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Environmental fate & pathways

Hydrolysis

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Description of key information

Two hydrolysis studies performed with commercial alkyl ketene dimer preparations.
At pH 8 by Marton (1990) and at pH 3 by Hercules European Test Laboratories (2003).

Key value for chemical safety assessment

Additional information

Alkyl ketene dimers are readily biodegradable and poorly soluble in water. Studies on the hydrolysis as a function of the pH are therefore not required. 

 

Hydrolysis of commercial alkyl ketene dimer preparations have been studied but there are no valid hydrolysis studies available for alkyl ketene dimers identified by CAS numbers 84989-41-3 (Europe) and 68390-56-7 (USA). However in practice it is well known that under alkaline conditions at ambient temperatures, hydrolysis will occur, leading to formation of the dialkyl ketone. Hydrolysis studies with the commercial alkyl ketene dimer preparations showed half lives of between 23 and 140 hours at pH 8 and 30 °C(Marton 1990).Temperature correction of the halve lives to 25 °C at pH8 results in half lives between 35 and 210 hours (EUSUSES calculation). Commercial experience at low pH is not available because wastewater treatment plants are normally run at neutral-to-mild alkaline conditions. Alkyl ketene dimers are stored at relatively low pH, typically around 3, in cooled containers in order to avoid formation of the ketones in the products which reduces the technical sizing effect (Marton, 1990, Hercules European Test Laboratories, 2003). A stability study on an alkyl ketene dimer dispersion conducted at pH 3 over 4 weeks at temperatures 25˚C and 32˚C showed parent compound losses of 4.5 % and 16.6 % respectively (Hercules European Test Laboratories, 2003). In conclusion, based on the available data, alkyl ketene dimers are expected to hydrolyse readily under neutral and alkaline conditions in the environment and are assumed to be stable to hydrolysis at acidic pH values.