Heat-transfer compositions exhibiting improved miscibility with the lubricating oil

Abstract

The use of 1,1,1,2-tetrafluoroethane for increasing the miscibility of 2,3,3,3-tetrafluoropropene with a lubricating oil, and in particular with a polyalkylene glycol oil. Further included are heat-transfer compositions and also equipment and processes using these compositions. Also, a kit including a heat-transfer fluid including 2,3,3,3-tetrafluoropropene and 1,1,1,2-tetrafluoroethane, and a lubricant oil including a polyalkylene glycol, for use in a heat-transfer installation including a vapor compression circuit.

Claims

1. A method comprising replacing 1,1,1,2-tetrafluoroethane in a motor vehicle air-conditioning unit with a heat-transfer fluid, in which the heat-transfer fluid is combined with a lubricant oil to form a heat-transfer composition, said heat-transfer composition comprising the heat transfer fluid and polyalkylene glycol, wherein the heat transfer fluid comprises: 55-85% of 2,3,3,3-tetrafluoropropene; and 15-45% of 1,1,1,2-tetrafluoroethane, wherein the polyalkylene glycol has a viscosity from 20 to 100 Cst at 40 C.

2. The method as claimed in claim 1, wherein 2,3,3,3-tetrafluoropropene, 1,1,1,2-tetrafluoroethane and polyalkylene glycol represent at least 95% of the heat-transfer composition.

3. The method as claimed in claim 1, wherein 2,3,3,3-tetrafluoropropene, 1,1,1,2-tetrafluoroethane and polyalkylene glycol represent at least 99% of the heat-transfer composition.

4. The method as claimed in claim 1, wherein 2,3,3,3-tetrafluoropropene, 1,1,1,2-tetrafluoroethane and polyalkylene glycol represent at least 99.9% of the heat-transfer composition.

5. The method as claimed in claim 1, wherein the heat-transfer composition comprises from 1% to 99% of polyalkylene glycol.

6. The method as claimed in claim 1, wherein the heat-transfer composition comprises from 5% to 50% of polyalkylene glycol.

7. The method as claimed in claim 1, wherein the heat-transfer composition comprises from 10% to 40% of polyalkylene glycol.

8. The method as claimed in claim 1, wherein the heat-transfer composition comprises from 15% to 35% of polyalkylene glycol.

9. The method as claimed in claim 1, wherein the polyalkylene glycol has a viscosity from 40 to 50 centistokes at 40 C.

10. The method as claimed in claim 1, wherein the heat-transfer composition further comprises one or more additives chosen from heat-transfer compounds, lubricants, stabilizers, surfactants, tracers, fluorescers, odorant agents, solubilizers, and mixtures thereof.

11. The method as claimed in claim 1, wherein the heat-transfer composition further comprises one or more additives chosen from stabilizers, surfactants, tracers, fluorescers, odorant agents and solubilizers, and mixtures thereof.

12. The method as claimed in claim 1, wherein the heat-transfer composition consists of 2,3,3,3-tetrafluoropropene, 1,1,1,2-tetrafluoroethane, polyalkylene glycol, and optionally one or more additives chosen from stabilizers, surfactants, tracers, fluorescers, odorant agents and solubilizers, and mixtures thereof.

13. A method comprising replacing 1,1,1,2-tetrafluoroethane in a motor vehicle air-conditioning unit with a heat-transfer fluid, in which the heat-transfer fluid is combined with a lubricant oil to form a heat-transfer composition, said heat-transfer composition comprising 2,3,3,3-tetrafluoropropene, 1,1,1,2-tetrafluoroethane and polyalkylene glycol, wherein the polyalkylene glycol has a viscosity from 20 to 100 Cst at 40 C.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a graph representing the miscibility of various mixtures of HFO-1234yf and HFC-134a with a polyalkylene glycol ND8 oil. The proportion of HFC-134a relative to the mixture of HFO-1234yf and HFC-134a is indicated on the x-axis and ranges from 0 to 100%, and the temperature from which the mixture ceases to be miscible with the oil is indicated on the y-axis (in C.). The experimental data are represented by black circles. The abbreviations NM and M denote, respectively, the non-miscibility zone and the miscibility zone. All the results are obtained with a content of oil ND8 of 17% relative to the sum of the three compounds HFO-1234yf/HFC-134a and oil ND8. Reference will be made to the example below for further details.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(2) The invention is now described in greater detail and without limitation in the description that follows.

(3) Unless otherwise mentioned, throughout the application the indicated proportions of compounds are given as mass percentages.

