1,1,1-Trichloroethane is stabilized for use as a replacement for trichloroethylene in vapor degreasing applications by employing from about 3.6 to about 7.6 volume percent based on the total composition of the following components in 1,1,1-trichloroethane: PA1 Volume % PA1 1 to 3 1,4-dioxane PA1 1 to 3 t-amyl alcohol PA1 0.2 to 0.6 nitromethane or a mixture of nitromethane and nitroethane containing up to 75 volume percent nitroethane PA1 0.5 to 1 1,2-butylene oxide.

BACKGROUND OF INVENTION 
1,1,1-Trichloroethane is a widely used industrial cleaning solvent. With 
the recent restrictions placed on the use of trichloroethylene, as for 
example, vapor degreasing, more people are substituting 
1,1,1-trichloroethane into uses to which the trichloroethylene was 
employed. Many of these uses place a severe stress on the 
1,1,1-trichloroethane. Previous inhibitor systems for the 
1,1,1-trichloroethane have been found weak or ineffective in protecting 
the solvent and/or the parts being cleaned. Thus, it is necessary to find 
new inhibitor systems for the 1,1,1-trichloroethane which will permit the 
extended uses industry is making of this useful solvent. 
The prior art has added numerous members from most classes of organic 
compounds in attempts to improve the stability of 1,1,1-trichloroethane to 
degradation in the presence of heat, metals (particularly aluminum) and 
water. For example, esters, ethers, amines, cyano compounds, alcohols, 
ketones, aldehydes and the like have been suggested alone and in 
combination in the literature and in patents. However, commercial grades 
of 1,1,1-trichloroethane used in the major industrial countries contain at 
least one inner ether (an epoxide and/or dioxane, dioxolane, or trioxane), 
usually a nitroalkane (nitromethane and/or nitroethane) then one or more 
of the following acetylenic alcohol, nitrile (acetonitrile or 
.beta.-methoxypropionitrile), ortho ester (trimethyl ortho formate), lower 
alkanol (t-butyl or t-amyl alcohol), a ketone (methyl ethyl ketone). These 
compounds account for the components used in the main in the present day 
inhibitor systems. 
One of the largest suppliers used dioxane, nitromethane and butylene oxide 
for years. However, even this recognized superior system has shown 
weaknesses in certain fields of use wherein trichloroethylene was 
previously employed. Such weaknesses are a result of operator's lack of 
care in maintenance of their equipment, a chore not usually undertaken on 
a regular basis when trichloroethylene was employed. However, any rusting, 
heavy metals fines, particularly aluminum, grinding and buffing compounds, 
lubricant oils and fluxes such as employed in miniature printed circuits 
increase the degradation of the solvent and create corrosive atmospheres 
which attack the metal parts being cleaned. In the past, the manufacturers 
have been able to screen the new uses and monitor the uses. Such is not 
possible with the widespread usage to which the solvent has been put in 
recent months. 
It is, therefore, an object of the present invention to provide a 
stabilized grade of 1,1,11-trichloroethane suitable for the severe use 
conditions encountered in the substitution of 1,1,1-trichloroethane for 
trichloroethylene 
BRIEF DESCRIPTION OF INVENTION 
In accordance with the present invention it has been found advantageous to 
combine 1,4-dioxane, tertiary amyl alcohol, nitromethane and/or 
nitroethane, and butylene oxide in the hereinafter proportions to 
stabilize 1,1,1-trichloroethane for industrial usage as a vapor degreasing 
solvent in applications wherein 1,1,2-trichloroethylene was previously 
employed. 
