3,3'-dimethylbiphenyl-4,4'-diyl diisocyanate

Endpoint summary

Description of key information

Appearance/physical state/colour

TODI is a solid white-yellowish and odourless substance in pelleted form.

Melting point/freezing point

The melting point of TODI (purity 99.9 %) was determined to be 71.7 °C at 101.29 hPa using a linear heating rate of 1 °C/min.

Boiling point

The test material (TODI) was determined to decompose at approximately 644 K (371°C) at 101.42 kPa before boiling. Thus, no value for boiling temperature could be determined.

Density

Following EU-method A.3, the relative density (D20/4) of TODI was determined to be 1.331 g/cm3 at 20 °C (95 % confidence interval).

Particle size distribution (Granulometry)

After determination of the tap density (0.75 g/mL), the particle size distribution of TODI was found to be [1000 µm; 2000 µm] applying machine sieving, specified by the range [x1, x2] of two sieves where Rx1 >= 90% and Rx2 <= 10%. Seven sieves of sizes (µm) 63, 125, 250, 500, 1000, 2000 and 4000 were used. No particles with a diameter below 63 µm were found (and with 125 µm only 0.2%).

Vapour pressure

The vapour pressure of TODI was calculated by means of the program MPBPVPWIN, which is part of the program compilation EPI Suite. The chemical structure was entered into MPBPVPWIN by SMILES (Simplified Molecular Input Line Entry System) notations. The vapour pressure of TODI at 25 °C was estimated to be 2.21E-05 mm Hg corresponding to 0.00295 Pa using the Modified Grain method.

As experminental measurements of substances with appreciable very low vapour pressure and instability in presence of humidity provide technical difficulties, an experimental study on the vapour pressure of TODI was not performed.

The vapour pressure TODI's hydrolysis degradation product 3,3'-Dimethylbenzidine (TODA) was reported to be 6.92E-07 mmHg at 25 °C corresponding to 9.225E-07 mbar at 25 °C. Furthermore, the vapour pressure of 3,3'-Dimethylbenzidine (TODA) was estimated by calculation to be 2.14E-5 Torr at 25 °C corresponding to 2.85E-05 mbar at 25 °C.

Partition coefficient

The log Pow of TODI at 25 °C was estimated to be 6.05 using KOWWIN of EPI Suite compilation.

By applying published data of a supporting substance the log Pow of TODI can be estimated to be in a range similar to the supporting substance, because of the analogy of their molecular structures. The log Pow of the supporting substance (Methylenediphenyl diisocyanate, CAS 26447-40-5, EINECS 247-714-0) was found to be 4.5 measured by HPLC, which is in quite good accordance with the calculated value. An experimental determination of the partition coefficient of TODI is technically not feasible, because of the very fast hydrolysis of the substance (see: IUCLID Section 5.1.2: Hydrolysis as a function of pH).

The log Pow of TODA (substance name: 4,4'-bi-o-toluidine; alternative name: 3,3'-Dimethyl-4,4'-diamino-biphenyl, CAS no. 119 -93 -7, EC no. 204 -358 -0, the product of hydrolysis of TODI) at 25 °C was estimated to be 3.02 (KOWWIN v1.67 estimate) or 2.34 (Exper. database match) using KOWWIN of EPI Suite.

Water solubility

In accordance with column 2 of REACH Annex VII, the test on water solubility (required in REACh Regulation, ANNEX VII; Section 7.7) does not need to be conducted if the substance is hydrolytically unstable at pH 4,7 and 9 (half-life less than 12 hours). According to the study on determination of the hydrolysis of TODI as a function of pH (see: IUCLID Section 5.1.2), the half-life of TODI was determined to be far below 12 hours (max.: 1.2 h at pH 7) and therefore found to be hydrolytically unstable.

Additionally, the water solubility of TODI's hydrolysis degradation product 3,3'-Dimethylbenzidine (TODA) was reported to be 1.3 g/L at 25 °C.

Surface tension

In accordance with column 2 of REACH Annex VII, the test on surface tension (required in REACh Regulation, Annex VII, section 7.6) does not need to be conducted if the water solubility is lower than 1 mg/L at 20°C (see IUCLID Section 4.8: water solubility).

According to the study on hydrolysis as a function of pH (IUCLID Section 5.1.2) TODI was found to be hydrolytically unstable.

The degradtion products are

- found to be insoluble in organic and aqueous solvents. (See IUCLID sections 6.1.1, short-term toxicity to fish and 6.1.3, short-term toxicity to aquatic invertebrate) and

- assumed to form inert, insoluble polyureas in water (see IUCLID Section 5.2.3: biodegradation in soil).

Thus, determination of surface tension for TODI is scientifically not feasible.

Flash point

TODI is a solid (pelleted form). Thus, the determination of the flash-point according to EU Method A.9 is not applicable as this method is only applicable to liquid substances whose vapour can be ignited.

Auto Flammability

Using a linear heating rate of 0.5 °C/min, no self-ignition temperature of TODI was observed up to 72 °C (melting point was determined to be 71.5 °C).

Flammability

The test item TODI did not ignite in the preliminary test. Thus, it was not considered highly flammable. No further testing is required. Additionally, based on the hydrolysis study (IUCLID Section 5.1.2) and on experience in handling and use, neither flammability in contact with water nor pyrophoric abilities are expected. These studies are thus been waived.

Explosiveness

In accordance with column 2 of REACH Annex VII, the determination of explosiveness (required in IUCLID Section 7.11) does not need to be conducted as there are no chemical groups associated with explosive properties present in TODI (refer to Guidance on information requirements and chemical safety assessment, Chapter R.7a).

Oxidising properties

A test on oxidising properties (required in section 7.13 of REACH, Annex VII) does not need to be conducted as there are no chemical groups associated with oxidising properties present in TODI (refer to Guidance on information requirements and chemical safety assessment, Chapter R.7a).

Stability in organic solvents and identity of relevant degradation products

In accordance with column 2 of REACH Annex IX, the test on stability in organic solvents and identity of relevant degradation products (required in REACh Regulation, ANNEX IX, section 7.15) does not need to be conducted as the stability of TODI in organic solvents is not considered as a relevant (chemical) property.

Dissociation constant

In accordance with column 2 of REACH Annex IX, the test on dissociation constant (required in REACh Regulation ANNEX IX Section 7.16) does not need to be conducted if the substance is hydrolytically unstable at pH 4, 7 and 9 (half-life less than 12 hours). According to the study on determination of the hydrolysis of TODI as a function of pH (see IUCLID Section 5.1.2) , the half-life of TODI was determined to be far below 12 hours (max.: 1.2 h at pH 7) and therefore found to be hydrolytically unstable.

Furthermore, the pKa of TODI's hydrolysis degradation product [1,1'-Biphenyl]-4,4'-diamine, 3,3'-dimethyl- (TODA) was reported to be 4.59+/- 0.10 at 25 °C.

Viscosity

TODI is solid (pelleted form) at room temperature. A test on viscosity is only applicable for liquid substances. Thus, the test is scientifically unjustified.