(4) According to the present patent application, the global warming potential (GWP) is defined relative to carbon dioxide and relative to a duration of 100 years, according to the method indicated in The scientific assessment of ozone depletion, 2002, a report of the World Meteorological Association's Global Ozone Research and Monitoring Project.

(5) The term heat-transfer compound or, respectively, heat-transfer fluid (or coolant fluid) means a compound or, respectively, a fluid that is capable of absorbing heat by evaporating at low temperature and low pressure and of expelling heat by condensing at high temperature and high pressure, in a vapor compression circuit. In general, a heat-transfer fluid may comprise one, two, three or more than three heat-transfer compounds.

(6) The term heat-transfer composition means a composition comprising a heat-transfer fluid and optionally one or more additives that are not heat-transfer compounds for the intended application.

(7) The invention is based on the use of two heat-transfer compounds, namely HFO-1234yf and HFC-134a, and of a lubricant oil, to form a heat-transfer composition.

(8) The heat-transfer composition may be introduced in unmodified form into a vapor compression circuit. Alternatively, the heat-transfer fluid (namely HFO-1234yf and HFC-134a), on the one hand, and the lubricant oil, on the other hand, may be introduced separately into the circuit, at the same point or otherwise. The individual heat-transfer compounds (HFO-1234yf and HFC-134a) may also be introduced separately.

(9) The lubricant oil is preferably of the polyalkylene glycol type.

(10) In general, the polyalkylene glycol oil that is suitable for use in the context of the invention comprises from 5 to 50 repeated oxyalkylene units, each containing from 1 to 5 carbon atoms.

(11) The polyalkylene glycol may be linear or branched. It may be a homopolymer or a copolymer of 2, 3 or more than 3 groups chosen from oxyethylene, oxypropylene, oxybutylene and oxypentylene groups and combinations thereof.

(12) Preferred polyalkylene glycols comprise at least 50% of oxypropylene groups. For the purposes of the invention, the polyalkylene glycol may comprise polyalkylene glycols of different formulae as a mixture.

(13) Suitable polyalkylene glycols are described in document U.S. Pat. No. 4,971,712. Other suitable polyalkylene glycols are polyalkylene glycols containing hydroxyl groups at each end, as described in document U.S. Pat. No. 4,755,316. Other suitable polyalkylene glycols are polyalkylene glycols having a capped hydroxyl end. The hydroxyl group may be capped with an alkyl group containing from 1 to 10 carbon atoms (and optionally containing one or more heteroatoms such as nitrogen), or a fluoroalkyl group containing heteroatoms such as nitrogen, or a fluoroalkyl group as described in document U.S. Pat. No. 4,975,212, or other similar groups.

(14) When the two hydroxyl ends of the polyalkylene glycol are capped, the same end group or a combination of two different groups may be used.

(15) The end hydroxyl groups may also be capped by forming an ester with a carboxylic acid, as is described in document U.S. Pat. No. 5,008,028. The carboxylic acid may also be fluorinated.

(16) When the two ends of the polyalkylene glycol are capped, one or the other may be capped with an ester, or alternatively one end may be capped with an ester and the other end may be free or may be capped with one of the abovementioned alkyl, heteroalkyl or fluoroalkyl groups.

(17) Examples of commercially available lubricant oils of polyalkylene glycol type are the Goodwrench oils from General Motors and Mopar-56 from Daimler-Chrysler. Other suitable oils are manufactured by Dow Chemical and Denso.

(18) The viscosity of the lubricant oil may be, for example, from 1 to 1000 centistokes at 40 C., preferably from 10 to 200 centistokes at 40 C., more particularly preferably from 20 to 100 centistokes at 40 C. and ideally from 40 to 50 centistokes at 40 C.

(19) The viscosity is determined according to the ISO viscosity grades, in accordance with standard ASTM D2422.

(20) The oil sold by Denso under the name ND8, with a viscosity of 46 centistokes, is particularly suitable.

(21) The proportion of lubricant oil that needs to be used in combination with the heat-transfer fluid mainly depends on the type of installation concerned. Specifically, the total amount of lubricant oil in the installation depends mainly on the nature of the compressor, whereas the total amount of heat-transfer fluid in the installation depends mainly on the exchangers and on the pipework.

(22) In general, the proportion of lubricant oil in the heat-transfer composition, or, in other words, relative to the sum of the lubricant oil and of the heat-transfer fluid, is from 1% to 99%, preferably from 5% to 50%, for example from 10% to 40% or from 15% to 35%.

(23) According to one particular embodiment, the lubricant oil used consists of the polyalkylene glycol described above, with the exception of any other lubricant compound.

