WO1993016215A2

WO1993016215A2 - Azeotrope-like compositions of 1,1-dichloro-1-fluoroethane; dichloroethylene; alkane having 6 carbon atoms or cyclopentane; and alkanol; and optionally nitromethane

Info

Publication number: WO1993016215A2
Application number: PCT/US1993/000859
Authority: WO
Inventors: Ellen Louise Swan; Peter Brian Logsdon; Rajat Subhra Basu
Original assignee: Allied-Signal Inc.
Priority date: 1992-02-05
Filing date: 1993-02-02
Publication date: 1993-08-19
Also published as: WO1993016215A3; AU3601893A

Abstract

Azeotrope-like compositions comprising 1,1-dichloro-1-fluoroethane; dichloroethylene; alkane having 6 carbon atoms or cyclopentane; and alkanol; and optionally 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

AZEOT OPE-LI E COMPOSITIONS OF

1.1-DICHLORO-1-FLUOROETHANE: DICHLOROETHYLENE:

ALKANE HAVING 6 CARBON ATOMS OR CYCLOPENTANE:

AND ALKANOL: AND OPTIONALLY NITROMETHANE

FIELD OF THE INVENTION

This invention relates to azeotrope-like mixtures of 1,1-dichloro-l-fluoroethane; dichloroethylene; alkane having 6 carbon atoms or cyclopentane; and alkanol; and optionally nitromethane. These mixtures are useful in a variety of vapor degreasing, cold cleaning and solvent cleaning applications including defluxing and dry cleaning.

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.

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 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.

The art is continually seeking new fluorocarbon, hydrofluorocarbon, and hydrochlorofluorocarbon 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, hydrofluorocarbon, and hydrochlorofluorocarbon based azeotrope-like mixtures with minimal or no chlorine which are considered to be stratospherically safe substitutes for presently used chlorofluorocarbons (CFCs) . 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-l-fluoroethane (known in the art as HCFC-141b) , will not adversely affect atmospheric chemistry, being negligible contributors to ozone depletion and to green-house global warming in comparison to chlorofluorocarbons such as 1,1,2- trichloro-1,2, 2-trifluoroethane (CFC-113) . HCFC-141b is known to be useful as a solvent.

DETAILED DESCRIPTION OF THE INVENTION

Our solution to the need in the art for substitutes for chlorofluorocarbon solvents is mixtures comprising 1, 1-dichloro-l-fluoroethane; dichloroethylene; alkane having 6 carbon atoms or cyclopentane; and alkanol; and optionally nitromethane. Also, novel azeotrope-like or constant-boiling compositions have been discovered comprising 1, 1-dichloro-l-fluoroethane; dichloroethylene; alkane having 6 carbon atoms or cyclopentane; and alkanol; and optionally nitromethane. The dichloroethylene is selected from the group consisting of trans-1,2-dichloroethylene; cis-1, 2-dichloroethylene; and mixtures thereof. The alkane having 6 carbon atoms is selected from the group consisting of n-hexane; 2-methylpentane; 3-methylpentane; 2,2-dimethylbutane; 2,3-dimethylbutane; isohexane, and mixtures thereof. The alkanol is selected from the group consisting of methanol and ethanol.

Preferably, the novel azeotrope-like compositions comprise effective amounts of 1,1-dichloro- 1-fluoroethane; dichloroethylene; alkane or cyclopentane; and alkanol; and optionally nitromethane. The term "effective amounts" as used herein means the amount of each component which upon combination with the other component, results in the formation of the present azeotrope-like composition.

