NO178438B - Azeotrope-like mixtures of dichloropentafluoropropane and a C 1-4 alkanol - Google Patents

Description

The present invention relates to azeotrope-like mixtures of dichloropentafluoropropane and a C 3 -alkanol. These compositions can be used in a number of steam degreasing, cold cleaning and solvent cleaning applications including defluxing and dry cleaning.

Fluorocarbon-based solutions have been widely used for degreasing and other cleaning of solid surfaces, especially intricate parts and dirt that has been difficult to remove.

In its simplest form, vapor degreasing or solvent cleaning consists of exposing an object to be cleaned at room temperature to vapors of a boiling solvent. Steam that condenses on the object produces a pure distilled solvent that washes away grease or other contamination. Final evaporation of the solvent from the object leaves the object free of residue. This is in contrast to liquid solvents which leave a deposit on the object after rinsing.

A steam degreaser is used for dirt that is difficult to remove where high temperatures are required to improve the cleaning effect of the solvent and for high volume assembly line operations where cleaning of metal parts and units 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 most of the dirt, then immersing the part in a sump containing freshly distilled solvent near room temperature and finally exposing the part to solvent vapors above the boiling sump which condenses on the cleaned part. In addition, the part can also be sprayed with distilled solvent before final rinsing.

Steam degreasers which are suitable for such operations are well known. For example, US-PS 3,085,918 describes such suitable steam degreasers comprising a boiling sump, a clean sump, a water separator and other auxiliary 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 covered with cloths soaked in solvents and then allowed to air dry.

In recent times, non-toxic, non-flammable fluorocarbon solvents such as trichlorotrifluoroethane have been widely used in degreasing and other solvent cleaning applications. Trichlorotrifluoroethane was found to have satisfactory dissolving power for fats, oils, waxes and the like. The compound has therefore found extensive use for cleaning electric motors, compressors, heavy metal parts, delicate precision metal parts, printed circuit boards, gyroscopes, control systems, aerospace and missile objects, aluminum parts and the like.

The technique has turned in the direction of azeotropic mixtures with fluorocarbon components because the fluorocarbon components also contribute with desirable properties such as polar functionality, increased resolving power and stabilization. Azeotropic mixtures are desired because they do not fractionate on boiling. This behavior is desirable in the above-described steam degreasing equipment with which these solvents are used, redistilled material is formed for the final rinse cleaning. Thus, the steam degreasing system acts as a distillation apparatus.

If the solvent mixture is not essentially constant boiling, fractionation would therefore occur and unwanted solvent distribution could cause a disruption of the cleaning and the safety of the treatment. Preferential evaporation of more volatile components in the solvent mixtures, which would be the case if they were not azeotrope or azeotrope-like, would result in mixtures that changed their composition to those with less desirable properties such as lower solvent power against dirt, less inertness against metals, plastics - or elastomer components and increased flammability against toxicity.

The art has continuously searched for new fluorocarbon-based azeotropic mixtures or azeotrope-like mixtures which provide alternatives for new and special applications for steam degreasing and other cleaning applications. In recent times, fluorocarbon-based azeotrope-like mixtures have gained particular interest because they are considered to be stratospherically safe substitutes for the fully halogenated chlorofluorocarbons used today. The latter are implicated in causing environmental problems associated with a deterioration of the earth's protective ozone layer. Mathematical models have substantiated that fluorochlorocarbons such as dichloropentafluoropropane have a much lower ozone depletion potential and a global warming potential than the fully halogenated species. EP-A-347 924 in the name of Asano describes the use of hydrogen-containing chlorofluoropropanes as solvents. The dichloropentafluoropropane isomers HCFC-224ca, HCFC-225cb and HCFC-225cc are among the specified hydrogen-containing chlorofluoropropanes. The reference also states that when the compounds according to the invention are used as cleaning solvents, an organic solvent, for example a hydrocarbon, an alcohol such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol or tert-butyl alcohol, a ketone, a chlorinated hydrocarbon, an ester or a aromatic compound or a surface-active agent, is incorporated to improve the cleaning effect of the solvent. The reference also states that "when azeotropy or pseudo-azeotropy exists with a mixture obtained by a combination of the compound according to the invention with (an) other compound, it is preferred to use them under an azeotrope or pseudo-azeotrope...". However, this reference does not describe or suggest the present binary or ternary mixtures. More importantly, there is no teaching or suggestion in the reference that they here required combinations

(or the combination of any other compound indicated in the reference to the principle solvent mixtures) will result in the formation of an azeotrope-like mixture.

