Azeotrope-like compositions of 1,1-dichloro-1-fluoroethane, dichloromethane and optionally alkanol

FIELD OF THE INVENTION
This invention relates to azeotrope-like compositions containing 1,1-dichloro-1-fluoroethane, dichloromethane and optionally alkanol. These mixtures are useful in a variety of cleaning applications including defluxing. One of the compositions is also useful as a blowing agent in the preparation of polyurethane foams.
BACKGROUND OF THE INVENTION
Fluorocarbon based solvents have been used 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 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 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 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 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. Pat. No. 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. 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 azeotropic compositions having fluorocarbon components because the fluorocarbon components contribute additionally desired characteristics, such as polar functionality, increased solvency power, and stabilizers. 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 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 are of particular interest because they are considered to be stratospherically safe substitutes for presently used fully halogenated chlorofluorocarbons. 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 hydrochlorofluorocarbons, like 1,1-dichloro-1-fluoroethane (HCFC-141b) have a much lower ozone depletion potential and global warming potential than the fully halogenated species.
Accordingly, it is an object of the invention to provide novel environmentally acceptable azeotropic compositions useful in a variety of industrial cleaning applications and as a blowing agent in the preparation of polyurethane foams.
It is another object of the invention to provide azeotrope-like compositions which are liquid at room temperature and which will not fractionate under conditions of use.
Other objects and advantages of the invention will become apparent from the following description.
SUMMARY OF THE INVENTION
The invention relates to novel azeotrope-like compositions which are useful in a variety of industrial cleaning applications. One of the compositions is also useful as a blowing agent in the preparation of polyurethane foams. Specifically, the invention relates to compositions of 1,1-dichloro-1-fluoroethane, dichloromethane and optionally alkanol which are essentially constant boiling, environmentally acceptable, non-fractionating, and which remain liquid at room temperature.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, novel azeotrope-like compositions have been discovered consisting essentially of from about 79.6 to about 99.95 weight percent 1,1-dichloro-1-fluoroethane (HCFC-141b), from about 0.05 to about 15.9 weight percent dichloromethane and optionally from about 0 to about 4.5 weight percent alkanol which boil at about 32.0.degree. C. .+-. about 0.6.degree. C. at 760 mm Hg.
As used herein, the term alkanol will refer to either of the following two compounds: methanol or ethanol.
The 1,1-dichloro-1-fluoroethane component of the invention has good solvent properties. The alkanol and chlorinated alkane also have good solvent capabilities. The alkanol dissolves polar organic materials and amine hydrochlorides while the chlorinated alkane enhances the solubility of oils. Thus, when these components are combined in effective amounts an efficient azeotrope-like solvent results.
In a preferred embodiment of the invention, the azeotrope-like compositions consist essentially of from about 96 to about 99.95 weight percent 1,1-dichloro-1-fluoroethane and from about 0.05 to about 4 weight percent dichloromethane and boil at about 32.2.degree. C. .+-. about 0.3.degree. C. at 760 mm Hg.
In a more Preferred embodiment of the invention, the azeotrope-like compositions consist essentially of from about 97.5 to about 99.95 weight percent 1,1-dichloro-1-fluoroethane and from about 0.05 to about 2.5 weight percent dichloromethane.
When the alkanol is methanol, the azeotrope-like compositions of the invention consist essentially of from about 83.7 to about 96.9 weight percent 1,1-dichloro-1-fluoroethane, from about 0.1 to about 12.9 weight percent dichloromethane and from about 3 to about 3.8 weight percent methanol and boil at about 31.8.degree. C. .+-. about 0.3.degree. C. at 760 mm Hg.
In a preferred embodiment utilizing methanol, the azeotrope-like compositions of the invention consist essentially of from about 92.2 to about 96.95 weight percent 1,1-dichloro-1-fluoroethane, from about 0.05 to about 4 weight percent dichloromethane and from about 3 to about 3.8 weight percent methanol.
In a more preferred embodiment utilizing methanol, the azeotrope-like compositions of the invention consist essentially of from about 93.7 to about 96.7 weight percent 1,1-dichloro-1-fluoroethane, from about 0.05 to about 2.5 weight percent dichloromethane and from about 3.3 to about 3.8 weight percent methanol.
