CA1049568A - Stabilized methylene chloride - Google Patents

Abstract

ABSTRACT
Diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylenes and optionally methyl alcohol in admixture with methylene chloride have been found to prevent degradation of methylene chloride in the presence of metals, metal halides, combin-ations thereof, and aliphatic compounds. Reactions of aliphatic organic compounds with said metals, metal halides and combinations thereof to form products which result in deterioration of methylene chloride are inhibited. A
method for vapor degreasing metals with the stabilized methylene chloride is described.

Description

~1~49~
BACKCROUND OF THE INVEMTION

Methylene chloride is a highly versatile and useful -solvent for various industrial applications at both normal and elevated temperatures. A particularly important industrial use is the vapor degreasing of metals. Methylene chloride is known to be more stable than other chlorinated hydrocarbons solvent~
such as perchloroethylene, trichloroethylene and methyl chloro-form when the solvents are used in unstabilized condition. For example, methylene chloride is more resistant to oxidation, ;
10 hydrolysis and pyrolysis than other chlorinated solvents and ;
: ..
does not substantially react with aluminum in the aluminum scratch ~
test commonly used to indicate unstabilized or minimally stabil- -ized methyl chloroform. In addition, methylene chloride may be used to greater advantage ln vapor degreasing of metals than `~

other known degreasing solvents since it may be used effectively ~
,. :,' ,: :-, ~, ", .:

~''.'` '' :`

., ,~ .
.~

:, . .:
`''.,; '' 3~ ,`''~.' .
, ~,

-2-- ' ,': '' .

` `` ' ~49S68 at lower temperatures due to its lower boiling point and ex-cellent stability. Methylene chloride is particularly desirable for such degreasing operations since it is substantially resistant to photochemical activity and therefore does not con-tribute to air pollution by smog formation. Methylene chloride disadvantageously suffers degradation by reaction of aliphatic organic compounds such as trans-dichloroethylene l,l,l-tri-chloroethane and carbon tetrachloride with said metals, metal halides and combinations thereof. The reaction products are colored tar-like masses which render the methylene chloride un-suitable for use as a solvent, particularly in vapor degreasing -of metals. Aliphatic organic compounds of this nature and metals such as aluminum, iron and zinc, their halides and com-~ . ' ,.
binations are generally introduced into the methylene chloride from various cutting oils and lubricants used in metal fabri-cating operations which are carried over into the methylene chloride solvent during vapor degreasing or other cleaning of the fabricated metal parts. Solvent manufacturing, handling and stora~e equipment is another source for introduction of such impurities. To prevent degradation and other types of deteriora-tion such as oxidation, hydrolysis and pyrolysis which may occurin some instances, it has been the practice to incorporate minor quantities of various organic compounds into methylene chloride, which compounds act as stabilizers to substantially prevent such degradation. It is desirable to provide methylene chloride ~ , stabilized to effectively prevent degradation in various appli-cations, and the demand still exists for a low cost stabilized methylene chloride composition that can be easily prepared and which provides optimum stabilization under many different opera~
ting conditions ,;~
'''`'~

-3- ~
"' .. ~ ~, , - .

~0~956~
SUMM~RY OF THE INVEMlION

An ob;ect of this invention is to prevent deterioration or degradation of methylene chloride in association with metals, metal halides and combinations including aluminum, iron and zinc, halides of said metals and an aliphatic organic compound capable of reacting with these metals, metal halides and combinations thereof in the presence of methylene chloride.
A further ob~ect of this invention is to provide a stabilized methylene chloride composition in which the stabilizerc ~ -are low in cost and capable of being incorporated with ease into the methylene chloride.
A still further ob~ect of this invention is to provide a process for the degreasing of metals by contacting the metals with methylene chloride stabilized to prevent degradation of the : .:
methylene chloride in the presence of metals, metal halides and combinations thereof including aluminum iron and zinc, halides of ;
said metals and combinations and aliphatic organic compounds Which react with the metals, metal halides and combinations thereof.
These and additional objects of the present invention will become apparent to those skilled in the art from the des~

cription and claims which follow. ` --- ,. ~. -.