An object of the invention is to provide new environmentally acceptable azeotrope-like compositions useful in a number of industrial cleaning applications.

It is another object of the invention to provide azeotrope-like mixtures which are liquid at room temperature and which do not fractionate under the conditions of use.

Further objects and advantages of the invention will appear from the following description.

The invention relates to new azeotrope-like mixtures which are useful in a number of industrial cleaning applications. Specifically, the invention relates to mixtures of dichloropentafluoropropane and a C^_^-alkanol which is essentially constant boiling, environmentally acceptable and which remains liquid at room temperature.

According to the invention, new azeotrope-like mixtures have been discovered which are characterized in that they essentially consist of from 82 to 99.99% by weight of dichloropentafluoropropane and from 0.01 to 18% by weight of a C^^-alkanol where the azeotrope-like components in the mixture consists of dichloropentafluoropropane and a C^_^-alkanol and which boils at 50.6°C ± 5.6°C at 101 kPa (760 mm Hg).

Dichloropentafluoropropane exists in nine isomeric forms:

(1) 2,2-dichloro-1,1,1,3,3-pentafluoropropane (HCFC-225a); (2) 1,2-dichloro-1,2,3,3,3,-pentafluoropropane (HCFC-225ba); (3) 1,2-dichloro-1,1,2,3,3-pentafluoropropane (HCFC-225bb ); (4) 1,1-dichloro-2,2,3,3,3-pentafluoropropane (HCFC-225ca ); (5) 1,3-dichloro-1,1,2,2,3-pentafluoropropane (HCFC-225cb ); (6) 1,1-dichloro-1,2,2,3,3-pentafluoropropane (HCFC-225cc); (7) 1,2-dichloro-1,1,3,3,3-pentafluoropropane (HCFC-225d); (8) 1,3-dichloro-1,1,2,3,3-pentafluoropropane (HCFC-225ea); and

(9) 1,1-dichloro-1,2,3,3,3-pentafluoropropane (HCFC-225eb).

For the purposes of the invention, the term dichloropentafluoropropane will refer to any of the isomers or a mixture of the isomers in any proportions. However, 1,1-dichloro-2,2,3,3,3-pentafluoropropane and 1,3-dichloro-1,1,2,2,3-pentafluoropropane are the preferred isomers.

The dichloropentafluoropropane component of the invention has good dissolving properties. The alkanol component also has good dissolving power with a view to dissolving polar organic materials and amine hydrochlorides. Thus, when these components are combined in effective amounts, effective azeotropic solvents result.

When the alkanol is methanol, the azeotrope-like mixture according to the invention consists essentially of from 82 to 97 wt-# of dichloropentafluoropropane and from 3 to 18 wt-# of methanol and boils at 47.2°C ± 1.9°C at 101 kPa.

When the alkanol is ethanol, the azeotrope-like mixture according to the invention consists essentially of from 8.6 to 99 wt-# of dichloropentafluoropropane and from 1 to 14 wt-# of ethanol and boils at 52.1°C ± 2.2°C at 101 kPa.

When the alkanol is 1-propanol, the azeotrope-like mixture according to the invention consists essentially of from 96 to 99.99 wt-# dichloropentafluoropropane and from 0.01 to 4 wt-# 1-propanol and boils at 53.6°C ± 2 .5°C at 101 kPa.

When the alkanol is 2-propanol, the azeotrope-like mixture according to the invention consists essentially of from 94 to 99.99 wt-# dichloropentafluoropropane and from 0.01 to 6 wt-# 2-propanol and boils at 53.6°C ± 2 .3°C at 101 kPa.

When the alkanol is 2-methyl-2-propanol, the azeotrope-like mixture according to the invention essentially consists of from 98 to 99.99% by weight of dichloropentafluoropropane and from 0.01 to 2% by weight of 2-methyl-2-propanol and boils at 53.6°C ± 2.5°C at 101 kPa.

When the dichloropentafluoropropane component is 225ca and the alkanol is methanol, the azeotrope-like mixture according to the invention essentially consists of from 82 to 97 wt-$ 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 3 to 18 wt- % methanol and boils at 45.4°C ± 0.5°C at 99.3 kPa.

