New Toyota Painting System Easy on Environment

Tokyo―TOYOTA MOTOR CORPORATION (TMC) announced today that it has developed a new automobile painting technology for use with water-based paints, which have little negative environmental impact. TMC began introducing this revolutionary system to its painting lines in August.

The new technology incorporates a robotic paint sprayer equipped with a cartridge-type tank that enables water-based paints to be used in electrostatic painting, which is recognized for its exceptional covering efficiency and high productivity. This new spraying equipment also allows frequent and quick changes in paint colors. Moreover, the amount of paint thinner needed to clean the inside of the equipment during color changes is only one tenth of that used in conventional painting systems.

Standard automobile metallic body painting is comprised of tour coats: an undercoat, or primer; a middle coat, or surfacer; a base coat; and a clear coat. For many years, organic solvents were the most commonly used solvent media for paints in paint sprayers, except in the case of the primer. This is because it is easy to maintain a degree of freedom in the control of an organic solvents viscosity, and to obtain the electrostatic charge required for the painting process.

The use of such solvents, however, creates vapor and wastewater that can have negative impact on the environment. TMC, therefore, has been making determined efforts to improve the efficiency of paint applications and to retrieve thinner used for cleaning, lowering the volume of solvent discharge VOC^* on painting lines to 64g/m². The introduction of the new water-based paint technologies, however, has slashed that figure nearly in half.

Viscosity control of water-based paints is inherently more difficult, and can produce inconsistent paint quality due to changes in the application environment, such as in temperature and humidity. Also, electrostatic

painting using conventional water-based paints does not improve productivity. TMC has resolved these issues by developing a metallic water-based paint with a much higher level of productivity than those in the past, and which is not easily affected by the working environment.

Furthermore, by using this paint in a small, cartridge-type paint tank attached to a robot paint sprayer, it is now possible to generate an electrostatic charge directly in the paint itself for optimum covering efficiency. Using the new system for applying the base coat, which has the largest volume of solvent discharge, the VOC in painting processes at TMC's Takaoka Plant has been reduced to 35g/m², resulting in one of the world's most environmentally-sound painting lines.

TMC plans to gradually expand application of this technology to other plants and is further developing it for application of the surfacer coat and, using powder-type paints, the clear coat, in order to fully integrate the low-environmental-impact technology and to further protect the environment.