Compositions and methods for cleaning vapor compression systems

Abstract

Disclosed are azeotrope-like compositions comprising HFC-134a and at least one of HFC-245fa, HFC-365, and HFC-43-10 and methods for using the same to remove contaminants from a vapor compression system.

Description

FIELD OF INVENTION

The present invention relates to non-azeotrope, azeotrope, and azeotrope-like compositions. More specifically, this invention relates non-azeotrope, azeotrope, and azeotrope-like mixtures of hydrofluorocarbons and methods of using the same for removing contaminants from vapor compression systems.

BACKGROUND OF THE INVENTION

There exists a need to remove contaminants from vapor compression systems and their ancillary components when these systems are manufactured and serviced. As used herein, the term “contaminants” refers to processing fluids, lubricants, particulates, sludge, and/or other materials that are used in the manufacture of these systems or generated during their use. In general, these contaminants comprise compounds such as alkylbenzenes, mineral oils, esters, polyalkyleneglycols, polyvinylethers and other compounds that are made primarily of carbon, hydrogen and oxygen.

Vapor compression systems are used in a wide variety of applications such as heating and refrigeration. By compressing and expanding a heat transfer agent, such as a refrigerant, these systems are capable of absorbing and releasing heat according to the needs of a particular application. Common components of a vapor compression system include: vapor or gas compressors; liquid-cooled pumps; heat transfer equipment such as gas coolers, intercoolers, aftercoolers, heat exchangers, and economizers; vapor condensers such as reciprocating piston compressors, rotating screw compressors, centrifugal compressors, and scroll expanders; control valves and pressure-drop throttling devices such as capillaries; refrigerant-mixture separating chambers; steam-mixing chambers; connecting piping; and the like. These components are typically fabricated from copper, brass, steel, and the like, and have conventional gasket materials.

Many components of a vapor compression system require lubrication to reduce friction caused by their relative physical contact and movements. These lubricants, which are compounds primarily composed of carbon, hydrogen, and oxygen, operate by coating the surfaces of component that are subjected to friction. Lubricants of a vapor compression system are typically mixed with the heat transfer agent which carries and disperses the lubricant throughout the system. However, during certain processes or procedures, it is desirable to remove these lubricants from the component surfaces, particularly during service operations. Such a need arises, for example, during the retrofitting of a chlorofluorocarbon (CFC) or hydrochlorofluorocarbon (HCFC) refrigerant-based system to a hydrofluorocarbon (HFC)-based system. There is also a need to remove processing lubricants during the manufacturing of a system. Failure to remove these types of contaminants from the system may lead to decreased efficiency or even to the failure of one or more components.

In addition, a vapor compression system may require cleaning after a catastrophic event, such as a compressor blowout. This type of event can create contaminants, such as acids, sludge, and particulates, within the sealed system. Failure to remove these types of contaminants from the system may also lead to decreased efficiency or failure of one or more components.

The aforementioned contaminants can typically be removed by flushing the vapor compression system with a flushing agent in which the contaminants are soluble or miscible. Generally, such flushing agents contain one or more cleaning agents (for example, solvents for various types of hydrocarbons) and a propellant that carries the cleaning agent through the vapor compression system. In some cases, the cleaning agent may also serve as the propellant. Until recently, chlorofluorocarbons (CFC's) such as tricholormethane (R-11) and dichlorofluoroethane (R-141) were used as flushing agents for such systems. Although effective, CFC's are now considered environmentally unacceptable because of their contribution to the depletion of the stratospheric ozone layer. As the use of CFC's is reduced and ultimately phased out, new flushing agents are needed that not only perform well, but also pose no danger to the ozone layer.

Many environmentally acceptable flushing compositions and methods have been proposed, but their use has met with limited success. For example, terpenes and low viscosity esters are known solvents of several types of lubricants commonly used in vapor compression systems, such as polyalkylene glycols, polyol esters, polyvinyl ethers, and the like. However, many of these solvents have a boiling point above 100° C. and are difficult to remove from system components once they have been introduced during cleaning. Conventional techniques for removing these high boiling solvents prolongs the flushing operation which is economically disadvantageous. In addition, solvent remnants can have a deleterious effect on the performance of the vapor compression system.

