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Environmental fate & pathways

Hydrolysis

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Description of key information

A preliminary hydrolysis test was conducted by Bayer AG (1999) in order to determine the dissipation half-life of isophorone diisocyanate. The test medium was 30 % acetonitrile / 70 % water (no buffer) at 23 °C. Samples of the test solution were taken every 11 minutes and analysed by GC/FID. Approx. 84 % of the test substance were found to dissipate within a period of 121 minutes. The dissipation half-life was determined as 0.84 hours (approx. 50 minutes). Degradation products have not been analysed.
The observed half-life is in agreement with the results of Infracor GmbH (2000) who performed a preliminary study in unbuffered aqueous solution. The results show that the half-life at 23 °C is below 7.2 hours.

Key value for chemical safety assessment

Half-life for hydrolysis:
0.84 h
at the temperature of:
23 °C

Additional information

According to experience with the substance itself as well as with similar diisocyanates, the amines formed in the initial hydrolysis step, which is associated with elimination of carbon dioxide, have a high reactivity towards unreacted isocyanate. The consequence is that in the hydrolysis of isophorone diisocyanate predominantly polyurea molecules are formed. They are insoluble in water. Their formation was observed in the study of Infracor GmbH (2000) who reported that droplets settled on the bottom of the test vessel and became increasingly coated with a white layer.

Beside these insoluble main hydrolysis products minor amounts of other hydrolysis products having a low to moderate molecular weight and being more or less water soluble (e.g. isophorone diamine). They were determined by unspecific TOC analysis in aqueous phases of ecotoxicity studies where their potential for adverse environmental effects was investigated (see section 6.1).