EP0542796B1

EP0542796B1 - Azeotrope-like compositions of 1,1-dichloro-1-fluoroethane; ethanol; and nitromethane

Info

Publication number: EP0542796B1
Application number: EP91913860A
Authority: EP
Inventors: Ellen Louise Swan; Rajat Subhra Basu; Earl A.E. Lund
Original assignee: AlliedSignal Inc
Current assignee: Honeywell International Inc
Priority date: 1990-08-09
Filing date: 1991-07-10
Publication date: 1996-09-25
Anticipated expiration: 2011-07-10
Also published as: KR930701583A; ATE143419T1; JPH05508880A; AU8288891A; EP0542796A1; MX9100409A; CA2087847A1; DE69122396D1; WO1992002666A1; ES2091936T3

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

Field of the Invention

This invention relates to azeotrope-like mixtures of 1,1-dichloro-1-fluoroethane; ethanol; and nitromethane. These mixtures are useful in a variety of vapor degreasing, cold cleaning and solvent cleaning applications including defluxing.

CROSS-REFERENCE TO RELATED APPLICATIONS

Co-pending, commonly assigned patent application Serial No. 345,732, filed May 1, 1989, discloses azeotrope-like mixtures of 1,1-dichloro-1-fluoroethane; dichlorotrifluoroethane; nitromethane; and methanol or ethanol.
Co-pending, commonly assigned patent application Serial No. 417,134, filed October 4, 1989, discloses azeotrope-like mixtures of 1,1-dichloro-1-fluoroethane; dichlorotrifluoroethane; and nitromethane.