One method that has been proposed to deliver a flushing composition through a vapor compression system involves the use of compressed nitrogen as the propellant. However, this method of delivery is difficult and uncertain because the amount of pressure applied by the compressed nitrogen varies. The use of pressurized nitrogen as a propellant is also expensive. As an alternative to compressed nitrogen, compressed air may be used. However, the use of compressed air brings the disadvantage that it often contains an unacceptably high amount of moisture. Once introduced, this moisture can be difficult to remove from the vapor compression system.

Therefore, Applicants have recognized a need for methods, systems, and compositions that are environmentally-acceptable and which are capable of effectively and efficiently removing contaminants from vapor compression systems.

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

Certain embodiments of the present invention meet the aforementioned needs, among others, by providing novel non-azeotrope, azeotrope, and azeotrope-like compositions comprising HFC-mixtures of 1,1,1,2-tetrafluoroethane (HFC-134a) and one or more of 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3-pentafluorobutane (HFC-365), and 1,1,1,2,2,3,4,5,5,5-decafluoropentane (HFC-43-10). Applicants have surprisingly discovered that when an effective amount of HFC-134a is combined with HFC-365, an azeotrope is formed, and when combined with HFC-245fa, HFC 43-10, or some combination of HFC-245fa, HFC-365, and HFC 43-10, an azeotrope-like composition is formed. Economical and efficient methods for using such compositions to remove contaminants from vapor compression systems in an environmentally acceptable manner are also provided.

The term “effective amount”, as used herein, refers to the amount of HFC-134a, that when combined with one or more of the other aforementioned components, results in the formation of an azeotrope or azeotrope-like composition.

The term “azeotrope-like”, as used herein, refers to a combination of two or more compounds that behave substantially like a single compound in so far as the vapor in substantial equilibrium with the liquid has substantially the same concentration of components present in the liquid. The term “azeotrope-like” is intended to refer to both true azeotrope compositions and to compositions which are not strictly azeotropic, but in which the concentration of components in the vapor phase of the composition are so close to the concentration of components in the equilibrium liquid phase of the composition as to make separation of the components by ordinary distillation not practically possible. In essence, the admixture distills without substantially changing its composition. This is to be contrasted with non-azeotrope (or “zeotrope”) compositions wherein the liquid composition changes to a substantial degree during boiling or evaporation.

Azeotropes-like compositions according to the present invention include absolute azeotropes (compositions in which azeotropic conditions are satisfied over all values of temperature (up to the critical stage)) or limited azeotropes (compositions in which azeotropic conditions are satisfied only in a certain temperature range). Azeotropes-like compositions according to the present invention also include homoazeotropes, wherein the composition exists in a single liquid phase, or heteroazeotropes, wherein the composition exists as two or more liquid phases. Moreover, azeotrope-like compositions according to the present invention can be binary, ternary, quaternary, or quinary azeotropes depending on whether the composition is composed of 2, 3, 4, or 5 compounds, respectively.

The compounds HFC-245fa, HFC-365, and HFC-43-10 can be used as flushing agents. However, when any of these compounds are used in a flushing apparatus such as a flushing gun, or the like, a propellant may also be required. Applicants have discovered that HFC-134a can serve as such a propellant. Moreover, as stated above, applicants have discovered that certain azeotrope-like compositions are formed by mixing an effective amount of HFC-134a with HFC-245fa, HFC-365, HFC 43-10, or some combination thereof. The azeotrope-like nature of these compositions is useful when the composition is utilized as a flushing agent, as a heat transfer agent, as a blowing agent for foams, or as an aerosols because it allows for uniform condensation and vaporization to occur at a single temperature. For example, in closed-loop systems such as flushing machines, an azeotrope-like flushing composition can be recycled because of its constant composition ratio in both liquid and vapor states. However, it is understood that azeotrope-like compositions according to the present invention may also be used in open-loop systems, such as flush guns, although non-azeotrope compositions are preferred.

