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EC number: 924-669-1
CAS number: -
on physico-chemical properties, oral and dermal absorption is expected
to be low for the parent compound. Since hydrolysis of the parent
compound occurs very rapidly oral and dermal absorption is expected for
these hydrolysis products. These assumptions are supported by the
results of repeated dose toxicity studies in vivo where clinical signs
have been observed. Absorption via the inhalation route is, due to
physico-chemical properties of the test item, not expected. Reaction
product of Hexamethylene diisocyanate, oligomers with
Mercaptopropyl-trimethoxysilane hydrolyzes rapidly and therefore, no
bioaccumulation of the parent substance is expected after continuous
exposure. The test substance and/or its metabolites are expected to be
excreted mostly via faeces and only partially via urine.
is a property of a substance to diffuse across biological membranes.Generally,
oral absorption is favored for molecular weights below 500 g/mol andlog
Pow values between -1 and 4.Absorption
of highly lipophilic substances with log Pow > 4 may be limited by the
inability of the substance to dissolve in the fluids of the
gastrointestinal tract and hence make contact with the mucosa. However,
highly lipophilic substances, particularly those that are poorly soluble
in water (1 mg/L or less) may form micelles and be absorbed into the
lymphatic system to some extent. Therefore, from
the physicochemical properties of Reaction product of Hexamethylene
diisocyanate, oligomers with Mercaptopropyl-trimethoxysilaneis
can be assumed that the oral bioavailability of the parent substance
will be low.
However, the parent substance undergoes rapid hydrolysis which might
indicate that the parent compound may only be present in the GI-tract
for a limited period of time and the resulting hydrolysis products,
which are more hydrophilic than the parent compound, dissolve rapidly in
the GI-fluids. The predicted hydrolysis products of the target substance
are presented in Table 1, showing higher water solubility and log Pow
values between 4.16 and 0.97.The
repeated dose toxicity study where clinical signs have been observed and
changes in pancreas at 1000 mg/kg bw/day in male and female rats and at
300 mg/kg bw/day in female rats indicate that oral absorption of the
hydrolysis products must have been occurred.
via the respiratory route also depends on physico-chemical properties
like vapor pressure, log Pow and water solubility. In general, highly
volatile substances are those with a vapor pressure greater than 25 kPa
or boiling point below 50°C. Substances with log Pow values between -1
and 4 are favored for absorption directly across the respiratory tract
epithelium by passive diffusion. Due to its low vapor pressure of
3.93E-4 Pa at 20°C and 5.9E-4 Pa at 25°C Reaction product of
Hexamethylene diisocyanate, oligomers with
Mercaptopropyl-trimethoxysilane is unlikely to be available as a vapor
to a large extent and exposure and uptake via inhalation is considered
As the substance is a liquid no generation of dust is possible.
general, dermal absorption is favored by small molecular weights and
high water solubility of the substance. Log Pow values between 1 and 4
favor dermal absorption, particularly if water solubility is high.
Therefore, for Reaction product of Hexamethylene diisocyanate, oligomers
with Mercaptopropyl-trimethoxysilane low dermal absorption is predicted
because of its low water solubility, a molecular weight above 500 g/mol
and an estimated log Pow value of 7.11.
In cases were the molecular weight is above 500 and log Pow outside the
range of -1 to 4 are observed a maximum worst case value of 10% skin
absorption can be assumed for risk assessment purposes.
assumption is supported by the results of an acute dermal toxicity study
where neither systemic toxicity norbehavioral
changes were noted in male and female rats up to the highest applied
dose of 2000 mg/kg bw. The test item caused dermal irritation symptoms
as well defined and slight erythema,dry
skin and desquamation. As the substance is identified as skin
sensitizer, some dermal uptake of the applied substance must have been
general, the smaller the molecule the broader is its distribution. Small
water-soluble molecules will diffuse through aqueous channels and pores
in the membranes. If
the molecule is lipophilic (log Pow >0), it is likely that the substance
distributes into cells and the intracellular concentration may be higher
than its extracellular concentration particular in fatty tissues.
Reaction product of Hexamethylene diisocyanate, oligomers with
Mercaptopropyl-trimethoxysilane a slow distribution into the body water
is expected. However, as the substance shows rapid hydrolysis to more
hydrophilic compounds it is expected that the hydrolysis products are
distributed through-out the body water to reach various tissues. As
target tissue the pancreas (enlargement, pale color; increased amount of
zymogen granules and flattened and basophilic acinar cells) was reported
in a 14-day repeated dose toxicity study after oral application. Daily
exposure to a substance with a log Pow of around 4 or higher could
result in a built up of the substance in the body. As the substance
hydrolyzes rapidly, no bioaccumulation of the parent compound in fatty
tissue is expected after repeated exposure. For the hydrolysis products
a low potential of bioaccumulation is expected since they are more
hydrophilic and only one hydrolysis product has a predicted log Pow slightly
aqueous hydrolysis half-life of Reaction product of Hexamethylene
diisocyanate, oligomers with Mercaptopropyl-trimethoxysilane was
calculated using HYDROWIN v 2.00 as part of EPISuite v4.11 from US
Environmental Protection Agency. The hydrolysis half-life of the test
item was calculated to be <10 min even at low pH indicating fast
formation of hydrolysis products.
further compound of the target substance is trimethoxysilane, which is
reported to hydrolyze very rapidly to produce methanol and silanetriol.
Depending on the pH and concentration of the substance, the silanetriols
may condense to form oligomers and polymers . Methanol is metabolized
mainly via alcohol dehydogenases and further via aldehyde hydrogenases
to form CO2and H2O.
general, from the in vitro genotoxicity tests no remarkable differences
in regard to genotoxicity and cytotoxicity in the presence or absence of
metabolic S9 Mix could be detected, which might indicate that no
metabolic activation of the substance occurs in vitro and probably also
general, urinary excretion is favored by low molecular weight (below 300
g/mol in the rat) good water solubility, and ionization of the molecule.
Substances with a molecular weight above 300 are likely to be excreted
via bile and may undergo hepatic circulation. Molecules having strong
polarity and high molecular weight are less likely to re-circulate.
the parent compound Reaction product of Hexamethylene diisocyanate,
oligomers with Mercaptopropyl-trimethoxysilane and its metabolites are
expected to be excreted mostly via the bile into faeces. A low potential
for enterohepatic circulation is expected due to the high lipophilicity
of the parent substance and high molecular weight of the hydrolysis
products. Highly lipophilic substances like the target substance with a
log Pow between 4 and 6 that come into contact with the skin will
penetrate the lipid rich stratum corneum and persist in this layer until
its sloughed off.
ECHA (2017), Guidance on information requirements and chemical safety
assessment, Chapter R.7c: Endpoint specific guidance, Version 3.0, June
OECD SIDS Initial Assessment profile, CAS No. 2487-90-3,
Trimethoxysilane, SIAM 24, 19-24 April 2007
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.
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