Patent Description:
The use of trifluoroiodomethane (CF<NUM>I) as a refrigerant has been proposed. The attraction of CF<NUM>I as a refrigerant component is that it can chemically suppress the flammability of flammable refrigerants with which it is blended. Blends comprising flammable refrigerants, such as R-1234yf (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluopropene) with non-flammable refrigerants, such as R-134a (<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane), already exist. However, in the absence of any chemical flame suppression effect, the flammability can only be mitigated by physical dilution with the non-flammable refrigerant. This means that even a weakly flammable refrigerant like R-1234yf must be mixed in almost <NUM>/<NUM> proportions with non-flammable R-134a. Furthermore, as non-flammable fluorinated refrigerants like R-134a and R-<NUM> tend to have high Global Warming Potentials (GWP), a non-flammable mixture comprising at least one flammable, low GWP refrigerant like R-1234yf and a non-flammable, fluorinated refrigerant will still have a relatively high GWP compared to that of the flammable refrigerant alone. Regulations restricting the quantity of high-GWP refrigerants that can be used already exist in Europe and are pending in the Kigali Amendment to the Montreal Protocol. As a result, it is desirable to find mixtures and preferably non-flammable mixtures with lower GWPs than are currently available. Trifluoroiodomethane has a very low effective GWP and so is potentially of interest in suppressing the flammability of any flammable refrigerants with which it is mixed in binary, ternary and higher refrigerant mixtures.

<NUM>,<NUM>-difluoroethylene is a high capacity, flammable refrigerant with a boiling point of -<NUM>. It is classified by ASHRAE in flammability class <NUM> by the ASHRAE Standard <NUM>:<NUM> test method.

Non-flammable refrigerants have traditionally been considered the most desirable and versatile class of refrigerant, but the growing desire for refrigerants having very low GWPs means that there is increasing acceptance of refrigerants which are flammable, but whose flammability is reduced compared to highly flammable refrigerants like propane, or even compared to moderately flammable refrigerants. In particular, the use of refrigerants classed as "weakly flammable" (<NUM>) by ASHRAE Standard <NUM>:<NUM> is now being considered by the industry. Several manufacturers already offer equipment for refrigeration, air-conditioning and heat pump applications using <NUM> flammability class refrigerants. <NUM> refrigerants are distinguished from other moderately flammable refrigerants by exhibiting a low burning velocity of less than <NUM>/s.

There is a need for a non-flammable or weakly flammable refrigerant composition with a low GWP that can operate efficiently in vapour compression cycles for refrigeration, air-conditioning and heat pump applications. In particular, there is a need for a non-flammable or weakly flammable refrigerant composition that exploits the beneficial properties of <NUM>,<NUM>-difluoroethylene (R-1132a) and, in particular, its high refrigeration capacity.

<CIT> relates to a refrigerant composition comprising <NUM>,<NUM>-difluoroethene (R-1132a); trifluoromethane (R-<NUM>); and one or more compound selected from hexafluoroethane (R-<NUM>), ethane (R-<NUM>) and carbon dioxide (R-<NUM>, CO<NUM>).

<CIT> is directed to a composition comprising <NUM>,<NUM>-difluoroethene (R-1132a); a second component selected from the group consisting of hexafluoroethane (R-<NUM>), ethane (R-<NUM>) and mixtures thereof; and, optionally carbon dioxide (CO<NUM>, R-<NUM>).

<CIT> relates to a composition comprising <NUM>,<NUM>-difluoroethene (R-1132a), difluoromethane (R-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoropropene (R-1234yf). Optionally, the composition also comprises carbon dioxide (CO<NUM>, R-<NUM>), and/or <NUM>,<NUM>,<NUM>-trifluoroethene (R-<NUM>).

<CIT> is directed to a composition comprising: (i) <NUM>,<NUM>-difluoroethene (R-1132a); (ii) carbon dioxide (CO<NUM>, R-<NUM>); (iii) pentafluoroethane (R-<NUM>); and (iv) one or more of trifluoromethane (R-<NUM>) and hexafluoroethane (R-<NUM>).

We have found that compositions comprising <NUM>,<NUM>-difluoroethylene (R-1132a; vinylidene fluoride) and trifluoroiodomethane (CF<NUM>I) and at least one further refrigerant compound as defined in the claims are useful as working fluids in vapour compression cycles for refrigeration, air-conditioning and heat pump applications. Furthermore, the non-flammable trifluoroiodomethane can in preferred embodiments effectively supress the flammability of flammable refrigerants including <NUM>,<NUM>-difluoroethylene contained in the compositions to result in refrigerant compositions that are either weakly flammable (flammability class <NUM>) and preferably non-flammable as determined in accordance with the test method of ASHRAE Standard <NUM>:<NUM>. The compositions may also be used as solvents, foam blowing agents, propellants, degreasing agents, and as working fluids in Organic Rankine Cycle equipment for generation of mechanical or electrical power.

