Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to the stabilisation of
l,l,l-trichloroethane.
It is well known that l,l,l-trichloroethane is unstable
when it is brought into contact wlth metals such as aluminium and
its alloys and magnesium and its alloys. The instability of 1,1,1-
trichloroethane is revealed by decomposition with accompanying for-
mation of hydrochloric acid and other decomposition products, and
colouring of the l,l,l-trichloroethane. This is a serious dis-
advantage from the point of view of its use as a solvent for de-
greasing and/or cleaning metal members or parts.
A very large number of compounds have been put forward
as agents for inhibiting decomposition, or for stabilising 1,1,1-
trichloroethane. Thus, United States Patent No. 2,371,644
proposes primary, secondary tertiary monohydroxyl aliphatic alcohols.
The tertiary alcohols such as tertiary amyl alcohol are described
as being less efficient than primary and secondary alcohols, while
United States Patent No. 3,000,978 refers to tertiary butyl alcohol
as being moreefficient than tertiary amyl alcohol and also more
efficient than secondary butyl alcohol, isopropanol, n-propanol or
~ ethanol.
Moreover, United States Patent No. 2,371,645 describes
cyclic ethers such as propylene oxide and isobutylene oxide and
Canadian Patent No. 627,411 proposes incorporating nitromethane in
l,l,l-trichloroethane.
However, these constituents, taken separately, provide
only a very unsatisfactory degree of stability, in particular for
prolonged uses of l,l,l-trichloroethane in degreasing and/or
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cleaning metal or other articles.
In order to improve the degree of stability of the
chlorinated solvent, British Patent No. 912,118 discloses the
addition to l,l,l-trichloroethane, of a nitroalkane and an epoxide
simultaneously, or a nitroalkane and a monohydroxylic aliphatic
alcohol containing up to 5 carbon atoms. However, as the 1,1,1-
trichloroethane is itself made particularly sensitive to decompo-
sition at the temperature at which it is used as a degreasing and/
or cleaning agent, because of the presence of greases, metal
surfaces and metal impurities in suspension in the cleaning bath,
such combinations of stabilizing agents are unable to provide 1,1,1-
trichloroethane with an effective degree of stability.
Even the ternary combination of nitromethane, tertiary
butyl alcohol and l,2-butylene oxide mentioned in United States
Patent No. 3,281,480 cannot prevent the formation of an amber-
coloured precipitate in the solvent, after contact with aluminium
for 24 hours. The same also applies in regard to monohydroxyl
aliphatic acetylenic al~ohols containing less than 8 carbon atoms,
more particularly 2-methylbut-3-yn-2-ol, which are associated with
1,4-dioxan, in accordance with United States Patent No. 2,838,458.
According to the invention, stabilization of 1,1,1-
trichloroethane is achieved by incorporating therein:
~ a) from 0.1 to 5% and preferably from 0.5 to 3.5% by
weight of tertiary butyl alcohol;
(b) from 0.1 to 5% and preferably from 0u3 to 3% by
weight of at least oneof 2-methylbut-3-yn-2-ol and ~trioxan;
(c~ from 0.1 to 5% by weight of at least one C3 8
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epoxide or chlorinated epoxide;
(d) from 0.1 to 3% by weight of at least one C1 3
nitroalkane; and
(e) from 0.001 to 1% and preferably from 0.005 to
0.1% by weight of at least one aliphatic, cyclic or heterocyclic
C4_10 amine of a basic nature.
The amines used according to the invention include C4 10
aliphatic amines, preferably secondary or tertiary, with a straight
or branched carbon-bearing chain; C6 aromatic amines substituted
by halogen atoms or Cl to C3 alkyl groups; and heterocyclic amines
having 1 to 2 nitrogen atoms in the molecule, e.g. diethylamine,
triethlamine, diisopropylamine, di-sec-butylamine, amylamines,
hexylamines, pyridines, picolines, morpholine, N-(Cl 3 alkyl)
morpholines, pyrrolidine, and N-(Cl 3alkyl)pyrrolidines.
Particularly advantageous amine for use in accordance
with the invention are N-methyl-morpholine, diisopropylamine and
pyrrolidine.
In the following description , in order not to encumber
the text,the percentages given are expressed by weight unless
indicated to the contrary.
When the mixture of tertiary butyl alcohol and 2-methyl-
but-3-yn-2-ol is associ.ated with l,l,l-trichloroethane, this
binary mixture comprises from 1 to 99% of tertiary butyl alcohol
and from 99 to 1% of 2-methylbut-3-yn-2-ol and preferably from
25 to 80% of tertiary butyl alcohol for from 75 to 20% of 2-
methylbut-3-yn-ol.
In accordance with an advantageous embodiment of the
invention, trioxan is incorporated in the l,].,l-trich.loroethane,
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in proportions of from 0.5 to 3%, without 2-methylbut-3-yn~2-ol.
