WO1993016163A1

WO1993016163A1 - Azeotrope-like compositions of 1,1-dichloro-1-fluoroethane, c5 or c6 alkane or cycloalkane and dichloromethane

Info

Publication number: WO1993016163A1
Application number: PCT/US1993/000861
Authority: WO
Inventors: Ellen Louise Swan; Peter Brian Logsdon; Rajat Subhra Basu; Leonard Michael Stachura
Original assignee: Allied-Signal Inc.
Priority date: 1992-02-05
Filing date: 1993-02-02
Publication date: 1993-08-19
Also published as: AU3602093A

Abstract

The invention relates to stable azeotrope-like compositions of 1,1-dichloro-1-fluoroethane, a C5 or C6 alkane or cycloalkane, dichloromethane and optionally an alkanol and/or nitromethane which are useful in a variety of industrial cleaning applications including cold cleaning and defluxing of printed circuit boards.

Description

AZEOTROPE-LIKE COMPOSITIONS OF 1,1-DICHLORO-l-FLUOROETHANE, C5 OR C6 ALKANE O CYCLOALKANE AND DICHLOROMETHANE.

10

Fluorocarbon based solvents have been used 15 extensively 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 20 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 leaves the.object free of 25 residue. This is contrasted with liquid solvents which leave deposits on the object after rinsing.

A vapor degreaser is used for difficult to remove soils where elevated temperature is necessary to

30 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. The conventional operation of a vapor degreaser consists of immersing the part to be cleaned

35 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 decreasers 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 cloths soaked in solvents and allowed to air dry.

Recently, nontoxic nonflammable fluorocarbon solvents like trichlorotrifluoroethane have been used extensively in degreasing applications and other solvent cleaning applications. Trichlorotrifluoro¬ ethane 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.

Azeotropic 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. Therefore, unless the solvent composition is essentially constant boiling, fractionation will occur and undesirable solvent distribution may act to upset the cleaning and safety of processing. For example, preferential evaporation of the more volatile components of the solvent mixtures, would result in mixtures with changed compositions which may have less desirable properties, like lower solvency towards soils, less inertness towards metal, plastic or elastomer components, and increased flammability and toxicity. The art has looked towards azeotropic compositions having fluorocarbon components because the fluorocarbon components contribute additionally desired characteristics, such as polar functionality, increased solvency power, and stabilizers.

The art is continually seeking new fluorocarbon based azeotrope mixtures or azeotrope-like mixtures which offer alternatives for new and special applications for vapor degreasing and other cleaning applications. Currently, fluorocarbon-based azeotrope-like mixtures with minimal or zero amounts of chlorine are of particular interest because they are considered to_. be stratospherically safer substitutes than presently used chlorine-containing halogenated fluorocarbons (CFC's). The latter have been implicated in causing environmental problems associated with the depletion of the earth's protective ozone layer. Mathematical models have substantiated that hydrochlorofluόrocarbons, like 1,1-dichloro-l- fluoroethane (HCFC-141b) have a much lower ozone depletion potential and global warming potential than trichlorotrifluoroethane (CFC-113) . Description of the Invention

Our solution to the need in the art for strato¬ spherically safer substitutes for CFC-based solvent compositions is mixtures comprising 1,1-dichloro-l- fluoroethane (HCFC-141b) , a C₅ or C₆ alkane or cycloalkane, dichloromethane and optionally an alkanol and/or nitromethane. The alkanol may be methanol or ethanol. The term C₅ or C₆ alkane or cycloalkane shall mean a compound selected from the group consisting of n-hexane; 2-methylpentane; 3-methylpentane; 2,2- dimethylbutane; 2,3-dimethylbutane; isohexane and mixtures thereof.

HCFC-141b has a good solvent properties The alkanol, C₅ or C₆ alkane or cycloalkane and dichloro- methane components of the invention also have good solvent capabilities. The alkanol dissolves polar organic materials and amine hydrochlorides while the dichloromethane component enhances the solubility of oils. Nitromethane is a stabilizer. Thus, when these components are combined in effective amounts a stable, efficient azeotrope-like solvent results.

The compositions of the preferred azeotrope-like compositions of the invention are summarized in the tables which follow. Note that the composition ranges reported are in weight percent and that the composition and boiling point ranges are understood to be prefaced by the term "about". TABLE I

TABLEΠ

TABLE m

TABLE IV

TABLE V

TABLE VI

* Commercial grade isohexane comprises about 35 to about 75 weight percent 2-methylpentane, about 10 to about 40 weight percent 3-methylpentane, about 7 to about 30 weight percent 2,3-dimethylbutane, about 7 to about 30 weight percent 2,2-dimethylbutane, and about 0.1 to about 10 weight percent n-hexane.