As aforestated in the Background of Invention, 1,1,1-trichloroethane is a 
unique chlorinated hydrocarbon solvent having low toxicity and good 
ecological properties and is gradually replacing trichloroethylene in the 
vapor degreasing field. In the new use as a vapor degreasing solvent the 
1,1,1-trichloroethane comes under severe use conditions, i.e., contact 
with metal parts containing aluminum, iron, copper, zinc and alloys 
thereof, acid compositions used in metal finishing operations, oils and 
resins, i.e., as in printed circuitry manufacture, and the like. Some of 
these conditions have been met before in the special uses to which 
1,1,1-trichloroethane have been put, but the manufacturers and their 
distributors have taken care to monitor these uses. Today, however, with 
the widespread and expanding usage attributable largely to the general ban 
on use of trichloroethylene, monitoring becomes substantially humanly 
impossible or extremely expensive. Therefore, extensive efforts have been 
undertaken to prepare a stabilized grade of 1,1,1-trichloroethane which 
will be suitable for total replacement of trichloroethylene in the 
industrial area. A further effort was undertaken to employ as inhibitors, 
compounds in small quantities, compounds which presently appear to have no 
ecological or safety hazards, and employ only a minor number of compounds 
and a major proportion of 1,1,1-trichloroethane. Such a formulation has 
been found in the above set forth invention, to wit: 
1 to 3 volume percent 1,4-dioxane; 
1 to 3 volume percent t-amyl alcohol; 
0.2 to 0.6 volume percent nitromethane, or a mixture of nitromethane and 
nitroethane containing up to 75 volume percent nitroethane; 
0.5 to 1 volume percent butylene oxide. 
wherein the total of dioxane and t-amyl alcohol must be 3 volume percent 
and the total inhibitor concentration must be 3.6 volume percent. It is 
contemplated the total maximum inhibitor volume will be 7.6 volume percent 
in order to eliminate any vapor or liquid health hazards which the 
inhibitors might exhibit in the ambient atmosphere or bodily contact 
toward humans as well as maintain the potential of creating a flammability 
problem to the minimum. 
It is to be understood that various combinations of the inhibitors named 
are known to prevent degradation of the 1,1,1-trichloroethane but that 
they have not been combined in the aforesaid manner or amounts. The 
results of the enumerated combination establish an unexpected and unique 
property of the combination in that while the boiling points of the 
inhibitor components would indicate loss of nitro--methane and butylene 
oxide, in fact this does not occur. Repeated usage, that is vaporization 
and condensation in a vapor degreasing operation, drag-out of solvent 
vapors on parts, with periodic make-up of inhibited solvent to operating 
volumes have confirmed that each component of the inhibitor systems 
remains in a sufficient quantity to stabilize the solvent in both the 
liquid and vapor state over extended continuous periods of time without 
build-up of high boilers or loss of low boilers. 
The preferred composition consists of 
2 to 3 percent dioxane; 
1 to 2 percent t-amyl alcohol; 
0.3 to 0.6 percent nitromethane, or a mixture of nitromethane and 
nitroethane containing up to 75 volume percent nitroethane; 
0.6 to 0.8 percent butylene oxide.

DETAILED DESCRIPTION OF THE INVENTION 
A series of glassware experiments were performed in the laboratory to 
determine the feasibility of a dioxane/t-amyl alcohol system as the 
primary aluminum inhibitor. Also, a nitromethane/nitroethane combination 
was investigated as the secondary metal stabilizer. The following 
abbreviations will be used throughout: Diox = 1,4-Dioxane, TAA = t-amyl 
alcohol, BO = 1,2-butylene oxide, NM = nitromethane, NE = nitroethane, 
bottom = liquid phase, top = vapor condensate phase. 
The following 1,1,1-trichloroethane solutions were formulated for testing 
(all concentrations are as volume percent): 
______________________________________ 
Formu- 
lation 
Code # Formulation Composition 
______________________________________ 
A 3.2% Diox, ------, 0.75% BO, 0.4% NM 
B 3% Diox, 1% TAA, 0.75% BO, 0.4% NM 
C 2% Diox, 2% TAA, 0.75% BO, 0.4% NM 
D 2% Diox, 2% TAA, 0.75% BO, 0.2% NM, 0.2% NE 
E 2% Diox, 2% TAA, 0.75% BO, ------, 0.4% NE 
F 1% Diox, 3% TAA, 0.75% BO, 0.4% NM 
G ------, 4% TAA, 0.75% BO, 0.4% NM 
______________________________________ 
DESCRIPTION AND RESULTS OF EXPERIMENTS 
There are three steps in this series of experiments: (1) partitioning; (2) 
aluminum hot scratch; and, (3) 7-day reflux. 
(1) Partitioning (Table I) -- each formulation is distilled into two equal 
fractions (top and bottom) to obtain solutions with inhibitor profiles 
similar to that found in vapor degreasers. Adequate concentrations of 
inhibitors in both the boiling liquid phase and the vapor phase of a vapor 
degreaser is a very important requirement of a good inhibitor package. 
