Note: Descriptions are shown in the official language in which they were submitted.
10~240
Perchloroethylene (1,1,2,2-tetrachloroethylene)
is a well known chlorinated solvent widely used by industry
to clean metals and fabrics. It, like methyl chloroform
(l,l,l-trichloroethane), has been gaining wide spread usage
in areas previously employing trichloroethylene (1,1,2-
trichloroethylene) because of the publicity of the alleged
unfavorable ecological impact on the atmosphere of this
latter solvent. The increased use of perchloroethylene
and l,l,l-trichloroethane in the metal cleaning fields
previously employing trichloroethylene has ~ubjected these
solvents to unusual conditions which often results in
solvent decomposition, generating hydrogen chloride which
then reacts with the metals to produce metal chloride, a
reaction product which causes the decomposition of the solvent
thus producing more hydrogen chloride. Also, these same
degradation products and me,tal halides attach or catalyze
the decomposition of chain fatty acids and oils, causing
the production of compounds having a disagreeable odor.
The art has attempted to meet these problems as they arise
by resorting to known stabilizers such as, for example,
epichlorohydrin, epibromohydrin, butylene oxide, and cyclo-
hexane oxide, alone or in combination with various other
well known inhibitors such as dioxane, dioxolane, trioxane,
nitromethane, nitroethane, and the nitriles. While these
known combinations give satisfactory results under well
regulated and careful clean housekeeping of the solvent
and the equipment, unfortunately, many operations are not
well run from the housekeeping standpoint. This results
in excessive corrosion of equipment, metal parts being
cleaned, and decomposition of the solvent and polishing
.'
17,952-F -l-
~07~Z~O
and grinding compounds dissolved in the solvent. Once
the inhibitor level of a solvent is decreased without
decrease of the contaminating components, corrosion
and decomposition are accelerated.
The present invention resides in perchloroethy-
lene stabilized against degradation in the presence of
hydrogen chloride and metals and containing from 0.1 to
5.0 weight percent of tertiary butyl glycidyl ether.
The present invention further resides in a
process for stabilizing perchloroethylene against degra-
dation in the presence of hydrogen chloride and metals
comprising adding to the perchloroethylene from 0.1 to
5.0 weight percent of tertiary butyl glycidyl ether.
The tertiary butyl glycidyl ether is the
principal and essential mineral acid acceptor when this
solvent is used as vapor degreasing solvent and substan-
tially eliminates degradation of the solvent and corrosion
of the metals in contact therewith. l-Tertiary butoxy
2,3-epoxypropane (hereafter called TBGE) has the formula
CH3
H3C-C-O-CH2-C~-~CH2
CH3 o
The use of TBGE to maintain the solvent substantially
free of mineral acids is unique because numerous reac-
tions occur under the use condition which result in the
acid acceptance of the compound being greater than the
expected value of 1. The following equations illustrate
the reactions and products found in the solvent under
use conditions.
*Acid acceptors.
17,952-F -2-
.
1~712~0
" .
C~H \H H+ ~ C/H \H + / CH3 :
CH2 CH2H CH3
OtBu
~I) (II) (III)
:: .
(I) * or M Cl > ClCH2CHOH - (III) - > ClCH2CH-OH :~
X yCH20tBu CH2H
(IV) (V)
(I)* H20 3 HOCH2CHOH-(III) > HOCH2CH-OH
,, CH2otBu CH2H
~ (VI) (VII)
, . .
(I)* Act ve Hydrogen? -(CH2CHO)- -(III) ~ -(CH2CHO)x
(H20 or ROH) CH20tBu 2
; ~VIII) (IX)
, . . .
I)* ZnCl
or FeCl > CH3CCH20tBu -(III) > CH3CCH20H (XI)
2 ll
;., Rearrangement enol H2o > CH2=CH=CH20tBu
(X) (XII)
CH3 CH3* CH3*
CH C H20 ~ HO-C-CH3 + HC-CH20H
3 CH3 CH3
~, (III) (XIII) (XIV)
17,952-F _3_
. , .
