Note: Descriptions are shown in the official language in which they were submitted.
~3t~ 7
This invention concerns a stabilized 1J 1
trichloroethane (methyl chloroform) composition.
l,l,l-Trichloroethane has become a promising
solvent for the metal working and textile industries
because of its low toxicity and good ecological properties
and is being widely used by industry to replace both
trichloroethylene and perchloroethylene. However, 1,1,1-
trichloroethane is known to exhibit a high degree of in-
stability in the presence of aluminum, iron, or alloys
thereof, and when inhibitors are present to increase sta-
bility, then often zinc becomes a problem. Various com-
pounds and mixtures of compounds for stabilizing the 901-
~ent, particularly in the pre~ence of aluminum, have been
proposed. While a few of the prior stabilizer~ are used
commercially, none exhibit the degree of stabilizing effect
which is necessary if the solvent is to be used in an un-
restricted manner by industry, especially in vapor de-
greasing. The criteria for establishing a commercial -~
grade of l,l,l-trichloroethane which has unrestricted
utility in industry should include an equal degree of
stability of the liquid and its vaporsJ less than about ten
percent total inhibitors, and a substantial ability to be
distilled without loss of stability by concentration of
the low boiler~ in the overhead and high boilers in the
bottoms of the still, and the like. Even today these
criteria are not all found in the commercial compositions.
This invention provides compositions which are effective
at concentrations of from between about four to about six
percent and which meet the criteria set out above.
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Accordingl~, the present invention provides a l,l,l-trichloro-
ethane composition comprising as essential stabilizers against metal induced
degradation: a) 0.2 to 1.2 weight percent of a C3 8 monoepoxide, mono-
chloro monoepoxide or mixture of epoxides, and b) 3.8 to 4.8 weight
percent of a mixture of one component from each group: 1) l,l-dimethoxy-
ethane or t-butyl alcohol, 2) dioxene, dioxolane or trioxane, and 3) nitro-
methane in the proportions within the shaded areas of Figures 1-5, the
stabili~ers being added in amounts to keep the composition stabilized against
undesirable degradation and partitioning in both the liquid and the vapour
form, with the provision that the l,l-dimethoxyethane-nitromethane-dioxolane
system is employed in a concentration of 4.3 to 4.8 weight percent.
Figures 1-5 represent graphic illustrations of compositions of
the named three-component systems which, when employed in accordance with
the present invention, provide the protection of the solvent, both liquid
and vapor, and metal in contact with the solvent, both liquid and vapor.
The vertical line shaded area in each figure represents the compositions of
the named ingredients which are effective at 3.8 weight percent of a mixture
of the three ingredients in the proportions derivable from the graph. The
45 left_angled lined shaded area and the vertical lined area together
represent the compositions of the named ingredients which are effective at
4.3 percent of a mixture of the three ingredients in the proportions derivable
from the graph which fall within the scope of the present invention. The
45 right-angled lined shaded area plus the left-angled lined shaded area
- plus the vertical lined shaded area represent the compositions of the named
ingredients which are effective at about 4.8 weight percent of a mixture of
the three ingredients in the proportions derivable from the graph. The
compositions
within the shaded areas and which contain the additional
stabilizer noted above, an epoxide, are stable in their
liquid form as well as their vaporous form, can be distilled
with the distillate being stable to attack on and by metals,
can be repeatedly vaporized and condensed, as in vapor de-
greasing, without loss of stability, and can be partially
lost, as in vapor degreasing, with frequent make-up added
without build-up of high boilers in the liquid.
The useful epoxides include propylene oxide, butyl-
ene oxide, isobutylene oxide, the pentylene oxides, the
hexylene oxides, heptylene oxides, the octylene oxides and
their monochloro derivatives, such as epichlorohydrin. The ;
preferred epoxides are propylene oxide, epichlorohydrin,
butylene oxide, isobutylene oxide and mixtures of these
oxides.