(24) According to an alternative embodiment, another lubricant oil is used in combination with the polyalkylene glycol. It may be chosen especially from oils of mineral origin, silicone oils, paraffins of natural origin, naphthenes, synthetic paraffins, alkylbenzenes, poly--olefins, polyol esters and/or polyvinyl ethers. Polyol esters and polyvinyl ethers are preferred. When another lubricant oil is used in combination with the polyalkylene glycol it is preferable for the miscibility of the HFO-1234yf and/or of the HFC-134a with this oil to be greater than the respective miscibility of HFO-1234yf and/or of HFC-134a with the polyalkylene glycol. This is especially the case for at least some of the oils of polyol ester or poly vinyl ether type.

(25) The heat-transfer compounds mainly used in the context of the present invention are HFO-1234yf and HFC-134a.

(26) However, the heat-transfer compositions according to the invention may optionally comprise one or more additional heat-transfer compounds, besides HFO-1234yf and HFC-134a. These additional heat-transfer compounds may be chosen especially from hydrocarbons, hydrofluorocarbons, ethers, hydrofluoro ethers and fluoro olefins.

(27) According to particular embodiments, the heat-transfer fluids according to the invention may be ternary compositions (consisting of three heat-transfer compounds) or quaternary compositions (consisting of four heat-transfer compounds), in combination with the lubricant oil to form the heat-transfer compositions according to the invention.

(28) However, binary heat-transfer fluids are preferred.

(29) The term binary fluid means either a fluid consisting of a mixture of HFO-1234yf and HFC-134a; or a fluid consisting essentially of HFO-1234yf and HFC-134a, but which may contain impurities to a proportion of less than 1%, preferably less than 0.5%, preferably less than 0.1%, preferably less than 0.05% and preferably less than 0.01%.

(30) According to particular embodiments, the proportion of HFO-1234yf in the heat-transfer fluid may be: from 0.1 to 5%; or from 5 to 10%; or from 10 to 15%; or from 15 to 20%; or from 20 to 25%; or from 25 to 30%; or from 30 to 35%; or from 35 to 40%; or from 40 to 45%; or from 45 to 50%; or from 50 to 55%; or from 55 to 60%; or from 60 to 65%; or from 65 to 70%; or from 70 to 75%; or from 75 to 80%; or from 80 to 85%; or from 85 to 90%; or from 90 to 95%; or from 95 to 99.9%.

(31) According to particular embodiments, the proportion of HFC-134a in the heat-transfer fluid may be: from 0.1 to 5%; or from 5 to 10%; or from 10 to 15%; or from 15 to 20%; or from 20 to 25%; or from 25 to 30%; or from 30 to 35%; or from 35 to 40%; or from 40 to 45%; or from 45 to 50%; or from 50 to 55%; or from 55 to 60%; or from 60 to 65%; or from 65 to 70%; or from 70 to 75%; or from 75 to 80%; or from 80 to 85%; or from 85 to 90%; or from 90 to 95%; or from 95 to 99.9%.

(32) The values given in the three preceding paragraphs apply to the heat-transfer fluid without lubricant oil, and not to the heat-transfer composition which comprises the heat-transfer fluid, the lubricant oil and optionally other additives.

(33) The other additives that may be used in the context of the invention may be chosen especially from stabilizers, surfactants, tracers, fluorescers, odorant agents and solubilizers.

(34) The stabilizer(s), when they are present, preferably represent not more than 5% by mass in the heat-transfer composition. Among the stabilizers, mention may be made especially of nitromethane, ascorbic acid, terephthalic acid, azoles such as tolutriazole or benzotriazole, phenolic compounds such as tocopherol, hydroquinone, t-butylhydroquinone, 2,6-di-tert-butyl-4-methylphenol, epoxides (optionally fluorinated or perfluorinated alkyl, or alkenyl or aromatic) such as n-butyl glycidyl ether, hexanediol diglycidyl ether, allyl glycidyl ether or butylphenyl glycidyl ether, phosphites, phosphonates, thiols and lactones.

(35) As tracers (which can be detected), mention may be made of deuterated or non-deuterated hydrofluorocarbons, deuterated hydrocarbons, perfluorocarbons, fluoro ethers, bromo compounds, iodo compounds, alcohols, aldehydes, ketones, nitrous oxide and combinations thereof. The tracer is different from the heat-transfer compound(s) of which the heat-transfer fluid is composed.

(36) Examples of solubilizers that may be mentioned include hydrocarbons, dimethyl ether, polyoxyalkylene ethers, amides, ketones, nitriles, chlorocarbons, esters, lactones, aryl ethers, fluoro ethers and 1,1,1-trifluoroalkanes. The solubilizer is different from the heat-transfer compound(s) of which the heat-transfer fluid is composed.

