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Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Stability

According to REACH Regulation (EC) 1907/2006 information about the phototransformation in air, water and soil is not mandatory for a registration of a chemical at a tonnage band of 100 - 1000 tons/year. However, the phototransformation in air was predicted by the computer program AOPWIN v1.92, resulting in an atmospheric half-life of 0.322 days (3.87 minutes; Chemservice S.A., 2011).

Bis(2,6-diisopropylphenyl)carbodiimide is considered as hydrolytically unstable at pH 4, 7 and 9 and temperatures up to 50 °C. (Holzaht-Grimme, 2020). The major degradation rate products is DIPA (2,6 -diisopropylaniline; CAS 24544 -04 -5). This result of the keystudy is in line with the provided supporting information (Cizek, 2012 and EFSA 2010) regarding hydrolysis.The rate of hydrolysis increases with decreasing pH and temperature. 2,6 -Diiospropyleaniline is the hydrolyisis product.

A Scientific Opinion of the European Food Safety Agency (EFSA) deals with the risk assessment of bis(2,6-diisopropylphenyl)carbodiimide, (CAS No. 2162 -74 -5 (EFSA, 2010). The EFSA Panel considered that the substance hydrolyses first into the corresponding diisopropylphenyl isocyanate (DIPI; CAS No. 28178 -42 -9) which is chemically unstable and readily hydrolyses into the 2,6-diisopropylaniline (DIPA; CAS-No. 24544 -04 -5) which is the final and chemically stable and quantifiable decomposition product. CDI is also chemically reactive during the manufacturing process and forms DIPI in the polymer.

Biodegradation

The biodegradation potential of bis(2,6-diisopropylphenyl)carbodiimide was investigated in experiments conducted according to OECD Guideline 301 F (Weyers, 2009) and OECD Guideline 301 B (Mead, 2001). In both studies, the substance was found to be "not readily biodegradable", which is confirmed by a QSAR prediction with BIOWIN v4.10 (Chemservice S.A., 2011) and an evaluation with the Start plug-in in Toxtree v2.5.0. (Chemservice S.A., 2011).

The prediction for biodegradability of main hydrolytical degradation product DIPA was also done with BIOWIN v4.10 (Chemservice S. A., 2016). A probability greater than or equal to 0.5 indicates "Biodegrades fast". A probability less than 0.5 indicates "Does NOT biodegrade fast". The Expert Survey Biodegradation Results (Biowin model 3 & 4) are clearly above the 0.5 threshold indicating a potential biodegradation. However, as the other Biowin models show, it is assumed that DIPA is not readily biodegradable.

Bioaccumulation

A bioaccumulation study is currently performed at a test laboratory following on to the final decision of ECHA on a compliance check, which was issued 01 August 2017.

Due to difficulties in the setup of the study, it is still under progress. Details can be found in the up to date endpoint study record under 5.3.1 and the statments by the test facility attached as background material for complete information.

Because new data is generated at this time, the BCF value is under revision and the previous data generated via QSAR is regarded only as supporting information.

As no experimental results are available for bis(2,6-diisopropylphenyl)carbodiimide up to now, the bioconcentration factor (BCF) was determined by the computer program BCFBAFWIN v3.01 (EPIWIN software) by US-EPA (Chemservice S.A., 2011) as supporting information. The regression-based estimate (traditional method) results in a BCF of 1912 L/kg wet-wt. Using the Arnot-Gobas method, which is based on the mechanistic first principles, the BCF results in a value of 1209 L/kg wet-wt.

For DIPA (2,6 -diisopropylaniline) as the relevant hydrolytical degradation product of carbodiimide BCF was also determined also by BCFBAFWIN v3.01 (Chemservice S.A., 2016). Using the regression-based estimate (traditional method) a BCF of 58.23 L/kg wet-wt was calculated. Using the Arnot-Gobas method, the BCF results in a value of 69.94 L/kg wet-wt. It can be concluded that relevant bioaccumulation of carbodiimide and of the hydrolysis product DIPA is not to be expected.Regarding environmental fate, DIPA should be assessed, since Carbodiimide is hydrolytically unstable.

An investigation of the terrestrial bioaccumulation potential is no mandatory endpoint in accordance with REACH Regulation (EC) 1907/2006 for a registration of a substance in a tonnage band of 100 - 1000 tons/year.

Transport and distribution

The adsorption coefficient (Koc) of bis(2,6-diisopropylphenyl)carbodiimide was determined using the HPLC screening method in accordance with OECD Guideline 121 (Garcia-Sanchez, 2011). As result a logKoc greater than 5 is reported, the extrapolated value is 6.4 at 40 °C and 25 °C.

Additionally, the Koc was predicted by the computer program KOCWIN v2.00, resulting in a value of 17,320,000 L/kg using the MCI method (Chemservice S.A., 2011). The traditional method gives a value of 36,960,000 L/kg.

Henry´s law states that the solubility of a gas in a liquid solution at a constant temperature will be proportional to the partial pressure of the gas which is above the solution (Henry, 1803). This information is not mandatory for a registration under REACH Regulation (EC) 1907/2006 in a tonnage band of 100 - 1000 tons/year. However, the Henry´s Law Constant can be predicted with the help of HENRYWIN v3.20 (Chemservice S.A., 2011). A constant of 2.93 E+001 Pa*m³/mol was estimated at 25 °C for the substance bis(2,6-diisopropylphenyl)carbodiimide.

Monitoring data

In accordance to REACH Regulation (EC) 1907/2006 this information is not mandatory for a registration of a chemical at a tonnage band of 100 - 1000 tons/year.