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Патент USA US2111253

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‘Patented Mar. 15, 1938
2,111,253 '
UNITED STATES PATNT OFFICE‘
“
~
5311.253
INHIBITOR FOR GHLORINATED SOLVENTS
Sylvia M. Stoesser and Francis N. Alquist, Mid
land, Mich., assignors to The Dow Chemical
Company, Midland, Mich, a corporation of
Michigan
No Drawing. Application August 9, 1935
Serial No. 35,483
3 Claims. (Cl. 23-250)
This invention relates to the stabilization of
tively small percentage of apiperazine' compound,
such as tetramethyl piperazine or piperazine hy
chlorinated aliphatic hydrocarbons against de
composition and the improved composition of. drate, to the chlorinated aliphatic hydrocarbon,
matter obtained thereby, as well as to a method preferably during manufacture or directly after
5 of inhibiting the corrosive action of chlorinated the material has been puri?ed by distillation.
aliphatic hydrocarbons upon metal surfaces in The proportion of the piperazine compound
which we have found su?‘icient in admixture with
contact therewith.
‘
The marked tendency of chlorinated aliphatic chlorinated aliphatic hydrocarbons to suppress
decomposition is relatively small, generally be
hydrocarbons, e. g. carbonv tetrachloride, tetra
tween about 0.01 and 1.0 per. cent by volume. A
10 chloroethylene, propylene chloride, etc., to un
dergo decomposition during storage and/or dis I greater percentage of stabilizing agent may be
tillation, particularly in the presence 0! moisture, employed in instances where the corrosion rate
of the chlorinated hydrocarbon is found to be
is well known; Such decomposition, when it oc
curs, imparts to the chlorinated hydrocarbons greater‘ than normal, or where the stabilizing
agent is vadded to material already somewhat
l5 corrosive properties which render them objec
tionable for many purposes.
decomposed°
We have now found that chlorinated aliphatic
hydrocarbons can be rendered stable during stor
age and/or distillation by incorporating there
20 with a relatively small amount of a piperazine
compound. We have also found that the addi
tion of a piperazine compound to such chlori
nated solvents results in stabilizing these mate
rials against decomposition in sunlight. The
25 term “piperazine compoun " as hereinafter em
ployed refers to any compound containing the
piperazine nucleus. The invention, then, con
sists in the stabilization‘ of ‘chlorinated aliphatic
hydrocarbons, in the improved composition ob
‘30 tained by such stabilization, and to a method of
inhibiting the corrosive action upon metal sur
’ faces of unstabilized chlorinated aliphatic hy
drocarbons in contact therewith, hereinafter fully
described and particularly pointed out in the
35 claims.
-
_
In the practice of our invention we add a rela
'
5
'
10
15
,
The following table shows the results which
have been obtained in practicing our invention,
using tetramethyl piperazine and piperazine hy
drate for stabilizing against decomposition of 20
certain chlorinated aliphatic hydrocarbons in
contact with various metals.
As a measure of
the decomposition occurring in a chlorinated ali
phatlc hydrocarbon during contact with ‘the
metal, we have determined the weight of metal . 25
corroded away per unit area under re?uxing
conditions for 24 hours in the presence of water. . v
The tests were conducted by immersing a
weighed and measured strip of metal in 50 milli
liters of chlorinated hydrocarbon and 20 milli- 30 ,
liters of water, in a round-bottomed ?ask con-1
nected with a re?uxing‘column, and heated under
re?uxing conditions. Thereafter the metal strips
were re-weighed and’ the corrosion rate com
puted in milligrams per square inch of exposed 35
metal area per day.
Table
40
Corrosion rate
Run No.
45
50
Solvent
Inhibitor employed
40
sm?'lsq- Ill-[2* .
hours
a. P .
45
50
8,111,258
Corrosion rate
Inhibitor employed
[ml-‘IQ.
inJM
ours
ee.
'l‘otmmotlll
i
sine. y_pm
0. 10
20
25
None ................ -.
'l‘etramethyl pipers
80
sine.
None................ ..
Tetramethyl pipers
zine.
.
From the above table it will be seen that the
tains only ‘about 1.2 per cent 01 the quantity of
corrosion rate of hot, moist chlorinated solvents _ decomposition ‘products contained in an equal
upon the commonly used metals may be reduced
quantity or unstabilized tetrachloroethylene.
per cent of a simple compound 01 piperazine.
in place of a derivative thereof, but it is believed
that piperazine, when added to an aqueous sol
40 very materially by the addition 01 less than one
To illustrate the stabilizing e?ect obtained by
adding a piperazine compound to commercial
chlorinated solvents which are to be subjected to
45 the in?uence of light, we have exposed samples of
both stabilised and upstabilized solvents to the
action of ultra-violet light rays for 24 hour peri
ods, and subsequently determined the extent of
the resultant decomposition. A test demonstrat
ing the extent of the decomposition is a?orded
by washing the solvent under test with caustic
alkali, neutralizing the mixture, and titrating the
same with tenth-normal silver nitrate i'or reac
tive chlorine. Thus, when 4 samples of tetra
chloroethylene which had been subjected to the
rays of a sun-lamp for 24 hours were tested, it was
found that 50 milliliters of unstabilized mate
rial required the addition of 14.2 milliliters of sil
ver nitrate to precipitate the free chlorine there
60 in, while 50 milliliters of material stabilized by
the addition of 0.2 per cent by volume of tetra
methyl piperazine required only 0.15 milliliter of
silver nitrate. These results indicate that tetra
chloroethylene stabilized by the addition of a
65 minute amount of tetramethyl piperazine con
If desired, piperazine itself may be employed 40
vent, is immediately converted to piperazine hy
drate and the latter compound becomes the sta
bilizing agent.
‘
45
Other modes of applying the principle 01' our
invention may be employed instead of those ex
plained, change being made as regards the ma
terials employed, provided the step or material
mentioned in any of the following claims or equiv 50
alents of such stated step or material be em
ployed.
We therefore particularly point out and dis
tinctly claim as our invention:
1. A chlorinated aliphatic hydrocarbon con 55
taining a relatively small amount of tetramethyl
piperazine.
2. A composition'oi matter comprising tetra
chloroethylene containing a relatively small
60
amount of tetramethyl piperazine.
3. A composition of matter comprising carbon
tetrachloride containing a relatively small amount
of tetramethyl piperazine.
SYLVIA M. STOESSER.
FRANCIS N. ALQUIST.
65
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