(37) Fluorescers that may be mentioned include naphthalimides, perylenes, coumarins, anthracenes, phenanthracenes, xanthenes, thioxanthenes, naphthoxanthenes and fluoresceins, and derivatives and combinations thereof.

(38) Odorant agents that may be mentioned include alkylacrylates, allylacrylates, acrylic acids, acrylic esters, alkyl ethers, alkyl esters, alkynes, aldehydes, thiols, thio ethers, disulfides, allylisothiocyanates, alkanoic acids, amines, norbornenes, norbornene derivatives, cyclohexene, heterocyclic aromatic compounds, ascaridole and o-methoxy(methyl)phenol, and combinations thereof.

(39) The heat-transfer process according to the invention is based on the use of an installation comprising a vapor compression circuit which contains a heat-transfer composition (namely a heat-transfer fluid and at least one lubricant oil). The heat-transfer process may be a process for heating or cooling a fluid or a body.

(40) The vapor compression circuit comprises at least one evaporator, a compressor, a condenser and a depressurizer, and also lines for transporting the fluid between these components. The evaporator and the condenser comprise a heat exchanger for exchanging heat between the heat-transfer fluid and another fluid or body.

(41) As compressor, use may be made especially of a single-stage or multi-stage centrifugal compressor or a centrifugal mini-compressor. Rotary, piston or screw compressors may also be used. The compressor may be driven by an electric motor or by a gas turbine (for example fed with the exhaust gases of a vehicle, or mobile applications) or by gearing.

(42) The installation may comprise an electricity-generating turbine (Rankine cycle).

(43) The installation may also optionally comprise at least one heat-exchange fluid circuit used for transmitting heat (with or without a change of state) between the heat-transfer fluid circuit and the fluid or body to be heated or cooled.

(44) The installation may also optionally comprise two (or more) vapor compression circuits, containing identical or different heat-transfer fluids. For example, the vapor compression circuits may be coupled together.

(45) The vapor compression circuit operates according to a standard vapor compression cycle. The cycle comprises the change of state of the heat-transfer fluid from a liquid phase (or liquid/vapor two-phase system) to a vapor phase at a relatively low pressure, followed by compression of the fluid in vapor phase up to a relatively high pressure, the change of state (condensation) of the heat-transfer fluid from the vapor phase to the liquid phase at a relatively high pressure, and reduction of the pressure to recommence the cycle.

(46) In the case of a cooling process, heat derived from the fluid or body that is being cooled (directly or indirectly, via a heat-exchange fluid) is absorbed by the heat-transfer fluid, during the evaporation of the latter, this taking place at a relatively low temperature relative to the environment. The cooling processes comprise air-conditioning processes (with mobile installations, for example in vehicles, or stationary installations), refrigeration and freezing processes or cryogenic processes.

(47) In the case of a heating process, heat is yielded (directly or indirectly, via a heat-exchange fluid) from the heat-transfer fluid, during the condensation of the latter, to the fluid or body that is being heated, this taking place at a relatively high temperature relative to the environment. In this case, the installation for transferring heat is known as a heat pump.

(48) It is possible to use any type of heat exchanger for the implementation of the heat-transfer fluids according to the invention, and especially co-current heat exchangers or, preferably, counter-current heat exchangers. It is also possible to use micro-channel exchangers.

(49) The invention in particular makes it possible to use cooling processes at moderate temperature, i.e. those in which the temperature of the cooled fluid or body is from 15 C. to 15 C., preferably from 10 C. to 10 C. and more particularly preferably from 5 C. to 5 C. (ideally about 0 C.).

(50) The invention also makes it possible to use heating processes at moderate temperature, i.e. those in which the temperature of the heated fluid or body is from 30 C. to 80 C., preferably from 35 C. to 55 C. and more particularly preferably from 40 C. to 50 C. (ideally about 45 C.).

(51) In the processes of cooling or heating at moderate temperature mentioned above, the inlet temperature of the heat-transfer fluid into the evaporator is preferably from 20 C. to 10 C., especially from 15 C. to 5 C., more particularly preferably from 10 C. to 0 C., for example about 5 C.; and the condensation start temperature of the heat-transfer fluid in the condenser is preferably from 25 C. to 90 C., especially from 30 C. to 70 C., more particularly preferably from 35 C. to 55 C., for example about 50 C. These processes may be refrigeration, air-conditioning or heating processes.