Representative compounds of the C3 to C8 epoxide
and chlorinated epoxide include in particular l,2-butylene
oxide, which is preferred, epichlorohydrin, gylcidol and its
primary, secondary and tertiary methyl, ethyl, propyl, iso-
propyl, allyl and butyl ethers, l,2-propylene oxide, styrene oxide
and cyclohexene oxide. The preferred proportion of epoxide is
from 0.2 to 3~ with respect to the l,l,l-trichloroethane.
The nitroalkanes are represented by nitromethane, nitro-
ethane and the two isomers of nitropropane. The preferred pro-
portion is from 1 to 2% with respect to the l,l,l-trichloroethane.
It has in fact been found that the association of the
above-mentioned compounds can be particularly advantageous
because, in a comparable concentration, it has a stabilizing action
substantially better than that achieved by the addition of each
of the constituents taken in isolation.
The association of the above-indicated compounds may
further be reinforced by the addition, as an anti-oxident, of at
least one phenol and/or nitrogenous heterocycle having from 3 to
S carbon atoms and from 1 to 2 nitrogen atoms with optionally an
oxygen atom in the ring, in amounts of up to 1% and preferably
from O.OQl to G.1% with respect to the l,l,l-trichloroethane.
Amoung examples of suitable phenols are monohydric phenols
such as phenol, cresols, ethylphenols, butylphenols, in particular
_-ter-butylphenol, thymol, naphthols, methylnaphthols and eugenol;
Cl or C2 alkyl ethers of monophenols such as anisol, guaiacol and
2-ethoxy phenol; diphenols such as resorcinol, pyrocatechol,
naphthoquinone and in particular hydroquinone; Cl and C2 alkyl
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ethers of said diphenols such as the monomethyl ether of hydro-
quinone; and triphenols such as pyrogallol, phloroglucinol,
hydroxyhydroquinone; and triphenols such as pyrogallol, phloro-
glucinol, hydroxyhydroquinone and trihydroxytoluenes.
Examples of heterocycles with one nitrogen atom include
pyrrole, N(Cl 4alkyl)pyrroles, preferably N-methylpyrrole, indole,
l-methylindole, 2-butylindole, 2-phenylindole, 2-toluylindole, 1-
benzylindole and their respective isomers; oxazole and isoxazole
are representative of heterocycles with one nitrogen atom and an
oxygen atom.
Examples of nitrogen heterocycles with 2 nitrogen atoms
include imidazole, pyrazole, pyrazoline, pyrazolidine, imidazoline,
imidazolidine, piperazine and their N-(Cl 4alkyl)ated derivatives,
pyrazine, pyrimidine and pyridazine.
The invention also provides a composition which comprises
l,l,l-trichloroethane containing:
(a) from 0.1 to 5% and preferably from 0.5 to 3.5% by
weight of tertiary butyl alcohol;
(b) from 0.1 to 5% and preferably from 0.3 to 3% by
weight of at least one of 2-methylbut-3-yn-2-ol and trioxan;
(cl from 0.1 to 5% by weight of at least C3 8 epoxide
or chlorinated epoxide;
td) from 0.1 to 3% by weight of at least one Cl 3
nitroalkane;
(e) from 0.001% to 1% and preferably from 0.005% to 0.1%
by weight of at least one aliphatic, cyclic or heterocyclic C4 10
amine of a basic nature; and
(f) as anti-oxidant, from 0 to 1% and preferably less
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than 0.2% of at least one phenol and/or nitrogen heterocycle having
from 3 to 5 carbon atoms, 1 or 2 nitrogen atoms and possibly an
oxygen atom in the ring, as defined above; the said proportions
being expressed with respect to the l,1,1-trichloroethane in the
composition.
The preferred compositions of the invention essentially
comprise l,l,l-trichloroethane containing:
(a) from 1 to 3% of tertiary butyl alcohol;
(b) from 0.5 to 2.5% of 2-methylbut-3-yn-2-ol and up
to 2.5% of trioxan;
(c) from 0.2 to 3% of 1,2-butylene oxide;
(d~ from 0.5 to 1.5% of nitromethane and/or nitroethane;
and
(e~ from 0.005 to 0.1% of N-methyl-morpholine and/or
diisopropylamine.
The following Examples are given to illustrate but not
limit the invention and to set forth its specific advantages.
EXAMPLE 1
The following compounds were incorporated in 1,1,1-
trichloroethane: %
tertiary butyl alcohol 2.0
2-methylbut-3-yn-2-ol 1.5
1,2-butylene oxide 0.45
nitromethane 1.3
N-methylmorpholine 0.008
The resultïng composition was tested by successive
distillation. This comprises distilling it four times in succes-
sion and in each distillation step collecting only the first 90%
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by volume that passes. The test in respect o scratching of
aluminium plates in accoxdance with standard ASTM D 2943-7]T was
carried out on each of the four distillates.
