amount of heating can easily be optimized for each body size and paint color. The technology means the water can be efficiently removed using the smallest possible amount of electricity.
This new system results in a 17% reduction in CO2 emissions compared with the common flash-off processes.
Applying this technology to color development also enabled Mazda to deliver design colors such as Soul Red.
The Prime Minister Award (Manufacturing and Production Process Category) acknowledges individuals or groups who have created a production revolution through the introduction and development of ground-breaking systems or techniques in manufacturing or production processes. This is the first time Mazda has received the Prime Minister’s Award (Manufacturing and Production Process Category).