CA2087847A1 - Azeotrope-like compositions of 1,1-dichloro-1-fluroethane; ethanol; and nitromethane - Google Patents

Abstract

Azeotrope-like compositions comprising 1,1-dichloro-1-fluoroethane; ethanol; and nitromethane are stable and have utility as degreasing agents and as solvents in a variety of industrial cleaning applications including cold cleaning and defluxing of printed circuit boards and dry cleaning.

Description

W092/02~6 1 PCT/US91/o~
D~SCRI~TI~?N 2 0 ~ 7 8 ~ 7 ~`
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; AZEOTROPE-LIKE COMPOSITIONS OF
DICHLORO-l FLUOROETHANE, E~HANOL: AND NITROMETHANE
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Field of the Invention -This invention relates to azeotrope-like mi~tures ; of l,l-dichloro-l fluoroethane; ethanol; and ~; nitromethane. These mi~tures are useful in a variety of ;; 10 vapor degreasing, cold cleaning and solvent cleaning applications including defluxing. ~
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~RO~ ~REFERENCE TO RELATED APPLICATIQNS
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Co-pending, commonly assigned patent application Serial No. 345,732, filed May 1, 1989, discloses azeotrope-lik~ mi~tures of l,l-dichloro-l-fluoroethane;
I dichlorotrifluoroethane; nitromethane; and methanol or ethanol.
, 20 Co-pending, commonly assigned patent application Serial No. 417,134, filed October 4, 1989, discloses azeotrope-like mi~tures of l,l-dichloro-l-fluoroethane;
dichlorotrifluoroethane; and nitromethane.

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BACXGROUND OF THE INV~NTION
:.", ~` Vapor degreasing and solvent cleaning with ` fluorocarbon based solvents have found widespread use in :; 30 industry for the degreasing and otherwise cleaning of solid surfaces, especially intricate parts and difficult to remove soils.

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W~92/02 ~ ~ PCT/US91/0~2_ In its simplest form, vapor degreasing or solvent cleaning consists of e~posing a room temperature object to be cleaned to the vapors of a boiling solvent. Vapors condensing on the object provide clean distilled solvent to wash away grease or other contamination. Final evaporation of solvent from the object leaves behind no ~ residue as would be the case where the object is simply ; washed in liquid solvent.

For difficult to remove soils where elevated temperature is necessary to improve the cleaning action of -. the solventi or for large volume assembly line operations where the cleaning of metal parts and assemblies must be done efficiently and quickly, the conventional operation -l5 of a vapor degreaser consists of immersing the part to be cleaned in a sump of boilin~ solvent which removes the bulk of the soil, thereafter immersing the part in a sump containing freshly distilled solvent near room ~`temperature, and finally e~posing the part to solvent `~;20 vapors over the boiling sump which condense on the cleaned part. In addition, the part can also be sprayed with distilled solvent before final r nsing.

Vapor degreasers suitable in the above-described - operations are well known in the art. For e2ample, Sherliker et al. in U.S. Patent 3,085,9l8 disclose such suitable vapor degreasers comprising a boiling sump, a clean sump, a water separator, and other ancillary equipment.

Cold cleaning is another application where a number of solvents are used. In most cold cleaning applications, the soiled part is either immersed in the fluid or wiped with rags or similar objects soaked in solvents and allowed to air dry.

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W092/02~6 ~ 0 8 ~ 7 PCT/~s91/~2 - Fluorocarbon solvents, such as trichlorotrifluoroethane, have attained widespread use in recent years as effective, nontoxic, and nonflammable agents useful in degreasing applications and other solvent cleaning applications. Trichlorotrifluoroethane has been found to have satisfactory solvent power for greases, oils, wa~es and the like. It has therefore found widespread use for cleaning electric motors, compressors, heavy metal parts, delicate precision metal parts, printed circuit boards, gyroscopes, guidance systems, aerospace and missile hardware, aluminum parts and the like.

