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Hydrolysis

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Description of key information

The hydrolysis as a function of pH of 3-isocyanatomethyl-3,5,5-trimethylcyclo-hexylisocyanate homopolymer was determined by AQura (2010) based on the OECD guideline 111 (2004) and EU test method C.7 (2008) with modifications at room temperature (22.1 – 23.0 °C) and using the isophorone diisocyanate trimer as a representative of the whole test item.
Test series pH co-solvent concentration Kobs [h–1] t½ [h]
1 4 30 % acetonitrile in water 0.6556 1.06
2 7 30 % acetonitrile in water 0.1783 3.89
3 9 30 % acetonitrile in water 1.3128 0.53
4 7 15 % acetonitrile in water 0.0904 7.66
5 7 7.5 % acetonitrile in water 0.1916 3.62
The hydrolysis half-life was always clearly below 12 hours. Both acidic and basic media appear to accelerate the hydrolysis. No simple relationship between the rate of hydrolysis and the concentration of the organic co-solvent acetonitrile could be observed.

Key value for chemical safety assessment

Half-life for hydrolysis:
3.89 h
at the temperature of:
22.6 °C

Additional information

According to experience with the substance itself as well as with diisocyanates and similar polyisocyanates, 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 oligomer predominantly polyurea molecules are formed. They are insoluble in water and thereby have a negligible mobility (including accumulation potential) in the environment.