In a preferred embodiment of the invention which uses 225ca and methanol, the azeotrope-like mixture essentially consists of from 86 to 96 wt.-# 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 4 to 14 wt. -$ methanol.

In a more preferred embodiment of the invention which uses 225ca and methanol, the azeotrope-like mixture consists essentially of from 88 to 96 wt.# of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 4 to 12 wt-# methanol.

In a most preferred embodiment of the invention using 225ca and methanol, the azeotrope-like mixture consists essentially of from 89 to 95 wt.# of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 5 to 11 wt-# methanol.

When the dichloropentafluoropropane component is 225ca and the alkanol is ethanol, the azeotrope-like mixture according to the invention essentially consists of from 92 to 99 wt.# 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 1 to 8 wt. # ethanol and boils at 50.0°C ± 0.5°C at 99.3 kPa.

In a preferred embodiment which uses 225ca and ethanol, the azeotrope-like mixture according to the invention essentially consists of from 94 to 99 wt.-$ 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 1 to 6 wt. -# ethanol.

In a more preferred embodiment which uses 225ca and ethanol, the azeotrope-like mixture according to the invention essentially consists of from 94 to 98.5 wt # of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 1 .5 to 6 wt-# of ethanol.

When the dichloropentafluoropropane component is 225ca and the alkanol is 2-propanol, the azeotrope-like mixture according to the invention essentially consists of from 96 to 99.99% by weight of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 0 .01 to 4 wt # 2-propanol and boils at 51.0°C ± 0.3°C at 99.3 kPa.

In a preferred embodiment which uses 225ca and 2-propanol, the azeotrope-like mixture according to the invention essentially consists of from 97.5 to 99.99% by weight of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 0.01 to 2.5 wt # of 2-propanol.

In a more preferred embodiment which uses 225ca and 2-propanol, the azeotrope-like mixture according to the invention essentially consists of from 98 to 99.99 wt.-$ 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 0.01 to 2 wt # of 2-propanol.

When the dichloropentafluoropropane component is 225cb and the alkanol is methanol, the azeotrope-like mixture according to the invention essentially consists of from 82 to 97 wt.# of 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 3 to 18 wt. # methanol and boils at 47.9°C ± 0.8°C at 97.8 kPa.

In a preferred embodiment of the invention using 225cb and methanol, the azeotrope-like mixture consists essentially of from 84 to 96 wt.-# 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 4 to 16 wt. -# methanol.

In a more preferred embodiment of the invention using 225cb and methanol, the azeotrope-like mixture consists essentially of from 86 to 96 wt.#> 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 4 to 14 wt # of methanol.

In a most preferred embodiment of the invention using 225cb and methanol, the azeotrope-like mixture essentially consists of from 88 to 95% by weight 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 5 to 12 wt-$ methanol.

When the dichloropentafluoropropane component is 225cb and the alkanol is ethanol, the azeotrope-like mixture according to the invention essentially consists of from 86 to 97 wt-$ 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 3 to 14 wt- # ethanol and boils at 53.1°C ± 0.4°C at 98.1 kPa.

In a preferred embodiment using 225cb and ethanol, the azeotrope-like mixture according to the invention consists essentially of from 88 to 97 wt.# 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 3 to 12 wt. -$ ethanol.

In a most preferred embodiment using 225cb and ethanol, the azeotrope-like mixture according to the invention consists essentially of from 89 to 97 wt.-$ 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 3 to 11 wt-# ethanol.

When the dichloropentafluoropropane component is 225cb and the alkanol is 1-propanol, the azeotrope-like mixture according to the invention essentially consists of from 96 to 99.99 wt.-$ 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 0 .01 to 4 wt% 1-propanol and boils at 55.5°C ± 0.2°C at 99.3 kPa.

In a preferred embodiment which uses 225cb and 1-propanol, the azeotrope-like mixture according to the invention essentially consists of from 97 to 99.99 wt.-$ 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 0.01 to 3 wt # 1-propanol.

In a most preferred embodiment which uses 225cb and 1-propanol, the azeotrope-like mixture according to the invention essentially consists of from 98 to 99.99% by weight of 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 0.01 to 2 wt # 1-propanol.

When the dichloropentafluoropropane component is 225cb and the alkanol is 2-propanol, the azeotrope-like mixture according to the invention essentially consists of from 94 to 99 wt% of 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 1 to 6 weight # 2-propanol and boils at 55.0°C ± 0.3°C at 98.9 kPa.