The art has looked towards azeotrope or azeotrope-like compositions including the desired - lS fluorocarbon components such as trichlorotrifluoroethane which include components which contribute additionally desired characteristics, such as polar functionality, increased solvency power, and stabilizers. Azeotropic or azeotrope-lik 3 compositions are desired because they do not fractionate upon boiling. This behavior is desirable ; because in the previously described vapor degreasing equipment with which these solvents are employed, redistilled material is generated for final rinse-cleaning. Thus, the vapor degreasing system acts as a still. Unless the solvent composition eshibits a constant boiling point, i.e., is azeotrope-like, fractionation will occur and undesirable solvent ; distribution may act to upset the cleaning and safety of processi~g. Preerential evaporation of the more volatile components of the solvent mi~tures, which would be ~he case if they were not azeotrope-like, would result in mi~tures with changed compositions which may have less desirable properties, such as lower solvency towards soils, less inertness towards metal, plastic or elastomer :: jS components, and increased flammability and toYiClty.

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wc~s2~2666 ~ ,`,1 Pcr/ussl/04~47_ The art is continually seeking new fluorocarbon hased azeotrope-like mi~tures which offer alternatives for new and special applications for vapor degreasing and other cleaning applications. Currently, of particular interest, are fluorocarbon based azeotrope-like mi~tures which are considered to be stratospherically safe substitutes for presently used fully halogenated chlorofluorocarbons. The latter are suspected of causing environmental problems in connection with the earth's protective ozone layer. Mathematical models have substantiated that hydrochlorofluorocarbons, such as l,l-dichloro-l-fluoroethane ~HCFr-141b), will not ~-~ adversely affect atmospheric chemistry, being negligible contributors to ozone depletion and to green-house global warming in comparison to the fully halogenated species.
HCFC-141b is known to be useful as a solvent. HCFC-141b ~; has a boiling point of about 32C.
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The use of the aerosol packaging concept has long been found to be a convenient and cost effective means of dispensing solvents. Aerosol products utilize a propellant gas or mi2ture of propellant gases, preferably in a liquified gas rather than a compressed gas state, to generate sufficient pressure to e~pel the active ingredients, i.e. product concentrates such as solvents, from the container upon opening of the aerosol valve. The propellants may be in direct contact with the solvent, as in most conventional aerosol systems, or may be isolated from the solvent, as in barrier-type aerosol systems.

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2~8~7 WO 92/0266~ - 5 - PCI/US91/0q842 - Csrnrronly assigned U.S. Patent 4,836,947 discloses azeotrope-like mi~tures of l,l-dichloro-l-fluoroethane and ethanol. Commonly assigned U.S. Patent 4,842,764 discloses azeotrope-like mi~tures of 5 l,l-dichloro-l-fluoroethane and methanol. Commonly assigned U.S. Patent 4,816,174 discloses axeotrope-like mi~tures of l,l-dichloro-l-fluoroethane, methanol, and nitromethane. Commonly assigned U.S. Patent 4,863,630 discloses azeotrope-like mixtures of ~` 10 l,l-dichloro-l-fluoroethane; dichlorotrifluoroethane; and ethanol.

Kokai Patent Publication 103,686, published April 20, 1989, discloses an azeotropic mi:~ture of 55 to 80 lS weight percent dichlorotrifluoroethane and 20 to 45 weight percent 1,1-dichloro-1-fluoroethane. Kokai Patent Publication 136,981, published May 30, 1989, discloses a degreasing cleanin~ agent of 25 weight percent ethanol and 75 weight percent of an azeotropic composition of 25 2 weight percent 1,1-dichloro~l-fluoroethane and 50 weight percent l,l-dichloro-2,2,2-trifluoroethane.