DESCRIPTION OF THE PREFERRED EMBODIMENTS ~
. . - , The ob~ects set forth above have been found to be ~ ;

attained by providing a composition consisting essentially of ~ ~
.
methylene chloride containing stabilizing amounts of from about 0.001 to about 2.0 percent by weight of the methylene chloride , ~ .
'',`'; .
..... . .
. ;. , .
' : '' ~` : ~ ,' .. . . . ., . , . , ~ , , , ~ `\

of each of diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate; acetone, tertiary amylene and optionally methyl alcohol.
The quantity of the stabilizing agents useful in the practice of this invention will vary depending upon the conditions of use, the identity and quantity of other stabilizers incor- ;
porated into the methylene chloride and other practical operating considerations. Each stabilizing agent or compound may generally ~-be used within the range of from about .001 to about 2.0 percent and preferably from about 0.002 to about 1.0 percent by weight of the methylene chloride. Although higher concentrations may be used, if desired, no additional benefit is obtained and the -cost is unnecessarily increased. While the above composition containing stabilizing agents provides optimum prevention of degradation of the methylene chloride under a variety of operating -conditions it is also possible to stabilize methylene chloride by deleting the propylene oxide depending on the stabilization required for the particular operating condition.
- ~ The stabilized composition may be used for the de~
greasing of metals by contacting the metals with the stabilized composition. Thus, the process for vapor degreasing metals com-prises contacting the metals to be degreased with the above described stabilized methylene chloride compositions wherein the '~; methylene chloride contains an admixture of stabilizing amounts f 25 of diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate, acetone, te~tiary amylene and optionally methyl alcohol. In degreasing metals with the above described preferred stabilized methylene chloride in the presence of an aliphatic organic compound which reacts with metals, metal ~ -, ~ :

~0495~8 ., , halides and combinations thereo~ including aluminum, iron, zinc, halides of said metals and combinations, there exists upon con-tact of the metal with the stabilized methylene chloride a com-position comprising me~hylene chloride, a stabilizing amount of from aboutO.OOl to about 2.0 weight percent of the methylene chloride of each of diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylene and optionally methyl alcohol and an aliphatic organic compound . ~
which reacts with said metals, metal halides and combinations.
The metals,metal halides and combinations may be present from any source such as chloride ~ormed by drilling or other machining o~ aluminum or aluminum-containing materials with various working fluids such as cuttin~ oils, lubricants and the like, or aluminum c~loride may be present ~rom the reaction of methylene chloride 1~ with aluminum. The degradation of methylene chloride in the -~
presence of aliphatic organic compounds such as trans-dichloro-ethylene, carbon tetrachloride and l,l,l-trichloroethane, metals, -metal halides and combinations may be inhibited by admixingme~-Y~
' chloride with the above noted quantities of diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate, acetone 9 tertiary amylenes and optionally methyl alcohol.
In order that those skilled in the art ma~ readily understand the present invention and certain specific embodiments by which it may be carried into e~ect the foll~ing illustrative examples are presented.
In Examples 1 to 4, inclusive, an aluminum reflux stability test was - carried out by placing 190 ml o~ substantially water free methylene chloride ~ -~
containing 5 Vol. % of a commercially a~ailable l,l,l-trichloroethane and the same solvent system containing the stabilizin~ coDosition of this in~ention.
In Examples 3 and 4, respectively, anhydrous aluminum chloride and anhydrous 3 ferric chloride were added to the solvent system in a flat bottom 300 ml ':

. , ~1~4956~
boiling flask fitted with a condenser. About 1.0 gram of 20 mesh granular aluminum ~as placed in the liquid in the ~lask and an all~inum coupon about 1- x 6 cm was suspended in the condenser. During the extended period o~ rerlu~
the sol~ent vapor surrounded, condensed, and dripped ~rom the suspended strip.
- In all cases the pH and alkalinity content, as ~aOH, trere determined after the system was refluxed for varying time periods noted, The results of the various tests are sh~ m in Table I bel~w. ~ - ~
...
.
' ' . . . . ., ~

.

