CA1177730A - Method of vapor degreasing - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A unique solvent blend and method of conducting vapor degreasing operations is disclosed, wherein synergism is obtained by the addition of a component to three known vapor degreasing solvents. The vapor degreasing solvents of the invention comprise a blend selected from the group consisting of perchlorethylene and trichlorethylene or 1, 1, 1, trichlorethylene and methylene chloride or methylene chloride and trichlorethylene. The trichlorethylene or methylene chloride component comprises about 0.1 to 90 volume percent of the total degreasing solvent, while the other component of the blend comprises the remainder of the solvent blend.
The resulting vapor degreasing solvent, has a number of advantages over perchlorethylene alone or 1, 1, l trichloro-ethane alone, or in combination with stabilizers, or tri-chlorethylene alone, or in combination with stabilizers.
Addition of either trichlorethylene or methylene chloride to the solvent blends of the invention extends the normal life of the degreasing solvents alone, or in combination with conventional stabilizers and the like. The degreasing sol-vent blend of the invention not only extends the operational life of perchlorethylene of 1, 1, 1 trichloroethane or trichlorethylene based vapor degreasing solvents, but also reduces the cost of conducting vapor degreasing operations using the conventional vapor degreasing solvents, because initial operational temperatures, for effective vapor de-greasing, are reduced. The unique solvent blends used in the method of the invention evidence unique results when used in vapor degreasing process wherein one of the components of each of the novel blends is found to stabilize the other components of the blend in the presence of contaminants en-countered in the conventional vapor degreasing process.

Description

1~ 77730 BACKGROUND OF THE INVEI~TION
With the advent of OP~C, and the high cost and short supply of hydrocarbons,'alternatives for existing vapor de-greasing solvents has intensified.
The'ordinary vapor degreasing solvents are normally chlorinated hydrocarbon ones, which meet the'criteria of having no flash point and possessing good contaminant solvency and reusability through reclamation processes.
The prior art has utilized, as the basic vapor degreas- ' ing solvent p~rchlorethylene or 1, 1, 1 trichloroethane or trichlorethylene for use in the ubiquitous vapor degreasing machine and operation. These s'o~lvents are ordinarily used in co~junction with a stabilizer which will extend the use-ful life of the vapor degreasing solvent.
In the vapor degreasing process, a non-flammable sol-vent is boiled to produce a vapor zone,' the heigh~ of whi,ch is controlled by condensing coils, Cold work is introduc d into the vapor, causes vapor condensation thereon, and the contaminant carried on the cold work, usually oil, grease or flux, is flushed off by the liquid solvent condensate. The ` contaminant, along with the condensate, is returned to the boiling sump of the vapor degreasing machine. This con-densate or distillate, then is revaporized to repeat the cycle of cleansing through condensation.
The work piece which is ~ be cleansed is held in the vapor zone until the temperature thereof reaches the vapor temperature within the vapor zone, at which time con-' densation stops. Vapor flushing is usually followed by pure distillate spray and/or liquid immersionO The cool pure distillate reduces ~le temperature of the metal surface below the vapor temperature producing a second vapor aondensation.

