3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999-05-14 to 1999-05-21

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Test procedure in accordance with generally accepted scientific standards, documentation not very detailed.

Principles of method if other than guideline:

See Test Conditions: Decrease of test substance concentration monitored over time.

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Samples for GC/FID analysis were taken every 11 minutes

Buffers:

none

Details on test conditions:

PREPARATION OF TEST SOLUTION:   
- 1 g test substance was dissolved in acetonitrile; total volume 100 ml; concentration: 10 g/l; 10 ml of this solution was taken, 30 ml acetonitrile was
added and filled up with water to 100 ml; Concentration: 1 g/l

- Test temperature: 23 °C

Duration:

121 min

Temp.:

23

Initial conc. measured:

1 g/L

Number of replicates:

1

Positive controls:

no

Negative controls:

no

Preliminary study:

Initial test: Minimum concentration of acetonitrile to obtain a clear solution = 30 %.

Test performance:

Stock solution in acetonitrile: Stable over the time of the experiment.

Transformation products:

not measured

Temp.:

23 °C

Hydrolysis rate constant:

0 s-1

DT50:

ca. 50 min

Type:

not specified

Other kinetic parameters:

- Rate constant k = [ln (Co/Ct)] / (t-to) = 2.30319E-4 1/s
Half-life = ln(2)/k = 3009 s = 50.15 min
r = -0.95722

- Time-concentration data of test solution:
  Concentration Ct at time t as percent of initial concentration Co:
     0 seconds: 100.0 %
   664 seconds:  88.8 %
  1317 seconds:  77.0 %
  1980 seconds:  70.4 %
  2634 seconds:  69.4 %
  3298 seconds:  67.7 %
  3959 seconds:  55.4 %
  4615 seconds:  45.4 %
  5275 seconds:  41.6 %
  5933 seconds:  29.5 %
  6594 seconds:  22.4 %
  7252 seconds:  15.9 %

Validity criteria fulfilled:

not specified

Conclusions:

The half-life of the test substance was determined as 0.84 hours (approx. 50 min)

Executive summary:

A preliminary hydrolysis test was conducted in order to determine the dissipation half-life of isophorone diisocyanate. The test medium was 30 % acetonitrile / 70 % water (no buffer) at 23 °C. Samples of the test solution were taken every 11 minutes and analysed by GC/FID. Approx. 84 % of the test substance were found to dissipate within a period of 121 minutes. The dissipation half-life was determined as 0.84 hours (approx. 50 minutes). Degradation products have not been analysed.

 

The study was assessed as "reliable with restrictions".

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2000-01-25 to 2000-01-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study meets generally accepted scientific principles, acceptable for assessment; Restriction: Presence of solubilizer (1 % v/v) slightly increases water solubility.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

Simplified screening test only; full test not possible

Principles of method if other than guideline:

Method: simplified preliminary tests based on OECD Test Guidelines 105 (water solubility) and 111 (hydrolysis as a function of pH) as well as
on corresponding EU methods

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

- no buffer was used

Details on test conditions:

- TEST 1: Approximately 1 g test substance was dissolved in 10 ml  acetonitrile (CAS RN 75-05-8) and stirred into 1000 ml of purified water. Stirring 
was discontinued. After 1 hour, a sample was taken from the centre of the solution and analyzed.

- TEST 2: Approximately 100 mg test substance was dissolved in 10 ml  acetonitrile and stirred into 1000 ml of purified water. Stirring was  continued for 24 hours except for sampling after 1 hour and 24 hours.  After settling of droplets, samples were taken from the centre of the solution.

Duration:

24 h

Temp.:

23 °C

Initial conc. measured:

100 mg/L

Number of replicates:

1

Positive controls:

no

Negative controls:

no

Preliminary study:

- TEST 1: Droplet formation was observed. The droplets settled on the bottom of the test vessel and became increasingly coated with a white layer. 14 mg test substance/l water were determined in the analysis after  1 hour.

- TEST 2: Droplet formation was observed. 16 mg test substance/l water were determined in the analysis after 1 hour. < 10 mg/l were determined after 24 hours. After this time instead of droplets fine distributed and white solids were observed.

- Half-life: The half-life of < 7.2 hours is based on a decrease from 100 mg/l to < 10 mg/l within 24 hours in TEST 2. (It should be noted that 100 mg is above the water solubility. Therefore only part of the test substance was dissolved initially but further test substance was dissolved as dissolved molecules were removed from the aqueous phase by hydrolysis.)

Transformation products:

not measured

Temp.:

23 °C

DT50:

< 7.2 h

Validity criteria fulfilled:

not applicable

Conclusions:

OECD Test Guideline 111 (hydrolysis as a function of pH) is not applicable because the water solubility is too low for analytical monitoring of the test substance concentration, even when a solubilizer is used.
OECD Test Guideline 105 (water solubility) is not applicable because the test substance is not sufficiently stable to obtain equilibrium.
The hydrolysis half-life is below 7.2 hours at 23 °C.

Executive summary:

The dissipation of isophorone diisocyanate was investigated in a preliminary study similar to OECD TG 111 Tier 1. The observations allow concluding that the half-life at 23 °C is below 7.2 hours.

Description of key information

A preliminary hydrolysis test was conducted by Bayer AG (1999) in order to determine the dissipation half-life of isophorone diisocyanate. The test medium was 30 % acetonitrile / 70 % water (no buffer) at 23 °C. Samples of the test solution were taken every 11 minutes and analysed by GC/FID. Approx. 84 % of the test substance were found to dissipate within a period of 121 minutes. The dissipation half-life was determined as 0.84 hours (approx. 50 minutes). Degradation products have not been analysed.
The observed half-life is in agreement with the results of Infracor GmbH (2000) who performed a preliminary study in unbuffered aqueous solution. The results show that the half-life at 23 °C is below 7.2 hours.

Key value for chemical safety assessment

Half-life for hydrolysis:

0.84 h

at the temperature of:

23 °C

Additional information

According to experience with the substance itself as well as with similar diisocyanates, the amines formed in the initial hydrolysis step, which is associated with elimination of carbon dioxide, have a high reactivity towards unreacted isocyanate. The consequence is that in the hydrolysis of isophorone diisocyanate predominantly polyurea molecules are formed. They are insoluble in water. Their formation was observed in the study of Infracor GmbH (2000) who reported that droplets settled on the bottom of the test vessel and became increasingly coated with a white layer.

Beside these insoluble main hydrolysis products minor amounts of other hydrolysis products having a low to moderate molecular weight and being more or less water soluble (e.g. isophorone diamine). They were determined by unspecific TOC analysis in aqueous phases of ecotoxicity studies where their potential for adverse environmental effects was investigated (see section 6.1).