Therefore the use of inhibitors with proper boiling point ranges and 
partitioning profiles is important in designing an adequate inhibitor 
combination. Various combinations of dioxane, t-amyl alcohol, butylene 
oxide, nitromethane, and nitroethane dissolved in 1,1,1-trichloroethane at 
various concentrations were distilled into two equal fractions (liquid and 
vapor phases) to obtain inhibitor profiles from solutions and vapors 
similar to that found in vapor degreasers. The resulting inhibitor 
concentrations were obtained by gas chromatographic analysis. Listed below 
are the average partitioning from the results obtained in the partitioning 
of the compositions listed in Table I: 
______________________________________ 
% In Vapor Phase 
% In Liquid Phase 
______________________________________ 
Dioxane 27 73 
t-Amyl Alcohol 
42 58 
Nitromethane 
62 38 
Nitroethane 34 66 
______________________________________ 
It can be seen that the distribution of a combination of dioxane and t-amyl 
alcohol would afford superior protection in both phases than would dioxane 
alone. Also, it is evident that a 50/50 mix of the two nitroalkanes would 
give almost equal protection in the two phases. 
(2) Aluminum Hot Scratch (Table I) -- a series of hot scratch tests were 
run with 2024 aluminum coupons (Al/Cu alloy) using each original 
formulation and each top and bottom fraction. This test demonstrates the 
ability of a stabilizer system to inhibit the 1,1,1-trichloroethane 
reaction with the aluminum in both the liquid and vapor phases. 
Specifically, 50 cc of the formulation is placed in a Pyrex petri dish (9 
cm diameter by 2.5 cm deep) and placed on a hot plate. The solvent is 
allowed to heat to just below rolling boil and then taken off the hot 
plate. A 2024 Al coupon (21/2 .times. 1/2 .times. 1/8 inches thick) is 
immediately placed in the petri dish and the surface of the coupon is 
scratched with a stylus while the coupon is submerged. Three scratches are 
made lengthwise of the coupon and five scratches across the coupon. The 
petri dish is then removed from the hot plate, covered, and observed for 
one hour. After one hour a "scratch rating" is given to that solution 
according to the appearance of the scratch sites: 
______________________________________ 
"Scratch Rating" 
Description 
______________________________________ 
0 Scratches are completely inhibited 
with no reaction products visible 
to the eye. 
1 Scratches immediately cure with 
isolated sites of reaction product. 
2 Scratches rapidly cure but with 
some formation of reaction products. 
3 Scratches slowly cure with much 
formation of reaction products. 
4 Little inhibition at scratch sites 
with a slow continuing reaction. 
5 "Runaway" reaction during the 
one-hour observation period; the - solution turns black, 
HCl is gener- 
ated, and a fast ongoing reaction 
is present at scratch sites. 
______________________________________ 
TABLE I 
______________________________________ 
Partitioning Hot Scratch Rating 
Form. Bot- Bot- 
# Inhibitor 
Original Top tom Original 
Top tom 
______________________________________ 
% Diox 3.30 1.78 4.73 
A % NM 0.54 0.66 0.42 0 0 0 
% BO 0.71 0.83 0.59 
% Diox 2.96 1.65 4.20 
B % TAA 1.06 0.90 1.20 0 0 0 
% NM 0.53 0.63 0.44 
% BO 0.71 0.83 0.57 
% Diox 1.99 1.04 2.95 
C % TAA 1.93 1.60 2.17 0 1 0 
% NM 0.50 0.63 0.38 
% BO 0.72 0.83 0.60 
% Diox 1.95 1.13 2.87 
% TAA 2.04 1.79 2.20 
D % NM 0.25 0.35 0.21 0 2 0 
% NE 0.21 0.17 0.29 
% BO 0.71 0.82 0.62 
% Diox 2.20 1.17 2.99 
E % TAA 2.02 1.73 2.21 0 3 0 
% NE 0.44 0.29 0.58 
% BO 0.71 0.80 0.60 
% Diox 1.06 0.56 1.52 
% TAA 2.73 2.31 3.16 
F % NM 0.52 0.70 0.36 1 2 0 
% BO 0.71 0.82 0.62 
% TAA 3.71 3.07 4.34 
G % NM 0.42 0.60 0.50 4 5 3 
% BO 0.72 0.81 0.60 
______________________________________ 
It is observed that: 
1. As the dioxane concentration decreases and the t-amyl alcohol increases, 
the ability of the formulation to inhibit the solvent/aluminum reaction 
decreases. 