~ :
,., ~, - , . ' --. '' ''.`' ;''--.
r ~ , . : ~ . . . ' , ' :i ~ ' ' ' ', , ' ' ' ' ' "' ' 1 :' i ' ' . ' . ' ''I - ' ~ . ' 'i. . ' ' .'' .. ' ~ ' ' ',':
.', ' ' ' ' .
:, i. ' ' ' ' ' , ~: . -. , . . : . . ' '. . ' .

.

,' ' ' ' . ~ ' : ' . . ' ' ~ - ' ' . ~. . . - . :
" .. ` ., ' ' . . ' . ' ' , ' -- : -7-. . ~ . .. - ~
~ .
.. . ,: ,., .... -~: , :
. .

~04956~ : -~ ~ "
q~
o ~
o ~ C~ ~ o ;~
a v v~ m ~ v *
. .: . .
a~ ~
~a ri a a~ o o a) a ~ ~ .
VV V ~;
`~: ' ~ ~ ~ ~ V ~ O

''.~ .
V ~ ~ Lr ~
o V So ' ' ~n~
, ..~' .. .
H O ~ td C~ \ ~ : .
~ '~ ~i~ ~1 ~1 "
v h I I . :
v o rl Ha) $~
~ E~ "
l ~ ~rl .~ O .~ a) , O E~ ~1 ~ ~1 o ~1 0 v ~~ ¢ ~ o ~ o ~ -E-l H :. :. . :
~$ H
`. .
¢ u~
o ~ ~ o o g ~ ~ ~ ~ Q) a~ ~ ~ . ~ . :
E~ h a) ,1 ~1 ~ o ~ ~ +~ . a) O
V ~1 ~ ~ ~ ~ X ~ ~ "
u~ V 'V O ~ ~1 ~ O X ~
hu~ v ~o h~ ~ ~0~ ~~ ~,~ ~ :
F~l ~ ~ ~ N ~3: 0 +' r~ ¢

a) P ~ ,~ O L~ ~ ~ O
P ~ ,~ o u~ o a) 1~I ~o ~
r-l ~ ~ ~ O ~rl O ~ O ~1 ~ C~l ~ O C~ O ~ ~
u~ ~ ¢ u~ o 1:~1 0 ~; O ~ O ~:1 0 ~ O ¢ O E-l O ~
.; ' ~1 .. ~ ' ' i~ O .': ':
~d z; '`~

': ' . , ~049568 ~ ~,;'i o o ~
iGi r--i ~.'i o ~ ~ o ~ . , ~-i ~~'i ~i a O O r-i O r~
v~ v ~ v~
~. g :...... .

a~ o o : , ~i iG~ ~ ~ ~`i , !
~ ~ ~i i~i i_' O O O O O 'I ' ' VVV ~ ~ ~
~'"~ ''" ' .
f .
~f ~ ~ "f N ~
1~ . , `, CO C~
,_ ~i ~O ~ ':
~j h q~ ~i C~
O ~ ~ :
V
H O
~1 '' ~
m ~i ~ ~i G ~,) ~ ~i ¢ ~? ~
r-i I ~i ~i C.`i ~i r~ ~ ~
O ~ ~ h ~ ~ 7~ ~i p ¢ L~E~ a, ~i i~i ,, , ,.
. ' : C'l t~ 0 :
~ O ~o i o ~i a,'i ,Q i~i ~ V ~' ~ i~i ifi . v ~ ~ .
,~ -i ~ O bD ~i ~ 3 0 b~
U~ ~ r'i ¢ ~ 1~
V~ ~ ri O k d O ~i ~ri O ki ,~i S-' ~ ~ G ~ ~
.~`i U~ ~ O O O U~ ~ O O p ~
~i d d G i_i ~ ~ i O
-1-'' ~
P a~
~i ,~ ~ O ,~ O ,5~i .i O d ~i ,~' i~ i d d ~ ,Q ~ td M~ v~ ~ d d d ~ u~ ~ d d d :, .` `i . '~.
d _g_ , : ~ , . , , :-' ,~, , . , . . . : ,~