`` ~, , . ' , ~
.:. . : - .- --
1071240
CH3 CH3
(III) HCl~ Cl-C-CH + HC-CH2Cl
CH3 C~13
(XV) (XVI)
C~3 CH3
(III) ~ > CH3-C-CH2-C=CH2
CH3
(XVII)
/0\ ~ CH3
(III) (o) > CH -C H20 > HO-C-CH20H
, CH3 CH3
(XVIII)* (XIX)
CH3
(XVIII)* HCl ~ Cl-C-CH20H
CH3
.,.
(XX)
It i8 thus seen that TBGE has unique properties not pos-
sessed by the conventional acid acceptors, e.g. epichloro-
hydrin, cyclohexane oxide and butylene oxide or by methyl
glycidyl ether or isopropyl glycidyl ether. The unique
property is its ability to react with the hydrogen chloride,
metal chlorides and water to produce intermediate reaction
products which are capable of further reaction with these
same reactants, i.e. the reaction products of the expected
reaction have labile groups reactive with hydrogen chloride,
metal chlorides and water. This unique property makes the
TBGE unexpectedly superior to the prior art acid acceptors.
:,
17, 952-F -4-
.
l 071Z40
TBGE has a favorable partitioning factor, i.e.
; the volume ratio of the amount of TBGE which goes to the
vapor from a boiling solvent to the amount of TBGE which
stays in the liquid. This factor varies from about 1 to
1.4 to 1 to 2 respectively, depending on the oils and con-
taminants present in the boiling solvent. It is advantageous
that such a partitioning factor exists since the metal
chips accumulate in the liquid and the metal chlorides are
formed in the liquid. The favorable partitioning assures
that there is adequate TBGE in the liquid to tie-up the
chlorides and remove them from this reactive state. The
additions of make-up solvent containing the TBG~ in the
abo~e-noted ranges will provide adequate ~BGE in the liquid
and vapor under use conditions. Further, the partitioning
actor also allows only a slow accumulation of TBGE in the
sump and still so that while some increase or build-up
occurs in the sump and still, excessive build-up does not
occur, thus limiting losses from the unit during solvent
purification in the sludge or still bottoms.
The amount of tertiary butyl glycidyl ether
employed to achieve the improved stability under the acid
generating conditions is from about 0.1 to about 5 and
preferably between about 0.25 and about 1.5 percent by
weight based on the weight of the total composition. It
i6, o course, understood that while quantities greater
than 1.5 weight percent i.e. up to about 5 percent can
be employed, unless extremely severe conditions exist it
is uneconomical to employ these quantities greater than
about 1.5 weight percent. It is further to be understood
that best results are obtained when there is also added
17,592-F -5~
:` , , ' .:
` - ~ .: ,' ' :
: 1071Z40
' from 10 to 500 ppm of an antioxidant, i.e. an amine such
as N-methyl morpholine, or a phenolic, since perchloro-
ethylene undergoes oxidation in the presence of heat,
light, and oxygen.
Example 1
A 2' x 5 1/2' x 5' (0.61 x 1.68 x 1.52 m.) two-
-chamber open top vapor degreaser was used in the test.
Perchloroethylene containing about 0.~5 weight percent -
TBGE and 50 ppm by weight M-methyl morpholine was used in
the test. The degreaser was heated with a two-deck heat
exchanger at 45-48 psi (3.18-3.38 kg./cm. ) steam pressure.
Cooling was provided by means of perimeter water coils
and a freeboard water jacket. Solvent from the degreaser
boiling sump was pumped by a transfer pump to a steam
heated still equipped with an automatic level control.
Condensate solvent in the degreacer was routed
through a water cooled water separator into a warm dip
chamber which overflowed into a boiling sump compartment.
