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Патент USA US2125381

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Patented Aug. ‘2,1938 0|
V
1‘
A I '
UNITED STATES PATENT‘
; 12,125,381
‘ OFFICE.
STABILIZATION or
POUNDS
Arthur A. Levine and Oliver w. Cass, Niagara '
Falls, N. Y., asslgnors to E. I. du Pont d'e»
, Nemours & Company, Wilmington, M, a cor
poration of Delaware
" No Drawing. Application March 8, 1937,
_
_
ScrialNo.'12,9,684
.5 Claims.
This invention relates to the stabilization vof
, ,chlorinatedhydrocarbons. More particularly, it
relates to the stabilization of the chlorinated hy
drocarbon, trichlorethylene, CzHCls.
The chemical changes which occur in the chlo
rinated hydrocarbon, trichlorethylene, upon stor- .
age‘or during use of the solvent for commercial
or industrial purposes, result in the development
of acidity in the product; The amount of acid
developed, which is readily'determined by tiltra
tion with a base, is an index, of the degree of de
composition of the solvent.
'
>
(01. 23-250)
_
‘While many chlorinated hydrocarbons which
are commercially employed for various solvent
15 purposes‘ are subject to decomposition as the
result of hydrolysis occurring during storage or
use, the decomposition of trichlorethylene is. not
the result of any chemical reaction with the wa
ter which: may be present in greater .or less
amounts in the liquid. While solvents, such as
carbon tetrachloride, tend to decompose upon
.
'
f
.
detergent uses, as a vehicle for" impregnating
agents in coating (or impregnating processes, for
the extraction‘ of oils, fats and waxes-of animal,
mineral or vegetable origin, in the treatment of
mineral oils, forlmetal degreasing operations, for
dry-cleaning textile fabrics, as a solvent in vari
ous chemical manufacturing operations and for
many other similar purposes. Certain of the
stabilizers >for trichlorethylene now' known func
tion more effectively when the solvent is used‘
for one purpose or in one typev of machine, and
some function‘ with greater etfectiveness when
the solvent is used for other purposes. Accord
ingly, it has been usually necessary to select sta
bilizers for the trichlorethylene in accordance 15
with the use to which the solvent is to be put
or, as an alternative, to include several stabl
lizers to insure satisfactory stability of the chloro
hydrocarbon under varying conditions .of storage
or use.
-
20
‘ We have‘now found that one speci?c stabi- ,
lizer for trichlorethylene is su?clent by itself to
stabilize this chlorohydrocarbon against chemi
chlorethylene is not subject to chemical decom > cal decomposition when the solvent is employed
position in this manner. It has been observed, for almost any commercial use. We have found
however, that considerable quantities of acid will that when this stabilizing agent is present in small
develop in a batch of trichlorethylene, during‘ a amounts in the solvent, it is unnecessary [to em
period of use or storage, unless that solvent has ploy several stabilizers toins'ure satisfactory sta
previously been stabilized by the addition there- bility of'the chlorinated hydrocarbon, as the
single agent may be termed of universal sta 30
to of some stabilizing agent. As a result of ob
servations-carried out in connection with the bilizing activity. .
The single stabilizer which we have foundef
formation of acid substances in trichlorethylen'e
. incident to storage or use of that chlorohydro~ fective for stabilizing trichlorethylene under all
carbon, i. e. decomposition of thesolvent, it has conditions encountered in the commercial uti
been concluded ,that the decomposition is an lization of this solvent is the compound, tri 35
oxidation phenomenon. Inasmuch as this type phenyl guanldine, CcHsN=C(NHCsHs)2. Tri
of decomposition -is not encountered with those phenyl guanidine, when present in small amounts
chlorohydrocarbons subject to, the carbon tetra
in trichlorethylene, amounts ranging from 0.001%
chloride type of decomposition, it follows that to'?ll% by weight based on the weight of tri
40 the stabilizers emplo’yed for stabilizing trichlor-v ‘chlorethylene stabilized, has been found to pre 40
ethylene against decomposition must be different vent the development of any substantial quanfrom those used for carbon‘ tetrachloride sta
tity of acidity in the solvent overlreasonable pe
standing or during use as the result of the ac
tion of water on the chlorinated compound, tri
_
riods of storage or use. This‘ action is an inhibit
Since'trichlorethylene is widely used in in
ing action, 1. e. a form of anti-catalysis. >
dustrial establishments for various purposes, such
The advantages. of being able to utilize a 45.