Kokai Patent Publication 136,982, published May 30, 1989, discloses a buff-grinding cleaning agent of 25 weight percent ethanol and 75 weight percent of an azeotropic composition of 25 weight percent l,l-dichloro-l-fluoroethane and 50 weight percent 1,1-dichloro-2,2,2-trifluoroethane. Kokai Patent Publication 137,253, published May 30, lsas! discloses a resist developing agent of 25 weight percent ethanol and 75 weight percent of an azeotropic composition of 25 weight percent l,l-dichloro-l-fluoroethane and 50 weight percent l,l-dichloro-2,2,2-trifluoroethane.
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' ,; . ' ' :~ : : , ' . , W092/02~6 ~a~ 6 - PCT/US91/0~2_ Kokai Patent Publication 137,259, published May 30, 1989, discloses a resist separating agent of 15 weight ~: percent ethanol, 10 weight percent alkyl benzene sulfonic acid, and 75 weight percent of an azeotropic composition : 5 o~ 2S weight percent 1,1-dichloro-1-1uoroethane and 50 weight percent 1,1-dichloro-2,2,2-tr;fluoroethane. Kokai Patent Publication 138,300, published May 31, 1989, : discloses a flu~ cleaning agent of 25 weight percent methanol and 75 weight percent of an azeotropic composition of 25 weight percent dichloro-l-fluoroethane and 50 weight percent 1,1-dichloro-2,2,2-trifluoroethane.
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Kokai Patent Publication 139,104, published May 31, 1989, discloses a solvent of 5 weight percent . trichloroethylene, 20 weight percent ethanol, and 75 : weight percent of an azeotropic composition of 25 weight percent l,l-dichloro-l fluoroethane and 75 weight percent 1,1-dichloro-2,2,2-trifluoroethane. Kokai Patent Publication 139,~61, published June 1, 1989, discloses a . dry-cleaning agent of 25 weight percent ethanol and 75 ; weight percent of an azeotropic composition of 25 weight percent l,l-dichloro-l-fluoroethane and 75 weight percent : 1,1-dichloro-2,2,2-tri~luoroethane.
It is an object of this invention to provide novel :;~ azeotrope-like compositions bssed on ~CFC-141b which are liguid at room temperature, which will not ractionate ~ substantially under the process of distillation or ; 30 evaporation, and which are useful as solvents for use in vapor degreasing and other solvent cleaning applications - . including deflu~ing applications and dry cleaning.
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W~2/02~6 _ 7 ~ ~ 7 ~ ~ ~7CT/US91/04~ :
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Another object of the invention is to provide novel environmentally acceptable solvents for use in the aforementioned applications~

Other objects and advantages of the invention will become apparent from the following description.

~ESCRIP~ION OF THE INVENTI~N
'~' ' ' In accordance with the invention, novel mi~tures have been discovered comprising dichloro-l-fluoroethane; ethanol; and nitromethane.
Also, novel azeotrope-like or constant-boili~g compositions have been discovered comprising l,1-dichloro-1-fluoroethane; ethanol; and nitromethane.

~-~ Preferably, the novel azeotrope-like compositions comprise effective amounts of l,l-dichloro-l-fluoroethane;
ethanol; and nitromethane. The term ~effective amounts~
as used herein means the arnount of each component which upon combination with the other component, results in the - -;~ formation of the present a:zeotrope-like composition.
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Preferably, novel azeotrope-like compositions ~ 25 comprise l,l-dichioro-l-fluoroethane; ethanol; and ,'~ nitromethane which boil at about 32.3C at 760 mm Hg (101 - kPa).
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More preferably, the azeotrope-like compositions of 10. the invention comprise from about 96.1 to about 9~.05 :; weight percent of l,l-dichloro-1-fluoroethane; from about ' . 0.9 to about 3.0 weight percent of ethanol; and from about : 0.05 to about 0.9 weight percent of nitromethane.

15 Most preferably, the azeotrope-like compositions of -~ the invention comprise rom about 97.1 to about 98.75 weight percent of 1,1-dichloro-1-fluoroethane; from about 1.2 to about 2.0 weight percent of ethanol; and from about - ' 0.05 to about 0.9 weight percent of nitromethane.
': 20 Although it is not be:Lieved that a true azeotropic system is formed with l,1-dichloro-1-fluoroethane, ethanol, and nitromethane, the term ~azeotrope-like" is ' used herein for the mi~tures of the invention because in the claimed proportions, the compositions of l,l-dichloro-l-fluoroethane, ethanol, and nitromethane are constant-boiling or essentially constant-boiling and for some reason, which is not fully understood, remain or hang together in a vapor degreaser.