It is known in the art that the use of more active solvents, such as lower alkanols in combination with certain halocarbons such as trichlorotrifluoroethane, may have the undesirable result of attacking reactive metals such as zinc and aluminum, as well as certain aluminum alloys and chromate coatings such as are commonly employed in circuit board assemblies. The art has recognized that certain stabilizers, like nitro- methane, are effective in preventing metal attack by chlorofluorocarbon mixtures with such alkanols. Other candidate stabilizers for this purpose, such as disclosed in the literature, are secondary and tertiary amines, olefins and cycloolefins, alkylene oxides, sulfoxides, sulfones, nitrites and nitriles, and acetylenic alcohols or ethers. It is contemplated that such stabilizers as well as other additives may be combined with the azeotrope-like compositions of this invention.

The precise or true azeotrope compositions have not been determined but have been ascertained to be within the indicated ranges. Regardless of where the true azeotropes lie, all compositions within 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 - AST D 1310-86.

For purposes of this discussion, the term "azeotrope-like composition" is intended to mean that the composition behaves like a true azeotrope in terms of its constant-boiling characteristics or tendency not to fractionate upon boiling or evaporation. Such composition may or may not be a true azeotrope. 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 slightly. This is contrasted with non-azeotrope-like rl2- compositions in which the liquid composition changes substantially during boiling or evaporation.

In the 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 con¬ ventional 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, chloro- fluorocarbons, hydrochlorofluorocarbons, hydrofluoro- carbons, dimethyl ether, carbon dioxide, nitrogen, nitrous oxide, methylene oxide, air, and mixtures thereof.

The HCFC-141b, C₅ or C₆ alkane or cycloalkane, dichloromethane, alkanol and nitromethane components of the invention are known materials. Preferably they should be used in sufficiently high purity so as to avoid the intro-duction of adverse influences upon the solvency properties or constant-boiling properties of the system.

The present invention is more fully illustrated by the following non-limiting Examples.

Exam le 1 The azeotropic properties of the compositions of the invention were determined through the use of distillation techniques designed to provide higher rectification of the distillate than found in most vapor degreaser systems. For this purpose, a five theoretical plate Oldershaw distillation column with a cold water condensed, manual liquid dividing head was used. Typically, approximately 350 grams of liquid were charged to the distillation pot. In this example, the liquid was a mixture comprised of HCFC-141b, cyclopentane and dichloromethane.

The mixture was heated at total reflux for about one hour to ensure equilibration. The distillate was obtained using a 3:1 reflux ratio at a boil-up rate of 250-300 grams per hour. Approximately 150 grams of product were distilled and 4 approximately equivalent sized overhead cuts were collected. The vapor temperature (of the distillate) , pot temperature, and barometric pressure were monitored. A constant boiling fraction was collected and analyzed by gas chromato- graphy to determine the weight percentages of its components.

To normalize observed boiling points during different days to 760 mm of mercury pressure, the approximate normal boiling points of HCFC-141b rich mixtures were estimated by applying a barometric correction factor of about 26 mm Hg/°C, to the observed values. However, it is to be noted that this corrected boiling point is generally accurate up to ± 0.4°C and serves only as a rough comparison of boiling points determined on different days. By the above-described method, it was discovered that mixtures comprising from about 78.0 to about 98.0 weight percent HCFC-141b, from about 1.0 to about 7.0 weight percent cyclopentane and from about 1.0 to about 15.0 weight percent dichloro¬ methane are constant boiling at about 32.2°C ± 1.3°C at 760 mm Hg.

Examples 2-3

The azeotropic properties of the following compositions were studied by repeating the experiment outlined in Example 1 above.

a) HCFC-141b/cyclopentane/dichloromethane/methanol; and

b) HCFC-141b/cyclopentane/dichloromethane/ethanol.

By the above-described method, it was determined that the following mixtures are azeotropic at the stated temperature:

a) about 58-99.7/0.1-7/0.1-30/0.1-5 weight percent HCFC-141b/cyclopentane/dichloromethane/methanol respectively at about 30.3°C; and

b) about 54-99.7/0.1-7/0.1-34/0.1-4 weight percent HCFC-141b/cyclopentane/dichloromethane/ethanol respectively at about 32.5°C.