It has now been found that with the exception noted
at page 2 line lO above, l,l,l-trichloroethane containing
from 3.8 to about 4.8 percent by weight of one of the compo-
sitions within the shaded areas as shown in Figures 1-5 of
the drawings in combination with about 0.2 to about 1.2
? percent by weight of a C3 8 monoepoxide or chloromonoepoxide
will be stable against deterioration in the presence of - - :
- metals, particularly aluminum, zinc, iron, or alloys thereof
in the liquid state and/or vapor state under the use con-
:. . .
ditions encountered in industry. Thus, compositions of ,
l,l,l-trichloroethane containing one of the compositions ;
illustrated in the figures of the drawings and epoxide will
remain substantially colorless, without deterioration or
attack upon aluminum, whether in the liquid or vapor state,
. 30 longer than known stabilized ~-
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16,059-F -3- ~-
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compositions. Tests indicate that inhibitors which
are illustrated in the figures of the drawings will
satisfactorily stabilize l,l,l-trichloroethane in the
vapor and liquid state without, through partitioning,
lo~s of inhibitors or build-up of inhibitors to a degree
to affect stability and/or safety, will permit di~tillation
without los~ of inhibitors to below the safe level and
will tolerate the presence of the common acidic contaminants,
grease, oil, and metal fines without losing their inhibit-
ing qualities.
ExamPles
A series of tests was conducted to determine
the partitioning properties of the ~everal compounds here
employed. The apparatus consisted of a one liter, round
bottom flask. To this flask was attached a one liter,
round bottom flask which had been altered by placing a
glas~ pipe through the bottom extending to a point in
the interior such that the flask would hold 450 ml. of
liquid to the upper lip of the pipe. The exterior portion
of the pipe extending from the bottom was fitted into
the neck of the first flask. A water condenser was fitted
to the neck of the dified flask in a manner such that
; condensate dripping from its interior wall will fall into
the body of liquid retained in the upper flask.
oPeration-
Nine hundred milliliters of the solvent composi-
tion (l,l,l-trichloroethane plus the enumerated inhibitor)
under study was placed into the bottom flask. The entire
apparatus was covered with aluminum foil to exclude light
and to retain some warmth in the overhead flask, su~h as ~
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16,059-F -4-
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occurs in the warm dip of a degreaser. Heat was applied
to the lower fla~k and a moderate reflux rate maintained
for 24 hours.
At the end of this period, the apparatus was
allowed to ~ool and the two solvent portions analyzed for
stabilizer concentrations and aliquots ~ubjected to
a "Blender Test" as hereinafter defined.
In this manner, there i~ obtained the data
to calculate a factor representing the proportion of the
inhibitor which will go overhead with the vapors and that
proportion which will remain behind in the sump liquid
in a conventional vapor degreaser. The factors determined
by this experiment are referred to a~ partitioning factors
for the top and bottom. The partitioning factor~ were
determined by analyzing the top fraction and the bottom
fraction of the partitioning experiment for each inhibitor,
determining the percent inhibitor in each of the top and
bottom fractions and normRlizing these values to a decimal
value on the basis of that fraction of solvent to a unit
(100% basis). Thus, for dioxolane, it was determined that
ca. 55 weight percent of the inhibitor in the original
~ composition was found in the top fraction of the partition-
; ing experiment t50% by volume of the original amount)
and ca. 45 weight percent wa~ found in the bottom fraction.
Normalizing the~e value~:
Top Partitioning Factor = 0.55 = 1.1
; 5
....
Bottom Partitioning Factor = 0.45 = 0.9
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16,059-F -5-
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The partitioning factors for each inhibitor were run
- several times, and the average of the values obtained
from these several runs was calculated. The values
for each inhibitor under consideration are set forth below:
Partition Factor
Partition Factor as Percent in:
Top Bottom Top Bottom
Dioxolane 1.06 0.9 55 45
DMEl 1.16 0.88 55.8 44.2
~Ml 1.28 0.72 64.7 35.3
BOl 1.2 0.8 60 40
1. DME = l,l-Dimethoxyethane; NM = ~itromethane; and
BO = Butylene Oxide
: :
The "Blender Test" comprises placing 100
ml. of the composition being tested, at room temperature,
in a blender with 10 grams of aluminum chip~ and running ;
the blender for 10 minutes, then filtering the sample
and determining the APHA color of the filtrate.
The results of such testing e~tablished the
minimum concentration of each inhibitor which was required
to be present in an original composition to enable the
condensate of the vapors as well as the sump to be
essentially nonreactive to aluminum. Table 1 gives the
results obtained employing only the named inhibitor and
l,l,l-trichloroethane.