Applicants have discovered that the preferred azeotrope-like compositions of the present invention have a number of attributes or properties that render them particularly effective as flushing agents for cleaning vapor compression systems. Many contaminants, including lubricants, that are commonly found in vapor compression systems are adequately miscible or soluble in the preferred azeotrope-like compositions of the present invention. The term “adequately miscible”, as used herein, refers to the azeotrope-like composition's ability to interact with a contaminant to form a solution, emulsion, suspension, or mixture under normal cleaning conditions in such a way that the contaminant can be effectively removed from the surface needing to be cleaned. Examples of such lubricants include, but are not limited to, mineral oils, alkylbenzenes, polyvinylethers, polyalkylene glycols, and polyol ester oils.

One advantage of the preferred azeotrope-like compositions according to the present invention is that it is possible to substantially remove these compositions from the treated surface, preferably with relatively little effort or complication. For example, the preferred azeotrope-like compositions evaporate readily using conventional techniques known in the art such as flushing the system with an inert gas, pulling a vacuum on the system, and/or heating the system. Factors that affect evaporation include vapor pressure, the amount of heat that is applied, the heat conductivity of the liquid, the specific heat of the liquid, the latent heat of vaporization, surface tension, molecular weight, the rate at which the vapor is removed. The most appropriate method for removing the flushing agent for any given application is dependent upon the characteristics of the application involved and one skilled in the art could readily determine which method would be the most appropriate for each such application.

One advantage of the present compositions is that each of HFC-245fa, HFC-134a, and HFC-43-10 are nonflammable as defined by ASTME681-94, and therefore azeotrope-like compositions made from mixtures of these materials are also non-flammable. Additionally, other azeotrope-like composition according to the present invention, such as certain azeotrope-like mixtures of HFC-365 and HFC134a, may also be non-flammable. Generally, non-flammable mixtures of the present invention are preferred because they are less dangerous and therefore easier to handle. How, it is understood that mixtures according to the present invention may also be flammable, and that in certain application, the flammability of these mixtures may be advantageous.

The preferred azeotrope-like compositions of the present invention are generally compatible with the materials of vapor compression systems, including metals and sealants.

The preferred azeotrope-like compositions of the present invention are environmentally acceptable and do not to contribute to the depletion of the earth's stratospheric ozone layer.

Data is presented that demonstrates the existence of binary azeotrope-like compositions. Non-flammable, substantially constant boiling compositions can also be formed using ternary compositions that comprise HFC-134a and two of the other components. However, it should be understood that the present invention also provides compositions that may also include additional components so as to form new azeotrope-like compositions. Any such compositions are considered to be within the scope of the present invention provided that the compositions are essentially azeotrope-like and contain all of the essential components described herein.

Preferred azeotrope-like compositions of the present invention include: suitable mixtures of HFC-245fa and HFC-134a having from about 1 to about 99 weight percent HFC-134a and from about 99 to about 1 weight percent HFC-245fa; suitable mixtures of HFC-134a and HFC-365 having from about 60 to about 99 weight percent HFC-134a and from about 1 to about 40 weight percent HFC-365; and suitable mixtures of HFC-134a and HFC-43-10 having from about 45 to about 99 weight percent HFC-134a and from about 1 to about 55 weight percent HFC43-10.

The preferred ratio of components for these preferred azeotrope-like compositions would depend on many factors, such as material availability and cost, the particular equipment to be cleaned, and the composition of the contaminants. In view of the teaching contained herein, one skilled in the art could readily select the ratio of components for a specific application.