Example 4

The azeotropic properties of still other compositions of the invention were determined through the use of distillation techniques designed to provide higher rectification of the distillate than found in most vapor degreaser systems. For this purpose, a five-plate Oldenshaw distillation column with a cold water condensed automatic liquid dividing head was used. In this Example, the distillation column was charged with HCFC-141b, 2-methylpentane, dichloro¬ methane and methanol. Then, the composition was heated under total reflux for about an hour to ensure equilibration. A reflux ratio of 5:1 was employed for this distillation. Approximately 50 percent of the original charges were collected in four similar-sized overhead fractions. The composition of the fractions was determined 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-1ike.

Tfr^g-ampl B 5 - 7

The experiment outlined in Example 4 above was repeated for the following compositions:

a) HCFC-141b/ethanol/2-methylpentane/dichloromethane;

b) HCFC-141b/methanol/2,2-dimethylbutane/dichloro- methane;

c) HCFC-141b/ethanol/2,2-dimethylbutane/dichloro- methane;

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.

Examples 8 - 9

The experiment outlined in Example 4 above was repeated for the following compositions except that a reflux ratio of 3:1 was employed:

a) HCFC-141b/methanol/3-methylpentane/dichloro- methane; and

b) HCFC-141b/ethanol/3-methylpentane/dichloro- methane.

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.

Rrampl _»« 1Q - 27

The experiment outlined in Example 4 above is repeated for the following compositions:

a) HCFC-141b/2-methylpentane/dichloromethane;

b) HCFC-141b/2-methylpentane/dichloromethane/ nitromethane;

c) HCFC-141b/2-methylpentane/dichloromethane/ nitromethane/methanol;

d) HCFC-l41b/2-methylpentane/dichloromethane/ nitromethane/ethanol;

e) HCFC-141b/3-methylpentane/dichloromethane;

f) HCFC-141b/3-methylpentane/dichloromethane/ nitromethane;

g) HCFC-141b/3-methylpentane/dichloromethane/ nitromethane/methanol;

h) HCFC-141b/3-methylpentane/dichloromethane/ nitromethane/ethanol;

i) HCFC-14lb/2,2-dimethylbutane/dichloromethane;

j ) HCFC-141b/2,2-dimethylbutane/dichloromethane/ nitromethane;

k) HCFC-141b/2,2-dimethylbutane/dichloromethane/ nitromethane/methanol; 1) HCFC-141b/2,2-dimethylbutane/dichloromethane/ nitromethane/ethanol;

m) HCFC-141b/2,3-dimethylbutane/dichloromethane;

n) HCFC-141b/2,3-dimethylbutane/dichloromethane/ nitromethane;

o) HCFC-141b/2,3-dimethylbutane/dichloromethane/ nitromethane/methanol;

p) HCFC-141b/2,3-dimethylbutane/dichloromethane/ nitromethane/ethanol;

q) HCFC-14lb/commercial grade isohexane/dichloro- methane/nitromethane/methanol;

r) HCFC-141b/commercial grade isohexane/dichloro- methane/nitromethane/ethanol.

The averages of the distillate fraction 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.

Examples 28 - 55

Performance studies are conducted wherein metal coupons are cleaned using the present azeotrope-like compositions as solvents. 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 are degreased in a three-sump vapor phase degreaser machine. In this typical three-sump degreaser, condenser coils around the lip of the machine are used to condense the solvent vapor which is then collected in a sump. The condensate overflows into cascading sumps and eventually goes into the boiling sump.

The metal coupons are held in the solvent vapor and then vapor rinsed for a period of 15 seconds to 2 minutes depending upon the oils selected. The azeotrope-like compositions of Examples 1 through 27 are used as the solvents. Cleanliness (i.e., the total residual material left after cleaning) of the coupons is determined by measuring the weight change of the coupons using an analytical balance.

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.