The concentration for APHA color of ~1000 is
chosen as the criterion for substantially no reaction
after the "Blender Test." The analysis for inhibition
in the top fraction and bottom fraction i8 set forth in
percent of inhibitor found. The minimum concentration
for protection in top and bottom is found by dividing
16,059-F -6-
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the value determined as the concentration for APHA
color <1000 by the smallest partitioning factor for ` -
the inhibitor.
Thus, for dioxolane:
Minimum concentration for dioxolane = <1000 APHA conc.
Partition Fraction
4.0 = 4,4.
The final concentration in each of the top and bottom
of a system empIoying the minimum concentration is found
in the la~t column.
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To demonstrate the effectiveness of the
compositions of the present invention against build-up
of high boiling components in the sump as well as to
demonstrate that the loss of low boiling components is
not such as to impair stability in the sump or create
toxic or hazardous vapor mixtures, a series of calculation~
are set forth in Table 2 based upon partitioning data -
- actually obtained as shown above for each component.
The calculations are based on observations and experiences
in operating commercial degreasers. Thus, in commercial
operations, a degreaser of about 4 gallons (15 liters)
capacity having an electric heating coil in the bottom -
and cold water condensing coils about the upper interior
. . . .
walls is operated in a manner such that over a period of
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lS about one week about 1/2 of the initial charge of solvent
is lost. The original solvent charge was l,l,l-trichloro-
.:
ethane plus 2.8 wt. % dioxolane, 0.8 wt. % l,l-dimethoxy-
` ethane, 0.5 wt. % nitromethane, and 0.5 wt. % butylene
: . :
oxide. Replacement of the solvent lost on a once-a-week i;
basis with fresh stabilized composition over a 2 nth
period would result in the compositions set forth in
Table 2, in the sump (Col. 4), the vapor from the sump
at the end of each week (Col. 5) and the ma~e-up to original
volume at the end o each week (Col. 6).
All calculations are normalized to 100 percentage
basis; thus, when 50/O of the original solvent composition
is lost or vaporized, the Qump contains a weight of
`~ inhibitor in one-half of the original volume. Therefore,
the new percentage of inhibitor is obtained by dividing
the actual weight percent in the fraction under consideration
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16,059-F -9-
3~7
~y a fraction which reflect3 the solvent weight under
consideration, e.g., 100 grams of ~olvent containing
2.8 weight percent dioxolane would have, when 50 weight
percent is lost,
2.8 x 0.45 = 2.53 weight percent dioxolane
o,5 (100% basis)
2.8 i9 the percent dioxolane.
0.45 is the percent dioxolane remaining in the sump as
determined by partitioning data.
0.5 is the weight percent solvent remaining.
Similarly, the inhibitor in the solvent lost (e.g., as
vapor) is calculated as follows:
2.8 x 0.55 = 3.08 weight percent dioxolane
0 5 (lOOYo basis)
In the table, in order to have linear calculation~,
the following formula is u~ed:
% wt. inhibitor x % partitioning x 2 = % wt. inhibitor
(100% basis)
The calculation~ to obtain the data ~et forth
in Table 2 are:
Col. 3 - Original weight percent (Col. 1) times percent
inhibitor to the top (obtained in partitioning experiment~)
to obtain actual weight of each inhibitor lost in the
vapor lost to the atmosphere. The figure in parenthesis
is the percent by weight of inhibitor in the lost qolvent
on a 100% wt. ba~
Col. 4 - Original weight percent (Col. 1) times percent
inhibitor in the bottomq partitioning to obtain actual
weight of each inhibitor remaining in sump as solvent
i9 lost. The figure in parenthesis is the percent by
weight of inhibitor in the qump on a 100% wt. basis.
16,059-F -10-
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Col. 5 - Weight o~ itor in vapor from ~ump after
loss of 50% of original solvent volume, Col. 4 times
- percent inhibitor to the top. The figure in parenthesis
is the weight percent of inhibitor in the tops on a
100% basis.
Col. 6 - Total inhibitor in sump after addition of
enough fresh solvent to make-up sump to original volume
with material containing original weight percent of each
inhibitor. Col. 4 actual weight percent plu~ actual
weight percent in make-up volume (e.g., for dioxane,
1.4); thus, 2.14 (from Col. 4) plus 1.4 = 3.54 of Col. 6.
16,059-F -11- ,
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