Progress Report 2: Plant-derived Polyurethane
World's First Commercial “Eco-car” Materials
One of the products of Mitsui Chemicals' initiatives to develop non-fossil, inedible raw materials is the commercialization of a seat cushion made from plant-derived polyurethane in Toyota Motor Corporation's environmentally friendly Prius and other vehicles.
High Quality Attained through Repeated Strict Human Sensory Assessments
Polyurethane is used in a wide range of applications, including car seat cushions and interiors, insulator, and bedding. Polyurethane is made from polyols and isocyanates. A seat cushion made from polyurethane in which some of the polyols were replaced with castor oil derivatives (made from castor seeds) was adopted for use in the driver's seat of the 2009 model Prius.
This plant-derived seat cushion was jointly developed by Toyota Motor Corporation, Toyota Boshoku Corporation, and Mitsui Chemicals. The policy for mounting driver's seats in the next-generation Prius was published in 2006, and the subsequent year was “extremely busy,” says Kazuto Usaka, who develops plant-derived polyurethane in the Polyurethane Business Sector.
“Plant-derived polyurethane has lower resilience than the petroleum-derived type,” says Usaka, “but seat cushions need to be highly resilient as well as highly durable, and pass ‘human sensory assessments.' A human sensory assessment relates to riding comfort, and some of the items are quite hard to express clearly with numerical value, but after repeated testing, we were able to add improvements. The human sensory assessment gradually improved,” says Usaka. “And ultimately, we got a very high assessment. They told us that this seat was more comfortable than any before. And with that, we had overcome this challenge.”
Kazuto Usaka
Manager
Polyurethane Development Division
Polyurethane Business Sector
We Are Also Working on a 100% Plant-derived Material, and Are Expanding Applications as Well
“We were the first in the world to commercialize a car seat cushion made from plant-derived polyurethane,” says Usaka. “The plant-derived portion is still about 15%, but we plan to increase this ratio. In the future, if we can also make plant-derived isocyanates, then we will have a 100% plant-derived, recyclable polyurethane that is carbon-neutral.”
The castor oil used as a raw material is inedible, so it does not pose any problems in terms of competition with food.
“Castor oil is an easy-to-use material. It is stable and has low variability,” says Usaka. “It drew our attention because it has long been used in paints and adhesives.”
Mitsui Chemicals is committed to developing applications other than seat cushions. This material has promise in bedding that makes use of low resilience, and in insulator for buildings, refrigerators, etc.
“If we can make plant-derived insulating material that contributes to energy saving,” says Usaka, “then we can also contribute to the environment when using it. Although it still costs more than the petroleum-based equivalent, if we can expand the applications and increase the production volume, then we will be able to offer it more cheaply.”
The Carbon-neutral Concept
VOICE
Toyota Motor is committed to reducing CO2 —a major cause of global warming— by using eco-plastics.
Due to the characteristics of car seats, it is difficult to introduce plant-derived constituents while satisfying the demands for functionality and safety. But Toyota Motor jointly developed biourethane with Mitsui Chemicals and Toyota Boshoku, succeeding at making a car seat cushion that is 15% plant-derived. This is the world's highest ratio of plant-derived material in a car seat cushion. In fiscal 2010, this seat cushion was used in the Prius, LEXUS HS250h, and SAI, and the company plans to expand its usage as it brings down the cost.
Although the business climate surrounding automakers is growing increasingly severe, we have expectations that material manufacturers will develop products that can delight customers, through the development of materials that are friendly to both people and the environment.
Kiyoshiba Mase
General Manager
Organic Material Department
Vehicle Material Engineering Division
Toyota Motor Corporation