as the degreasing’w'or cleaning of metals prior to‘ single stabilizer, regardless of the purpose for
plating, and in dry cleaning establishments for which the trichloretlrvlene is subsequently uti
the dry cleaning of textile fabrics, it has been lized, are immediately obvious. We have observed
1151181 to stabilize trichlorethylene against decom
that triphenyl guanldine is an emcient stabilizer
position during storage or use." As a result of regardless of whether the trichlorethylene is uti 50
experiments on the. stabilization of the, chlorin
lized for degreasing, for ‘dry-cleaning textile
ated hydrocarbons, certain characteristics have fabrics, for-extracting vegetable vor mineral oils,
been found to be essential in any stabilizer which fats or waxes, for impregnation, or for any other
is to prove effective. However, to date, no one purpose. It is, however, not volatile with the
stabilizer has been entirely suitable for all batches ‘chlorinated hydrocarbon and where the’ tri 55
of solvent. One of the reasons for this is the chlorethylene is subjected to distillation and
wideuvariety of uses to which the solvent is put
asis usual in processes for puri
.- in industrial establishments. Trichlorethylene is condensation,
fying
and
recovering
the solvent after use, it
such an excellent solvent that it is used for a
bilization.
wide variety of commercial operations including
must be remembered that the triphenyl guani
2
2,125,881
dine will remain behind inthe residue and will
chemical decomposition. As previously speci?ed,
not be found in the puri?ed condensate. For
however, we prefer to use amounts ranging from
this reason it is necessary to add a new amount
0.0001% to 0.1% by weight. and ordinarily our _
preferred range is from 0.01% to 0.05%.
'
Since various changes or modi?cations may be
made in our invention as disclosed, such as
of triphenyl guanidine to the puri?ed conden
sate, ‘before subjecting the puri?ed solvent to
re-use for any commercial solvent purpose.
However, in the distillation of trichlorethylene
changing the proportions or amounts of the
stabilizer utilized‘ in the trichlorethylene, our in
it is advantageous that the residue shall at all
times contain an adequate amount of the sta- . vention is not to be restricted except as necessi
bilizer. The property of triphenyl guanidine of
remaining behind in the residue since it is not
volatile with the chlorinated hydrocarbon ren
ders it especially valuable as a stabilizer.
tated by the prior art and appended claims.
We claim:
1., A composition of matter comprising tri
__chlorethylene and stabilizing amounts of tri
The following table shows the superiority of
phenyl guanidine.
15 triphenyl guanidine over various other stabi
lizers when employed for the stabilization of
trichlorethlvlene.
in each case- an amount of
each stabilizer equivalent to 0.01% by volume,
-
based on the weight of said trichlorethylene.
3. A composition of matter comprising tri
based on the volume of the chlorinated hydro
20 carbon, was added and the samples then stored
ohlorethylene and triphenyl guanidine dissolved
therein, said triphenyi guanidine being present
in direct sunlight for the periods indicated. At
the conclusion of each of these periods the
in amounts ranging from 0.01 to'0.05% by weight
based on the weight of said trichlorethylene.
amount of acid present in 25 cubic centimeter
samples of each batch of solvent was deter
4. Trichlorethylene stabilized by the addition
thereto of triphenyl guanidine in stabilizing '25
amounts.
25 mined by titration with 0.01 normal sodium by
drom'de solution.
_
Z. A composition of matter comprising tri 15
chlorethylene and from ‘0.001 to 0.1% of tri
phenyl guanidine, said amount being by weight
'
Quantity 010.01 N NnOH required to neutralize acidity in 25 cc. sample after speci?ed period of storage in direct ,Bu?light
Compound tmted
30
56 hrs. mom-s. 29511115. '
'
Cc.
Unstabilized trichlorcthylone___
75
Trichlorethylene stabilized with
35
0.01% triphonyl guanidine.
'
1'. 0
8. 0
15. 0
Cc.
185
1. 0
1.0 cc-
15. 0
'
'Colorles.
1.0 cc-
2.0 cc-
1.0
Too acid to
titrate.
0.5
_
Very faint yel
Colorless.
_
12.0 cc- __-_- 27.0 cc- _____ Too acid to
'
Trichlorethylene stabilized with
Remarks
.
Too acid to
titraie.
I
0.01% ortho-benzyl-phenol.
45
200 days
low; no unid
ual odor.
a
Trichlorethylane stabilized with
0.01% carvacrol.
665 hrs.
,
Trichlorethyl?ne stabilized with
0.01% thymol.
1. 0
C'c.
110
404 his.
4.0
'
_
tin-ate.
27cc__.'__-__ Too acid-to-
,
_‘
Our invention is not to be restricted‘ to any
speci?c proportions or amounts of stabilizer as
all amounts ranging from a small fraction of
one per cent up to 1% of triphenyl ‘guanidine by
weight have been found satisfactory for sta
bilizing the chlorinated hydrocarbon against
Color bad after
two weeks. '
Colorless.
titrate.
'5. A process ‘of stabilizing trichlorethylene
which involves dissolving therein, in stabilizing
amounts, triphenyl guanidine.
ARTHUR A. LEVINE.
OLIVER W. CASS.
35
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