BACKGROUND OF THE INVENTION

Vapor degreasing and solvent cleaning with fluorocarbon based solvents have found widespread use in industry for the degreasing and otherwise cleaning of solid surfaces, especially intricate parts and difficult to remove soils.
In its simplest form, vapor degreasing or solvent cleaning consists of exposing 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 solvent, or for large volume assembly line operations where the cleaning of metal parts and assemblies must be done efficiently and quickly, the conventional operation of a vapor degreaser consists of immersing the part to be cleaned in a sump of boiling solvent which removes the bulk of the soil, thereafter immersing the part in a sump containing freshly distilled solvent near room temperature, and finally exposing the part to solvent vapors over the boiling sump which condense on the cleaned part. In addition, the part can also be sprayed with distilled solvent before final rinsing.
Vapor degreasers suitable in the above-described operations are well known in the art. For example, Sherliker et al. in U.S. Patent 3,085,918 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.
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, waxes 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 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-like 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 exhibits 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 processing. Preferential evaporation of the more volatile components of the solvent mixtures, which would be the case if they were not azeotrope-like, would result in mixtures with changed compositions which may have less desirable properties, such as lower solvency towards soils, less inertness towards metal, plastic or elastomer components, and increased flammability and toxicity.
The art is continually seeking new fluorocarbon based azeotrope-like mixtures which offer alternatives for new and special applications for vapor degreasing and other cleaning applications. Currently, of particular interest, are fluorocarbon based azeotrope-like mixtures 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 1,1-dichloro-1-fluoroethane (HCFC-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 32°C.
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 mixture of propellant gases, preferably in a liquified gas rather than a compressed gas state, to generate sufficient pressure to expel 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.
Commonly assigned U.S. Patent 4,836,947 discloses azeotrope-like mixtures of 1,1-dichloro-1-fluoroethane and ethanol. Commonly assigned U.S. Patent 4,842,764 discloses azeotrope-like mixtures of 1,1-dichloro-1-fluoroethane and methanol. Commonly assigned U.S. Patent 4,816,174 discloses azeotrope-like mixtures of 1,1-dichloro-1-fluoroethane, methanol, and nitromethane. Commonly assigned U.S. Patent 4,863,630 discloses azeotrope-like mixtures of 1,1-dichloro-1-fluoroethane; dichlorotrifluoroethane; and ethanol.
Kokai Patent Publication 103,686, published April 20, 1989, discloses an azeotropic mixture of 55 to 80 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 cleaning agent of 25 weight percent ethanol and 75 weight percent of an azeotropic composition of 25 weight percent 1,1-dichloro-1-fluoroethane and 50 weight percent 1,1-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 1,1-dichloro-1-fluoroethane and 50 weight percent 1,1-dichloro-2,2,2-trifluoroethane. Kokai Patent Publication 137,253, published May 30, 1989, discloses a resist developing agent of 25 weight percent ethanol and 75 weight percent of an azeotropic composition of 25 weight percent 1,1-dichloro-1-fluoroethane and 50 weight percent 1,1-dichloro-2,2,2-trifluoroethane.
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 of 25 weight percent 1,1-dichloro-1-fluoroethane and 50 weight percent 1,1-dichloro-2,2,2-trifluoroethane. Kokai Patent Publication 138,300, published May 31, 1989, discloses a flux cleaning agent of 25 weight percent methanol and 75 weight percent of an azeotropic composition of 25 weight percent 1,1-dichloro-1-fluoroethane and 50 weight percent 1,1-dichloro-2,2,2-trifluoroethane.
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 1,1-dichloro-1-fluoroethane and 75 weight percent 1,1-dichloro-2,2,2-trifluoroethane. Kokai Patent Publication 139,861, 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 1,1-dichloro-1-fluoroethane and 75 weight percent 1,1-dichloro-2,2,2-trifluoroethane.
It is an object of this invention to provide novel azeotrope-like compositions based on HCFC-141b which are liquid at room temperature, which will not fractionate substantially under the process of distillation or evaporation, and which are useful as solvents for use in vapor degreasing and other solvent cleaning applications including defluxing applications and dry cleaning.
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.
In accordance with the invention, novel mixtures have been discovered comprising from 95.5 to 99.49 weight percent of 1,1-dichloro-1-fluoroethane; from 0.5 to 3.5 weight percent of ethanol; and from 0.01 to 1.0 weight percent of nitromethane which boil at 32.8°C ± 0.5°C at 760 mm Hg (101 kPa).
More preferably, the azeotrope-like compositions of the invention comprise from 96.1 to 99.05 weight percent of 1,1-dichloro-1-fluoroethane; from 0.9 to 3.0 weight percent of ethanol; and from 0.05 to 0.9 weight percent of nitromethane.
Most preferably, the azeotrope-like compositions of the invention comprise from 97.1 to 98.75 weight percent of 1,1-dichloro-1-fluoroethane; from 1.2 to 2.0 weight percent of ethanol; and from 0.05 to 0.9 weight percent of nitromethane.
Although it is not believed that a true azeotropic system is formed with 1,1-dichloro-1-fluoroethane, ethanol, and nitromethane, the term "azeotrope-like" is used herein for the mixtures of the invention because in the claimed proportions, the compositions of 1,1-dichloro-1-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.
The precise azeotrope compositions have not been determined but have been ascertained to be 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. exhibit no flash point when tested by the Tag Open Cup test method - ASTM D 1310-86.
From fundamental 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 mixture cannot be separated during distillation, and therefore are useful in vapor phase solvent cleaning as described above.
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 original liquid composition. Hence, during boiling or evaporation, the liquid composition, if it changes at all, changes only to a minimal or negligible extent. This is to be contrasted with non-azeotrope-like compositions in which during boiling or evaporation, the liquid composition changes to a substantial degree.
Thus, one way to determine whether a candidate mixture 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 expected to separate the mixture into its separate components. If the mixture is non-azeotrope-like, the mixture will fractionate, i.e. separate into its various components with the lowest boiling component distilling off first, and so on. If the mixture is azeotrope-like, some finite amount of a first distillation cut will be obtained which contains all of the mixture components and which is constant-boiling or behaves as a single substance. This phenomenon cannot occur if the mixture 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.
It follows from the above that another characteristic of azeotrope-like compositions is that there is a range of compositions containing the same components in varying 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 example, 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 but with a variable composition depending on temperature and/or pressure. With 1,1-dichloro-1-fluoroethane; ethanol; and nitromethane, the mixtures boil within ± 0.5°C (at 760 mm Hg (101 kPa)) of the 32.8°C 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.