In a preferred embodiment which uses 225cb and 2-propanol, the azeotrope-like mixture according to the invention consists essentially of from 95 to 98.5% by weight of 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 1.5 to 5 wt.-$ 2-propanol. 1 a most preferred embodiment which uses 225cb and 2-propanol, the azeotrope-like mixture according to the invention essentially consists of from 95.5 to 98.5 weight # 1,3-dichloro-1,1,2,2,3- pentafluoropropane and from 1.5 to 4.5 wt # of 2-propanol.

When the dichloropentafluoropropane component is 225cb and the alkanol is 2-methyl-2-propanol, the azeotrope-like mixture according to the invention essentially consists of from 98 to 99.99% by weight of 1,3-dichloro-1,1,2,2,3- pentafluoropropane and from 0.01 to 2 wt # 2-methyl-2-propanol and boils at 55.7°C ± 0.2°C at 99.6 kPa.

The exact or true azeotropic mixtures are not determined, but are. determined to lie within the indicated areas. Regardless of where true azeotropes lie, all mixtures within the indicated ranges as well as certain mixtures outside the indicated ranges are azeotrope-like as defined more precisely below.

Based on 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. An azeotrope is a unique characteristic of a system of two or more components where X and Y are equal at a given P and T. In practice, this means that the components of a mixture cannot be separated during distillation and are therefore usable in vapor phase solution purification as described above .

For the purposes of this discussion, azeotrope-like mixture means that the mixture behaves like a true azeotrope as expressed by its constant boiling characteristics or its tendency not to fractionate on boiling or evaporation. Such mixtures may possibly be a true azeotrope. Thus, in such mixtures, the composition of the vapor formed during boiling or evaporation is identical or essentially identical to the original liquid composition. During boiling or evaporation, the liquid composition, if it changes at all, will therefore change only to a small extent. This is in contrast to non-azeotrope-like mixtures where the liquid composition changes significantly during boiling or evaporation.

Thus, one method of determining whether a candidate mixture is "azeotrope-like" within the scope of the invention is to distill a sample under conditions (ie, resolution - number of plates) that would be expected to separate the mixture into its separate components. If the mixture is non-azeotropic or non-azeotrope-like, the mixture will fractionate, that is, separate into the various components with the lowest boiling component being the first to distill off and so on. If the mixture is azeotrope-like, a final quantity of a first distillation cut will be obtained which contains all 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. not part of an azeotropic system. If the degree of fractionation of the candidate mixture is too great, a composition closer to the true azeotrope must be chosen to minimize fractionation. Of course, when distilling an azeotrope-like mixture, such as in a steam degreaser, the true azeotrope will form and tend to concentrate.

It follows from the above that another characteristic of an azeotrope-like mixture is that there is a range of mixtures containing the same components in varying proportions that are azeotrope-like. All such mixtures are intended to be within azeotrope-like as the term is used here. As an example, it is well known that at different pressures, the composition for a given azeotrope will vary at least somewhat in the same way as the boiling point of the mixture. 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 the invention is to state that such a mixture boils within ± 5.6°C (at 101 kPa) of the 50.6°C boiling point described here. As the person skilled in the art will readily understand, the boiling point of the azeotrope will vary with pressure.

In the embodiment of the invention, the azeotrope-like mixtures according to the invention can be used to clean solid surfaces by treating the surfaces with the mixtures in any way known in the art, for example by dipping or spraying or using conventional degreasing equipment.

As noted above, azeotrope-like compositions discussed herein are useful as solvents for a number of cleaning applications including steam degreasing, defluxing, cold cleaning, dry cleaning, dewatering, decontamination, spot removal, aerosol driven workup, extraction, particle removal, and surfactant cleaning applications. These azeotrope-like mixtures are also useful as propellants, Rankine cycle and absorption refrigerants as well as propellant fluids.

The dichloropentafluoropropane and alkanol components according to the invention are known substances in and of themselves. Preferably, they should be used in sufficiently high purity to avoid introducing adverse effects on the dissolution or constant-boiling properties of the system.