~1~7'~30 When the work piece again reaches vapor temperature, it is withdrawn from the vapor zone, clean and dry.
The vapor degreasing solvent is used at its boiling point in order to produce the vapor zone necessary for vapor condensation and resultant cleaning.
Where perchlorethylene or 1, 1, 1 trichloroethane or trichlorethylene either alone or in conjunction with certain stabilizers to prolong the life thereof are utilized, serious drawbacks occur.
That is, during the degreasing operations, the degreas-ing solvent is adversely affecte~ by the increasing amounts of contaminan~s finding their way into the boiling sump in that the ~oiling temperature of the solvent in the sump increases as the amount of contaminant increases. To com-pensate for this added contamination, solvent manufacturers add acid inhibitors or stabilizers in an effort to extend its vapor degreasing life.
When the temperature in the boiling sump of the vapor degreasing device reaches and exceeds a designated temperature range, normally signifying extensive contamination, depletion of the stabilizers is nearly complete and additional usage of the solvent is not recommended because of acidic breakdown and failure. For pe~chlorethylene this range is about 256-258F
whereas for 1, 1, 1 trichloroethane this range is about 172-174F; whereas for trichlorethylene it is 195-198F.
Vapor degreasing handbooks recommend that vapor degreasers be shut down and the degreasing operation terminated to allow clean-out of the boiling sump once the boiling sump temperatures reach about 256F for perchlorethylene, 172F for 1,1,1 tric~oro-ethane and 195F for trichlorethylene. The general criteria, measur-~ in other terms for solvent rejuvenation, are when the boil sump specific gravity is between 1.21 and 1 44 or has an ~77~730 acid acceptance ~alue of about 0.02 - 0.06, or wherein the pH value is between about 5~5 - 6Ø
In order to extend the life of the~solvent by as much as 50%, and to reduce the boiling sump temperature,' even with contamination present, and to provide a satisfactory vapor degreasing solvent of lower overall cost, it has been found that the addition of triehlorethylene to,perchlorethylene or m~thylene chloride to 1, 1, 1 trichloroethane, or trichlor-ethylene in an amount to reduce the initial boiling temperature of the resultant blend to about 240F, 110F to 190F
respectively ~for the resultant blends, achieves' definite attributes, while alleviating many of the detriments found in prior art uses and methods of vapor degreasing using other solvents alone or with stabilizers to extend its use-ful life.
In the United States, environment protection regulations, (~PA) dictate that a degreasing solvent may not contain more than 20% by volume of trichlorethylene. Thus, a solvent blend in accordance with this invention of about 20-10 volu~me percont of tr:iehlorethylene and 80-90 volume percent methylene chloride is efficacious and better than trichlorethylene alone or methylene ehloride alone.
In the'conventional vapor degreasing process, there ideally exists about a 45-50F temperature differential between the temperature of the inlet cooling water and the temperature of the degreasing vapors~ Thus, where refrigerated or cooler temperatures are made'available, a solvent blend of the in-vention using higher methylene chloride proportions may be utilized. In suchcases a preferred percentage of methylene chloride in the blends of the invention will be abou~ 70-90 volume percen~ disregarding environmental regulatio~s.

~177'730 The lower boiling point of the resultant blends of the invention not only extends solvent life, but also lowers energy or heating requirements since the boiling point tem-peratures of the vapor degreasing solvents of the invention are lowered.
OBJECTS AND SUr~ARY OF THE INVENTION
-According to one aspect of the present invention there is provided a method of vapor degreasing by contacting a contaminated article with the vapors of a solvent consisting essentially of trichloroethylene, the improvement which comprises, (a) adding a sufficient amount of methylene chloride to the solvent to reduce the initial boiling point of the resultant solvent blend to about 120F, (b) continuing vapor degreasing operations with the solvent blend of step (a) at reflux temperatures until the acid acceptance value of the contaminated solvent blend is within the range of about 0.01 to 0.06.
According to a further aspect of the present invention there is provided a method of vapor degreasing by contacting a contaminated article with vapors of solvent consisting essentially of perchloroethylene, the improvement which comprises, (a) adding a sufficient amount of trichloroethylene to the solvent to reduce the initial boiling point of the resultant solvent blend to about 240F., and (b) conducting vapor degreasing opera~ions with the solvent blend of step (a) at reflux temperatures and removing contaminants with said solvent until the temperatures of the contaminated solvent blend reaches about 256F.

1~7~730 DESCRIPTION OF TilE BEST EMBODIMENTS CONTEMPLATED
In the conventional vapor degreasing apparatus, a boiling chamber of sump contains a heating element thereby forming a boiling zone. Positioned above the boiling zone is a vapor condensation zone wherein condensing coils and cooling J acket may be employed to condense vapors therein. In operation on a straight vapor cycle, the work piece to be cleaned is ]owered into the vapor zone and is washed by solvent vapors which condense on the work piece surface. The resulting condensate flows from the surface of the work piece together with the contaminants and drips back into the boiling solvent contained in the boiling chamber or boiling sump.
When the work piece temperature reaches that of the vapors in the vapor zone, condensation and cleaning action ceases.
In some instances, vapor losses ofEthe solvent contained in the boiling chamber or boiling sump are maintained at the operational level by addition of solvent, and by the continuous return of the condensate from the work piece being cleaned, which, of course, will also take with it into the boiling sump or boiling chamber, contaminants comprising oil, grease and the like.
In this type of vapor degreasing apparatus, which is of the ~onventional type, vapor degreasing may continue until such time as adversely high temperatures resul-t in the boiling sump 11~7~3(~
or boiling zone. This is for the reason that, while the initial boiling point of the boiling sump or boiling zOnQ
may be that of the degreasing solvent being used, vapor degreasing action may only continue until such time as the contaminants in the boiling sump or boiling zone raise the temperature to certain points depending on solvent mixtures and as will be seen hereinafter, at which time breakdown and failure of the solvent may result. When this occurs, the vapor degreasing operation must be shut down, and the boiling sump cleaned out, and the vapor degreasing solvent replaced or subjected to a reclamation process, in order to remove the contaminants therefrom.
~ necessary property or a vapor degreasing solvent is its ability to be reclaimed, that is, to be subjected to a process that separates the solvent from the solvent-contaminant mixture so that the solvent may be used again.
That process which is used throughout the vapor degreasing industry is distillation. The solvent blends of the invention may be reclaimed, or distilled for re-use.
In the normal course of vapor degreaser operation, the solvent condensate is returned to the boiling solvent-contaminant mixture in the boil sump. A vapor degreaser is commonly design~d by the vapor degreaser manufacturer to also function as a solvent recovery still. To functiDn as a sol-vent recovery still, design~ted valves are opened and/or closed to cause the solvent condensate to be directed to sol-vent storage tanks or to drum storage instead of being returned to the boil sump . The solven'c is thus separated from the solvent-contaminant mixture and, following removal of the residual contaminant from the boil sump of the vapor degreaser, the solvent may be transferred back into the vapoF degreaser ~or re-use.