Accordingly, one aspect of the present invention provides a ternary or higher refrigerant composition comprising from <NUM> to <NUM>% by weight trifluoroiodomethane (CF<NUM>I), from <NUM> to <NUM>% by weight <NUM>,<NUM>-difluoroethylene (R-1132a), and at least one additional compound of lower volatility than <NUM>,<NUM>-difluoroethylene selected from the group consisting of <NUM>,<NUM>,<NUM>-trifluoroethylene (R-<NUM>), difluoromethane (R-<NUM>), propane (R-<NUM>), propylene (R-<NUM>), fluoroethane (R-<NUM>), pentafluoroethane (R-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (R-134a), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluopropene (R-1234yf), isobutane (R-600a), n-butane (R-<NUM>), trans-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluopropene (R-1234ze(E)), <NUM>,<NUM>,<NUM>-trifluoropropene (R-1243zf), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropene (R-1225ye), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-heptafluoropropane (R-227ea), <NUM>,<NUM>-difluoroethane (R-152a), cis-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluopropene (R-1234ze(Z)), <NUM>-chloro-<NUM>,<NUM>,<NUM>-trifluoropropene (R-1233zd(E/Z)) and <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoro-<NUM>-butene (R-1336mzz(E/Z)).

As used herein, all % amounts mentioned in compositions herein, including in the claims, are by weight based on the total weight of the compositions, unless otherwise stated.

For the avoidance of doubt, it is to be understood that the stated upper and lower values for ranges of amounts of components in the compositions of the invention described herein may be interchanged in any way, provided that the resulting ranges fall within the broadest scope of the invention.

The terms "binary", "ternary", "quaternary" and the like as used herein in connection with the compositions of the present invention include the meaning that such compositions can comprise a certain amount of other components, e.g. impurities and/or additives, such as those resulting from the manufacture of said compositions and/or from putting the compositions of the invention into practice.

In an embodiment, compositions of the invention defined as "binary", "ternary", "quaternary", and/or any other compositions of the invention disclosed herein, may consist essentially of the stated components.

By the term "consist essentially of", we include the meaning that the compositions of the invention contain substantially no other components, particularly no further (hydro)(fluoro)compounds (e.g. (hydro)(fluoro)alkanes or (hydro)(fluoro)alkenes) known to be used in heat transfer compositions. The term "consist of" is included within the meaning of "consist essentially of".

In an embodiment, the compositions of the invention are substantially free of any component that has heat transfer properties (other than the components specified). For instance, the compositions of the invention may be substantially free of any other hydrofluorocarbon compound.

By "substantially no" and "substantially free of", we include the meaning that the compositions of the invention contain <NUM>% by weight or less of the stated component, preferably <NUM>% by weight or less, based on the total weight of the composition.

The compositions of the invention contain R-1132a in an amount of from about <NUM> to about <NUM> weight %, preferably from about <NUM> to about <NUM> weight %, such as from about <NUM> to about <NUM> weight %, for example from about <NUM> to about <NUM> weight %, based on the total weight of the composition.

The CF<NUM>I is present in the composition in an amount of from about <NUM> to about <NUM> weight %, preferably from about <NUM> to about <NUM> weight %, such as from about <NUM> to about <NUM> or <NUM> weight %, for example from about <NUM> to about <NUM> weight %, based on the total weight of the composition.

Certain preferred compositions according to this embodiment include those comprising:.

The compositions of the invention may further comprise CO<NUM>. When included, the CO<NUM> is typically present in an amount of from about <NUM> to about <NUM> weight %, preferably from about <NUM> to about <NUM> weight %, such as from about <NUM> to about <NUM> weight %, for example from about <NUM> to about <NUM> weight %, based on the total weight of the composition. Preferred compositions containing CO<NUM> include the following compositions comprising:.

Other preferred compositions according to the present invention include those comprising:.

In one embodiment, the compositions of the present invention comprise from <NUM> to <NUM>% by weight CF<NUM>I, from <NUM> to <NUM>% by weight R-1132a and R-1234yfbased on the total weight of the composition.

In another embodiment, the compositions of the present invention comprise from <NUM> to <NUM>% by weight CF<NUM>I, from <NUM> to <NUM>% by weight R-1132a, R-<NUM> and R-1234yf based on the total weight of the composition.

The compositions of the invention may also comprise a stabilizer, e.g. as described in <CIT> at paragraphs [<NUM>] to [<NUM>]. Where a stabiliser is included, the amounts in the composition of the invention are typically in the range of from <NUM> to <NUM> weight %, preferably in the range of from <NUM> to <NUM> weight %, more preferably in the range of from <NUM> to <NUM> weight % and particularly in the range of from <NUM> to <NUM> weight % based on the total weight of the composition.