The scratching test is to determine the aptitude of the
association of stablizing agents in l,l,l-trichloroethane, to
prevent degradation of the chlorinated solvent in the presence of
aluminium or aluminium alloys. It comprises taking a piece of
metal that has been cleaned and degreased, of quality AA 1100
(Standard ASTM corresponding to AFNOR A 45 symbol aluminium),
immersing it in 50 cc of stabilized l,l,l-trichloroethane at
ambient temperature, and scratching it by means of a mild steel
rod. After a period of time (1 hour) sufficient to allow any
reaction to occur, the presence or absence of bubbles, colouring
of the solvent or the presence of dark-coloured resinous products
is noted. The l,l,l-trichloroethane is suitably stabilized if no
reaction is observed.
The above composition passes this test, without any
trace of reaction on the aluminium plates being observed.
A very severe long-term stabilization test was also
carried out, viz. the test of the BAM (German Federal Institute
for Testing of Materials). This test comprises carrying out three
operations on a mixture of 100 cc of sta~ilized l,l,l-trichloro-
ethane and 100 cc of toluene:
operation 1: addition of 18 g of aluminium in the form
of thin sheets or plates, and 0.7 g of
aluminium chloride
operation 2: as operation 1, also adding 1 g of zinc
stearate
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operation 3: as operation 1, also adding 10 ml of oleic
acid.
For each operation, the mixtures were refluxed, the bath
temperature being 114C, for a period of 18 hours.
The stabilized l,l,l-trichloroethane was then distilled
into three equal porions, in accordance with standard DIN 51 751,
and then operation 1 was carried out on 100 cc of each of the
distilled portions, mixed with 100 cc of toluene~
The solvent was admitted as satisfying the test if there
was no violent exothermic reaction recorded in the course of each
of the six operations considered separately.
The composition set out hereinbefore passed the test,
without any violent exothermic reaction being observed.
EXAMPLE 2
l,l,l-trichloroethane containing:
tertiary butyl alcohol 2.0
2-methylbut-3-yn-2-ol 1.85
1,2-butylene oxide 0.45
nitroethane 1.3
pyrrolidine 0.01
successfully passed the successive distillation tests and the BAM
tests described in Example 1.
EXAMPLE 3
l,l,1-trichloroethane to ~hich the following were added:
tertiary butyl alcohol 1.7
2-methylbut-3-yn-2-ol 2.0
1,2-butylene oxide 0~45
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nitroethane 0.6
nitromethane 0.5
N-methylmorpholine 0.005
also successfully passed the successive distillation and B~ tests
described in Example 1.
XAMPLE 4
l,l,l-Trichloroethane to which the following were added:
%
1 tertiary butyl alcohol 2.0
2-methylbut-3-yn-2-ol 1.5
1,2-butylene oxide 0.45
nitromethane 1.3
N-methylpyrrole 0.008
N-methyl-morpholine 0.01
also successfully passed the successive distillation and BAM tests
described in Example 1.
EXAMPLE 5
In order to demonstrate the attraction of adding an as-
sociated amine to the other stabilizing agents of the invention,
the following test was carried out:
98 ml of stabilized l,l,l-trichloroetnane, mixed with 2
ml of a mixture of white spirit and water (in a proportion of 90%
by volume of wh;te spirit for 10% by volume of ~ater) was boiled
under reflux for 72 hours. The pH of the solvent was measured
before and after the test.
With stabilizing l,l,l-trichloroethane in accordance with
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the formula set out in Example 4, but without N-methyl-morpholine,
the pH changed from 6.7 before the test to 4.5 after 72 hours of
refl.ux (for this pH, it is known that the solvent is particularly
corrosive for degreasing machines).
With l,l,l-trichloroethane stabilized in accordance with
the formula set out in Example 4 (containing 0.01~ of N-methyl-
morpholine), the pH remained at 8.3 after 72 hours of reflux
(at this pH there is virtually no corrosion of degreasing machines).
EXAMPLE 6
l,l,l-trichloroethane containing the following substances:
tertiary butyl alcohol 2.4
2-methylbut-3-yn-2-ol 2.1
methylglycidic ether 0.5
nitromethane 1.3
diisopropylamine 0.005
successfully passed the successive distillation and BAM test
described in Example 1.
EXAMPLE 7
The following composition also successfully passed the
successive distillation and BAM tests described in Examplel:
%
l,l,l-trichloroethane 94.~95
tertiary butyl alcohol 2.5
trioxan 1.4
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1,2-butylene oxide 0.4
nitromethane 0.7
N-methyl-morpholine 0.005
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