When the alkanol is ethanol, the azeotrope-like compositions of the invention consist essentially of from about 83 to about 98.95 weight percent 1,1-dichloro-1-fluoroethane, from about 0.05 to about 14.8 weight percent dichloromethane and from about 1 to about 2.2 weight percent ethanol and boil at about 31.8.degree. C. .+-. about 0.3.degree. C. at 760 mm Hg.
In a preferred embodiment utilizing ethanol, the azeotrope-like compositions of the invention consist essentially of from about 94 to about 98.45 weight percent 1,1-dichloro-1-fluoroethane, from about 0.05 to about 4 weight percent dichloromethane and from about 1.5 to about 2 weight percent ethanol.
In a more preferred embodiment utilizing ethanol, the azeotrope-like compositions of the invention consist essentially of from about 95.5 to about 98.45 weight percent 1,1-dichloro-1-fluoroethane, from about 0.05 to about 2.5 weight percent dichloromethane and from about 1.5 to about 2 weight percent ethanol.
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 nitromethane, 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 - 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 in vapor phase solvent cleaning as described above.
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 compositions in which the liquid composition changes substantially during boiling or evaporation.
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 components. If the mixture is non-azeotropic or non-azeotrope-like, the mixture will fractionate, with the lowest boiling component distilling off first, etc. 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 is not part of an azeotropic system. If the degree of fractionation of the candidate mixture is unduly great, then a composition closer to the true azeotrope must be selected to minimize fractionation. 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 discussion 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. All such compositions are intended to be covered by the term azeotrope-like as used herein. As an example, it is well known that at different pressures, the composition of a given azeotrope will vary at least slightly as does the boiling point of the composition. Thus, an azeotrope of A and B represents a unique type of relationship but with a variable composition depending on temperature and/or pressure. Accordingly, another way of defining azeotrope-like within the meaning of this invention is to state that such mixtures boil within about .+-.0.6.degree. C. (at 760 mm Hg) of the boiling point of the most preferred compositions disclosed herein. As is readily understood by persons skilled in the art, the boiling point of the azeotrope will vary with the pressure.
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 1-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. Pat. No. 4,843,181 and HCFC-133 may be prepared by a known process such as that taught by U.S. Pat. No. 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 prepared by any known method such as that disclosed by U.S. Pat. No. 4,851,595. More preferred propellants include hydrochlorofluorocarbons, hydrofluorocarbons, and mixtures thereof. The most preferred propellants include chlorodifluoromethane and 1,1,1,2-tetrafluoroethane.
In another process embodiment of the invention, the azeotrope-like compositions of the invention may be used to form polyurethane and polyisocyanurate foams by reacting and foaming a mixture of ingredients which will react to form polyurethane and polyisocyanurate foams in the presence of a blowing agent comprising the azeotrope-like compositions.
The compositions of the invention may be used as auxiliary or primary blowing agents for the preparation of polyurethane foams. Polyurethanes are polymers of polyols and isocyanates. A wide variety of polyols may be employed as disclosed in the prior art, such as polyether polyols and polyester polyols. Illustrative suitable polyether polyols are polyoxypropylene diols having a molecular weight of between about 1,500 and 2,500, glycerol based polyoxypropylene triols having a molecular weight of between about 1,000 and 3,000, trimethylolpropane-based triols having a hydroxyl number of about 390, sorbitol-based hexol having a hydroxyl number of about 490, and sucrose-based octols having a hydroxyl number of about 410. Illustrative suitable polyester polyols are the reaction products of polyfunctional organic carboxylic acids such as succinic acid, adipic acid, phthalic acid and terephthalic acid with monomeric polyhydric alcohols such as glycerol, ethylene glycol, trimethylol propane, and the like.
A wide variety of isocyanates may be employed as disclosed in the prior art. Illustrative suitable isocyanates are the aliphatic isocyanates such as hexamethylene diisocyanate, aromatic isocyanates such as toluene diisocyanate (TDI), preferably the isomeric mixture containing about 80 weight percent of the 2,4 isomer and 20 weight percent of the 2,6 isomer, crude TDI, crude diphenylmethane diisocyanate and polymethylpolyphenyl isocyanate.
The amount of blowing agent to be employed will depend on whether it is to be used as a primary or auxiliary blowing agent and the nature of the foams desired, i.e, whether flexible or rigid foam is desired.
The amount of blowing agent employed can be readily determined by persons of ordinary skill in the art. Generally, about 1 to about 15 weight percent based on the polyurethane forming reaction mixture is employed and preferably, about 5 to about 10 weight percent.