1177~30 A second and less frequently used procedure for the dis-tillation of vapor degreasing solvents is the use of a sepa-rate still.
Conventionally, a simple one-plate still, such as commonly found and as those of ordinary skill in the vapor degreasing art are familiar, will do a satisfactory job of reclaiming chlorinated solvents. Such units may be operated on a batch basis or can be coupled directly to the degreaser and operated continuously. With the latter arrangement,con-taminated solvent is pump~d directly to the still from thedegreaser. Solvent leveI in the still is maintained by an automatic level control which actuates a solvant transfer pump. This affords maximum cleaning efficiency in the de-greaser while minimizing shut-down time to clean the unit and 1~ refill with fresh solvent. Many solvent recovery stills use live steam injectinn to maximize efficiency.
Thus,by usual and conventional distillation, the solvent blends of the invention are recovered for reuse in the practice of the invention.

Where trichlorethylene alone or with stabilizers is utilized, its boiling point is approximately 188F., and its use in a vapor degreasing operation wherein the boiling sump approached 250F. would be contraindicated because of its well-known tendency for thermal decomposition or pyrolysls at this temperature.
However, contrary to what the prior art would indicated, and in accordance with this ~nvention, a solvent blend com-prising perchlorethylene and trichlorethylene in an amount sufficient to reduce the initial boiling point of the resultant solvent blend to about 240F., has been found to satisfactorily extend the useful life of a vapor degreasing solvent in a vapor degreasing operation, subject to the contaminatinn referred ~177730 to hereinabove. ~ttendant energy savings result because of th~se lower temperature requirements.
Thus, it is has been found by the addition of trichlo~-ethylene in about the range of about 0~1 volume percent to 50.0 volume percent to perchlorethylene, a blended solvent is obtained which has a lower initial boiling point than perchlorethylene alone, and wherein the resultant solvent blend is capable of operating at temperatures substantially higher than those that would normally be predicted for trichlorethylene alone without pyrolysis. The preferred range for ~he solvent blend in order to increase useful life there-of is 81 volume percent for perchlorethylene and 19 volume percent for trichlorethylene.
The solvent blend comprising the perchlorethylene and trichlorethylene provides a constant boiling point solvent exhibiting stable operating characteristics in a vapor de-gr0aser. The theory which would appear to explain the lack of fractionati~n of the two disparate solvents, making up the solvent blend of the invention, would appear to be as a re-sult of Raoult's Law.

By addition of methylene chloride in about the range of about 0~1 volume percent to 90.0 volume percent to 1, 1,1 trichloroethane or trichlorethylen~, a blonded solvent is obtained which has a lower initial boiling point than 1, 1, 1 trichloroethane or trichlorethylenealone. The solvent blend comprising the 1, 1, L trichloroethane and methylene chloride or trichlorethylene and methylene chioride provides a constant boiling point solvent exhibiting stable operating characteristics in a vapor degreaser. The theory which would appear to ex-plain the lack of fractionation of the two disparate solvents,making up the solvent blends of the invention, would appear to be as a result of Raoult's Law.