The azeotrope-like compositions comprise from about 87 to about 98.8 weight percent of 1,1-dichloro-l-fluoroethane, from about 0.5 to about 5 weight percent of trans-1,2-dichloroethylene, from about 0.1 to about 4 weight percent of cyclopentane or alkane having 6 carbon atoms selected from the group consisting of 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, commercial grade isohexane wherein said 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, and mixtures thereof, from about 0.5 to about 4 weight percent of methanol or ethanol, and from 0 to about l weight percent nitromethane wherein said compositions with said cyclopentane and said methanol boil at about 29.5°C at 760 mm Hg, said compositions with said cyclopentane and said ethanol boil at about 31.6°C at 760 mm Hg, said compositions with said 2-methylpentane and said methanol boil at about 29.4°C at 760 mm Hg, said compositions with said 2-methylpentane and said ethanol boil at about 30.8°C at 760 mm Hg, said compositions with said 3- methylpentane and said methanol boil at about 29.3°C at 760 mm Hg, said compositions with said 3-methylpentane and said ethanol boil at about 32.1°C at 760 mm Hg, said compositions with said 2,2-dimethylbutane and said methanol boil at about 30.8°C at 760 mm Hg, said compositions with said 2,2-dimethylbutane and said ethanol boil at about 31.8°C at 760 mm Hg, said compositions with said 2,3-dimethylbutane and said methanol boil at about 30.8°C at 760 mm Hg, said compositions with said 2,3-dimethylbutane and said ethanol boil at about 31.8°C at 760 mm Hg, said compositions with said commercial grade isohexane and said methanol boil at about 29.4°C at 760 mm Hg, and said compositions with said commercial grade isohexane and said ethanol boil at about 30.8°C at 760 mm Hg.

The present azeotrope-like compositions are advantageous for the following reasons. The 1,1- dichloro-1-fluoroethane component is a negligible contributor to ozone depletion and has good solvent properties. The dichloroethylene, alkane, and alkanol components also have good solvent properties. Thus, when these components are combined in effective amounts, an efficient azeotrope-like solvent results. The preferred cyclopentane based azeotrope-like compositions are in Table I below:

TABLE

The preferred 2-methylpentane based azeotrope-like compositions are in Table II below:

TABLE II

The preferred 3-methylpentane based azeotrope-like compositions are in Table III below:

TABLE

The preferred 2,2-dimethylbutane based azeotrope-like compositions are in Table IV below:

TABLE IV

The preferred 2,3-dimethylbutane based azeotrope-like compositions are in Table V below:

TABLEV

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. The preferred commercial grade isohexane based azeotrope-like compositions are in Table VI below:

TABLE VI

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 and Tag Closed Cup Test Method - ASTM D 56-82.

The term "azeotrope-like composition" as used herein 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.

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 and dry cleaning.

In one process embodiment of the invention, the azeotrope-like compositions of the invention may be used to dissolve contaminants or remove contaminants from the surface of a substrate by treating the surface with the compositions in any manner well known to the art such as by dipping or spraying or use of conventional degreasing apparatus wherein the contaminants are substantially dissolved or removed.

The 1,l-dichloro-1-fluoroethane; trans-1,2- dichloroethylene; cyclopentane; n-hexane; 2-methylpentane; 3-methylpentane; 2,2-dimethylbutane; 2,3-dimethylbutane; isohexane; methanol; ethanol; and nitromethane components of the novel solvent azeotrope-like compositions of the invention are known materials and are commercially available. Commercially available trans-1,2-dichloroethylene may contain from about 0.1 to about 10 weight percent cis-1,2-dichloroethylene.

The present invention is more fully illustrated by the following non-limiting Examples. EXAMPLES 1 AND 2

These examples confirm the existence of constant-boiling or azeotrope-like compositions of 1,l-dichloro-l-fluoroethane; trans-1,2-dichloroethylene; cyclopentane; and methanol or ethanol via the method of distillation. It also illustrates that this mixture does not fractionate during distillation.

A 5-plate Oldershaw distillation column with a cold water condensed automatic liquid dividing head was used for these examples. The distillation column was charged with HCFC-141b, trans-l,2-dichloroethylene (hereafter TDCE) , cyclopentane (hereinafter CP) , and methanol (hereinafter MeOH) (Example 1) or ethanol (hereinafter EtOH) (Example 2) in the amounts indicated in Table VII below for the starting material. The composition was heated under total reflux for about an hour to ensure equilibration. A reflux ratio of 3:1 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 mixture is constant-boiling or azeotrope-like. TABLE VII

STARTING MATERIAL (WT. %)

DISTILLATE COMPOSITIONS (WT. %)

From the above example, it is readily apparent that additional constan -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. EXAMPLES 3 AND 4

Example l was repeated for Example 3 except that 2-methylpentane was used instead of cyclopentane and Example 2 was repeated for Example 4 except that 2-methylpentane was used instead of cyclopentane.