Commercially available alkanols can be used according to the invention. Most dichloropentafluoropropane isomers, like the preferred HCFC-225ca isomer, are not available in commercial quantities, until the time they become commercially available they can therefore be prepared by following the organic syntheses described here. For example, 1,1-dichloro-2,2,3,3,3-pentafluoropropane can be prepared by reacting 2,2,3,3,3-pentafluorolpropanol and p-toluenesulfonate chloride to form 2,2,3,3,3- pentafluoropropyl p-toluenesulfonate. N-methylpyrrolidone, lithium chloride and the 2,2,3,3,3-pentafluoropropyl-p-toluenesulfonate are then reacted together to form 1-chloro-2,2,3,3,3-pentafluoropropane. Finally, chlorine and 1-chloro-2,2,3,3,3-pentafluoropropane react to form 1,1-dichloro-2,2,3,3,3-pentafluoropropane. A detailed synthesis is given in Example 1.

Synthesis of 2,2-dichloro-1,1,1,3,3-pentafluoropropane (225a) This compound can be prepared by reacting a dimethylformamide solution of 1,1,1-trichloro-2,2,2-trifluoromethane with chlorotrimethylsilane in the presence of zinc to form 1-(trimethylsiloxy)-2,2-dichloro-3,3,3-trifluoro-N,N-dimethyl-propylamine. This 1-(trimethylsiloxy)-2,2-dichloro-3,3,3-trifluoro-N,N-dimethylpropylamine is reacted with sulfuric acid to form 2,2-dichloro-3,3,3-trifluoropropionaldehyde. This 2,2-dichloro-3,3,3-trifluoropropionaldehyde is then reacted with sulfur tetrafluoride to form 2,2-dichloro-1,1,3,3-pentafluoropropane.

Synthesis of 1,2-dichloro-1,2,3,3,3-pentafluoropropane (225ba) This isomer can be prepared by the synthesis described by 0. Paleta et al. in "Bull. Soc. Chim. Fr.", (6 ), 920-4

(1986).

Synthesis of 1, 2- dichloro- 1, 1. 2, 3. 3- pentafluoropropane ( 225bb)

The synthesis of this isomer is described by M. Hauptschein and L.A. Bigelow in "J. Am. Chem. Soc", (73) 1428-30 (1951 ). The synthesis of this compound is also described by A.E. Feinberg and W.T. Miller, Jr. in "J. Am. Chem. Soc", (79) 4170-4, (1957).

Synthesis of 1, 3-dichloro-l. 1. 2. 2, 3- pentafluoropropane ( 225cb) The synthesis of this compound involves four steps.

Part A - Synthesis of 2,2,3,3-tetrafluoropropyl-p-toluenesulfonate. 406 g (3.08 mol) 2,2,3,3-tetrafluoropropanol, 613 g (3.22 mol) tosyl chloride and 1200 ml of water are heated to 50° C. with mechanical stirring. Sodium hydroxide (139.7 g, 3.5 ml) in 560 ml water is added in an amount such that the temperature remains below 65°C. After the addition is complete, the mixture is stirred at 50°C until the pH value in the aqueous phase is 6. The mixture is cooled and extracted with 1.5 1 methylene chloride. The organic layers are washed with 2 x 200 ml of aqueous ammonia, 350 ml of water, dried with magnesium sulfate and distilled, thereby obtaining 697.2 g or 79$ of a viscous oil.

Part B - Synthesis of 1,1,2,2,3-pentafluoropropane.

A 500 ml flask was fitted with a mechanical stirrer and a Vigreaux distillation column which in turn was connected to a dry ice trap, and kept under a nitrogen atmosphere. The flask was charged with 400 mL N-methylpyrrolidone, 145 g (0.507 mol) 2,2,3,3-tetrafluoropropyl-p-toluenesulfonate (prepared as under part A above) and 87 g (1.5 mL spray-dried KF. The mixture was then heated to 190-200°C for 3.25 hours during which time 61 g of volatile product distilled into the cold trap ($90 crude yield).After distillation the fraction boiling at 25-28°C was collected.

Part C - Synthesis of 1,1,3-trichloro-1,2,2,3,3-pentafluoropropane.

A 22 L flask was evacuated and charged with 20.7 g (0.154 mol) of 1,1,2,2,3-pentafluoropropane (prepared under Part B above) and 0.6 mL of chlorine. One was irradiated for 100 minutes with a 450 W Hanovia Hg lamp at a distance of approx. 7.6 cm. The flask was then cooled in an ice bath, nitrogen was added as needed to maintain a pressure of 101 kPa. The liquid in the flask was removed using a syringe. The flask was connected to a dry ice trap and slowly evacuated over 15 to 30 minutes. The contents of the dry ice trap and the original liquid phase totaled 31.2 g or 85$ with a GC purity of 99.7%. The product from several experiments was combined and distilled and a material with a boiling point of 73.5-74°C was obtained.