lO~9S~8 In Exa~ple l deterioration of the solvent system occurred due to the reaction of aluminum with the contained l,l,l-trichloroethane. In F~ample 2 the addition of the stabilizing compos-ition of this invention to this solvent system prevented such deterioration and in Example 3 even after about O.O~ grams anhydrous aluminum chloride was added and the system refluxed an additional day, In E~ample ~ even with the further addition of about 0.04 grams anhydrous ferric chloride and an additional seven days of refluxing no corrosion of the aluminum in the flask or the condenser was observed.
The inhibition of the degradation of methylene chloride by the reaction between 1,1,1-trichloroethane and aluNin~lm and metal salts by the stabilizing composition of this invention is especially surprising and unexpected when it is realized that the stabilizers included in the commercial vapor degreasing grade l,l,l-trichloroethane to prevent reaction of the l,l,l-trichloroethane with metals and/or metal salts in the presence of chlorinated 15 solvents failed to inhibit the degradation of the methylene chloride. Only ~-when the stabilizing composition of this invention was admixed ~7ith the methylene chloride containin~ the stabilized l,l,l-trichloroethane was degradation of the ;
methylene chloride prevented.

:

'' '. ' .
: :, .

~04956~ .
In Table II hydrolytic stability tests were made by placing 150 ml. of methylene chloride in Example 5 and 150 ml.
of methylene chloride containing the stabilizing composition specified in Example 6 into a 300 ml. boiling flask. The flask was fitted with a Soxhlet extractor equipped with a syphon break and a condenser vented to room air. Fifty milliliters of the solvent of each Example were first intro- -duced into the Soxhlet and -50 ml. of water was then added.
One gram of 20 mesh granular aluminum, about one gram of 30 mesh granular zinc and about 0.1 g of iron powder were placed in the flask. A 2 x 7 cm. zinc coupon of known weight was positioned in the Soxhlet and a 2 x 7 cm. weighed steel ,.. . .
coupon was mounted in the condenser. The contents of the flask were refluxed for the period of time specified by ~;
heating the boiling flask with an electric heater. At the end of the reflux period the pH and alkalinity, as NaOH, of the solvent contents of the Soxhlet and of the flask were determined from a portion of the aqueous phase obtained by extraction of the solvent with an equal volume of neutral distilled water after the solvent system had been refluxed for the time specified. The zinc and iron coupons were cIeaned of any accumulated corrosion products, weighed and the difference in initial and final weight recorded as weight loss.
The results are shown below in Table II.

~-:

r:

104~35~;~
. , .', r~
u~ 8 o ~r o _ ~ ~ .

~ ~ .. ..
~ X

o _ ~U
o ~ ~ ~ ., ,~ ~ ,~ , . .
, ,~
8 u~ ~ -H
P;
u~ ~ xl al rd O
Z U~

X ~ X ' ': ", ' ,~

~! 1:4 H O t` I`
~ m u~
Wl 2 E~

W 'd ~ O N ~1 0 't~ 'd O u~
l u~ ~r~ a~ h u~ r l ~ r l ~l ~ a) O
.` U~ ~ 0 ~ r~ ~ ~ r-l O ~ 0 0 ~ ~ ~0 ~ .
~' C) Q~ ~C ~ ~ R ~rl H ~ ~ r~ a~ (~ '~ r~ 5 ~ ~ ~d a) ~ a ~
~ a) ,~ o ~ ,~