~7~730 In accordance with Raoult's Law, groups of similar sol-vents are classified in specific classes andin accordance with theory, a solvent blend of two or more components of the same ' class of solvents will operate in a sta~e of total reflux (applied to vapor degreasing where the blend is boiled, vapors condensed, and condensate returned to boiling sump) and equilibrium will result wherein the temperatures and compo-sitions of both the vapor phase and the boiling liquid phase are constant.
In order-to comply with the criteria of the application of Raoult's Law, in the operation of the instant invention, minor losses of vapor and condensate in the vapor degreasing operation are'replaced through daily solvent make-up with solvent comprising the solvent blends of perchlorethylene and trichlorethylene or 1, 1, 1 trichloroethane and ~ethylene chloride or trichlorethylene and methylene chloride.
In order to ascertain the functionability of the applica-tion of the'theory behind the solvent blends as being appli_.
cable to the practice of the inventian, a commercially available grade of perchlorethylene, on one hand and 1, 1, 1 trichloroeth~ne on the other was re~luxed with different volumes of oil until acid breakdown of the solvent occurred.
The length of time which it took for the solvents to reach the breakdown point was recorded in each instance. Thereafter, a solvent blend of perchlorethylene and trichlorethylene and 1, 1, 1 trichloroethane and methylene chloride, in accordance with the volume percentages set forth herein, was similarly tested under the same conditions.
It was found that the perchlorethylene-trichlorethylene or 1, 1, 1 trichloroethane-methylene chloride solvent blend had an extended life and the initial boiling point of the solvent blend was lower than that of perchlorethyiene or 1, 1, 1 trichloroethane alone. In conducting the tests, a neutral _ g 11'7773() mineral oil is used in varying amounts to provide different boiling temperatures in the boiling zone or boiling sump to determine acid deterioration of the solvent. Esch of the solvents and solvent/oil blends was boiled at total re-flux for a number of days. That is, 500 milliliter flasks were connected to condensing columns measuring 400 millimeters in jacket length. These were, in turn, connected to water sources by 3/8 inch tubing to continuously cool the columns.
For maintained heating, the flasks and solvent solutions were placed on a 1~ inch square hotplate.
During the test periods and at selected intervals, each , of the samples was tested for acidic deterioration by determin-ing its acid acc~ptance value in accordance with A.S.T.M.
procedure D-2942. In this test method, a known amount of standard hydrochlorination reagent is used and ~ acid acceptance value is calculated following titration with 0.1 N
NaOII. The acid acceptance valua of virgin vapor degreasing grade l, 1, ~ trichloroethane is in the range of 0.10 to 0.20%.
The acid acceptance determinations use 10 and 25 millimeter volumetric pipettes to transfer the solutions into 400 millimeter beakers. The pH of the solution during the tests was checked further using a digital pH meter in conjunction with a stirring rod and magnetic stirrer in order to obtain a homogeneous mixture.
Solvent manufacturers usually recommend that perchlor-ethylene or 1, 1, 1 trichloroethane be cleaned out from the vapor d~greaser when the acid acceptance value drops to the range of about 0.02 to 0.06% for the first named solvent blend and 0.03 to 0.065' for the latter which correIates with oil contaminatiDn of about 25% to 30~. in the tests, the solvents were refluxed beyond the recommended clean out values to total acidic decomposition to determine maximum life of the solvent. ~-, 1~77730 , These tests are tabulated in the following Table I and IA :
TABLE I

Sample Oil, % Boil ~ours of Refluxing Volume Temp. Before Acidic Failure Run 1 Perchlorethylene 0 250F 2088*
Blend, perc./tri. 0 240F 2088*
Run 2 Perchlorethylene 25% 258F 1560 Blend, perc./tri. 25~ 247F 1920 Run 3 Perchlorethylene 40% 260F 432 Blend, perc./tri. 40~ 252F 696 Run 4 ~ . ~
Perchlorethylene 50~ 264F 192 Blend, perc./tri. 50% 254F &24 *Test discontinued at this time . Acid acceptance values of the two samples showed no significant difference and were both in the 0.01 to 0.02% range.

1 77~73() TABL~ IA

Sample Oil, ~ Boil Hours of refluxing Run 1 Volume Temp. before acidic ~ailure 1, 1, 1 trichloroethane 165F 3288*

Blend, 1, 1, 1 trich-loroethane/methylene 0 138F 3288*
chloride Run 2 1, 1, 1 trichloroethane 25% 172F 1704 Blend, 1, 1, 1 trich-loroethane/methylene chloride 25% 143F 2208 Run 3 1, 1, 1 ~richloroethane 50% 182F 528 Blend, 1, 1, 1 trich-loroethane/methylene chloride 50% 150F 864 * Test discontinued at this time. Acid acceptance valu~s of the two samples showed no significant difflerence and were both in the 0.06 to 0.07%
which is the safe operating range recommended by solvlent manufacturers.