All compositions within the indicated ranges, as well as certain compositions outside the indicated ranges, are azeotrope-like, as defined more particularly below.

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The precise azeotrope compositions have not been ;determined but have be~n ascertained to ~e within the above ranges. Regardless of where the true azeotropes lie, all compositions with the indicated ranges, as well as certain compositions outside the indicated ranges, are azeotrope-like, as defined more particularly below.

It has been found that these azeotrope-like compositions are on the whole nonflammable liquids, i.e.
10 e~hibit no flash point when tested by the Tag Open Cup -test method - ASTM D 1310-86.

From ~undamental principles, the thermodynamic state of a fluid is defined by four variables: pressure, temperature, liquid composition and vapor composition, or P-T-X-Y, respectively. An azeotrope is a unique .characteristic of a system of two or more components where X and Y are equal at the stated P and T. In practice, this means that the components of a mi~ture cannot be ~20 s~parated during distillation, and therefore are useful in : vapor phase solvent cleaning as described above.
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For the purpose of this discussion, azeotrope-like composition is intended to mean that the composition behaves like an azeotrope, i.e. has constant-boiling ^ ; characteristics or a tendency not to fractionate upon .
boiling or evaporation. Thus, in such compositions, the composition of the vapor formed during boiling or evaporation is identical or substantially identical to the ;~,,",30 original liquid composition. Hence, during boiling or evaporation, the liquid composition, if it changes at all, changes only to a minimal or negligible e~tent. This is to be contrasted with non-azeotrope-like compositions in which during boiling or eYaporation, the liquid composition changes to a substan~ial degree.

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., , ~ W092/02666 ~ b~ - lo- PCT/US91/04~' Thus, one way to determine whether a candidate mi~ture is "azeotrope-like" within the meaning of this invention, is to distill a sample thereof under conditions (i.e. resolution number of plates) which would be e~pected to separate the misture into its separate -components. If the mi~ture is non-azeotrope-like, the mixture will Cractionate, i.e. separate into its various components with the lowest boiling component distilling off first, and so on. If the mi~ture is azeotrope-like, ; lO some finite amount of a first distillation cut will be obtained which contains all of the misture components and which is constant-boiling or behaves as a single substance. This phenomenon cannot occur if the mi~ture is not azeotrope-like, i.e. it does not behave like an azeotrope. Of course, upon distillation of an azeotrope-like composition such as in a vapor degreaser, the true azeotrope will form and tend to concentrate.
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It follows from the above that another ` 20 characteristic of azeotrope--like compositions is that there is a range of compositions containing the same components in varyinq proportions which are azeotrope-like - or constant-boiling. All such compositions are intended to be covered by the term azeotrope-like or constant-boiling as used herein. As an esample, it is well known that at differing pressures, the composition of a given azeotrope-like composition will vary at least slightly as does the boiling point of the composition.
Thus, an azeotrope-like composition of A and B represents a unique type of relationship buc with a variable composition depending on temperature and~or pressure.
With l,l-dichloro-l-fluoroethane; ethanol; and nitromethane, the mi~tures boil within + about 0.5C (at about 760 mm Hg (lOl kPa)) of the 32.8C boiling point.
As is readily understood by persons skilled in the art, the boiling point of the azeotrope-like composition will vary with the pressure.

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w092/02~6 ~ 7 PCT/US91/04~

The azeotrope-like compositions of the invention are useful as solvents in a variety of vapor degreasing, cold cleaning and solvent cleaning applicati~ns including defluxing.