:, ~ ~ ~3 ~1 o ~ ~ I O

~ ~ o~O o~ 0\0 ~
u~ ~ o . dP o\ o\ o~ o~o , ,~ ~ ~ ~ ~ o 3 ~ ~ ~ :

Q ~ ,~ o o o o ~ ~ ~ o u~ ~ o u) u) u~ :
,~ ~ ~ ,~ o o ~ ,~ ~ o ~ ,~ ~ o ~ o . ,, o Q~
:~ o o o o ~ ~ 3 0 0 0 0 0 0 0 ,al ~ u~ .
: X ':

:' ~ '' , .

~956~3 :
The superiority of the stabilizing composition of this invention is evident from a comparison of the results of Example 6, the composition of the present invention, and Example 5, a stabilizing composition of known good stabilizing characteristics formulated by the applicant herein. Much less corrosion of the zinc coupon in the Soxhlet and the iron coupon located in the condenser occurred in the use of the composition of this invention during the 15 day reflux period.
In Examples 7 and 8 of Table III reflux stability tests were conducted by following Federal Specification O-T-236b modified by the use of 200 ml. of the solvent system in place of 100 ml. and by positioning a 6-watt untraviolet lamp about one inch from the vapor tube of the Soxhlet extractor. A
300 ml. boiling flash was fitted with a Soxhlet extractor, a condenser connected to the extractor, about 1.0 gram of granular zinc and about 0.5 ml. of water was added to the flask and a 2 x 7 cm. zinc coupon was inserted in the extractor and the condenser. The condenser was vented to a wat~r scrubber.
The results of the tests are presented in Table III.

~, ., , . , , ~ ' ' ~ ' ~1~49S68 U~ ~
U~ U~
o c ~, ~ ."
~ o .,~ ~, ~ ~ CO ,, ,, ~ ~ , o ~ , , - . .

a) ~o ~
U~ .,.
r~ ~ ~ ~ .
H O E~
1~ 1,1 ~ ~ , ' 1 ~
', E~ ~ , E~ E-l 2~ U~ ~ U~ . ,, ~1 H a H ~ .

H U~ _I
H p:
~1 3 El 3 .C :: -: C~ .,, ~ ` -, i O d P
': ~ : ~ o'P dP ~ ra-,~ ~ ~ ~ . :
l~ H Ei IJ ~ N ~ O ra r~
3 3 u~u~ X X ~ a n~ ~ ~1 0 ~ O ~ 40 0 ~ ~ O
2 ~ ~ o O~ h IH a) Q~ i U
u~ ~ ~ o . aJ ~ a .~ ~ ~ O ~ o ~ a~
~4 ~'o~ o ~ 'O~ O ~ 0~

~1 ,~ 3 3 r~ ~ ~1 0 ~ ~ rl .! .q .~ O o u~ ~ O u~
,~ ~ ~ o ~ ,~ o o ~ ~ ~ O ~ O
,~ ~ ~ s~m~z ~0OOOOOOO

., ~o .~
1 x ..
' . ~ .

:
,. . .

;: .

~49568 Storage stability tests of stabilized methylene chloride carried out in Examples 9 to 11 of Table 4. About 250 ml each of three stabilized methylene ~hloride compositions specified in the Examples was placed in a pint bottle contain~
ing three 1/16" diameter x 5" rusty steel rods and two 1/2" x 6" x 0.003" gauge rusty steel coupons. About 1.32 ml. (0.4 wt.~) of distilled water was added and the entire contents of the bottle thoroughly agitated at the start of the test period.
In Example 9 an additional 0.4 wt.~ was added to the bottle after one dayO The capped bottles were permitted to stand for five days after which visual observations of the steel coupons, the solvent and the surface of the solvent were made and recorded. The bottles were then uncapped and any detectable objectionable odor noted.
The results of the tests are included in Table IV.