~' From the foregoing tables, it will be noted that the addition of trichlorethylene to pe~chlorethylene or methylene chloride to 1, 1, 1 trichlo~ethane without ~il contaminant does nothing more than lower the initial boiling temperature as compared to perchlorethylene or 1, 1, 1 trichloroethane alone. However, upon the addition of oil and the like contaminants as would be found in the con-ventional vapor degreasing environment, the addition of trichlorethylene or methylene chloride not only has an effect on the initial boiling point or temperature of th,e solvent.
but also upon its useful life.

1~7~;'30 That is, the addition of trichlorethylene or methylene chloride, as, for example, in test 2, in each of tables 1 and lA
extended the useful life of the solvent by as much as 23.1% and 30%
respectively before acidic breakdown. As contamination grew, solvent life was extended 40-64% as compared to perchlorethylene or 1, 1, 1 trichlorethane alone.
In order to further prove the applicability of the solvent blend in vapor degreasing operations, another series of runs was conducted, utilizing commercially available vapor degreasing solvents, namely, perchlorethylene 1, 1, 1 trichloroethane and the solvent blends of the invention. Each of the solvents was boiled at total reflux in the presence of the types of contaminants usually found in typical industrial vapor degreasing applications including measured amounts of aluminum and iron metal fines with heavy duty machine oilO
At spaced intervals, each of the solvents was tested for acidic deterioration similar to that testing procedure as set forth for the runs tabulated in Table I and Table IA.
The results of the test runs are tabulated in Table II and Table IIA hereinafter following, wherein the first six runs and the first three runs of Tables II and IIA respectively employed commercially available perchlorethylene and 1, 1, 1 trichloroethane, whereas the seventh run ~Table II) fourth run (Table IIA) employed the perchlorethylene-trichlorethylene and 1, 1, 1 trichloroethane-methylene chloride blends respectively.
As noted in Tables II and IIA, a commercially available industrial solvent specifically designated for vapor degreasing, was compared to the solvent blends of the invention and this data is shown in the following Tables II and IIA:

;~', .~ 1.7'7730 O X
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~ IY ~ ~ X _~
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o X U- ~ ~ ~r !` 0 ~r o X _l _l ,~
og~ o o o o o o U~l X rC ~ ~ _ t~
I I I I I I a~
E~ O ~ O s O ~ O ~ O ~ O
Z

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o ~ O ~ O
u~ P. a~ m ~ o ~ ~ ,~
1:: ~ S ~0 S
~ ~ $ ~ ~

1~77~730 TABLE IIA

Manufacturing 25% 40% 50%
Source _ Oil O-l Oil Run 1 Vulcan `4at'1s Co. Inc 888 648 96 Run 2 PPG Corp. 888 816 192 Run 3 Dow Chemical Co. 840 504 144 Run 4 ., 1, 1, 1 trichloroethane/
methylene chloride blend 1608 1056 1008 The foregoing TABLE II illustrates that, as with increasing oil contamination by volume the perchlorethylene solvent becomes less effective and it was found that Run 7, comprising the blended solvent, had an extended useful life over the perchlorethylene solvent alone as used in Runs 1 -, 6 inclusive.
Table IIA illustrates the longevity of the 1, 1, 1trichloroethane-methylene chloride solvent blend of the in-vention in terms of both hoursof effective use under various levels of oil contamination.
Another series of tests were conducted using acid acceptance values (ASTM Procedure D~2942) to determine solvent longevity using conventional degreasing solvents alone and the solvent blends of the invention. This date is tabulated in Tables III and IIIA following:

1177~73(~

,~
C

., ' '"

o ~ o . o . o . . .

H H 'r X X . X . O O
~ ~ OX ~ X ~ X '7N ~1 ~ P~ O ~o oX O X X o -I '~
O ~ O~. . .. .
~ o X. o o o o o X NIr) I~ U') ~ ~
E~ 0~ ~D X o o o o _~ ~
'.,~ 3cn o o o o o o .~ o ul ~ o _l ~r X l ~

~1 N1~ ~11~ ~D C
C)~ O ~JO Q~
1~ F ~::~: C ~ ~:: ,~ C) _~
E.l. C) C~C) ~Dal o ~( ~1 .,1 U~ _l ~ ~ _l_~ ~ V ~ O
W :>~1 ~::- >1:~ ~ ~ (11 E`~ .c: ~: .C. ~:: .C U E~
E~ ~ 0 0 ~ ~Q) h q~ :~
: ~ ~ h ~ ~1~ ~ O _1 O O O O O O ~ O
:> ~1 ~1_~rl ~ ~ ~ 1 ~: ~ ~ ~ ~.C
O U ~ U U U U ~ C
Vl ~1 ~ h h ~ h U C) .q O ~~Q~ O O ~ ~
~1 P~. ;1~ P~ ~ P. P. a~ ~
. ~ ~ ~ ~ In~D 1` U) ~L~'77730 TABLE IIIA
-~IOURS OF OPERATION
SOLVENT OR