The azeotrope-like compositions of the invention are useful as solvents in a variety of vapor degreasing, cold cleaning and solvent cleaning applications 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.
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 dioxide, nitrogen, nitrous oxide, methylene oxide, air, and mixtures thereof.
Useful hydrocarbon propellants include isobutane, butane, propane, and mixtures thereof; commercially available isobutane, butane, and propane may be used in the present invention. Useful chlorofluorocarbon propellants include trichlorofluoromethane (known in the art as CFC-11), 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-11, CFC-12, CFC-113, and CFC-114 may be used in the present invention.
Useful hydrochlorofluorocarbon propellants include dichlorofluoromethane (known in the art as HCFC-21), chlorodifluoromethane (known in the art as HCFC-22), 1-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-1,1-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 trifluoromethane (known in the art as HFC-23), 1,1,1,2-tetrafluoroethane (known in the art as HFC-134a), and 1,1-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 available 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 include hydrochlorofluorocarbons, hydrofluorocarbons, and mixtures thereof. The most preferred propellants include chlorodifluoromethane and 1,1,1,2-tetrafluoroethane.
The 1,1-dichloro-1-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.
The present invention is more fully illustrated by the following non-limiting Examples.

EXAMPLE 1

To illustrate the constant-boiling nature of the mixtures of this invention under conditions of actual use in a vapor phase degreasing operation, a vapor phase degreasing machine was charged with a preferred mixture 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 mixture was evaluated for its constant boiling or non-segregating characteristics. The vapor 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 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 first rinse-sump, also by gravity. The capacity of the unit was approximately 5.68 litre (1.5 gallons). This degreaser was very similar to degreasers which are commonly used in commercial establishments.
The solvent charge was brought to reflux 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 mixture 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 ± 0.2°C. Refluxing was continued for about 30 hours and boil and condensate sump compositions were monitored throughout this time. A mixture was considered constant-boiling or non-segregating if the maximum concentration difference between sumps for any mixture component was ± 2 sigma around the mean value. Sigma is a standard deviation unit and it is our experience from many observations of vapor degreaser performance that commercial "azeotrope-like" vapor phase degreasing solvents exhibit at least a ± 2 sigma variation in composition with time and yet produce very satisfactory non-segregating cleaning behavior.

If the mixture 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 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 I below.

TABLE I

Degreaser Composition Stability Study
Condensate Sump
	Initial Composition	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) (kPa)	-	748.8 (100)	745.5 (99)

Boil Sump
	Initial Composition	24 hour	48 hour
HCFC-141b	98.5	98.2	98.1
Ethanol	1.2	0.9	0.9
Nitromethane	0.3	0.8	0.9
Temperature (°C)	-	32.3	32.4
Barometric Pressure (mm of Hg)	-	748.8 (100)	745.5 (99)

Temperature (°C) Corrected to 760 mm Hg Pressure (101 kPa)		32.8	32.9

EXAMPLE 2

Example 1 was repeated except that the vapor phase degreasing machine was charged with another preferred mixture in accordance with the invention, comprising about 97.7 weight percent of HCFC-141b, about 2.0 weight percent of ethanol, and about 0.3 weight percent of nitromethane.

If the mixture 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 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.

TABLE II

Degreaser Composition Stability Study
Condensate Sump
	Initial Composition	24 hour	48 hour
HCFC-141b	97.7	98.0	98.0
Ethanol	2.0	1.8	1.8
Nitromethane	0.3	0.1	0.1
Temperature (°C)	-	21.3	21.3
Barometric Pressure (mm of Hg) (kPa)	-	746.4 (99)	753.0 (100)

Boil Sump
	Initial Composition	24 hour	48 hour
HCFC-141b	97.7	96.5	96.0
Ethanol	2.0	2.7	3.0
Nitromethane	0.3	0.8	0.9
Temperature (°C)	-	31.9	32.6
Barometric Pressure (mm of Hg) (kPa)	-	746.4 (99)	753.0 (100)
Temperature Corrected to 760 mm Hg Pressure (101 kPa)		32.4	33.1