The distillation column was charged with HCFC-141b, trans-1,2-dichloroethylene (hereafter TDCE) , 2-methylpentane (hereinafter 2-MP) , and methanol

(hereinafter MeOH) (Example 3) or ethanol (hereinafter EtOH) (Example 4) in the amounts indicated in Table VIII below for the starting material.

TABLE VIII

STARTING MATERIAL (WT. %)

DISTILLATE COMPOSITIONS (WT. %)

EXAMPLES 5 AND 6

Example l was repeated for Example 5 except that 3-methylpentane was used instead of cyclopentane and Example 2 was repeated for Example 6 except that 3-methylpentane was used instead of cyclopentane.

The distillation column was charged with HCFC-141b, trans-1,2-dichloroethylene (hereafter TDCE) , 3-methylpentane (hereinafter 3-MP) , and methanol

(hereinafter MeOH) (Example 5) or ethanol (hereinafter EtOH) (Example 6) in the amounts indicated in Table IX below for the starting material.

TABLE IX

STARTING MATERIAL (WT. %)

EXAMPLES 7 AND 8

Example 1 was repeated for Example 7 except that 2,2-dimethylbutane was used instead of cyclopentane and Example 2 was repeated for Example 8 except that 2,2-dimethylbutane was used instead of cyclopentane.

The distillation column was charged with HCFC-141b, trans-1,2-dichloroethylene (hereafter TDCE) , 2,2-dimethylbutane (hereinafter 2,2-DMB) , and methanol (hereinafter MeOH) (Example 7) or ethanol (hereinafter EtOH) (Example 8) in the amounts indicated in Table X below for the starting material.

TABLE X

STARTING MATERIAL (WT. %)

EXAMPLES 9 THROUGH 16

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 8 are used as the solvents. Cleanliness testing of coupons are done by measurement of the weight change of the coupons using an analytical balance to determine the total residual materials left after cleaning.

EXAMPLES 17 THROUGH 24

Each solvent of Examples 1 through 8 above is added to mineral oil in a weight ratio of 50:50 at 27^βC. Each solvent is miscible in the mineral oil. EXAMPLES 25 THROUGH 32

Metal coupons are soiled with various types of oil. The soiled metal coupons are immersed in the solvents of Examples l through 8 above for a period of 15 seconds to 2 minutes, removed, and allowed to air dry. Upon visual inspection, the soil appears to be substantially removed.

EXAMPLES 33 THROUGH 40

Metal coupons are soiled with various types of oil. The soiled metal coupons are sprayed with the solvents of Examples 1 through 8 above and allowed to air dry. Upon visual inspection, the soil appears to be substantially removed.

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: alkanols having 4 to 7 carbon atoms, nitroalkanes having 1 to 3 carbon atoms, 1,2-epoxyalkanes having 2 to 7 carbon atoms, phosphite esters having 12 to 30 carbon atoms, ethers having 3 or 4 carbon atoms, unsaturated compounds having 4 to 6 carbon atoms, acetals having 4 to 7 carbon atoms, ketones having 3 to 5 carbon atoms, and amines having 6 to 8 carbon atoms. Other suitable inhibitors will readily occur to those skilled in the art. The inhibitors may be used alone or in mixtures thereof in any proportions. Typically, up to about 2 percent based on the total weight of the azeotrope-like composition of inhibitor might be used.

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, ethylene oxide, air, and mixtures thereof.

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

What is claimed is:

1. Azeotrope-like compositions consisting essentially of from about 87 to about 98.8 weight percent of 1,1-dichloro-l-fluoroethane, from about 0.5 to about 5 weight percent of trans-1,2- dichloroethylene, from about 0.1 to about 4 weight percent of cyclopentane or alkane having 6 carbon atoms selected from the group consisting of 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane,