In one process embodiment of the invention, the azeotrope-like compositions of the invention may be used to clean solid surfaces by treating said surfaces with said compositions in any manner well known to the art such as by dipping or spraying or use of conventional degreasing apparatus.
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When the present azeotrope-like compositions are used to clean solid surfaces by spraying the surfaces with the compositions, preferably, the azeotrope-like - compositions are sprayed onto the surfaces by using a propellant. Preferably, the propellant is selected from ~; the group consisting of hydrocarbons, chlorofluorocarbons, hydrochlorofluorocarbon, hydrofluorocarbon, dimethyl ether, carbon dio~ide, nitrogen, nitrous o~ide, methylene o~ide, air, and mi~tures thereof.
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Useful hydrocarbon propellants include isobutane, butane, propane, and mi~tures thereof; commercially available isobutane, butane, and propane may be used in the present inYention. Useful chlorofluorocarbon propellants include trichlorofluoromethane (known in the art as CFC-ll), dichlorodifluoromethane (known in the art as CFC-12), 1,1,2-trichloro-1,2,2-trifluoroethane ~known in the art as CFC-113), and 1,2-dichloro-1,1,2,2-tetrafluoroethane (known in the art as CFC-114); commercially available CFC-ll, CFC-12, CFC-113, and CFC-114 may be used in the present invention.

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WO9~/0~ 12 - PCT/~S91/~ ~2 Useful hydrochlorofluorocarbon propellants include dichlorofluoromethane (known in the art as HCFC-21), chlorodifluoromethane (known in the art as HCFC-22), - l-chloro-1,2,2,2-tetrafluoroethane (known in the art as HCFC-124), 1,1-dichloro-2,2-difluoroethane (known in the art as HCFC-132a), 1 chloro-2,2,2-trifluoroethane (known in the art as HCFC-133), and l-chloro-l,l-difluoroethane (known in the art as HCFC-142b); commercially available HCFC-21, HCFC-22, and HCFC-142b may be used in the present invention. HCFC-124 may be prepared by a known process such as that taught by U.S. Patent 4,843,181 and HCFC-133 may be prepared by a known process such as that taught by U.S. Patent 3,003,003.

Useful hydrofluorocarbon propellants include ~i. 15 trifluoromethane (known in the art as HFC-23), 1,1,1,2-tetrafluoroethane (known in the art as HFC-134a~, and l,1-difluoroethane (known in the art as HFC-152a);
commercially available HFC-23 and HFC-152a may be used in the present invention. Until HFC-134a becomes availabls in commercial quantities, HFC-134a may be made by a known method such as that disclosed by U.S. Patent 4,851,595.
More preferred propellants i.nclude hydrochlorofluorocarbons, hydrofluorocarbons, and mi~tures thereof. The most preferrecl propellants include chlorodifluoromethane and 1,1~1,2-tetrafluoroethane.
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The l,l-dichloro-l-fluoroethane; ethanol; and nitromethane components of the novel solvent azeotrope-like compositions of the invention are known materials. Preferably, the materials should be used in sufficiently high purity so as to avoid the introduction of adverse influences upon the desired properties or constant-boiling properties of the system.

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W092/02~6 - 13 - PCT/VSg1/0~2 2~87~7 It should be understood that the present compositions may include additional components so as to form new azeotrope-like or constant-boiling compositions.
Any such compositions are considered to be within the scope of the present invention as long as the compositions - are constant-boiling or essentially constant-boiling and ~ contain all of th~ essential components described herein.
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The present invention is more fully illustrated by the following non-limiting Esamples.
'': ' ., , To illustrate the constan -boiling nature of the mixtures of this invention under conditions of actual use in a vapor phlse degreasing operation, a vapor phase degreasing machine was charged with a preferred mi~ture in accordance with the invention, comprising about 98.5 weight percent of HCFC-141b, about 1.2 weight percent of ethanol, and about 0.3 weight percent of nitromethane.
The mi~ture was evaluated for its constant boiling or non-segregating characteristics. The ~apor phase degreasing machine utilized was a small water-cooled, three-sump vapor phase degreaser which represents a type of system configuration comparable to machine types in the :-2~field today which would present the most rigorous test of solvent segregating behavior. Specifically, the degreaser employed to demonstrate the invention contained two overflowing rinse-sumps and a boil-sump. The boil-sump and the still were electrically heated, and each contained a low-level shut-off switch. Solvent vapors in both the degreaser and the still were condensed on water-cooled stainless-steel coils. The still was fed by gravity from the boil sump. Condensate from the still was returned to the ~irst rinse-sump, also by gravity. The capacity of the unit was approximately 1.5 gallons. This degreaser was very similar to degreasers which are commonly used in commercial establishments.
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The solvent charge was brought to ref lu2 and the compositions in the condensate sump containing the clear condensate from the still, the work sump containing the overflow from the condensate sump, the boil sump where the overflow from the work sump is brought to the mi~ture boiling points, and the still were determined with a Perkin Elmer Sigma 3 gas chromatograph. The temperature of the liquid in all the sumps was monitored with thermocouple temperature sensing devices accurate to +
0.2C. Reflu~ing was continued for about 30 hours and boil and condensate sump compositions were monitored throushout this time. A mi~ture was considered constant-boiling or non-segregating if the ma~imum concentration difference between sumps for any mi~ture component was + 2 sigma around the mean value. Sigma is a standard deviation unit and it is our esperience from many observations of vapor degreaser performance that commercial "aæeotrope-like~ vapor phase degreasing solvents e~hibit at least a + 2 sigma variation in composition with time and yet produce very satisfactory non-segregating cleaning behavior.

