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Environmental fate & pathways

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A study was performed to assess the ready biodegradability und the inherent biodegradability of Hexamethylene diisocyanate, oligomerisation product (allophanate type). Within 28 days, a degradation rate of 0 % and 1 % respectively was determined . Therefore, the substance is considered to be “Not Readily Biodegradable“ and “Not Inherently Biodegradable”.

For the substance the hydrolysis behaviour should be investigated. As the test item was found to be poorly soluble in water (water solubility study no. 2011/0034/14), it was therefore not possible to prepare an aqueous solution of the test item necessary to perform a hydrolysis test according to the requirements of OECD TG 111 (2004). Obviously the substance builds small layers of inert surface in water which inactivate a further reaction with water. On the other hand, isocyanates are known to react easily with water. For this reason, a non-guideline test was performed with the substance dissolved in an organic solvent which was then diluted with water. Under these conditions the substance hydrolyses rapidly with a half life of about 2 days.