Part D - Synthesis of 1,3-dichloro-1,1,2,2,3-pentafluoropropane.

106.6 g (0.45 mol) of 1,1,3-trichloro-1,2,2,3,3-pentafluoropropane (prepared in part C above) and 300 g (5 mol) of isopropanol were stirred under an inert atmosphere and irradiated for 4.5 hours with a 450 W Hanovia Hg lamp at a distance of 5 to 7.6 cm. The acidic reaction mixture was then poured into 1.5 L of ice water. The organic layers were separated, washed with 2 x 50 ml of water, dried with calcium sulphate and distilled and 50.5 g of C1CF2CF2CHC1F with a boiling point of 54.5-56°C (55*) were obtained.

1 H-NMR (CDCl 3 ): ddd centered at 6.43 ppm.

J H-C-F = 47 Hz, J H-C-C-Fa = 12 Hz, J H-C-C-Fb = 2 Hz.

Synthesis of 1, 1-dichloro-l, 2, 2. 3. 3- pentafluoropropane ( 225cc) This compound can be prepared by reacting 2,2,3,3-tetrafluoro-l-propanol and p-toluenesulfonate chloride to form 2 ,2,3,3-tetrafluoropropyl-p-toluenesulfonate. This 2,2,3,3-tetrafluoropropyl-p-toluenesulfonate is then reacted with potassium fluoride in N-methylpyrrolidone to form 1,1,2,2,3-pentafluoropropane. This 1,1,2,2,3-pentafluoropropane is then reacted with chlorine to form 1,1-dichloro-1,2,2,3,3-pentafluoropropane.

Synthesis of 1,2-dichloro-1,1,3,3.3-pentafluoropropane (225d) This isomer is commercially available from P.C.E. Incorporated and Gainsville, Florida. Alternatively, the compound can be prepared by adding equimolar amounts of 1,1,1,3,3-pentafluoropropane and chlorine gas to a borosilicate flask that has been purged of air. The flask is then irradiated with a mercury lamp. After complete irradiation, the contents of the flask are cooled. The resulting product will be 1,2-dichloro-1,1,3,3,3-pentafluoropropane.

Synthesis of 1, 3- dichloro-l. 1, 2, 3, 3- pentafluoropropane (225ca) This compound can be prepared by reacting trifluoroethylene with dichlorotrifluoromethane to form 1,3-dichloro-1,1,2, 3,3-pentafluoropropane and 1,1-dichloro-1,2,3,3,3-pentafluoropropane. The 1,3-dichloro-1,1,2,3,3-pentafluoropropane formed is separated from its isomer using fractional distillation and/or preparative gas chromatography.

Synthesis of 1,1-dichloro-1,2,3,3,3-pentafluoropropane (225eb) This compound can be prepared by reacting trifluoroethylene with dichlorodifluoromethane to form 1,3-dichloro-1,1,2,3 ,3-pentafluoropropane and 1,1-dichloro-1,2,3,3,3-pentafluoropropane. 1,1-Dichloro-1,2,3,3,3-pentafluoropropane is separated from its isomer using fractional distillation and/or preparative gas chromatography. Alternatively, 225eb can be prepared by a synthesis as described by 0. Paleta et al. in "Bull. Soc. Chim. Fr.", (6) 920-4 (1986). 1,1-dichloro-1,2 ,3 ,3,3-pentafluoropropane can be separated from its two isomers using fractional distillation and/or preparative gas chromatograph i.

It should be clear that the compositions of the invention may contain additional components which form new azeotrope-like compositions. Any such mixtures are considered to be within the scope of the invention as long as the mixtures are constant boiling or essentially constant boiling and contain all the essential components as described here.

Inhibitors may be added to the present azeotrope-like compositions to inhibit decomposition of the compositions; react with unwanted decomposition products in the mixtures; and/or to prevent corrosion of metal surfaces. Any of the following classes of inhibitors may be used according to the invention: epoxy compounds such as propylene oxide; nitroalkanes such as nitromethane; ethers such as 1,4-dioxane; unsaturated compounds such as 1,4-butynediol; acetals or ketals such as dipropoxymethane; ketones such as methyl ethyl ketone; alcohols such as tertiary amyl alcohol; esters such as triphenyl phosphite; and amines such as triethylamine. Other suitable inhibitors will be apparent to those skilled in the art.

