Mazda is actively engaged in recycling plastic automobile parts. We focus in particular on recycling bumpers, and have created bumper-to-bumper recycling technology for these large plastic parts. This technology is used to recycle damaged bumpers for reuse as material for new bumpers.
Mazda collects and recycles damaged bumpers in response to environmental issues and the need to use resources more efficiently. Mazda became the first automaker to recycle bumpers (as vehicle undercovers) in 1992. In 2001, Mazda began removing the paint which causes deterioration of mechanical properties from damaged bumpers and using the recycled material to reinforce bumper plastic. However, to use the recycled material for new vehicle bumpers, it was necessary to improve the degree of paint removal in order to ensure the recycled bumpers exhibit the required surface quality. This led Mazda to develop its paint removal process.
- Target paint removal rate
The paint removal rate for materials recycled with the conventional process is 98.50 percent, which means a 1.50 percent residual rate. With this method, new bumpers made from 30 percent recycled material do not possess sufficient surface quality to be painted. The recycled material content must be lowered to just three percent to satisfy the criteria. In order to achieve the desired 30 percent recycled material content, we first had to reduce the paint residual rate from 1.50 to 0.15 percent. This led to our target paint removal rate of 99.85 percent.
- How the paint removal rate was improved
Mazda conducted a detailed examination of crushed bumper pellets to determine the paint removal rate of the conventional process, and found that only a small proportion (14 percent) of the pellets still had residual paint; 86 percent were paint free.
Given this, we surmised that if we could detect and remove bumper pellets with an area of residual paint over 10 mm2, we would achieve a high yield of recycled material at the target paint removal rate. (Yield is defined as: 'the number of paint-free pellets/the total number of crushed pellets x 100.'
- Selection mechanism
Crushed bumper pellets are subjected to the paint stripping process, then collected in a hopper and passed through a shooter. As they exit the shooter, light is shone on them from various angles. Any paint adhered to the fragments reflects light more intensely than the (black) bumper material. Charged-coupled device (CCD) sensors detect the reflected light and an air jet immediately removes the unwanted pellets.
This mechanism to separate crushed bumper pellets successfully improves the average rate of paint removal from 98.50 to 99.85 percent.
Mazda has developed a world-first recycling technology which enhances the process it uses to recycle used bumpers from vehicles, whose useful life has ended, into raw plastic resin for use in new vehicle bumpers. The new technology is the first to enable recycling of used bumpers from different manufacturers at the same time. Additionally, by automating processes to remove metal attachments, it significantly increases recycling efficiency.
Until now, unwanted materials such as metal attachments had to be removed by hand before the bumpers were visually inspected. These labor-intensive processes were an obstacle to increasing efficiency. Mazda overcame this by developing technologies to automate the processes in collaboration with Satake Corporation, a company in Hiroshima Prefecture, western Japan. Once used bumpers are crushed into pellets, a machine similar to those used to separate contaminants from cereal grains, removes unwanted metal pieces by shaking the pellets and directing airflow over them. In this way, Mazda's new process enables higher efficiencies to be achieved.
Mazda's new technology also resolves another limitation of previous methods. Depending on the vehicle manufacturer and age of the vehicle, used bumpers vary considerably in terms of the composition of polypropylene plastic and the paint's adhesive properties. While this has forced previous systems to treat different bumpers separately, Mazda's new technology successfully enables all bumpers to be recycled together. The new process employs a kneading machine which is similar to those used for processing foodstuffs and chemicals such as rubber and plastics. The machine applies a powerful shear force to the crushed bumper pellets, effectively stripping off the paint regardless of the plastic composition or paint properties, and without having to heat the plastic.