The still condensate was also routed back into the warm
dip chamber.
Working Volumes of the Degreaser-Still
.~
Degreaser sump - 25.25 U.S. gallons (95.5 liters)
Degreaser warm dip - 31.17 U.S. gallonc (113 liters)
Still during operation 29.38 U.S. gallons (111 liters)
Test Procedure
Ater the initial solvent fill, the system
was put into operation for three days prior to any solvent
sampling. Sampling was commenced on the third day of
operation with samples taken from the sump, warm dip,
still condenser and still bottom.
17,952-F -6-
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1~71Z40
All solvent samples were analyzed by vapor
phase chromatography (VPC) determination of inhibitor
levels and were taken prior to any sol~ent make up addi-
tions or oil additions.
Three sets of eight 0.032" x 4" x 8!' (1.25mm. x
1.58cm. x 3.16cm.) 1010 steel panels were placed in the
degreaser at various positions:
Coupon Locations in Degreaser
Coupon # Position Vapor Liq.
1 A-trough sumpside x
2 B-trough sumpside x
3 C-liquid sumpside x
4 D-trough warm dipside x
E-liquid warm dipside x
6 F-below trough on
sumpside near trough x
7 G-below trough on
sumpside in center of
sumpside x
8 H-between trough and liquid
on warm dipside x
Average inhibitor partitioning during the 25-day test were
as follows:
Ratio Sump
% TBGE to Vapor
Degreaser Sump 0.449% 1.4
Degreaser Warm Dip 0.317% 1.0
Still Conden~ate 0.456% 1.4
Still Sump 0.768% 2.4
At the end of the 25-day test the degreaser was shut down
and the solvent in the warm dip chamber pumped into a
tared 55 U.S. gallon (208 liters) drum. At this point
there was a 25 percent oil content in the still pump. The
contents of the degreaser sump were then routed through
the still and distillate collected in the warm dip chamber.
17,952-F -7-
- ~)71240
The amounts and analysis of the recovered solvent are tab-
ulated in Tables I and II. Nine U.S. gallons (34.0 liters) ~:
. of solvent were recovered from the degreaser sump below
,.: the still transfer line, referred to as still bottoms below.
TABLE I
. Solvent
. Wt. in U.S. Gallons % TBGE
Solvent Source Lbs. (Kg.) ~Liters) in Solvent
1) Warm dip at 373 ~169)27.69 ~105) 0.33
shut down
.- 2) Distillate 289 ~131)21.46 ~81.4) 0.55
from still
; ~first batch)
3) Distillate 215 ~97.6) 15.96 ~60.2) 0.56
:~ from still
!' ~second batch)
4) Residue solvent 123 ~56.0) 9.13 ~34.5) 0.504
; from degreaser
sump
,
TOTALS 1000 ~453.6) 74.24 ~281.1)
Still Bottom8* 160 15.89 1.394
*Note: Still.bottoms contain 56% oil and 44% solvent, there-
fore 6.99 gallons (26.4 liters) of the still bottoms are
perchloroethylene with 1.394% wt. TBGE. Still bottoms also
contain 0.213% of the chlorohydrin product ~CH3)3C-OCH2-
CH-CH2Cl
OH
.~ 17,952-F -8-
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,~ ~
10~1240
.
TABLE II
,
Material Balance for TBGE Inhibitor
Solvent
Wt. inU.S. Gallons % TBGE
Solvent Source Lbs. (Kg.)(Liters) in Solvent
1) Solvent for 1965.3 (881)145.9 (551) 0.445
test
2) Recovered
from still
boil down1000.0 (453.6) 74.24 ~271) 0.4654
3) Still bottoms
contain 44
perchloro
(0.44 x
15.89) 94.1~ (42.8) 6.99 (26.4) 1.394
Total
Recovered
(2 and 3)1094.16 (496.4)81.24 (297.4) 0.545 -
(Calcd)
Comsumed*
(1 - (2+3))871.14 (384.6)64.67 (253.6) 0.296
:~ (Calcd)
*Note: 0.458 U.S. gallons (1.73 liters) of T~GE inhibitor
is accounted for by the 81.23 U.S. gallons (297 liters) of
total recovered solvent lincluded 0.0149 U.S. gallons
(0.560) of TBGE for chlorohydrin product in still bottoms).