Claims

1. Azeotrope-like compositions consisting essentially of from about 78.0 to about 98.0 weight percent 1,1-dichloro-l-fluoroethane, from about 7.0 to about 1.0 weight percent cyclopentane and from about 15.0 to about 1.0 weight percent dichloro¬ methane which boil at about 32.2°C at 760 mm Hg; or from about 58.0 to about 99.7 weight percent 1,1-dichloro-l-fluoroethane, from about 7.0 to about 0.1 weight percent cyclopentane, from about 0.1 to about 30.0 weight percent dichloromethane and from about 0.1 to about 5.0 weight percent methanol which boil at about 30.3°C at 760 mm Hg; or from about 54.0 to about 99.7 weight percent 1,1-dichloro-l-fluoroethane, from about 0.1 to about 7.0 weight percent cyclopentane, from about 0.1 to about 34.0 weight percent dichloromethane and from about 0.1 to about 4.0 weight percent ethanol which boil at about 32.5°C at 760 mm Hg; or from about 91 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 4 weight percent 2-methylpentane, from about 0.1 to about 5 weight percent dichloromethane and from about 0 to about 1 weight percent nitromethane which boil at about 30.5°C at 760 mm Hg; or from about 90.9 to about 97.4 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 2-methylpentane, from about 0.5 to about 3 weight percent dichloromethane, from about 2 to about 4 weight percent methanol and from about 0 to about 1 weight percent nitromethane which boil at about 30.3°C at 760 mm Hg; or from about 93 to about 97.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.2 to about 5 weight percent 2-methylpentane, from about 1 to about 2 weight percent dichloromethane, from about 0.5 to about 2 weight percent ethanol and from about 0 to about 1 weight percent nitromethane which boil at about 31.5°C at 760 mm Hg; or from about 91 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 4 weight percent 3-methylpentane, from about 0.1 to about 4 weight percent dichloromethane and from about 0 to about 1 weight percent nitromethane which boil at about 30.5°C at 760 mm Hg; or from about 93 to about 97 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.1 to about 2 weight percent 3-methylpentane, from about 0.5 to about 3 weight percent dichloromethane, from about 2 to about 4 weight percent methanol and from about 0 to about 1 weight percent nitromethane which boil at about 30.5°C at 760 mm Hg; or from about 92.5 to about 99 weight percent 1,1-dichloro-l- fluoroethane, from about 0.1 to about 2 weight percent 3-methylpentane, from about 0.5 to about 3 weight percent dichloromethane, from about 0.5 to about 2.5 weight percent ethanol and from about 0 to about 1 weight percent nitromethane which boil at about 31.8°C at 760 mm Hg; or from about 90 to about 96 weight percent 1,1 dichloro-1- fluoroethane, from about 1 to about 4 weight percent 2,2-dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 2 to about 4 weight percent methanol and from about 0 to about 1 weight percent nitromethane which boil at about 30.2°C at 760 mm Hg; or from about 91 to about 99 weight percent 1,l-dichloro-l-fluoro- ethane, from about 1 to about 4 weight pecent 2,2- dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 0.5 to about 3 weight percent ethanol and from about 0 to about 1 weight nitromethane which boil at about 31.9°C at 760 mm Hg; or from about 91 to about 99.8 weight percent 1,l-dichloro-l-fluoroethane, from about 0.1 to about 4 weight percent 2,3-dimethylbutane, from about 0.1 to about 4 weight percent dichloro¬ methane and from about 0 to about 1 weight percent nitromethane which boil at about 30.5°C at 760 mm Hg; or from about 90 to about 96 weight percent 1,1-dichloro-l-fluoroethane, from about 1 to about 4 weight percent 2,3-dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 2 to about 4 weight percent methanol and from about 0 to about 1 weight percent nitro¬ methane which boil at about 30.2°C at 760 mm Hg; or from about 91 to about 99 weight percent 1,1- dichloro-1-fluoroethane, from about 1 to about 4 weight percent 2,3-dimethylbutane, from about l to about 2 weight percent dichloromethane, from about 0.5 to about 3 weight percent ethanol and from about 0 to about 1 weight percent nitromethane which boil at about 31.9°C at 760 mm Hg; or from about 90 to about 97.4 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight commercial grade isohexane, from about 0.5 to about 3 weight percent dichloromethane, from about 2 to about 4 weight percent methanol and from about 0 to about 1 weight percent nitro¬ methane which boil at about 30.3°C at 760 mm Hg; or from about 93 to about 97.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.2 to about 5 weight percent commercial grade isohexane, from about 1 to about 2 weight percent dichloromethane, from about 0.5 to about 2 weight percent ethanol and from about 0 to about 1 weight percent nitromethane which boil at about 31.5°C at 760 mm Hg.

The azeotrope-like compositions of claim 1 wherein said compositions of 1,1-dichloro-l-fluoroethane, cyclopentane and dichloromethane boil at about 32.

2°C ± 1.3°C at 760 mm Hg.

3. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 85.0 to about 97.0 weight percent 1,1- dichloro-1-fluoroethane, from about 1.0 to about 5.0 weight percent cyclopentane and rom about 2.0 to about 10.0 weight percent dichloromethane.