EXAMPLE 3

This example confirms the existence of constant-boiling or azeotrope-like compositions of 1,1-dichloro-1-fluoroethane; ethanol; and nitromethane via 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 example. 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 reflux ratio of 5:1 was employed for this particular distillation. Approximately 50 percent of the original charges were collected in four similar-sized overhead fractions. The compositions of these fractions were analyzed using gas chromatography. The averages of the distillate fractions and the overhead temperatures are quite constant within the uncertainty associated with determining the compositions, indicating that the mixtures are constant-boiling or azeotrope-like. TABLE III

Starting Material (wt. %)

Example HCFC-141b ETHANOL NITROMETHANE

3 97.97 1.78 0.25

Distillate Composition (wt.%)

Example HCFC-141b ETHANOL NITROMETHANE

3 98.18 1.80 0.02

Example Boiling Point (°C) Barometric Pressure(mmHg)(kPa) Boiling Point Corrected to 760mmHg(101kPa)

3 30.8 740.87(99) 31.6
From the above example, it is readily apparent that additional constant-boiling or essentially constant-boiling 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 ranges which are constant-boiling. Anyone skilled in the art can readily ascertain other constant-boiling or essentially constant-boiling mixtures containing the same components.

EXAMPLE 4

Performance studies are conducted to evaluate the solvent properties of the azeotrope-like compositions of the invention. Specifically, metal coupons are cleaned using the present azeotrope-like composition of Example 1 as solvent. The metal coupons are soiled with various types of oils and heated to 93°C so as to partially simulate the temperature attained while machining and grinding in the presence of these oils.
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 cleaning performance of the azeotrope-like compositions is determined by visual observation of the coupons. The azeotrope-like composition of Example 1 is effective as a solvent.

EXAMPLE 5

Example 4 is repeated using the azeotrope-like composition of Example 2. The azeotrope-like composition of Example 2 is effective as a solvent.

EXAMPLE 6

Example 4 is repeated using the azeotrope-like composition of Example 3. The azeotrope-like composition of Example 3 is effective as a solvent.

EXAMPLE 7

A 177.5 cm³ (six-ounce) three-piece aerosol can is used. The azeotrope-like composition of Example 1 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.
A printed circuit board having an area of 244.85 cm² (37.95 square inches)and densely populated with dip sockets, resistors, and capacitors is precleaned by rinsing with isopropanol before wave soldering. The board is then fluxed 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 Example 1 is particularly useful as a solvent for spray cleaning applications.

EXAMPLE 8

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

EXAMPLE 9

Example 7 is repeated except that the azeotrope-like composition of Example 3 is used. The azeotrope-like composition of Example 3 is particularly useful as a solvent for spray cleaning applications.
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: epoxy compounds such as propylene oxide; ethers such as 1-4-dioxane; unsaturated compounds such as 1,4-butyne diol; acetals or ketals such as dipropoxy 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.

Claims

Azeotrope-like compositions comprising from 95.5 to 99.49 weight percent 1,1-dichloro-1-fluoroethane, from 0.5 to 3.5 weight percent ethanol, and from 0.01 to 1 weight percent nitromethane which boil at 32.8°C ± 0.5°C at 760 mm Hg (101 kPa).
The azeotrope-like compositions of claim 1 comprising from 96.1 to 99.05 weight percent said 1,1-dichloro-1-fluoroethane, from 0.9 to 3 weight percent said ethanol, and from 0.05 to 0.9 weight percent said nitromethane.
The azeotrope-like compositions of claim 1 comprising from 97.1 to 98.75 weight percent said 1,1-dichloro-1-fluoroethane, from 1.2 to 2 weight percent said ethanol, and from 0.05 to 0.9 weight percent said nitromethane.
A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 1.
A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 2.
A method of cleaning a solid surface which comprises treating said surface with said azeotrope-like composition as defined in claim 3.