2. The bottom fraction aluminum hot scratch ratings are better than the 
ratings for the top fractions due to the higher total primary metal 
stabilizer present, caused by the partitioning behavior of dioxane and 
t-amyl alcohol. 
3. More protection is afforded due to better partitioning in the vapor 
phase utilizing dioxane/t-amyl alcohol combinations rather than dioxane 
alone. 
4. Substitution of nitroethane for nitromethane (#C vs. #E) results in less 
protection in the top fraction due to partitioning of nitroethane favoring 
the bottom fraction. 
5. A 50/50 mix of NM/NE (#D) gives better distribution of nitroalkane in 
both phases. 
6. Tertiary amyl alcohol as the principal inhibitor without dioxane is not 
an adequate Al stabilizer. 
(3) 7-Day Reflux Test -- This test consists of refluxing each top and 
bottom fraction in the presence of metal chips for 7 days. It is a good 
indication of how effective a stabilizer system would be in preventing 
1,1,1-trichloroethane reactions with metals. Each 100 cc fraction was 
refluxed in the presence of two different sets of metals: (a) 5 grams each 
1100 and 2024 aluminum chips and, (b) 5 grams each 70/30 brass chips and 
iron filings. After 7 days reflux the solutions are filtered and analyzed 
via gas chromatography for inhibitor losses (Table II). 
TABLE II 
______________________________________ 
% Lost After 7-Day Reflux 
Initial With Fe+ 
Form. Inhibitor With Al Chips Brass Chips 
# Concentration 
Top Bottom 
Top Bottom 
______________________________________ 
3.2% Diox No Loss (NL) 
NL NL NL 
A 0.4% NM 2 NL 1 6 
0.75% BO NL 1 2 7 
3% Diox NL NL NL NL 
1% TAA NL NL NL NL 
B 0.4% NM 5 11 5 13 
0.75% BO 2 2 11 14 
2% Diox NL NL NL NL 
2% TAA NL NL 6 NL 
C 0.4% NM 1 NL 5 5 
0.75% BO 2 3 19 12 
2% Diox 4 NL 7 NL 
2% TAA 9 NL 6 NL 
D 0.2% NM 11 10 17 20 
0.2% NE 9 NL 15 4 
0.75% BO NL 4 13 10 
2% Diox 3 NL NL NL 
2% TAA NL NL 6 NL 
E 0.4% NE NL 19 NL 4 
0.75% BO 20 58 12 6 
1% Diox NL NL NL NL 
3% TAA NL NL NL NL 
F 0.4% NM 12 NL 13 NL 
0.75% BO 2 2 17 17 
4% TAA NL 1 3 40 
G 0.4% NM 8 44 3 40 
0.75% BO 3 41 24 98 
______________________________________ 
it is observed that: 
1. Inhibitor losses of &lt;20 percent during the 7 days are considered 
acceptable since the hot scratch tests show protection, i.e., ratings of 
0-2, while losses of &gt;20 percent are considered to have failed in 
preventing metal/1,1,1 reactions since the hot scratch tests show lack of 
protection. This pass/fail inhibitor loss level is not entirely arbitrary 
but is based on our wide experience with inhibitor system behavior in 
industrial vapor degreasing where stabilizer losses of greater than 20-25 
percent indicate some solvent decomposition. 
2. Comparing #C and #E, it is evident that NE alone is not as effective a 
secondary inhibitor for Al/ 1,1,1 reaction as is NM alone. However, an 
NM/NE mix (#D) is an effective secondary Al stabilizer. 
3. TAA alone is not as effective as metal/1,1,1 primary inhibitor as is 
DIOX alone (#G vs. #A). 
4. Combinations of DIOX/TAA do prevent metal/1,1,1 reactions (#B, #C, #D, 
and #F) and afford better overall inhibitor distribution in top and bottom 
phases. 