4. The azeotrope-like compositions of claim 1 wherein said compositions of 1,1-dichloro-l-fluoroethane, cyclopentane, dichloromethane and methanol boil at about 30.3°C ± 0.8°C at 760 mm Hg.

5. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 70.0 to about 97.0 weight percent 1,1- dichloro-1-fluoroethane, from about 1.0 to about 5.0 weight percent methanol, from about 1.0 to about 5.0 weight percent cyclopentane and from about 1.0 to about 20.0 weight percent dichloromethane.

6. The azeotrope-like compositions of claim 1 wherein said compositions of 1,1-dichloro-l-fluoroethane, cyclopentane, dichloromethane and ethanol boil at about 32.5°C + 0.8°C at 760 mm Hg.

7. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 62.0 to about 97.0 weight percent 1,1- dichloro-1-fluoroethane, from about 1.0 to about 3.0 weight percent ethanol, from about 1.0 to about 5.0 weight percent cyclopentane and from about 1.0 to about 30.0 weight percent dichloromethane.

8. The azeotrope-like compositions of claim l wherein said compositions consist essentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 2-methylpentane, from about 0.1 to about 3 weight percent dichloromethane and from about 0 to about 0.5 weight percent nitromethane.

9. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 93 to about 97 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.1 to about 2 weight percent 2-methylpentane, from about 0.5 to about 2 weight percent dichloromethane, from about 2.5 to about 4 weight percent methanol and from about 0 to about 0.5 weight percent nitromethane.

10. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 95- to about 97 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.2 to about 2 weight percent 2-methylpentane, from about 1 to about 1.8 weight percent dichloromethane, from about 1 to about 2 weight percent ethanol and from about 0 to about 0.5 weight percent nitromethane.

11. The azeotrope-like compositions of claim 1 wherein said compositions consist esseentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 3-methylpentane, from about 0.1 to about 3 weight percent dichloromethane and from about 0 to about 0.5 weight percent nitromethane.

12. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 93 to about 96 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.1 to about 1.5 weight percent 3-methylpentane, from about 1 to about 2 weight percent dichloromethane, from about 2.5 to about 4 weight percent methanol and from about 0 to about 0.5 weight percent nitromethane.

13. The azeotrope-like compositions of claim l wherein said compositions consist essentially of from about 94.5 to about 98 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 1.5 weight percent 3-methylpentane, from about 1 to about 2 weight percent dichloromethane, from about 1 to about 2 weight percent ethanol and from about 0 to about 0.5 weight percent nitromethane.

14. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 2,2-dimethylbutane, from about 0.1 to about 3 weight percent dichloromethane and from about 0 to about 0.5 weight percent nitromethane.

15. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 91 to about 95 weight percent 1,l-dichloro- 1-fluoroethane, from about 2 to about 3 weight percent 2,2-dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 3 to about 4 weight percent methanol and from about 0 to about 0.5 weight percent nitromethane.

16. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 93 to about 97.5 weight percent 1,1- dichloro-l-fluoroethane, from about 1 to about 3 weight percent 2,2-dimethylbutane, from about l to about 2 weight percent dichloromethane, from about 0.5 to about 2 weight percent ethanol and from about 0 to about 0.5 weight percent nitromethane.

17. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 2,3-dimethylbutane, from about 0.1 to about 3 weight percent dichloromethane and from about 0 to about 0.5 weight percent nitromethane.

18. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 91 to about 95 weight percent 1,1-dichloro- 1-fluoroethane, from about 2 to about 3 weight percent 2,3-dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 3 to about 4 weight percent methanol and from about 0 to about 0.5 weight percent nitromethane.

19. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 93 to about 97.5 weight percent 1,1- dichloro-1-fluoroethane, from about 1 to about 3 weight percent 2,3-dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 0.5 to about 2 weight percent ethanol and from about 0 to about 0.5 weight percent nitromethane.

20. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 93 to about 97 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.1 to about 2 weight percent commercial grade isohexane, from about 0.3 to about 2 weight percent dichloromethane, from about 2.5 to about 4 weight percent methanol and from about 0 to about 0.5 weight percent nitro¬ methane.

21. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 95 to about 97 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.2 to about 2 weight percent commercial grade isohexane, from about 1 to about 1.8 weight percent dichloromethane, from about 1 to about 2 weight percent ethanol and from about 0 to about 0.5 weight percent nitromethane.