After a detailed description of the invention and with reference to preferred embodiments, it should be clear that modifications and variations are possible without going outside the spirit and scope of the invention as defined in the accompanying claims.

The invention shall be illustrated in more detail with reference to the following examples.

Example 1

This example is aimed at producing the preferred dichloropentafluoropropane component according to the invention, 1,1-dichloro-2,2,3,3,3-pentafluoropropane (225ca).

Part A - Synthesis of 2,2,3,3,3-pentafluoropropyl-p-toluenesulfonate.

To p-toluenesulfonate chloride (400.66 g, 2.10 mol) in water was added 2,2,3,3,3-pentafluoro-1-propanol (300.8 g) at 25°C. The mixture was heated to 50°C in a 5-liter 3-neck separatory funnel-type reaction flask with mechanical stirring. Sodium hydroxide (92.5 g, 2.31 mol) in 383 mL of water (6M solution) was added dropwise to the reaction mixture via the addition funnel over 2.5 hours, while maintaining the temperature below 55°C. After the addition has been completed, when the pH value in the aqueous phase was approx. 6, the organic phase was drained from the flask while still hot and allowed to cool to 25°C. The crude product was recrystallized from petroleum ether and 500.7 g (1.65 mol, 82.3*) of white needles of 2,2,3,3,3-pentafluoropropyl-p-toluenesulfonate with melting point 47.0-52.5 °C.

% NMR: 2.45 ppm (S, 3H), 4.38 ppm (t, 2H, J=12Hz),

7.35 ppm (d, 2H, J=6Hz);

<19>F NMR: +83.9 ppm (S, 3F), +123.2 (t, 2F, J=12Hz),

upstream from CFCI3.

Part B - Synthesis of l-chloro-2,2,3,3,3-pentafluoropropane.

A 1 liter flask, equipped with a thermometer, Vigreaux column and distillation head was charged with 248.5 g (0.82 mol) of 2,2,3,3,3-pentafluoropropyl-p-toluenesulfonate (prepared as under A above) ', 375 ml of N-methylpyrrolidone and 46.7 g (1.1 mol) of lithium chloride. The mixture was then heated with stirring to 140°C at which temperature the product began to distill. Stirring and heating were continued until a pot temperature of 198°C was reached at which point no distillate was collected. The crude product was redistilled whereby 107.2 g or 78* of the product with a boiling point of 27.5-28°C was obtained.

<i>H NMR: 3.81 ppm (t, J=13.5 Hz).

<19>F NMR: 83.5 and 119.8 ppm, upstream from CFCI3.

Part C - Synthesis of 1,1-dichloro-2,2,3,3,3-pentafluoropropane. Chlorine (289 mL/min.) and 1-chloro-2,2,3,3,3-pentafluoropropane (prepared as under Part B above) (1.72 g/min.) were fed simultaneously to a 2.54 cm x 5.08 cm monel reactor at 300°C. This was repeated until 184 g of crude product had been obtained in the cold traps leading out of the reactor. After washing the crude product with 6M sodium hydroxide and drying with sodium sulfate, the whole was distilled and 69.2 g of starting material and 46.8 g of 1,1-dichloro-2,2,3,3,3-pentafluoropropane with a boiling point of 48 -50.5°C.

<1>E NMR: 5.9 (t, J=7.5H) ppm;

<19>F NMR: 79.4 (3F) and 119.8 (2F) ppm, upstream from CFC13.

Example 2

The composition range over which 225ca and methanol show constant boiling behavior was determined. This was achieved by charging measured amounts of 225ca into an ebulliometer. The ebulliometer consisted of a heated sump in which HCFC-225ca was brought to a boil. The upper part of the ebulliometer which was connected to the sump was thereby cooled and acted as a condenser for the boiling vapours, thereby allowing the system to operate at total reflux. After the HCFC-225ca had been brought to boiling at atmospheric pressure, measured amounts of methanol were titrated into the ebulliometer. The change in boiling point was measured with a platinum resistance thermometer.

