4,4'-methylenedicyclohexyl diisocyanate

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: "in house" method "Determination of the NCO-content by capillary GC-chromatography".

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on test conditions:

- approx. 1 g of the test substance were dissolved in acetonitrile and filled up 100 ml
- 10 ml of the stock solution and 30 ml acetonitrile were filled up with water to 100 ml
- every 20 min the solution was injected into the GC-system

Preliminary study:

Due to the rapid hydrolysis and the complex reaction of a Di-isocyanat in water, a special method developed by the laboratory has been used.

Transformation products:

not measured

Temp.:

23 °C

DT50:

1.97 h

Type:

(pseudo-)first order (= half-life)

Details on results:

The rate constant kobs was 9.78E-05 1/s.

Executive summary:

The half-life of 4,4-methylenedicyclohexyl diisocyanate in the the acetonitrile/water solution is approx. 1.97 hour at room temperature (23 °C). The concentration of the test substance in the acetonitrile solution without addition of water was stable over the measurement time (Bayer AG, 1999).

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

EC Guidelines Part C – Methods for the Determination of the ecotoxical properties C.7.(1992), “Hydrolysis as a function of pH”, Publication no. L 383 A, November 1992.

Deviations:

yes

Remarks:

Due to the low solubility the concentration of acetonitrile in the test was higher than proposed in the guideline.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Buffers:

Water was not buffered for the preliminary test.

Details on test conditions:

- Preliminary test only performed in demineralized water
- 2.64 g of the test substance were dissolved in 10 ml acetonitrile. 1 ml of this solution was diluted to 100 ml with demineralized water. The final solution was thus 0.01 mol/l (2.64 g/l). Incubation was at 50 °C during 5 days under continuous stirring.

Preliminary study:

Preliminary test only performed in demineralized water. The main issue was to determine the hydrolysis products.

Transformation products:

yes

No.:

#1

Details on hydrolysis and appearance of transformation product(s):

methylene bis(4-cyclohexyldiamine) (CAS 1761-71-3)

pH:

11

Temp.:

50 °C

Remarks on result:

other: Degradation in %: 100 after 5 days

Details on results:

Degradation (in %): 100 after 5day(s)

- The aqueous phase contained 3 isomers of dicyclohexylmethane-4,4'-diamine; they were identified by GC and HPLC (CAS 1761-71-3). - Additionally, HPLC showed traces of a trimeric diamine. The monomers were connected by urea-groups. - The insoluble droplets adhered to the glass wall were analysed with IR-Spectroscopy. They contained urea components (polyurea) as well as traces of isocyanate-groups. The polymeric urea compounds encapsulated isocyanate groups which slows down the complete hydrolysis of the isocyanate groups.

Executive summary:

At the end of the preliminary test (hydrolysis for 5 days at 50°C) an aqueous solution and adhered insoluble droplets at the glass wall were received. No 4,4-methylenedicyclohexyl diisocyanate could be detected by HPLC-MS or GC-MS. GC-MS analysis of an organic extract of the aqueous solution (after adjusting the solution to pH11) only shows the dicyclohexylmethan-4,4’-diamine.

Description of key information

4,4’-Methylenedicyclohexyl diisocyanate hydrolyses rapidly. A half-life of approximately 2 hours was determined experimentally (Bayer AG, 1999).

In this GLP study, 1 g/l 4,4’-methylenedicyclohexyl diisocyanate dissolved in an acetonitrile/water-mixture was investigated at 23 °C. The decrease of NCO-content was observed in this solution during the study period. For this purpose the concentration of 4,4’-methylenedicyclohexyl diisocyanate was determined by means of capillary gas chromatography using flame ionisation detection at periodical time intervals.

A preliminary test according to the OECD TG 111 was carried out with 4,4’-methylenedicyclohexyl diisocyanate to determine the resulting products from the reaction with water. A solution of 2.64 g/l was incubated in demineralised, unbuffered water at 50°C during 5 days under continuous stirring (Bayer Industry Services, 2004).

In the aqueous phase the three isomers (cis,cis; cis,trans; trans,trans) of methylene bis(4-cyclohexyldiamine) (CAS 1761-71-3) were identified with GC- and HPLC-MS. Additionally, the HPLC-analysis showed to a minor extent traces of a trimeric diamine compound; this was bound by urea-groups. Insoluble droplets obtained during hydrolysis testing adhered to the glass wall. They were analysed with IR spectroscopy and were found to contain urea components (polymeric urea) and encapsulated traces of isocyanate-groups. As no differences in the reaction products received in the hydrolysis of the test substances at pH 4, 7 and 9 were expected, no test have been performed at these pH values (Bayer Industry Services 2004).

Key value for chemical safety assessment

Half-life for hydrolysis:

2 h

at the temperature of:

23 °C

Additional information

If released to the environment, 4,4’-methylenedicyclohexyl diisocyanate will be rapidly degraded by hydrolysis.