If the mi~ture were not azeotrope-like, the high boiling components would very quickly concentrate in the still and be depleted in the rinse sump. This did not happen. Also. the concentration of each component in the sumps stayed well within + 2 sigma. These results indicate that the compositions of this invention will not segregate in any type of large-scale commercial vapor degreasers, thereby avoiding potential safety, performance, and handling problems. The pre erred composition tested was also found to not have a flash point according to recommended procedure ASTM D 1310-86 ~Tag Open Cup). The compositions in the sumps are shown in Table I below.

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W092/02666 - 15 - PCT/US91/04~2 ~873~7 TABLE I
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~ Degreaser Composition Stability Study .
5 ond~nsate SumP
Initial . ~om~osition 24 hour 48 hour HCFC-141b 98.5 98.5 98.6 Ethanol 1.2 1.3 1.3 Nitromethane 0.3 0.1 0.1 -~ Temperature (C) - 23.2 22.5 : Barometric Pressure -~' (mm of Hg) - 748.8. 745.5 ~ kPa) (100) (99) .. ~, .
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Boil SumP :
:. Initial . Com~ositiQn 24 hQur 48 hQur.
: HCFC-141b 98.5 98.2 98.1 .
20 Ethanol 1.2 o.g o.g Nitromethane 0.3 0O8 0.9 ;~ Temperature (C) - 32.3 32.4~ ~
Barometric Pressure :
~:~; (mm of Hg) - 748.8 745.5 (100) (99) Temperature (C) 32.8 32.9 Corrected to . 760 mm Hg Pressure (101 kPa) , .
EXAMP~E 2 ~ ~ E~ample 1 was repeated e~cept that the vapor phase : degreasing machine was charged with another preferred mi~ture in accordance with the invention, comprising about 97.7 weight percent of HCFC-141b, about 2.0 weight percent o ethanol, and about 0.3 ~eight percent of nitromethane.

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; W~92/02~ ~ 16 - PCT/US9l/04~7 If the mixture were not azeotrope-like, the high - boiling components would very ~u-ckly concentrate in the still and be depleted in the rinse sump. This did not happen. Also, the concentration of each component in the sumps stayed well within + 2 sigma. These results indicate that the compositions of this invention will not segregate in any type of large-scale commercial vapor degreasers, thereby avoiding potential safety, performance, and handling problems. The preferred composition tested was also found to not have a flash point according to recommended procedure ASTM D 1310-86 (Tag Open Cup). The compositions in the sumps are shown in Table II below.