_ SOLVENT with 25% OIL (Vol.) PLUS WATER, ALUMINUM AND IR~N
Perchlor~thylene xxxl32hr Perc~Tri, Blend xxxxxx28~hr 1,1,1 Trichloreoethane xxxxxxxxxxxxxxxxxx864hr-Trichlorethylene xxxxxxxxxxxxxxxxxxx984hr.
1,1,1 Trichloroethane~
Methylene Chloride blend. Xxxxxxxxxxxxxxxxx~xxxxxxxxxxxxxxl6o8hr.
(35% Methylene Chloride) SOLVENT with 40% OIL (Vol.) PLUS WATER, ALU~5INUM AND FIRNOWES

Perchlorethylene xx100 hr.(est.) Perc/Tri. Blend xxxx216hr.
1,1,1 Trichloroethane xxxxxxxxxxxxx656hr.
Trichlorethylene xxxxxxxxxxxxxxxx816hr.
1,1,l/Trichloroethane/ xxxxxxxxxxxxxxxxxxxxxl056hr.
Methylene Chloride blend (35% Methylene Chloride) SOLVENT with 50% OIL (Vol.) PLUS WATER, ~LUMINUM ~D IRON
FINES
_ . .
Perchlorethylene xx72hr.
Perc/Tri.Blend xxxl44hr.
1,1,1 Trichloroethane xxxl36hr.
Trichlorethylene xxxxxxxxxxx552hr.
l,l,l/Trichloroethane/ xxxxxxxxxxxxxxxxxxxxl 008hr.
Methylene Chlorid~ blend.
(35% Methylene Chloride) 773() To demonstrate the efficacy of the trichlorethylene and methylene chloride solvent, a series of tests were conducted directed to a solvent's acid acceptance value parameter. As is known, the acid acceptance value of a vapor degreasing solvent may be determinative and used to ascertain contamination levels of the solvent thereby indicating need to replace and/
or replenish the solvent.
A plurality of solvent samples were prepared having varying proportions of the methylene chloride component of the 10 trichlorethylene-methylene chloride solvent blend. To each of the samples 50 volume percent of oil was added as a con-taminant. Each sample was placed in a flask and subjected to boiling point temperatures for a number of hours and their acid acceptance level readinys taken. Acid acceptance values 15 were in accordance with ASTM procedure D-2942.
The data obtained from the foregoing tests are summarized in the following table IV:

~17~730 T~BLE IV
Acid SOL~7ENT Accept~
+ 50 oil No 24 48 72 96 120 144 168 Run ~ MC Initial l~rs hrs hrs hrs hrs hrs hrs 1 10.1229- -.1229 .1229-.1083 .1083 .0g91 .0991 .ogi8

2. 20.1331 .1331 .1331 .1130 .1130 .1038 .1038 .0963

3. 30- .1366 .1366 .1366 .1141 1141 .1104 .1104 .1010

4. 40.1341 .1341 .1341 o1152 .1152 .1152 .1152 .1133

5 50.1354 .1354 .1354 .1259-.1259 .125g .1259 .iI63

6 60.1349 .1349 .1349 .1175 .1175 .1272 .1272 .1175

7 70.1421 .1421 .1421 .1284 .1284 .1264 .1264 .1187

8 80.1317 .1317 .1317 .1337 .1337 .1297 .1297 .1199 .

