Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 905-806-4
CAS number: -
All measured values im
The values at 20, 40 and 70 °C
were calculated with Antoine equation as follows:
ln(p/bar) =- 20,0233 - 11294,.64
/ (273, 15 + t)
(t] in °C
Executive summary for
all 6 MDI`s
The vapour pressures of six different BASF methylenediphenyl
diisocyanate (MDI) based or MDI-modified substances were investigated in
this summary of 6 reports.
The MDI-based substances were commercially available samples of BASF
products: 4,4’-MDI (CAS 101-68-8 , EC 202-966-0), MDI mixed isomers (MI;
CAS 26447-40-5, EC 905-806-4; mixture of 4,4’-MDI and 2,4’-MDI) and
polymeric MDI (PMDI; CAS 9016-87-9, EC n/a; based on 4,4'-MDI containing
oligomers of high functionality and isomers with an typical average
functionality of 2.7; viscosity at 25 °C of approx. 200 mPa*s).
The MDI-modified substances are commercially available BASF
“Prepolymers”: MDI-DPG (modified 4,4’-MDI with dipropylenglycole; CAS
n/a, EC 701-041-3), MDI-BD/DEG/PD (modified 4,4’-MDI with butadiole,
dietehylenglycole and propanediole; CAS 158885-29-1, former EC
500-415-1, new EC 701-276-1) and MDI homopolymer (polymerized 4,4’-MDI;
CAS 25686-28-6, EC 500-040-3). All investigated substances contain a
significant amount of free 4,4’-MDI (m-MDI).
The following table shows the proportion by weight of monomeric MDI in
the test substances:
For measuring the vapour pressures the effusion method with a Knudsen
cell was used according to the procedure of OECD 104. The method is
based on the estimation of the mass of test substance flowing out per
unit of time of a Knudsen cell in the form of vapour, through a
rnicro-orifice under ultra-vacuum conditions. The mass of effused vapour
was obtained by determining by means of the temporal mass loss of the
test item at a constant temperature generated in a Knudsen cell under
vacuum. The vapour pressure was calculated by applying
the Hertz-Knudsen relation. Measurements were conducted from lower to
higher temperatures to prevent excessive depletion of the most volatile
compounds. For most of the samples, the measurements were conducted in
the temperature range of 30 to 70°C.
The regression parameters of the Antoine equation are given in the
measurement reports. Using this equation, the following vapour pressures
calculated (*values of 20°C are extrapolared values):
These “Prepolymers” should better be described as “Mixtures of MDI
Monomers with small amounts of some larger monomers” having a molecular
weight below 1000 g/mol. The total monomer contents of the investigated
substances start with approx. 40% (w/w) and increase to 100 % (w/w). The
monomer 4,4’-MDI is always the major component in all MDI based
products, except in PMDI, which reveals besides considerable 3 ring
monomers, some higher oligomers, larger than the 4 ring moieties. PMDI
therefore has the lowest vapour pressure of all MDI compounds. For the
“MDI-Prepolymers” it must be stated: The 4,4’-MDI
monomer is always the key molecule with a concentration for all REACH
registered substances around 50% (w/w) and above.
The 2,4’-MDI monomer is in the substances either not present or only at
a much lower concentration. The majority of the constituents, the so
called “higher oligomers”, are just simple diol-MDI adducts, having a
molecular weight below 1000 g/mol and < 1500 g/mol respectively,
depending on the used diol. The MDI mixed isomers contain both, the
4,4’-MDI and the 2,4’- MDI to each 50% (w/w).
The measured vapour pressures are completely in line with the
composition of MDI-modified “Prepolymers”. From the regression
parameters of the Antoine equation given in the substance data
measurement reports, vapour pressures can be calculated for 4,4’-MDI as
well as for MDI mixed isomers. By means of the Raoult law the vapour
pressure of 2,4’-MDI can be estimated
mathematically, since the proportion of 4,4’-MDI and 2,4’-MDI is known
from the composition of the used MDI mixed isomers substance sample. The
partial pressure of the 2,2’-MDI is neglected due to its low proportion.
At a temperature of 40°C a vapour pressure of the respective test
substance without heavy boiling components is calculated by means of the
Raoul law by normalising the content of 2,4’- MDI and 4,4’-MDI in the
test substance to 1 and calculating the respective partial pressures by
means of the pure substance vapour pressure of the corresponding MDI
multiplied by the weight component of the corresponding MDI, since the
substance quantity component is not
accessible. Due to the very low proportion of 2,2’-MDI in the test
substance, this partial pressure fraction is neglected. The vapour
pressures of the test substances calculated in this way represent a
reference pressure which the test substance would have without the
influence of the heavy boilers. The ratio of the vapour pressure
calculated at the same temperature from the regression parameters of the
Antoine equation of the measurements to this reference
pressure shows the influence of the respective heavy boilers on the
reduction of the vapour pressure. Only for MDI mixed isomers was the
vapour pressure of the 4.4-MDI calculated from the regression parameters
of the Antoine equation of the measurement chosen as the reference
pressure in order to demonstrate the influence of the 2,4’-MDI.
For all test substances other than 4,4’-MDI and 2,4’-MDI, the
ratio of measured vapour pressure to reference pressure is less than
one. In particular, PMDI and MDI homopolymers show an almost linear
relationship between the ratio of measured vapour pressure to reference
pressure and the proportion of free monomeric MDI in the test substance.
All MDI substances have extremely low vapour pressures at room temperature (<0.01 Pa). Only special laboratories with highest precision could apply the mass-loss Knudsen effusion method for MDI substances at elevated temperatures from 30 to 90°C in order to extrapolate to room temperature. Due to this fact, measurements are difficult to perform and only the most reliable will be taken into account for assessment.
Substances of the ‘Monomeric MDI’ subgroup (4,4’-MDI, 2,4’-MDI, 2,2’-MDI and MDI Mixed Isomers) have the highest vapour pressure, ranging from 0.7 to 8.05 mPa at 20°C. All modified MDI substances of the subgroups ‘Oligomeric MDI’, ‘MDI reaction products with glycols’ and ‘MDI condensation products’ have lower values compared to the basic monomers they are made from.
The overall content of monomeric MDI isomers in all substances and the ratio of 2,4’-MDI and 4,4’-MDI are the main driver of air exposure (shown elsewhere) within the MDI category. The higher molecular weight constituents, i.e. MDI oligomers, condensation adducts, or glycol adducts, all have much higher molecular weight and therefore much lower vapour pressure. These higher molecular weight constituents do not contribute to the overall vapour pressure of the MDI substances. Theoretical vapour pressure calculations support this hypothesis (see Chapter 126.96.36.199 of the Category Justification Document and supporting studies of Sadler 2019 cited there).
In a substance specific study according to the study design of OECD Guideline 104 (Vapour pressure curve) in 2016 using the effusion method in a Knudsen cell the following estimated vapour pressure at 20 °C was extrapolated from the regression equation:
Vapour pressure at 20°C: 0.00092 Pa
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
Esta web utiliza cookies para mejorar su experiencia de navegación en nuestros sitios web.
Welcome to the ECHA website. This site is not fully supported in Internet Explorer 7 (and earlier versions). Please upgrade your Internet Explorer to a newer version.
Do not show this message again