19 May 1998 02:02 [Source: ICIS news]
SINGAPORE (CNI)--Japan's Takeda Chemical Industries and Kobe Steel have developed an environmentally friendly method to recycle the residue from polyurethane (PU) production, CNI learned Tuesday.
A recycling plant for PU waste, using supercritical water technology, has begun commercial operation at Takeda's Kashima plant in Ibaraki prefecture, northeast of Tokyo.
A Takeda spokesman explained: "Supercritical fluids exist in a state above the critical temperature and critical pressure where gases and liquids co-exist. They exhibit unique properties that are different from those of either gases or liquids under standard conditions.
"By varying pressure and temperature, supercritical fluids can have the gaseous property of penetration and the liquid quality of dissolving materials into their components."
At its Kashima plant, Takeda makes the plastic intermediate material toluene di-isocyanate (TDI), which is used in making PU. TDI is made from toluene-diamine (TDA). Residue from TDA derived in the manufacture of TDI was previously not recovered.
Using supercritical water technology, the Kashima plant recovers the TDI waste for re-use in making TDA. The plant has a TDA recovery rate of 80%. Kobe Steel said this is the first time supercritical water has been used to recycle plastic intermediate material commercially.
Supercritical water is easy on the environment as the water serves as the solvent. No acids or alkalines are used, so waste water treatment is unnecessary.
PU is widely used in car seats, mattresses, cushions, refrigerator insulation, paint, adhesives and other consumer and industrial products.
In 1980, Kobe Steel and Tohoku University began pioneering research in supercritical fluids. Kobe Steel hopes eventually to apply supercritical fluid technology to recycle other plastics used in such products as cars and appliances.
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