3-Isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate homopolymer, isocyanurate type

Endpoint summary

Additional information

Soil exposure is unlikely during manufacture, formulation and industrial uses due to tailored operational conditions and effective risk management measures (see CSA). However, soil exposure could occur with respect to professional uses (especially spraying applications) which are widespread and for which effective risk management measures cannot always be warranted. With regard to professional uses, the substance is solely used in a two component mixture with alcohols, polyols or polyamines (pre-prepared). During application the two components are transformed into a polymeric product (polyurethane or polyurea) before they could enter the soil compartment. In order to demonstrate that the substance immediately reacts with the corresponding alcohol or polyol the reaction kinetic of the substance was investigated. For this purpose the substance was mixed with 1-butanole in presence of a catalyst and reaction kinetics were measured over 1 hour. The conditions were representative for professional spraying applications (temperature, catalyst, solvent, etc.). The experimental set-up, the test conditions and results are presented in the attached document.

The kinetic data demonstrate that ca. 80% of the substance (i.e. isocyanate groups (-NCO)) react within the first half an hour after spraying. After 1 hour, 97% of the substance has been transformed into a polymer. The various molecules that form IPDI homopolymer, isocyanaurate type, i.e. trimer, pentamer, heptamer, etc. bear at least three NCO-groups. Just before spraying, the substance is mixed with a polyol having usually a molecular weight (MW) of at least 3000 g/mol. The present OH/NCO-ratio is approx. 1. As soon as one NCO-group of the IPDI homopolymer reacted with the polyol a polymer of Mw >3000 is obtained. This polymer bears still NCO groups that will react further with remaining OH-groups of the polyol. Due to this, the major part of IPDI homopolymer has been converted to a Mw > 3000 polymer at a conversion of e.g. 80%. It is known from scientific literature that the reactivity of isocyanates with amines is even higher, i.e. it will take only a few seconds until all NCO groups have reacted. Considering the kinetic data and the available knowledge on transformation pathways it is concluded that the likelihood for direct soil exposure during outdoor spray applications is negligible.

Small amounts of the substance that may eventually reach the soil compartment hydrolyse when getting in contact with pore water. Upon contact with water the diisocyanate groups of IPDI homopolymer, isocyanurate type react by forming amines and CO2. The amines formed react further with unreacted diisocyanate groups of IPDI homopolymer resulting in oligo- and subsequently polyurea components (see hydrolysis studies Feldhues 2007, AQura 2010). The parent substance has an average molecular weight of 893 g / mol (residual monomers are negligible). However, it can be concluded from the structural formulae that the formed polyurea has a molecular weight amounting to multiples of that of the initial oligomers. Polyurea is therefore considered as not bioavailable and non-toxic to soil organisms.

Moreover, risk management measures preventing potential soil exposure are also stipulated for professional uses. Such risk management measures include amongst others housing, sealing of drains/drainages and other critical soil surfaces. The RMM’s prescribed for professional uses will be detailed in the CSA/CSR.

Indirect exposure to soil via air is unlikely due to the high vapour pressure of the substance (extrapolated value at 20 °C is 1.3 E-9 Pa). Indirect exposure via sewage sludge can also be excluded as the substance hydolyses immediately once it reaches the water compartment (see above).

In summary it is concluded that direct and indirect exposure to soil is unlikely to occur. This conclusion is based on the substance specific properties with its specific reaction kinetic and tailored risk management measures.