DEGREASER TEST 
The following formulation was tested in a laboratory-sized vapor degreaser: 
0.72 percent BO, 1.65 percent TAA, 2.58 percent DIOX, 0.46 percent NM, 
balance 1,1,1-trichloroethane. This degreaser had a 4-gallon boil sump and 
a 3-gallon clean dip side (fed from condensed solvent vapors). The 
degreaser was run at the solvent boiling point uncovered, 24 hours/day, 
for 24 days. Daily additions of fresh solvent were added to maintain a 
constant volume. Every effort was made to simulate actual degreasing 
operations and to subject the solvent formulations to many of the stresses 
that commonly occur in the field. Various metal alloys (100 g each) were 
placed in both the boil sump and warm dip. These metals are 2024 aluminum 
turnings, 70/30 brass turnings, and coarse steel wool; all of which expose 
a large metal surface area with potential reactive sites to the solvent. A 
lubricating oil (commonly used in metal machining operations) was added to 
the boil sump (constituting about 10 percent of the liquid volume of the 
boil sump). Finally, water was added to the boil sump on the 18th day of 
the test (constituting about 1 percent of the total degreaser charge). 
ANALYTICAL TEST PROCEDURE 
Both the boiling sump and the warm dip tank were sampled about every other 
day. Inhibitor distribution profiles were than obtained by vapor phase 
chromatography. Also, some of the samples were analyzed via emission 
spectroscopy for metal ion concentrations (Al, Cu, Fe, Zn). This reveals 
any metal corrosion problems and potential reactions between the solvent 
and particular metals due to inadequate stabilization. 
RESULTS OF DEGREASER TEST 
The distribution of the four inhibitors in the boiling sump and the warm 
dip tank is detailed in drawings, FIGS. 1 through 4. The partitioning of 
the inhibitors followed expected patterns and there were no unusual losses 
during the 24 days. 
Results of metal ion analysis are listed in Table III. The low levels of 
metal ions present in the solvent samples indicates negligible reaction 
between the metal chips and the solvent. Thus, the 24-day vapor degreaser 
test was successful and this combination of inhibitors provides excellent 
stability. 
TABLE III 
______________________________________ 
Metal Analysis 
During Degreaser Test 
ppm ppm ppm ppm 
Sample Description 
Fe Cu Al Zn 
______________________________________ 
Virgin formulation 
&lt;1 &lt;0.2 &lt;1 &lt;3 
Warm dip tank after 18 days 
&lt;1 &lt;0.2 &lt;1 &lt;3 
Boiling sump after 18 days 
&lt;1 &lt;0.2 &lt;1 &lt;3 
Warm dip tank after 24 days 
5 0.2 &lt;1 5 
Boiling sump after 24 days 
7 0.4 &lt;1 5 
______________________________________ 
DEGREASER TEST 
A 2 .times. 51/2 foot two-chamber, open-top Manpro vapor degreaser was 
charged with a stabilized 1,1,1-trichloroethane solvent having the 
following composition: 
2.5 volume percent 1,4-dioxane 
1.5 volume percent t-amyl alcohol 
0.15 volume percent nitromethane 
0.15 volume percent nitroethane 
0.75 volume percent 1,2-butylene oxide. 
25 Gallons to the sump, 31 gallons to the warm dip and 29 gallons to a 
still associated with the degreaser. The degreaser was operated for 38 
days. Solvent was pumped to and from the still although the still was not 
operated until the 22nd day of the test run. Solvent make-up was added on 
the 9, 14, 17, 24, 30 and 34 days and 1/2 gallon of a white cutting oil 
added on each of the 8, 9, 10, 13, 14, 22, 23, 24, 27, 30 and 35 days of 
operation. On the 16th day metals were added to the sump and the warm dip, 
viz; 
______________________________________ 
Warm Dip Sump 
______________________________________ 
2024 Al 200 gm 200 gm 
Steel wool 65 gm 65 gm 
Mossy zinc 500 gm 300 gm 
70/30 Brass chips 
500 gm 500 gm 
______________________________________ 
At the end of 38 days the test was stopped, the metals and solvent 
examined. The test was considered successful as a result of this 
examination. 
Samples of the final composition in the warm dip and sump were taken and 
each sample subjected to reflux for seven days with metals as follows: 
One hundred milliliters of each compartment were refluxed with either 5 
grams each of 2024 Al chips, 1100 Al pellets and iron filings or 5 grams 
each of zinc fines and 70/30 brass. The aluminum and iron showed no 
evidence of attack although the zinc and brass did evidence a small amount 
of corrosion.