Compositions according to the present invention, including the preferred azeotrope-like compositions, may include one or more components, such as additives, which may not form new azeotrope-like compositions. Known additives may be used in the present compositions in order to tailor the composition for a particular use. Inhibitors may also be added to the present compositions to inhibit decomposition, react with undesirable decomposition products, and/or prevent the corrosion of metal surfaces. Typically, up to about 2 percent of an inhibitor based on the total weight of the azeotrope-like composition may be used.

EXAMPLES

The following examples are illustrative of the practice of the present invention:

Example 1

Eighteen grams of HFC-134a were added to an ebulliometer at atmospheric pressure. It was determined that the compound boiled at about −25° C. HFC-245fa was added to the ebulliometer in increments until there was 7.04 weight percent (wt. %) of HFC-245fa. Surprisingly, the boiling point remained at about −25° C. to about −26° C., indicating that an azeotrope-like composition had formed.

Example 2

A composition comprising 93 wt. % HFC-134a and 7 wt. % HFC-245fa was produced and then transferred into a cylinder having a dip tube. To test the cleaning efficacy of this azeotrope-like composition, a flushing apparatus was assembled that included a cylinder to hold an initial charge of the azeotrope-like composition, a vaporizing expansion device, an oil separator, and a compressor. An article representing a typical vapor compression component, such as a condenser, was weighed and then soiled by depositing approximately 15 grams of polyalkylene glycol (PAG) oil onto its interior surface. The article was then attached to the dip leg of the cylinder containing the azeotrope-like composition so that it could be cleaned.

The azeotrope-like composition, while in liquid phase, was transferred from the cylinder and through the article. As it passed through the article, it contacted the soiled surface. As a result of this contact, the PAG oil was dissolved by the azeotrope-like composition, thereby removing it from the surface of the article. As the azeotrope-like composition and dissolved oil exited the article, they passed through the expansion device causing the liquid to evaporate. The resulting vapor was passed through an oil separator that removed the oil from the azeotrope-like composition. The azeotrope-like composition was then transferred to a compressor were it was transformed back to a liquid phase. The liquid azeotrope-like composition was then recycled through the article to further clean the article's surface.

After the azeotrope-like composition had circulated through the article for 45 minutes, it was found that substantially all of the PAG oil was removed from the article. The apparatus was turned off and the article was weighed and found to be approximately at its original weight. It was found that none of the azeotrope-like composition remained in the article.

Example 3

This example illustrates the formation of an azeotrope-like composition according to the present invention and the cleaning efficacy of that composition. For this example, a mixture of 10 wt. % of HFC-134a and 90 wt. % of HFC-245fa was formulated and utilized.

The procedure specified in Example 1 was followed to prepare the composition, except that a mixture of 10 wt. % of HFC-134a and 90 wt. % of HFC-245fa was formed. Surprisingly, this composition also exhibited azeotrope-like characteristics.

The cleaning efficacy of this composition was tested using the same procedure specified in Example 1. After this azeotrope-like composition had circulated through the article for 45 minutes, it was found that the substantially all of the PAG oil was removed from the article. The apparatus was turned off and the article was weighted and found to be approximately at its original weight. Thus, none of the azeotrope-like composition or PAG oil remained in the article.

Example 4

This example illustrates the cleaning efficacy of an azeotrope-like composition according to this invention when a flush gun apparatus is utilized. For this example, two pounds of a mixture of 20 wt. % of HFC-134a and 80 wt. % of HFC-245fa were formulated and then charged into a flush gun.

The interior of an air conditioning condenser was soiled with 15 grams of PAG oil. The condenser is arranged so that the azeotrope-like composition can flow through it. The outlet of the condenser is connected to an evacuated recovery cylinder via a high pressure refrigeration hose. The recovery cylinder is cooled by dry ice. The inlet of the condenser is attached to the nozzle of the flush gun by a secure fitting and valve.