Substracting 0.458 from the 0.6493 U.S. gallons (2.54 liters)
TBGE in the original solvent gives 0.1914 U.S. gallons
(0.72 liters) TBGE lost iwth the 64.67 U.S. gallons of
consumed solvent.
Therefore the percent of TBGE in the consumed (by vapor
losses and reaction with metal chlorides) solvent is
0.1914 x 100 = 0.2960% TBGE.
64.67
This figure of 0.2960% TBGE is very close to the average
warm dip inhibitor content during the test period of 0.311%
TBGE laverage of 9 determinations).
Normal degreaser-still operation involves dumping
and subsequent discarding of the boiled down still bottoms.
; 25 Accordingly, the amount of TBGE that would be lost is
calculated by dividing the amount of TBGE in the boiled
down still bottoms, i.e. 6.99 gal (25.4 liters) x 1.394% TBGE
by the amount of TBGE in the original solvent, 0.6493 gal.
17,952-F -9-
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.. .
(2.46 liters), or original would be lost. This loss is
not excessive as seen by the fact that the 74.24 U.S.
gallons (281 liters) of recovered solvent had an average
; 0.465% TBGE inhibitor content while the original solvent
had a 0.445~ inhibitor content.
The solvent comsu~ption in the idling degreaser
during the 25-day test was calculated as follows:
~, Cross section area of degreaser - 9.5 ft.2 (0.88 m.2)
- 871.14 lbs (396 kg.) solvent = 91.70 lbs/f~.
9.5 ft. ~0.88 m. ) (449 kg./m. )
for 25 days
600 hours in 25-day test
91 70 1bs/ft.2 (449 kg-/m- ) = 0.153 lbs/ft- /hr-
600 hrs. ~0.748 kg./m.2/hr.
,,
There was no rusting observed on any of the
three sets of 1010 steel coupons removed from the degreaser
and stored in the office. None of the removed coupons
has exhibited any post rusting after removal from the
degreaser, (20 days).
Example 2
A vapor degreasing grade of perchloroethylene
was used having the following composition:
0.005% ~Wt.) N-Methyl Morpholine
0.40% (Wt.) Tertiary Butylglycidyl ether
Balance - Perchloroethylene
A six-week degreaser test was undertaken to study the
ability of this formulation to withstand the stresses
commonly occurring in vapor degreasing operations. The
secondary purpose of this test was to look at the
inhibitor distribution in both the degreaser ~ump and
.~
17,952-F -10-
~ 1071Z40
condensate over an extended period of time, and to deter-
mine if this solvent exhibited stability and consistency
under simulated field conditions
Procedure
The degreaser used for this experiment was elec-
trically heated and measured 2' x 3' x 5' (0.61 x 0.92 x
,~ 1.52 m.). After the initial fill, the degreaser ran for
a period of 45 days with additional solvent being added
, intermittently as needed. Samples were taken every two
.7 10 days from both the degreaser sump and warm dip to deter-
mine if there was decomposition occurring with either the
perchloroethylene or TBGE. These samples were tested by
gas chromatography (GC) analysis which showed the changes
in inhibitor levels and also whether or not decomposition
products were present. During the test an effort was
made to create in the degreaser the variety of adverse
conditions that can occur during cleaning operations.
Consequently, there were added to the degreaser over the
45-day period 0.5 U.S. gallon (1.89 liter) of water, 1.25
U.S. gallons (4.73 liters) of commercial cutting oils,
0.5 lb. (0.23 kg.) steel chips, 0.5 lb. (0.23 kg.) zinc
chips.
