Compared to Three Layer Wet Paint System, Mazda's paint system currently installed at its production facilities, the Aqua-tech Paint System reduces volatile organic compounds (VOC) by 57 percent without increasing carbon dioxide (CO2) gas volumes. This is a paint system that has the lowest environmental impact achieving the world's highest standards for limiting emissions of VOC and CO2.
Mazda developed the Aqua-Tech Paint System with an aim to further reduce the environmental impact of the automobile manufacturing process.
Mazda achieved world-class low CO2 emission levels with the implementation of the Three Layer Wet Paint System. The next aim was to further reduce volatile organic compound (VOC) emissions to world-class levels as well and in doing so develop the most environmentally-friendly paint system in the world.
Water-based paints tend to produce far lower VOC emissions than solvent-based paints due to their low VOC content. However, they contain water as a diluent and this water 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. Therefore, 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.
In order to counter this issue, Mazda developed technologies that are categorized into two major groups.
Two new types of top coat paint were developed 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 percent lower than the Three Layer Wet Paint System and 50 percent 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 solved. 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.
Layered Paint Structure and the Main Function of Each Layer
Energy Saving Paint Booth Air Conditioning
By changing our approach to air-conditioning the paint booth, we achieved a 34 percent 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.
Energy saving Flash Off 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-percent reduction in CO2 emissions compared with common flash off processes.
Comparison between Aqua-Tech and conventional paint processes
The Three Layer Wet Paint System applies all three paint layers, primer, base and clear top coat while still wet and then employs just one drying process to finish. Through application of this new technology, CO2 emissions have been cut by more than 15 percent and volatile organic compound (VOC) emissions have been reduced by as much as 45 percent compared to conventional painting processes.
1) CO2 emissions have been significantly reduced with this newly developed coating system. It combines the primer coating process with that of the base and clear top coats. All three layers are applied in succession and then baked to a fine finish.
2) By combining extremely accurate paint control technology with a highly efficient robotic coating system, Mazda has achieved a uniform coating thickness and raised the efficiency of its painting line. Furthermore, in collaboration with a paint manufacturing company, Mazda has developed new low-solvent paints that allow the three layers to be applied in succession. These advances reduce volatile organic compound (VOC) emissions and overall costs while improving the finished quality.
(1) Low-solvent in the paint
Simply reducing the amount of solvent used in paint will increase the paint viscosity and make it unsuitable for coating. To prevent this, Mazda reduced the molecular weight of the coating resin and thereby the paint viscosity. By developing this low-solvent paint, Mazda has significantly reduced VOC emissions.
(2) Preventing the mixing of the primer and base coat
When the primer and base coat mix, it leads to a degradation of glossiness and color. To prevent this, we developed a new resin called an interface control polymer, and added it to the primer paint. When the primer is applied, the interface control polymer creates a barrier layer on the paint surface.
Thought uniformly dispersed throughout the primer when it is applied, the larger molecules of the interface control resin are soon drawn to the surface of the thin layer of paint by surface tension, where they form a highly viscous barrier layer at the interface between the primer and base coat. This technology prevents color degradation and ensures the finished quality is as good as or better than conventional coating methods.
(3) Improvement of coating efficiency
To eliminate the unnecessary application of paint to areas that do not need to be coated, and to obtain a uniform coating thickness with a minimum amount of paint and energy, the Three Layer Wet Paint System employs robotics instead of the conventional reciprocal automated painting method. The advantages of robotic painting are the paint can be sprayed from the ideal angle for any surface, it offers excellent repeatability, and a set distance can be accurately maintained between the nozzle and target surface, even when the surface is curved.
1) Reduced energy consumption
By combining the primer and top coat processes, the separate primer booth and primer drying furnace have been eliminated. As a result, total energy consumption in the paint shop has been reduced by 15 percent.
2) Reduced VOC emissions
The decreased in the volume of paint used and the development of Mazda's low-solvent paint have lowered VOC emissions by approximately 45 percent compared to the conventional paint process. As a result, Mazda is able to meet the European VOC regulations of 35 g/m2 without having to redesign its paint line for a switch to water-based paint.