As is well known in the art, the urethane-forming reaction requires a catalyst. Any of the well known urethane-forming catalysts may be employed. Illustrative organic catalysts are the amino compounds such as triethylenediamine N,N,N',N'-tetramethylethylenediamine, dimethylethanolamine, triethylamine and N-ethylmorpholine. Inorganic compounds such as the non-basic heavy metal compounds as illustrated by dibutyl tin dilaurate, stannous octoate and manganese acetyl acetonate may also be used as catalysts. In general, the amount of catalyst present in the foam forming mixture ranges from about 0.05 to about 2 parts by weight per 100 parts by weight of the polyol component.
As is well recognized in the art, a variety of other additives may be incorporated in the foam-forming mixtures including stabilizers, such as silicone oils; cross-linking agents such as 1,4-butanediol, glycerol, triethanolamine methylenedianiline; plasticizers, such as tricresyl phosphate and dioctyl phthalate; antioxidants; flame retardants; coloring material; fillers; and antiscorch agents.
Polyurethane foams are prepared according to the invention by reacting and foaming a mixture of ingredients which will react to form the foams in the presence of a blowing agent according to the invention. In practice, the foam forming ingredients are blended, allowed to foam, and are then cured to a finished product. The foaming and curing reactions, and conditions therefor are well-known in the art and do not form a part of this invention. Such are more fully described in the prior art relating to the manufacture of polyurethane foams. Thus, for example, the polyether may first be converted to a polyetherpolyisocyanate prepolymer by reaction in one or more stages with an excess amount of isocyanate at temperatures from about 75.degree.-125.degree. C. or by reacting the polyol and the isocyanate together at room temperature in the presence of a catalyst for the reaction such as N-methylmorpholine. The prepolymer would then be charged to the foam-forming mixture as the foam producing ingredient with or without the addition of additional isocyanate and foamed in the presence of the blowing agent, optionally with additional polyol cross-linking agents and other conventional optional additives. Heat may be applied to cure the foam. If a prepolymer is not employed, the polyether, isocyanate, blowing agent and other optional additives may be reacted simultaneously to produce the foam in a single stage.
The HCFC-141b, dichloromethane and alkanol components of the invention are known materials. Preferably they should be used in sufficiently high purity so as to avoid the introduction of adverse influences upon the solvency properties or constant-boiling properties of the system.
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 the essential components described herein.

The present invention is more fully illustrated by the following non-limiting Examples.
EXAMPLE 1
The compositional range over which 141b and dichloromethane exhibit constant-boiling behavior was determined. This was accomplished by charging approximately 8 ml. 141b into an ebulliometer, bringing it to a boil, adding measured amounts of dichloromethane and finally recording the temperature of the ensuing boiling mixture. A minimum in the boiling point versus composition curve occurred; indicating that a constant boiling composition formed.
The ebulliometer consisted of a heated sump in which the 141b was brought to a boil. The upper part of the ebulliometer connected to the sump was cooled thereby acting as a condenser for the boiling vapors, allowing the system to operate at total reflux. After bringing the 141b to a boil at atmospheric pressure, measured amounts of dichloromethane were titrated into the ebulliometer. The change in boiling point was measured with a platinum resistance thermometer.
The following table lists, for Example 1, the compositional range over which the 141b/dichloromethane mixture is constant boiling; i.e. the boiling point deviations are within .+-. about 0.5.degree. C. of each other. Based on the data in Table I, 141b/dichloromethane compositions ranging from about 84.1-99.9/0.1-15.9 weight percent respectively would exhibit constant boiling behavior.
TABLE I______________________________________Composition (wt. %) Temperature141b MeCl.sub.2 (.degree.C. @ 760 mm Hg)______________________________________99.89 0.11 32.0599.8 0.2 32.0599.16 0.84 32.0698.13 1.87 32.0896.13 3.87 32.1294.20 5.80 32.1590.59 9.41 32.2787.24 12.76 32.3784.10 15.9 32.48______________________________________
EXAMPLE 2
The compositional range over which 141b, dichloromethane and methanol exhibit constant-boiling behavior was determined. This was accomplished by charging 8 ml. of selected 141b-based binary compositions into an ebulliometer, bringing them to a boil, adding measured amounts of a third component and finally recording the temperature of the ensuing boiling mixture. In each case, a minimum in the boiling point versus composition curve occurred; indicating that a constant boiling composition formed.
