TOKYO - Bumper replacement has become big business for Japanese body shops. The number of units replaced has grown to more than 2 million annually, including scrap vehicles, and the total is closing in on the 5 million mark, double levels of a decade ago. And with plastic bumpers now installed on 70 percent of new cars and trucks in Japan, vehicle makers are facing a potential environmental crisis.
Unlike steel, plastic bumpers cannot be repaired after minor traffic accidents. Until the beginning of the decade, they invariably wound up in landfills or as fuel for waste-to-energy incinerators.
Since 1991 most of Japan's big carmakers have established bumper collection and recycling programs in major metropolitan areas. A continued shift away from reaction injection molded polyurethane to polypropylene has facilitated their efforts. They just now are considering instrument panels, but disassembly costs make this process prohibitive.
In the summer of 1991, Nissan inaugurated a trial bumper recycling program west of Tokyo, specifically in the area around its Zama, Oppama and Murayama plants.
Then in January 1993, Fuji Heavy Industries Ltd., the maker of Subaru cars, joined the program. The joint plan called for some 4,400 bumpers to be collected each month from 98 sales outlets in Tokyo and adjoining Kanagawa Prefecture.
The companies estimate it will take at least five years before a nationwide collection structure is in place.
Upon collection, bumpers are cut and shipped to NP Plastic Chemical Co., a subsidiary of Nihon Plast Co. Ltd., and Ishizuka Chemical Industries Co. Ltd., where they are pulverized and mixed with virgin PP. The material is used in air ducts, trunk finishers, rear bumper parts, footrests and pallets.
In Europe, bumpers are sent to a subsidiary of Hoechst AG, where they are crushed and repelletized.
In October 1992, Nissan Motor Manufacturing (UK) Ltd. began using the material for eight components in the Micra, including the engine undercover, splash guard, vent hose, bumper closing and protector filler - a covering for an oil tank hose. Each car uses 21 ounces of recycled material, one of the highest levels among European makes.
Urethane chips, produced from PU bumpers, are being recycled into plastic mats and ve-hicle floors.
In February 1994, Nissan and Mitsui Petrochemical introduced a new chemical process for recycling painted thermoplastic bumpers into reusable bumper material. The procedure involves dissolving paint in a reaction with an alkaline solution under high temperatures. The recycled material is used at its Oppama plant to make bumpers to replace damaged ones.
Honda, which exclusively uses PP bumpers, began a recycling program similar to Nissan's in August 1991.
At present, 2,200 Honda dealers, out of a nationwide total of 2,300, are involved, collecting 10,000 damaged and scrap bumpers each month.
The bumpers are shipped to two plastic suppliers - Kyowa Corp. in Tokyo and Naveka Corp. in Nagoya - where they are pulverized and the paint is removed.
The material is used to make seven components: air outlets, bumper stiffeners, fuel hose joint protectors, splash guards, splash shields, water screens and evaporator cases.
In December 1991, Toyota inaugurated its bumper recycling program at 26 sales branches and six dealerships in western Tokyo. The program, since expanded to Tokyo and Yokohama, has seen monthly collection rise to 3,000 units.
Unlike Nissan, Toyota concluded that no existing technology adequately removes paint from plastic components and has developed a process to neutralize paint without actually removing it.
The technology, called pressurized hydrolysis, hydrolyzes paint under high temperature and pressure conditions, breaking down its chemical structure.
The automaker eventually hopes to make bumpers from bumpers using the process, which was introduced in Japan on a trial basis last autumn at the company's Motomachi plant. The process was introduced two years ago in Europe.