~ABLE II

Degreaser Composition Stability Study Condensat~ Sump Initial Composition 24 hour 48 hour HCFC-141b 97.7 98.098.0 -~ Ethanol 2.0 1.81.8 Nitrom~thane 0.3 0.10.1 25 Temperature (C) - 21.321.3 Barometric Pressure (mm of Hg)(kPa) - 746.4753.0 gg)(100) ~oil S~
Initial ~omposition 24 hour 48 hour ~CFC-141b 97.7 96.596.0 Ethanol 2.0 2.73.0 - Nitromethane 0.3 0.80.9 Temperature (C) _31.9 32.6 Barometric Pressure (mm o~ ~g) - 746.4753.0 (kPa) (99)(100) Temperature Corrected 32.4 33.1 to 760 mm Hg Pressure (101 kPa) ., ., , . . ., . . :, ... . . . . .
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This e~ample confirms the e~istence of constant boiling or azeotrope-like compositions of l,l-dichloro-l-fluoroethane; ethanol; and nitromethane Vi2 the method of distillation. It also illustrates that these mixtures do not fractionate during distillation.

A 5-plate Oldershaw distillation column with a cold water condensed automatic liquid dividing head was used for this e~ample. The distillation column was charged with HCFC-141b, ethanol, and nitromethane in the amounts ;~ indicated in Table III below for the starting material.
Each composition was heated under total reflux for about an hour to ensure equilibration. A reflu~ ratio of 5:1 was employed for this particular distillation.
~; Appro~imately 50 percent of the original charges were `
collected in four similar-sized overhead fractions. Ths compositions of these fractions were analyzed using gas chromato~raphy. The averages of the distillate fractions and the overhead temperatures are quite constant within the uncertainty associated with determining the compositions, indicating that the mi~tures are constant-boiling or azeotrope-like.
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TABLE III

Starting Material (wt. %) Example HCFC-141b ETHANOL NITROMET~HANE

3 97.97 1.7a 0.25 - Distillate Composition (wt. %~
Example ~ÇFC-14lb ETHANOL NITRQMETHANE
3 98.18 1.80 0.02 ~oiling Point `~ ~oiling Barometric Corrected to E~ample Point (C)Press~re~_ H~2~kPa~ 760mmHg(101kPa~
3 30.8 740.87(99) 31~6 From the above e~ample, it is readily apparent that additional constant-boiling or essentially constant-~oiling mixtures of the same components can readily be identified by anyone of ordinary skill in this ~ art by the method described. No attempt was made to fully ;~ characterize and define the outer limits of the composition ranqes which are constant-boiling. Anyone ~. i -~ skilled in the art can readily ascertain other . . .
~`~ 25 constant-boilin~ or es entially constant-boiling mi~tures containing the same components.

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~-~ 30 Performance studies are conducted to evaluate the solvent properties of the azeotrope-like compositions of -' the in~ention. Specifically, metal coupons are cleaned ,- using the present azeotrope-like composition o~ E~ample 1 as solvent. The metal coupons are soiled with various types of oils and heated to 93C so as to partially , simulate the temperature attained while machining and grinding in the presence of these oils.

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W092/02~6 - ~&~ 3 ~ 7 PCT/US91/04~

The metal coupons thus treated were degreased in a ~ simulated vapor phase degreaser machine. Condenser coils ;` are kept around the lip of a cylindrical vessel to condense the solvent vapor which then drips down to the vessel. The metal coupons are held in the solvent vapor and rinsed for a period of 15 seconds to 2 minutes depending upon the oils selected.

The cleaninq performance of the azeotrope-like compositions is determined by visual observation of the coupons. The azeotrope-like co~osition of Esample 1 is . .
effective as a solvent.

~ EXAMPLE 5 : 15 Esample 4 is repeated using the azeotrope-like composition of Example 2. The azeotrope-like composition of E~ample 2 is effective as a solvent.

EXA~PLE76 E~ample 4 is repeated using the azeotrope-like~
~ composition of Example 3. The azeotrope-like composition .~ of E~ample 3 is effective 2S a solvent.
EXAM~LE 7 ,.~ .
A si~-ounce three-piece aerosol can is used. The azeotrope-like compositio~ of E~ample l is weighed into a tared aerosol can. After purging the can with tetrafluoroethane in order to displace the air within the container, a valve is mechanically crimped onto the can.
Liquid chlorodifluoromethane is then added through the valve utilizing pressure burettes.
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' ' ~ '. : ' , ; , , W092/02~6 ~ 20 - PCT/VS91/04~2_ A printed circuit board having an area of 37.95 square inches and densely populated with dip sockets, resistors~ and capacitors is precleaned by rinsing with isopropanol ~efore wave soldering. The board is then flu~ed and wave soldered using a Hollis TDL wave solder machine.