The ebulliometer consisted of a heated sump in which the 141b-based binary mixture was brought to a boil. The upper part of the ebulliometer connected to the sump was cooled thereby acting as a condenser for the boiling vapors, allowing the system to operate at total reflux. After bringing the 141b-based binary mixture to a boil at atmospheric pressure, measured amounts of a third component were titrated into the ebulliometer. The change in boiling point was measured with a platinum resistance thermometer.
The following table lists, for Example 2, the compositional range over which the 141b/dichloromethane/methanol mixture is constant boiling; i.e. the boiling point deviations are within .+-. about 0.5.degree. C. of each other. Based on the data in Table II, 141b/dichloromethane/methanol compositions ranging from about 83.7-96.1/0.1-12.9/3.5-3.8 weight percent respectively would exhibit constant boiling behavior.
TABLE II______________________________________Composition (wt. %) Temperature141b MeCl.sub.2 MeOH (.degree.C. @ 760 mm Hg)______________________________________96.05 0.11 3.84 29.5395.79 0.32 3.89 29.5395.33 0.85 3.82 29.5594.32 1.90 3.78 29.5792.37 3.93 3.70 29.6490.5 5.88 3.62 29.7286.97 9.55 3.48 29.8683.71 12.94 3.55 30.00______________________________________
EXAMPLE 3
The compositional range over which 141b, dichloromethane and ethanol exhibit constant-boiling behavior was determined by repeating the experiment outlined in Example 2 above. In each case, a minimum in the boiling point versus composition curve occurred; indicating that a constant boiling composition formed.
The following table lists, for Example 3, the compositional range over which the 141b/dichloromethane/ethanol mixture is constant boiling; i.e. the boiling point deviations are within .+-. about 0.5.degree. C. of each other. Based on the data in Table III, 141b/dichloromethane/ethanol compositions ranging from about 83.4-97.9/0.1-14.8/1.7-2 weight percent respectively would exhibit constant boiling behavior.
TABLE III______________________________________Composition (wt. %) Temperature141b MeCl.sub.2 EtOH (.degree.C. @ 760 mm Hg)______________________________________97.89 0.11 2.00 31.6497.69 0.32 1.99 31.6497.17 0.85 1.98 31.6496.66 1.37 1.97 31.6495.65 2.40 1.95 31.6693.70 4.39 1.91 31.7491.83 6.30 1.87 31.8090.02 8.14 1.84 31.8886.62 11.61 1.77 32.0083.42 14.82 1.70 32.11______________________________________
EXAMPLE 4
The azeotropic properties of 1,1-dichloro-1-fluoroethane, methanol and dichloromethane were also studied via the method of distillation. The results confirm that an azeotrope-like composition forms between the components and also illustrates that the composition does not fractionate during distillation.
A 5-plate Oldershaw distillation column with a cold water condensed automatic liquid dividing head was used in the example. The distillation column was charged with approximately 300 grams of a mixture of HCFC-141b, methanol and dichloromethane. The mixture was heated under total reflux for about an hour to ensure equilibration. A reflux ration of 3:1 was employed for these particular distillations. Approximately 50 percent of the original charge was collected in four similar-sized overhead fractions. The compositions of these fractions were analyzed using gas chromatrography. The results are reported in Table IV.
TABLE IV______________________________________ HCFC- DICHLORO- NITRO-EX 141b METHANOL METHANE METHANE______________________________________STARTING COMPOSITION (WT. %)4 94.8 4.0 1.0 0.2DISTILLATE COMPOSITION (WT. %)4 95.5 3.8 0.8 0.0______________________________________ BAROMETRIC BOILING POINT BOILING PRESSURE CORRECTED TOEX POINT (.degree.C.) (mm Hg) 760 mm Hg (.degree.C.)______________________________________1 29.0 744 29.7______________________________________
EXAMPLES 5-8
To illustrate the constant boiling and non-segregating properties of the compositions of the invention under conditions of actual use in vapor phase degreasing operations, a vapor degreasing machine is charged with the azeotrope-like composition of Example 1 (this experiment is repeated using the azeotrope-like compositions of Examples 2-4). The vapor phase degreasing machine utilized is a small water-cooled, three-sump vapor phase degreaser. This machine is comparable to machines used in the field today and presents the most rigorous test of solvent segregating behavior. Specifically, the degreaser employed to demonstrate the constant-boiling and non-segregating properties of the invention contains two overflowing rinse-sumps and a boil-sump. The boil-sump is electrically heated and contains a low-level shut-off switch. Solvent vapors in the degreaser are condensed on water-cooled stainless-steel coils. The capacity of the unit is approximately 1.2 gallons. This degreaser is very similar to degreasers which are commonly used in commercial establishments.