The results suggest that mixtures with 225ca/methanol in the range 82-97/3-18 and preferably 89-95/5-11 wt-* would show constant boiling behavior at 45.4°C ± 0.5°C at 101 kPa.

Examples 3-9

The azeotropic properties of the dichloropentafluoropropane components and the alkanols listed in Table I were studied. This was accomplished by charging a selected dichloropentafluoropropane isomer into an ebulliometer, bringing it to boiling, adding measured amounts of alkanol, and finally noting the temperature of the resulting boiling mixture. The range over which the mixtures boil constantly is indicated in

the table.

*The boiling point determinations for examples 3 to 9 were carried out at the following barometric pressure (kPa): 99.9, 99.9, 97.8, 98.1, 99.3, 98.9 and 99.5 respectively.

Examples 10 - 18

The azeotropic properties of the dichloropentafluoropropane components as indicated in Table II with methanol are studied by repeating the experiment as indicated in Examples 3 to 9 above. In each case, a minimum in the boiling point versus composition curve indicates that a constant boiling mixture is formed between each dichloropentafluoropropane component and methanol. continued

Examples 19 - 27

The azeotropic properties of the dichloropentafluoropropane components listed in Table II with ethanol are studied by repeating the experiments indicated in Examples 3-9 above. In each case, a minimum in the boiling point versus composition curve indicates that a constant boiling mixture is formed between the dichloropentafluoropropane component and ethanol.

Examples 28 - 36

The azeotropic properties of the dichloropentafluoropropane isomers as indicated in Table II with 2-propanol are studied by repeating the experiment indicated in Examples 3-9. In each case, a minimum in the boiling point versus composition curve suggests that a constant boiling mixture is formed between each dichloropentafluoropropane component and 1-propanol.

Examples 37 - 46

The azeotropic properties of the dichloropentafluoropropane isomers as indicated in Table III with 1-propanol are studied by repeating the experiment indicated in Examples 3-9. In each case, a minimum in the boiling point versus composition curve suggests that a constant boiling mixture is formed between each dichloropentafluoropropane component and 1-propanol.

Examples 47 - 57

The azeotropic properties of the dichloropentafluoropropane isomers as indicated in Table III with 2-methyl-2-propanol are studied by repeating the experiment indicated in Examples 3-9 above. In each case, a minimum in the boiling point versus composition curve suggests that a constant boiling mixture is formed between each dichloropentafluoropropane component and 2-methyl-2-propanol.

Claims (8)

1. Azeotrope-like mixtures, characterized in that they essentially consist of from 82 to 99.99 weight-* dichloropentafluoropropane and from 0.01 to 18 weight-* of a C^_^-alkanol where the azeotrope-like components in the mixture consist of dichloropentafluoropropane and a C^_^-alkanol and wherein the mixture boils at 50.6°C ± 5.6°C at 101 kPa (760 mm Hg) 2. Mixture according to claim 1, characterized in that it essentially consists of from 82 to 97 weight-* of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 3 to 18 weight-* of methanol and boils at 45.4°C at 99.9 kPa (752 mm Hg). 3. Mixture according to claim 1, characterized in that it essentially consists of from 92 to 99 weight-* of 1,1-dichloro-2,2,3,3,3-pentafluoropropane and from 1 to 8 weight-* of ethanol and boils at 50.0°C at 99.9 kPa (752 mm Hg). 4. Mixture according to claim 1, characterized in that it essentially consists of from 82 to 97 weight-* of 1,3-dichloro-1,1,2,3,3-pentafluoropropane and from 3 to 18 weight-* of methanol and boils at 47.9°C at 97.8 kPa (736 mm Hg). 5 . Mixture according to claim 1, characterized in that it essentially consists of from 86 to 97 weight-* of 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 3 to 14 weight-* of ethanol and boils at 53.1"C at 98.1 kPa (738 mm Hg). 6. Mixture according to claim 1, characterized in that it essentially consists of from 98 to 99.99 weight-* of 1,3-dichloro-1,1,2,2,3-pentafluoropropane and from 0.01 to 2 weight-* 2-methyl-2-propanol and boils at 55.7°C at 99.6 kPa (749.1 mm Hg). 7. Mixture according to claim 1, characterized in that an effective amount of inhibitor is optionally present in the mixture. 8. Mixture according to claim 7, characterized in that the inhibitor is selected from the group of epoxy compounds, nitroalkanes, ethers, acetals, ketals, ketones, alcohols, esters and amines.