9 90.1429 .1429 .1429 .1370 .1370 .1311 .1311 .1211

10 0.1315 .1315 .0858 .0858 .0675 .Q675 .0675 .0274 _

11 MC +
50~ Oil.1555 .1555 .1435 .1434 .1414 .1414 .1414 .1394 solvent ~ Trichlorethylene MC = methylene Chloride .

~17~;~730 TABLE IV Cont~d hrs hrs hrs hrs hrs hrs hrs hrs 1. cont'd .0918 .0711 .0711 .0587 .0587 .0587 .0275 .0128 2. cont'd .0963 .0945 .0945 ,0908 .0908 .0908 .0871 .0871 3. cont'd .1010 .0992 .0992 .0973 .0973 .0973 .0954 .0954 4. cont'd .1133 .1114 .1114 .1096 .1096 .1096 .1077 .1077 5. cont'd .1163 .1114 .1114 .1125 .1125 .1125 .1106 .1106 6. cont'd .1175 .1156 .1156 .1137 .1137 .1137 .1117 .1117 7. cont'd .1187 .1168 .1168 .1148-.1148 .1148-.1128 .1128 8. cont'd .1199 .0924 .0924 .0609 (DISCONTINUED DUE TO EQUIP.
FAILURE) cont'd .1211 .1188 .1188 .1169 .1169 .1169 .1149 .1149 .
lO.cont'd .0237 acid~
_ ll.cont'd .1394 .1394 .1252 .1252 .1252 .1212 .1212 .1212 solvent = Trichlorethylene MC = methylene chloride - l9a -7';'30 TABLE IV ~ont'd hrs hrs hrs hrs hrs hrs hrs hrs . cont'd acid~
2. cont'd .0871 .0648 .0502 .0502 acid---3. cont'd .0954 ~0823 .0823 .0823 .0748 .0748 .0748 .0542 4. cont'd .1077 .1058 .1058 .1058 .1039 .1039 .1039 .0888 5. cont'd .1106 .1087 .1087 .1087 .1049 .1049 .1049 .0953 6. cont'd .1117 .1098 .1098 .1098 .1059 .1059 .1059 .0983 7. cont'd .1128 .1109 .1109 .1103 .1070 .1070 .1070 .0973 8. cont'd DISCONTINUED DUE TO EQUIPMENT FAILURE
9. cont'd .1149 .1129 .1129 .1129 .1089 .1089 .1089 .1030 .
10.cont'd ------ll.cont'd .1192 .1192 .1192 .0202 ~cid----Solvent -= trichlorethylene MC - methylene chloride - l9b-1177'i'30 TABL~ IV Cont'd hrs hrs hrs hrs hrs hrs hrs hrs hrs .
1. cont'd 2. cont'd 3. cont'd 0542 .0542 .028i .0281 .0281 Acid~
4. cont'd .0888 .0388 .0737 .0737 .0737 Acid 5. cont'd .0953 .0953 .0805 .0805 .0805 .0095 Acid 6. cont',d .0983 .0983 .0809 .0809 .0~09 .1193 Acid 7. cont~d .0973 .0973 .08~7 .0817 .0817 .a4Qg .0233 ACid 8. cont'd (Acld---Estimated) 9. cont'd .rO30 .10~0 .0991 .0991 .0991 .0594 .0416.099ACid lO.cont'd ll.cont'd _ solvent = trichloret~ylene MC = methylene Chloride -- l9C_ 1~7773V
From Table IV, the synergism of the solvent combinations of the inventi~n become clear. For example, where trichlorethylene alone has a useful life of abou-t 216 hours and methylene chloride alone. a useful life of about 480 hours, a blend of the two within certain parameters extends . the useful life many more hours to a maximum for some blends of about 744 hours.
Thus, for a solvent blend, as dictated by EPA standards of 20 volume percent trichlorethylene and 80 volume percent methylene chloride, the useful life of the solvent under con-ventional degreasing conditions would be about 744 hours, extrapolating between runs 7 and 9 of Table IV.
Where cooling is available in the degreasing system and where it is desired to reduce energy input to the de-greaser, more methylene chloride may be used and initialboiling point temperatures and sump end operating temperatures determined in accordance with Table V following:

~l~177~73() TABLE V

INITIAL B.P. OF Solvent SOLVENT VAPOR TEMPF SUMP TEMP F Blend APPROX. of -Tri ~
10~ MC 173 195 175 20% MC 160 183 163 Tri +
30% MC 152 173 153 .
Tri +
40% MC 141 168 148 -Tri +
50~ MC 132 161 141 Tri + 127 153 133 70% MC 119 145 125 Tri +
80% MC 115 139 119 Tri +
90% MC 108 134 114 Tri = Trichlorethylene MC = Methylene Chloride li7773() ~ nother series of tests is conducted similar to those described with respect to Tables IA, IIA andIIIA utilizing the solvent blends of trichlorethylene amd methylene chloride and similar results obtainéd to illustrate the efficacy of the solvent blends of the invention.
Thus, there has been disclosed a unique method of carry-ing out vapor degreasing operations utilizing a solvent blend that has an extended useful life and lower initial boiling point. The resultant solvent blends by reason of lower boi`ling points require less energy and are more economical than the usual degreasing solvent alone in that lower heat requirements makes for increased fuel efficiency.
While the solvent blends of the invention have been dis-closed as comprising about 0.1 volume percent to 90.0 volume percent trichlorethylene or methylene chloride, those of ordinary skill in the vapor degreasing art will readily appreci-ate that a solvent blend in accordance with the invention may be selectively formulated to be used most effectively as dis-, closed hereinbefore. Because of unique operational characteris-tics of solvent blends, the perferred solvents for use in the ' selected degreasing method of the invention will be dictated by governmental regulations and the type of vapor degreasing operation being conducted.
While I have described particular embodiments of my invention for purposes of illustration, it is understood that other modifications and variations will occur to those skilled in the art, and the invention accordingly is not to be taken as limited except by the scope of the appended claims.Those of ordinary skill will recognize that the solvent blend of the invention is more economical because gallon for gallon more work product can be vapor degreased than with the unblended vapor ~aegreasing solvents alone.

