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Environmental fate & pathways

Endpoint summary

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Additional information

Summary

Stability (hydrolysis):

In a screening test at 50°C the substance(2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene) isocyanate (HDI Trimer) was found to hydrolyse by 84 – 89% within less than 1 hour at pH values of 4, 7, and 9 (Bayer Industry Services, 2007). Approximate mean half lives of 3 hours at 25°C were estimated at any pH and environmental relevant temperatures. A hydrolysis product based on the hydrolysis of the 3 Isocyanate groups to the corresponding amine functions has been proposed (BIS, 2007).

Based on the determination of the Isocyanate function, the half-time of HDI Trimer in the the acetonitrile/water solution is approx. 7.7 hour at room temperature (23 °C) (Bayer AG, 1999).Hydrolysis products have not been elucidated. However similar substances containing several isocyanate groups like HDI, MDI are known to react rapidly with water forming insoluble oligomeric and polymeric ureas. The below mentioned corresponding triamine is only a theoretical worst-case assumption in order to have a basis for assessment but which in reality reflects only insignificant traces.

Phototransformation in air:

The atmospheric oxidation rate constant of HDI trimer (Isocyanurat, n=3) is 37.5 * 10-12cm3/(molecule *s) and its atmospheric half-life is 10.3 hrs (Currenta, 2009a).

The atmospheric oxidation rate constant of the corresponding triamine of HDI trimer (Isocyanurat, n=3) is 129.1 * 10-12cm3/(molecule *s) and its atmospheric half-life is 3.0 hrs (Currenta, 2009b).

Biodegradation (in water, screening test):

Within 28 days, a degradation of 1 % was determined in a 'Closed Bottle Test' (Bayer AG, 2001). The substance is regarded as "not readily biodegradable".

Bioaccumulation:

The direct and indirect exposure of the aquatic compartment is unlikely because HDI Trimer hydrolysis completely in water within 7.7 hours. Therefore the BCF-values were calculated. Bioconcentration factors (BCF) of 3.16 and 367.7 for HDI Trimer (Isocyanurat, n=3) and its corresponding triamine were obtained (Currenta, 2009a).

Even the corresponding triamine of HDI Trimer (Isocyanurat, n=3) with a bioconcentration factor of 367.7 does not have high bioaccumulation potential (Currenta, 2009b).

Only minor amounts (ca. 4%) of the hydrolyses substance are soluble in water indicating that bioaccumulation are not expected. 

Adsorption / desorption:

HDI Trimer (Isocyanurat, n=3) is characterized by a Koc of 5.7 * 1007 being calculated with PCKOCWIN v. 1.66 (Currenta, 2009a). According to the method of Gerstl (1999) the Koc of 2.1 * 1007accounts for the main component (Currenta, 2009a).

The corresponding triamine of HDI Trimer (Isocyanurat, n=3) is characterized by a Koc of 6.1 * 1005 being calculated with PCKOCWIN v. 1.66 (Currenta, 2009b). According to the method of Gerstl (1999) the Koc of 2.7 * 1004 accounts for the corresponding triamine (Currenta, 2009b).

Volatilisation

With a vapour pressure of <0.0001 hPa volatilisation of the substance is unlikely.

Distribution modelling

HDI Trimer hydrolyses rapidly in the presence of water yielding a complex mixture of oligomeric and polymeric urea derivatives which are non-soluble in water. Due to the rapid hydrolysis of HDI Trimer, a transport of the substance between environmental compartments is unlikely. Consequently, a calculation of the distribution between the environmental compartments according to the Mackay fugacity model level 1 or 3 is not suitable.