~-" ~0~9S6~3 /~

a~
U~
U~
O ~ h P~ C~
h O
O
,1 ~ a~
~J ~ U~ S~
a~ ~ -,~
J) ~ h U~ ~
~n ~ ~
Q~ u~ h H R u~ h E~ . ., h h 3 tJ
~ .~
U O h a~ h ~ ' fd.~ ~ ~1 h ~ S
~,, aJ ~ a Q1::

~ ~ ` O ~ .,, C) O ~ "
d d ~1 h h ~1 ~ ~ h H OU~ ~, ~ O :.
8 ~ ~ ~ ~ 8 .~
~ ~ ` o `
Z a) h ,a h h ~ O ~ ~
m u~ c~ u~ ~ h C,) u~ . .
E~
~!u~ ~ .
~a In U~ n O (d E~
~n E~ ~P , ~, ~ ~ b' 1~ 3 .S~
~ ~ .

u~ ~ o'~l a) a) t~ h ~ ~ ~ u~ ~1 E( ~\ ~l rl ~ a) Q~ ~1 ~-rl ~1 ~ a~ o H ~: ~ X a ~ ~ ~ ~ ~:4 X ~
~:1a) ~1 o ~: a) ,1 Q~ rl Q, O O ~ O O
_1 :~ ~ h ~ h O ~1 a~ ~I C) ~D ~1 O ~ ~: ~ O ~ O Sl ~ O ~1 ~ ~ X ~ I Q~
E~ u~ ~ ~ a) o ~ ~ x ~ o u~ C~ a) o c~
~0~ ~ ~0 a~ a) Ql h ~) al O ~ O rl I Ql ~\
N ~: O ~ E~ ~: h I ~ ~ Z O
~ 1 O h rl rl a~ m a~
~1 ~ æ c~
,~ ~ ~Z
o o o ~ ~ o o n ~ o u~
~ U~ ~ ~ ~ O ~ ~ O O ~ ~ ~ O ~ O
U~ ~ O O ~ ~ O O O O O O O O
a~
. O~ O ~1 ': ~'z ~ ~ ~

.

., , `: :

lOg956~
The superiority of the composition of th.is invention in stabilizing methylene chloride on exposure to water and rusty steel storage conditions is evidenced by the results of Example ll as compared to the results of the tests in Examples 9 and lO in which two different stabilizing compo-sitions known in the art were used. In Example ll no uncharac-teristic odor was detected but both Examples 9 and lO had an objectionable putrid odor.
Although the present invention has been described with detailed reference to specific embodiments thereof, it is not intended to be so limited since modifications and alter-ations may be made therein which are with1n the complete intended scope of this invention as defined by the appended claims.

''' ''' ' , ~ .
: : :
'. ..

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for preventing the degradation of methylene chloride in contact with metals, metal halides or combinations thereof and an aliphatic organic compound capable of reacting with said metals, halides and combinations comprising maintaining in intimate admixture with said methylene chloride while in contact with the aliphatic organic compound and the metals, halides and combinations from about 0.001 to about 2.0 percent based on the weight of the methylene chloride of each of diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate, acetone and tertiary amylene.

2. The method of claim 1 wherein the admixture contains from about 0.002 to about 1.0 percent by weight of the methylene chloride of each of diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylene and optionally methyl alcohol.

3. The method of claim 1 wherein a material selected from the group consisting of aluminum, iron, zinc, halides of the metals and combinations thereof is present.

4. A process for degreasing metals which comprises contacting said metals with a methylene chloride composition stabilized against degradation by metal in the presence of ali-phatic compounds with stabilizing amounts of from about 0.001 to about 2.0 percent by weight of the methylene chloride of each of diisopropylamine, N-methyl pyrolle, butylene oxide, propylene oxide, methyl acetate, acetone and tertiary amylene.

5. The process of claim 4 wherein methyl alcohol is also present.