Claims (13)

I claim:

1. In the method of vapor degreasing by contacting a contaminated article with the vapors of a solvent consisting essentially of trichloroethylene, the improvement which comprises:
(a) adding a sufficient amount of methylene chloride to the solvent to reduce the initial boiling point of the resultant solvent blend to about 120°F
(b) continuing vapor degreasing operations with the solvent blend of step (a) at reflux temperatures until the acid acceptance value of the contaminated solvent blend is within the range of about 0.01 to 0.06.

2. The method in accordance with Claim 1 which additionally includes the step of:
(c) reclaiming the solvent blend from the contaminated solvent blend and forming the solvent blend of step (a) for reuse.

3. The method in accordance with Claim 1 wherein the methylene chloride component of said solvent blend exceeds about 20 volume percent.

4. The method in accordance with Claim 3 which includes maintaining a boiling sump zone and additionally includes the steps of collecting and returning condensed solvent blend vapors to the boiling sump zone.

5. The method in accordance with Claim 4 which includes the step of compensating for lost solvent by periodically adding additional solvent to said solvent blend to maintain the relative proportions of trichloroethylene to methylene chloride.

6 The method in accordance with Claim 5 wherein said solvent blend comprises about 20 volume percent trichloroethylene and about 80 volume percent methylene chloride.

7. The method of vapor degreasing comprising the steps of:
(a) creating a solvent boiling zone;
(b) forming a solvent blend consisting essentially of trichloroethylene and about at least 20 volume percent methylene chloride;
(c) introducing said solvent blend into said boiling zone;
(d) refluxing said solvent blend and removing contaminants therewith by contacting a contaminated article with vapors of the solvent blend in a degreasing zone;
(e) continuing said vapor degreasing and returning solvent.
and contaminants to said boiling zone until the acid acceptance value of the contaminated solvent is within the range of about 0.03 to 0.06, and (f) discontinuing said degreasing and subjecting the recovered contaminated solvent to a reclamation process.

8. In a method of vapor degreasing by contacting a contaminated article with vapors of a solvent consisting essentially of perchloroethylene, the improvement which comprises:
(a) adding a sufficient amount of trichloroethylene to the solvent to reduce the initial boiling point of the resultant solvent blend to about 240°F., and (b) conducting vapor degreasing operations with the solvent blend of step (a) at reflux temperatures and removing contaminants with said solvent until the temperatures of the contaminated solvent blend reaches about 256°F.

9. The method of vapor degreasing comprising the steps of:
(a) creating a solvent boiling zone;
(b) forming a solvent blend of about 81 volume percent perchloroethylene, and 19 volume percent trichloroethylene;
(c) introducing said solvent blend into said boiling zone;
(d) refluxing said solvent blend and removing contaminants therewith by contacting a contaminated article with vapors of the solvent blend in a degreasing zone, (e) continuing said vapor degreasing and returning solvent and contaminants to said boiling zone until the temperature in said boiling zone is about 256° F; and (f) discontinuing said degreasing.

10. The method in accordance with claim 8 wherein the trichloroethylene component of said solvent blend is within the range of about n. l volume percent - 50.0 volume percent.

11. The method in accordance with claim 10 which includes maintaining a boiling sump zone and additionally includes the steps of collecting and returning condensed solvent blend vapors to the boiling sump zone.

12. The method in accordance with claim 11 which includes the step of compensating for lost solvent by periodically adding additional solvent to said solvent blend to maintain the relative proportions of perchloroethylene to trichloroethylene.

13. The method in accordance with claim 12 wherein said solvent blend comprises 81 volume percent perchloroethylene and 19 volume percent trichloroethylene.