22. The azeotrope-like compositions of claim 1 wherein said compositions consist esseentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 2-methylpentane, from about 0.1 to about 3 weight percent dichloromethane and from about 0.1 to about 3 weight percent nitromethane.

23. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 94.6 to about 96.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about l weight percent 2-methylpentane, from about 0.5 to about 1.5 weight percent dichloromethane, from about 3.1 to about 3.7 weight percent methanol and from about 0 to about 0.3 weight percent nitro¬ methane.

24. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 95.9 to about 97 weight percent 1,1- dichloro-1-fluoroethane, from about 0.2 to about l weight percent 2-methylpentane, from about 1.4 to about 1.5 weight percent dichloromethane, from about 1.4 to about 1.6 weight percent ethanol and from about 0 to about 0.3 weight percent nitro¬ methane.

25. The azeotrope-like compositions of claim 1 wherein said compositions consist esseentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 3-methylpentane, from about 0.1 to about 3 weight percent dichloromethane and from about 0 to about 0.3 weight percent nitromethane.

26. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 93 to about 96 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.1 to about 1 weight percent 3-methylpentane, from about 1 to about 2 weight percent dichloromethane, from about 3 to

T about 4 weight percent methanol and from about 0 to about 0.3 weight percent nitromethane.

27. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 95 to about 98 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.1 to about 1 weight percent 3-methylpentane, from about 1 to about 2 weight percent dichloromethane, from about l to about 2 weight percent ethanol and from about 0 to about 0.3 weight percent nitromethane.

28. The azeotrope-like compositions of claim 1 wherein said compositions consist esseentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 2,2-dimethylbutane, from about 0.1 to about 3 weight percent dichloromethane and from about 0 to about 0.3 weight percent nitromethane.

29. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 92 to about 94 weight percent 1,1-dichloro- 1-fluoroethane, from about 2 to about 3 weight percent 2,2-dimethylbutane, from about 1.2 to about 1.7 weight percent dichloromethane, from about 3 to about 3.6 weight percent methanol and from about 0 to about 0.3 weight percent nitro¬ methane.

30. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 94 to about 97.5 weight percent 1,1- dichloro-1-fluoroethane, from about 2 to about 3 weight percent 2,2-dimethylbutane, from about 1.2 to about 1.7 weight percent dichloromethane, from about l to about 2 weight percent ethanol and from about 0 to about 0.3 weight percent nitromethane.

31. The azeotrope-like compositions of claim l wherein said compositions consist esseentially of from about 94 to about 99.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 3 weight percent 2,3-dimethylbutane, from about 0.1 to about 3 weight percent dichloromethane and from about 0 to about 0.3 weight percent nitromethane.

³². The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 91 to about 95 weight percent l,l-dichloro- 1-fluoroethane, from about 2 to about 3 weight percent 2,3-dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 3 to about 4 weight percent methanol and from about 0 to about 0.3 weight percent nitromethane,

₃₃. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 94 to about 97.5 weight percent 1,1- dichloro-1-fluoroethane, from about 2 to about 3 weight percent 2,3-dimethylbutane, from about 1 to about 2 weight percent dichloromethane, from about 1.2 to about 1.7 weight percent ethanol and from about 0 to about 0.3 weight percent nitromethane.

34 The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 94 to about 96.8 weight percent 1,1- dichloro-1-fluoroethane, from about 0.1 to about 1 weight percent commercial grade isohexane, from

SUBSTITUTE HEET about 0.3 to about 1.5 weight percent dichloro¬ methane, from about 3.1 to about 3.7 weight percent methanol and from about 0 to about 0.3 weight percent nitromethane.

35. The azeotrope-like compositions of claim 1 wherein said compositions consist essentially of from about 95 to about 97 weight percent 1,1-dichloro- 1-fluoroethane, from about 0.2 to about 2 weight percent commercial grade isohexane, from about 1 to about 1.8 weight percent dichloromethane, from about 1 to about 2 weight percent ethanol and from about 0 to about 0.3 weight percent nitromethane.

36. The azeotrope-like compositions of claim 1 wherein an effective amount of a stabilizer is additionally present in said compositions to prevent metal attack.

³⁷. The azeotrope-like compositions of claim 37 wherein said stabilizer is selected from the group consisting of nitromethane, secondary and tertiary amines, olefins, cycloolefins, alkylene oxides, sulfoxides, sulfones, nitrites, nitriles, acetylenic alcohols or ethers.

38. A method of cleaning a solid surface comprising treating said surface with an azeotrope-like composition of claim 1.

EET