The valve was opened to allow the azeotrope-like composition to flow from the flush gun through the condenser and ultimately into the recovery cylinder. As the azeotrope-like composition passed through the condenser, it contacted the condenser's soiled surface. As a result of this contact, the PAG oil was dissolved by the azeotrope-like composition, thereby removing it from the surface of the condenser. If required, any excess HFC-245fa that became trapped in the condenser was removed by dry nitrogen or by passing pure HFC-134a through the condenser.

After less than 45 minutes, the flushing procedure was stopped. It was found that the substantially all of the PAG oil was removed from the condenser. It was also found that the condenser was substantially free of the azeotrope-like composition.

Example 5

This example illustrates the cleaning efficacy of an azeotrope-like composition according to this invention when a flush gun apparatus is utilized. For this example, a mixture of 20 wt. % of HFC-134a, 30 wt. % of HFC-365, and 50 wt. % of HFC-245fa was formulated and utilized.

Two pounds of a mixture of 20 wt. % of HFC-134a, 30 wt. % of HFC-365, and 50 wt. % of HFC-245fa was charged into a flush gun. The cleaning efficacy of this composition was tested using the same procedure specified in Example 3.

After less than 45 minutes, the flushing procedure was stopped. It was found that the substantially all of the PAG oil was removed from the condenser. It was also found that the condenser was substantially free of the azeotrope-like composition.

Example 6

Approximately 18.97 grams of HFC-134a was added to an ebulliometer equipped with a vacuum jacket having a condenser on top and a quartz thermometer. HCF-365mfc is added in small increments. Temperature depression was observed when the HFC-365mfc is added, indicating a minimum boiling azeotrope. As shown in Table 1 below, the boiling point of this composition fluctuates only about 0.7° C. as the HFC134a: HFC-365mfc mixture changes from a weight ratio of 100:0 to a weight ratio of 65:35.

TABLE 1
HFC134a: HFC365mfc Composition at 14.4 psia
			Δ from 100% HFC
Wt. % HFC 365 mfc	Wt. % HFC 134a	T (° C.)	134a
0.00	100.00	−25.6	—
0.66	99.34	−26.2	−0.5
3.85	96.15	−26.3	−0.7
6.83	93.17	−26.2	−0.6
12.28	87.72	−26.1	−0.5
17.13	82.87	−25.9	−0.3
23.47	76.53	−25.8	−0.2
28.92	71.08	−25.6	0.0
35.07	64.93	−25.1	0.5

Example 7

Approximately 19.86 grams of HFC-134a was added to the ebulliometer described in Example 5. HCF-43-10 is added in small increments. Temperature depression was observed when the HCF-43-10 is added, indicating a minimum boiling azeotrope. As shown in Table 2 below, the boiling point of this composition fluctuates only about 0.7° C. as the HFC134a: HCF-43-10 mixture changes from a weight ratio of 100:0 to a weight ratio of 45:55.

TABLE 2
HFC134a: HFC-43-10 Composition at 14.4 psia
		T
Wt. % HFC-43-10	Wt. % HFC 134a	(° C.)	Δ from 100% HFC 134a
0.00	100.00	−25.2	—
0.80	99.20	−25.8	−0.6
3.12	96.88	−25.9	−0.7
5.34	94.66	−25.9	−0.7
7.46	92.54	−25.9	−0.7
10.78	89.22	−25.8	−0.6
16.76	83.24	−25.6	−0.4
22.00	78.00	−25.5	−0.3
26.61	73.39	−25.4	−0.2
30.70	69.30	−25.4	−0.2
37.66	62.34	−25.2	0.0
43.35	56.65	−25.0	0.2
49.16	50.84	−25.0	0.2
53.88	46.12	−24.9	0.3

Claims

1. An azeotrope or azeotrope-like composition comprising 1,1,1,2-tetrafluoroethane and one or more compounds selected from the group consisting of 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.

2. The azeotrope or azeotrope-like composition of claim 1, comprising 1,1,1,2-tetrafluoroethane and two or more compounds selected from the group consisting of 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.