The solvent charge is brought to reflux and the compositions in the rinse sump and the boil sump, where the overflow from the work sump is brought to the mixture boiling point, are determined using a Perkin Elmer 8500 gas chromatograph. The temperature of the liquid in the boil sump is monitored with a thermocouple temperature sensing device accurate to .+-.0.2.degree. C. Refluxing is continued for 48 hours and sump compositions are monitored throughout this time. A mixture is considered constant boiling or non-segregating if the maximum concentration difference between sumps for any mixture component is .+-.2 sigma around the mean value. Sigma is a standard deviation unit. It is our experience, based upon 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 still produce very satisfactory non-segregating cleaning behavior.
If the mixture is not azeotrope-like, the high boiling components will very quickly concentrate in the boil sump and be depleted in the rinse sump. This does not happen with the compositions of the invention. In addition, the concentration of each component in the sumps remains well within .+-.2 sigma. These results indicate that the compositions of the invention are constant boiling and will not segregate in any large-scale commercial vapor degreasers, thereby avoiding potential safety, performance and handling problems.
EXAMPLES 9-12
Performance studies are conducted to evaluate the solvent properties of the azeotrope-like compositions of the invention. Specifically, metal coupons are cleaned using the azeotrope-like composition of Example 1 as solvent (this experiment is repeated using the azeotrope-like compositions of Examples 2-4). The metal coupons are soiled with various types of oils and heated to 93.degree. 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 simulated vapor phase degreaser. Condenser coils are kept around the lip of a cylindrical vessel to condense the solvent vapor which then collects in 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 and by measuring the weight change of the coupons using an analytical balance to determine the total residual materials left after cleaning. The results indicate that the compositions of the invention are effective solvents.
EXAMPLES 13-16
For the following examples, six-ounce three-piece aerosol cans are used. The azeotrope-like composition of each of Examples 1-4 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 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 measures the ionic contamination of the board.
EXAMPLE 17
Free-rise rigid polyurethane foam is prepared from the formulation specified in Table V using a Martin Sweets Co. Modern Module III urethane foam machine at a delivery rate of 15 lbs./min. and by using the azeotrope-like composition of Example 1 as blowing agent. This polyurethane formulation is one example of a pour-in-place rigid polyurethane formulation which might be used as appliance insulation.
TABLE V______________________________________RIGID POLYURETHANE FORMULATIONComponent Parts by weight______________________________________Pluracol 1114.sup.1 (420-OH#) 100.0Silicone L-5340.sup.2 1.5Thancat TD-33.sup.3 0.5Thancat DME.sup.4 0.2Catalyst T-12.sup.5 0.1HCFC-141b/dichloromethane(84.1/15.9) 30.0Lupranate M20S.sup.6 (1.29 Index) 129.0______________________________________ .sup.1 BASF Wyandotte Corp. polyether polyol .sup.2 Union Carbide Corp. silicone surfactant .sup.3 Texaco Inc. 33% triethylene diamine in propylene glycol .sup.4 Texaco Inc. N,Ndimethylethanolamine .sup.5 Metal & Thermit Co. dibutyl dilaurate .sup.6 BASF Wyandotte Corp. polymethylene polyphenylisocyanate
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.

Number	Name	Date
4131561	Reusser	Dec 1978
4836947	Lund et al.	Jun 1989
4842764	Lund et al.	Jun 1989
4945119	Smits	Jul 1990
4996242	Lin	Feb 1991

Number	Date	Country
57-20333	Feb 1982	JPX
1-56760	Mar 1989	JPX
1-132814	May 1989	JPX
1-139779	Jun 1989	JPX
1-139780	Jun 1989	JPX
1-204999	Aug 1989	JPX

Azeotrope-like compositions of 1,1-dichloro-1-fluoroethane, dichloromethane and optionally alkanol

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