The printed circuit board is then spray cleaned using the aerosol can having the azeotrope-like composition therein. The cleanliness of the board is tested visually and also using an Omega-meter which measured the ionic contamination of the board. The azeotrope-like composition of E~ample l is particularly useful as a solvent for spray cleaning applications.

Example 7 is repeated except that the ~` azeotrope-like composition of E2ample 2 is used. The `~ 20 azeotrope-lik~ composition of Esample 2 is particularly ~ useful as a solvent for spray cleaning applications.

- EXAMPLE ~

Example 7 is repeated e~cept that the . 25 azeotrope-like composition of E~ample 3 is used. The azeotrope-like composition of Example 3 is particularly ~'~ useful as a solvent for spray cleaning applications.

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~ W092/02~6 - 21 - 2 ~ ~ 7~P~7~usg-/o4~2 Inhibitors may be added to the present azeotrope-like compositions to inhibit decomposition of the compositions; react with undesirable decomposition products of the compositions; and/or prevent corrosion of metal surfaces. Any or all of the following classes of inhibitors may be employed in the invention: ~po~y compounds such as propylene oxide; ethers such as 1-4-dioxane; unsaturated compounds such as 1,4-butyne diol; acetals or ketals such as dipropo~y methane; ketones such as methyl ethyl ketone; alcohols such as tertiary amyl alcohol; esters such as triphenyl phosphite; and amines such as triethyl amine. Other suitable inhibitors will readily occur to those skilled in the art.

Having described the invention in detail and by ,~ reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible ~ without departing from the scope of the invention defined ;~ in the appended claims.

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Claims (14)

What is claimed is:

1. Azeotrope-like compositions comprising effective amounts of 1,1-dichloro-1-fluoroethane; ethanol;
and nitromethane.

2. The azeotrope-like compositions of claim 1 comprising from about 95.5 to about 99.49 weight percent said 1,1-dichloro-1-fluoroethane, from about 0.5 to about 3.5 weight percent said ethanol, and from about 0.01 to about 1.0 weight percent said nitromethane.

3. The azeotrope-like compositions of claim 1 comprising from about 96.1 to about 99.05 weight percent said 1,1-dichloro-1-fluoroethane, from about 0.9 to about 3.0 weight percent said ethanol, and from about 0.05 to about 0.9 weight percent said nitromethane.

4. The azeotrope-like compositions of claim 1 comprising from about 97.1 to about 98.75 weight percent said 1,1-dichloro-1-fluoroethane, from about 1.2 to about 2.0 weight percent said ethanol, and from about 0.05 to about 0.9 weight percent said nitromethane.

5. Azeotrope-like compositions comprising 1,1-dichloro-1-fluoroethane, ethanol, and nitromethane which boil at about 32.8°C at 760 mm Hg.

6. The azeotrope-like compositions of claim 5 comprising from about 95.5 to about 99.49 weight percent said 1,1-dichloro-1-fluoroethane, from about 0.5 to about 3.5 weight percent said ethanol, and from about 0.01 to about 1.0 weight percent said nitromethane.

7. The azeotrope-like compositions of claim 5 comprising from about 96.1 to about 99.05 weight percent said 1,1-dichloro-1-fluoroethane, from about 0.9 to about 3.0 weight percent said ethanol, and from about 0.05 to about 0.9 weight percent said nitromethane.

8. The azeotrope-like compositions of claim 5 comprising from about 97.1 to about 98.75 weight percent said 1,1-dichloro-1-fluoroethane, from about 1.2 to about 2.0 weight percent said ethanol, and from about 0.05 to about 0.9 weight percent said nitromethane.

9. The azeotrope-like compositions of claim 5 which boil at about 32.8°C ? about 0.5°C at 760 mm Hg.

10. A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 5.

11. A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 6.

12. A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 7.

13. A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 8.

14. A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 9.