3. The composition of claim 1 comprising from about 1 to about 99 weight percent 1,1,1,2-tetrafluoroethane and from about 99 to about 1 weight percent 1,1,1,3,3-pentafluoropropane, wherein said composition has a boiling point of approximately −25° to −26° C. at 14.4 psia.

4. The composition of claim 1 comprising from about 1 to about 20 weight percent 1,1,1,2-tetrafluoroethane and from about 99 to about 80 weight percent 1,1,1,3,3-pentafluoropropane, wherein said composition has a boiling point of approximately −25° to −26° C. at 14.4 psia.

5. The composition of claim 1 comprising from about 1 to about 10 weight percent 1,1,1,2-tetrafluoroethane and from about 99 to about 90 weight percent 1,1,1,3,3-pentafluoropropane, wherein said composition has a boiling point of approximately −25° to −26° C. at 14.4 psia.

6. The composition of claim 1 comprising from about 1 to about 10 weight percent 1,1,1,2-tetrafluoroethane and from about 99 to about 90 weight percent 1,1,1,3,3-pentafluoropropane, wherein said composition has a boiling point of approximately −25° to −26° C. at 14.4 psia.

7. The composition of claim 2 consisting essentially of about 20 weight percent 1,1,1,2-tetrafluoroethane, about 30 weight percent 1,1,1,3,3-pentafluorobutane, and about 50 weight percent 1,1,1,3,3-pentafluoropropane.

8. An azeotrope-like composition consisting essentially of about 65 to 99 weight percent 1,1,1,2-tetrafluoroethane and 1 to 40 weight percent 1,1,1,3,3-pentafluorobutane, wherein said composition has a boiling point of approximately −25° to −26° C. at 14.4 psia.

9. An azeotrope-like composition consisting essentially of about 45 to 99 weight percent 1,1,1,2-tetrafluoroethane and 1 to 55 weight percent 1,1,1,2,2,3,4,5,5,5-decafluoropentane, wherein said composition has a boiling point from approximately −25° to −26° C. at 14.4 psia.

10. A method of removing a contaminant from a vapor compression system comprising the steps of:

a. providing a vapor compression system having at least a portion of at least one surface soiled with a contaminant;

b. contacting said soiled surface with an azeotrope or azeotrope-like composition according to claim 1; and

c. removing at least a portion of said azeotrope or azeotrope-like composition from said system.

11. The method of claim 10, wherein said contaminant is selected from the group consisting of lubricants, processing fluids, and sludge.

12. The method of claim 11, wherein said contaminant consists essentially of carbon, hydrogen, and optionally, oxygen atoms.

13. The method of claim 12, wherein said contaminant comprises alkylbenzenes, mineral oils, esters, polyalkyleneglycols, and polyvinylethers.

14. The method of claim 10, wherein said contacting step comprises flushing said contaminated surface with said azeotrope or azeotrope-like composition.

15. The method of claim 14, wherein said flushing comprises the use of a flushing apparatus.

16. The method of claim 15 wherein said flushing apparatus is a flush gun.

17. A non-azeotrope composition comprising 1,1,1,2-tetrafluoroethane and one or more compounds selected from the group consisting of 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.

18. The non-azeotrope composition of claim 17, comprising 1,1,1,2-tetrafluoroethane and two or more compounds selected from the group consisting of 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane.

19. A method of removing a contaminant from a surface comprising:

(a) contacting the surface with an azeotrope or azeotrope-like composition comprising 1,1,1,2-tetrafluoroethane and one or more compounds selected from the group consisting of 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane; and

(b) removing at least a portion of said azeotrope or azeotrope-like composition from said surface.

20. A method of removing a contaminant from a surface comprising:

(a) contacting the surface with a non-azeotrope composition comprising 1,1,1,2-tetrafluoroethane and one or more compounds selected from the group consisting of 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and 1,1,1,2,2,3,4,5,5,5-decafluoropentane; and

(b) removing at least a portion of said non-azeotrope composition from said surface.