(52) The invention also makes it possible to use cooling processes at low temperature, i.e. those in which the temperature of the cooled fluid or body is from 40 C. to 10 C., preferably from 35 C. to 25 C. and more particularly preferably from 30 C. to 20 C. (ideally about 25 C.).

(53) In the low-temperature cooling processes mentioned above, the inlet temperature of the heat-transfer fluid into the evaporator is preferably from 45 C. to 15 C., especially from 40 C. to 20 C. and more particularly preferably from 35 C. to 25 C., for example about 30 C.; and the condensation start temperature of the heat-transfer fluid in the condenser is preferably from 25 C. to 80 C., especially from 30 C. to 60 C. and more particularly preferably from 35 C. to 55 C., for example about 40 C.

(54) It should be noted that the addition of HFC-134a to a heat-transfer fluid consisting of HFO-1234yf (or comprising HFO-1234yf) improves the miscibility of the heat-transfer fluid with the lubricant oil, i.e. increases the threshold temperature for appearance of the non-miscibility zone (defined as being the temperature from which the compounds in the liquid phase form an emulsion), and thus makes it possible to increase the possibilities of use of the heat-transfer fluid, for example by enabling use at a higher condensation temperature.

(55) More generally, the invention enables the replacement of any heat-transfer fluid in all heat transfer applications, for example in motor vehicle air-conditioning. For example, the heat-transfer fluids and heat-transfer compositions according to the invention may serve to replace: 1,1,1,2-tetrafluoroethane (R134a); 1,1-difluoroethane (R152a); 1,1,1,3,3-pentafluoropropane (R245fa); mixtures of pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a) and isobutane (R600a), namely R422; chlorodifluoromethane (R22); the mixture of 51.2% chloropentafluoroethane (R115) and 48.8% chlorodifluoromethane (R22), namely R502; any hydrocarbon; the mixture of 20% difluoromethane (R32), 40% pentafluoroethane (R125) and 40% 1,1,1,2-tetrafluoroethane (R134a), namely R407A; the mixture of 23% difluoromethane (R32), 25% pentafluoroethane (R125) and 52% 1,1,1,2-tetrafluoroethane (R134a), namely R407C; the mixture of 30% difluoromethane (R32), 30% pentafluoroethane (R125) and 40% 1,1,1,2-tetrafluoroethane (R134a), namely R407F; R1234yf (2,3,3,3-tetrafluoropropene); R1234ze (1,3,3,3-tetrafluoropropene).

EXAMPLE

(56) The example that follows illustrates the invention without limiting it.

(57) In this example, the miscibility of HFO-1234yf, HFC-134a and mixtures thereof with a lubricant oil of the type PAG ND8 is studied.

(58) An autoclave is placed in a glass-paneled tank fed with a thermostatically maintained bath of water or of glycol-water depending on the test temperatures, from 30 C. to +80 C.

(59) For each heat-transfer fluid tested (mixture of HFO-1234yf and HFC-134a in given proportions), the heat-transfer fluid is introduced into the autoclave. Next, a first amount of defined lubricant oil is added, and the mixture is stirred. The temperature in the autoclave is increased until an emulsion is obtained, indicating the non-miscibility of the mixture. The mixture is then cooled, an additional amount of oil is added thereto and this operation is performed iteratively.

(60) This procedure makes it possible to produce, for each given HFO-1234yf/HFC-134a transfer fluid, a curve for visualization of the non-miscibility zone of the mixture with the oil PAG, as a function of the temperature.

(61) Reciprocally, exploitation of the data makes it possible to determine, for a given lubricant oil concentration, the non-miscibility threshold temperature as a function of the proportion of HFC-134a in the HFO-1234yf/HFC-134a mixture. This is shown in FIG. 1, for an amount of lubricant oil of 17%.

(62) When the mixture does not contain any HFC-134a, the emulsion appears at a temperature of 26 C. On the other hand, when the mixture does not contain any HFO-1234yf, the emulsion appears at a temperature of 69 C. This makes it possible to plot a theoretical dashed line, representing the expected temperature for the appearance of an emulsion with a mixture of HFO-1234yf and of HFC-134a, this being obtained by weighting of the respective miscibility temperatures.

(63) Experimentally, it is noted, however, that the miscibility zone is larger than that theoretically expected. This means that there is a synergistic effect between HFO-1234yf and HFC-134a with regard to the miscibility with the lubricant oil.

(64) A similar result is obtained with an amount of lubricant oil of 30%, for example, instead of 17%. It is thus observed that the addition of 20% HFC-134a to HFO-1234yf makes it possible to improve the miscibility zone by about 10 degrees relative to the expected value.