2,3-dimethylbutane, commercial grade isohexane wherein said 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, and mixtures thereof, from about 0.5 to about 4 weight percent of methanol or ethanol, and from 0 to about 1 weight percent nitromethane wherein said compositions with said cyclopentane and said methanol boil at about 29.5°C at 760 mm Hg, said compositions with said cyclopentane and said ethanol boil at about 31.6°C at 760 mm Hg, wherein said compositions with said 2- methylpentane and said methanol boil at about 29.4°C at 760 mm Hg, said compositions with said 2-methylpentane and said ethanol boil at about 30.8°C at 760 mm Hg, said compositions with said 3-methylpentane and said methanol boil at about 29.3°C at 760 mm Hg, said compositions with said 3-methylpentane and said ethanol boil at about 32.1°C at 760 mm Hg, said compositions with said 2,2-dimethylbutane and said methanol boil at about 30.8°C at 760 mm Hg, said compositions with said 2,2-dimethylbutane and said ethanol boil at about 31.8°C at 760 mm Hg, said compositions with said 2,3- dimethylbutane and said methanol boil at about 30.8°C at 760 mm Hg, said compositions with said 2,3- dimethylbutane and said ethanol boil at about 31.8°C at 760 mm Hg, said compositions with said commercial grade isohexane and said methanol boil at about 29.4°C at 760 mm Hg, and said compositions with said commercial grade isohexane and said ethanol boil at about 30.8°C at 760 mm Hg.

2. The azeotrope-like compositions of claim 1 consisting essentially of from about 89 to about 98.7 weight percent said 1,1-dichloro-l-fluoroethane, from about 0.5 to about 4 weight percent said trans-1,2- dichloroethylene, from about 0.3 to about 4 weight percent said cyclopentane, from about 0.5 to about 4 weight percent said methanol or ethanol, and from 0 to about 1 weight percent said nitromethane.

3. The azeotrope-like compositions of claim l consisting essentially of from about 91 to about 98.8 weight percent said 1,1-dichloro-l-fluoroethane, from about 0.5 to about 3 weight percent said trans-1,2- dichloroethylene, from about 0.2 to about 2 weight percent said 2-methylpentane, from about 0.5 to about 4 weight percent said methanol or ethanol, and from 0 to about 1 weight percent said nitromethane.

4. The azeotrope-like compositions of claim 1 consisting essentially of from about 91 to about 98.4 weight percent said 1,l-dichloro-1-fluoroethane, from about 0.5 to about 3 weight percent said trans-1,2- dichloroethylene, from about 0.1 to about 2 weight percent said 3-methylpentane, from about 1 to about 4 weight percent said methanol or ethanol, and from 0 to about 1 weight percent said nitromethane. 5. The azeotrope-like compositions of claim l consisting essentially of from about 87 to about 98.5 weight percent said 1,1-dichloro-1-fluoroethane, from about 0.5 to about 5 weight percent said trans-1,2- dichloroethylene, from about 0.5 to about 4 weight percent said 2,2-dimethylbutane, from about 0.

5 to about 4 weight percent said methanol or ethanol, and from 0 to about 1 weight percent said nitromethane.

6. The azeotrope-like compositions of claim 1 consisting essentially of from about 87 to about 98.5 weight percent said 1,1-dichloro-1-fluoroethane, from about 0.5 to about 5 weight percent said trans-1,2- dichloroethylene, from about 0.5 to about 4 weight percent said 2,3-dimethylbutane, from about 0.5 to about 4 weight percent said methanol or ethanol, and from 0 to about 1 weight percent said nitromethane.

7. The azeotrope-like compositions of claim l consisting essentially of from about 91 to about 98.8 weight percent said 1,1-dichloro-1-fluoroethane, from about 0.5 to about 3 weight percent said trans-1,2- dichloroethylene, from about 0.2 to about 2 weight percent said commercial grade isohexane, from about 0.5 to about 4 weight percent said methanol or ethanol, and from 0 to about 1 weight percent said nitromethane.

8. The azeotrope-like compositions of claim l wherein said compositions additionally contain an inhibitor selected from the group consisting of alkanols having 4 to 7 carbon atoms, nitroalkanes having 1 to 3 carbon atoms, 1,2-epoxyalkanes having 2 to 7 carbon atoms, phosphite esters having 12 to 30 carbon atoms, ethers having 3 or 4 carbon atoms, unsaturated compounds having 4 to 6 carbon atoms, acetals having 4 to 7 carbon atoms, ketones having 3 to 5 carbon atoms, and amines having 6 to 8 carbon atoms.

9. A method of dissolving contaminants or removing contaminants from the surface of a substrate which comprises the step of: using said azeotrope-like composition of claim

1 as solvent.

• 10. A method of dissolving contaminants or removing contaminants from the surface of a substrate which comprises the step of: using said azeotrope-like composition of claim

2 as solvent.