Results
The solvent showed no significant loss of inhi-
bitor in either the warm dip or degreaser sump during the
course of this six-week degreaser test. The inhibitor
partitioning of TBGE started out at a ratio 2-sump, l-warm
dip and remained that way consistently throughout the
45-day period. Neither of the above additions (oil or
chips) appeared to alter the condition of the solvent
~ '
, 17,952-F -11-
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107~Z40
'
significantly from a stability standpoint. The GG analysis
of samples taken during the study show no decomposition
products of the solvent present but did show the chlorohydrin
that occurs as a result of the reaction of HCl with TBGE.
The presence of one chlorohydrin shows that the inhibitor
was performing adequately as an acid acceptor. The average
TBGE concentration in the warm-dip was about 0.31 wt. percent
and in the sump was bout 0.6 wt. percent.
Example 3
A field degreaser trial was started to evaluate
the performance of the TBGE form~lation under field oper-
' ating conditions. Perchloroethylene with 0.4% of TBGE
and containing 50 ppm of N-methyl morpholine, based on
total composition, was used in the test. Steel panels
were suspended in the vapor zone to enable visual obser-
vation of rust formation during or after removal from the
degreaser.
Procedure and Test
-
A one chamber, open top degreaser with a spray
lance was used in the test. The degreaser was gas heated
with cooling being done by a free-board water jacket.
Initially, the degreaser was charged with 155 U.S
gallons ~585 liters) of the formulation with approximately
55 U.S. gallons (208 liters) of make-up being added weekly.
This rate of make-up ls essentially the same as it was for
the perchloroethylene used previously.
For the first week samples were taken daily.
After that, samples were taken weekly. The samples were
analyzed at two locations for acid acceptance levels and
whether degradation of the perchloroethylene and/or TBG~
17,952-F -12-
,
1~71240
was occurring. Analysis of the samples were done using
GB, the industry standard Acid ~cceptance Test Method,
and I.R.
After one month, four (4) sets of three 4" x 8"
(10.2 x 20.4 cm.) 1010 steel panels were placed in the
degreaser's vapor zone. The panels were exposed to the
vapors for varying periods of time.
~posure of 1010 Steel Panels
Panel Position Length of Exposure
A vapor zone 1 week
B vapor zone 2 weeks
C vapor zone 3 weeks
D vapor zone 4 weeks
At the end of the exposure times no appreciable
15 rusting or corrosion of the panels was observed. Acid
acceptance readings remained at an acceptable level
~ during the test.
,; ACID ACCEPTANCE DURING TEST
Source Acid Acceptance~2) Time
Drum~l) 0.108 0 hrs
Sump 0.140 24 hrs
Sump 0.150 48 hrs
Sump 0.165 8 days
Sump 0.187 20 days
Sump 0.187 28 days
Sump 0.215 34 days
Condensate 0.100 3 days
Condensate 0.105 8 days
Condensate 0.127 20 days
Condensate 0.130 28 days
Condensate 0.135 34 days
. ~
~, 17,952-F -13-
~` - .
.~! . .
~ lQ~7~240
.
(1) Sample was t~ken from formulation drun.
(2) Acid acceptance as ~ NaOH.
Samples generally were taken bef~re addition of
~, make-up solvent. The greatest increase occurred between
0 and 20 days. TBGE partition's at a rate of approximately
1.4 to 1 to condensate.
PARTI TI ONING TBC E TRIAL
Partitioning
Wt. ~ Wt. % Factor
TimeTBGE Sump CondensateSump/Cond.
2 days 0.44 - ~
3 days 0.46 - -
5 days - 0.31 1.45/1
10 days 0.51 0.33 1.54/1
22 days ~.57 0.39 1.46/1
30 days 0.57 0.40 1.42/1
37 days l).66 0.43 1.53/1
45 days ).76 0.52 1.46/1
17,952-F -14-
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