The compositions of the present invention preferably have zero ozone depletion potential.

The compositions according to the present invention typically have a GWP of less than about <NUM>, such as less than about <NUM>, for example less than about <NUM>. Preferably, the compositions of the invention have a GWP of less than about <NUM>, such as less than about <NUM>, for example less than about <NUM>.

The compositions of the invention preferably have a temperature glide in an evaporator or condenser of less than about <NUM>, even more preferably less than about <NUM>, and even more preferably less than about <NUM>.

In an embodiment, the compositions may consist essentially of the stated components. By the term "consist essentially of", we include the meaning that the compositions of the invention contain substantially no other components, particularly no further (hydro)(fluoro)compounds (e.g. (hydro)(fluoro)alkanes or (hydro)(fluoro)alkenes) known to be used in heat transfer compositions. The term "consist of" is included within the meaning of "consist essentially of". Typically, the compositions of the invention are of reduced flammability hazard when compared to R-1132a.

Flammability may be determined in accordance with ASHRAE Standard <NUM> incorporating the ASTM Standard E-<NUM> with test methodology as per Addendum 34p dated <NUM>.

In one aspect, the compositions have one or more of (a) a higher lower flammable limit; (b) a higher ignition energy (c) higher auto ignition temperature or (d) a lower burning velocity compared to R-1132a alone. Preferably, the compositions of the invention are less flammable compared to R-1132a in one or more of the following respects: lower flammable limit at <NUM>; lower flammable limit at <NUM>; breadth of flammable range at <NUM> or <NUM>; auto-ignition temperature (thermal decomposition temperature); minimum ignition energy in dry air or burning velocity. The flammable limits and burning velocity being determined according to the methods specified in ASHRAE-<NUM> and the auto-ignition temperature being determined in a <NUM> glass flask by the method of ASTM E659-<NUM>.

In a preferred embodiment, the compositions of the invention are non-flammable. For example, the compositions of the invention are non-flammable at a test temperature of <NUM> using the ASHRAE-<NUM> methodology. Advantageously, the mixtures of vapour that exist in equilibrium with the compositions of the invention at any temperature between about -<NUM> and <NUM> are also non-flammable.

In some applications it may not be necessary for the formulation to be classed as non-flammable by the ASHRAE-<NUM> methodology. It is possible to develop fluids whose flammability limits will be sufficiently reduced in air to render them safe for use in the application, for example if it is physically not possible to make a flammable mixture by leaking the refrigeration equipment charge into the surrounds.

In one embodiment, the compositions of the invention have a flammability classifiable as <NUM> or <NUM> according to the ASHRAE standard <NUM> classification method, indicating non-flammability (class <NUM>) or a weakly flammable fluid with flame speed lower than <NUM>/s (class <NUM>).

It is believed that the compositions of the invention exhibit a completely unexpected combination of low-/non-flammability, low GWP, improved lubricant miscibility and improved refrigeration performance properties. Some of these refrigeration performance properties are explained in more detail below.

The compositions of the invention are typically suitable for use in existing designs of equipment and are compatible with all classes of lubricant currently used with established HFC refrigerants. They may be optionally stabilised or compatibilised with mineral oils by the use of appropriate additives.

In one embodiment, the invention provides a heat transfer device comprising a composition of the invention. Preferably, the heat transfer device is a refrigeration device.

Conveniently, the heat transfer device is a residential or commercial air conditioning system, a heat pump or a commercial or industrial refrigeration system.

The invention also provides the use of a composition of the invention in a heat transfer device, such as a refrigeration system, as herein described.

Also described herein is a sprayable composition comprising a material to be sprayed and a propellant comprising a composition of the invention.

According to a further aspect of the invention, there is provided a method for cooling an article which comprises condensing a composition of the invention and thereafter evaporating said composition in the vicinity of the article to be cooled.

According to another aspect of the invention, there is provided a method for heating an article which comprises condensing a composition of the invention in the vicinity of the article to be heated and thereafter evaporating said composition.

Also described herein is a method for extracting a substance from biomass comprising contacting the biomass with a solvent comprising a composition of the invention, and separating the substance from the solvent.

Also described herein is a method of cleaning an article comprising contacting the article with a solvent comprising a composition of the invention.

Also described herein is a method for extracting a material from an aqueous solution comprising contacting the aqueous solution with a solvent comprising a composition of the invention, and separating the material from the solvent.

Also described herein is a method for extracting a material from a particulate solid matrix comprising contacting the particulate solid matrix with a solvent comprising a composition of the invention, and separating the material from the solvent.

Also described herein is a mechanical power generation device containing a composition of the invention.

Preferably, the mechanical power generation device is adapted to use a Rankine Cycle or modification thereof to generate work from heat.

According to another aspect of the invention, there is provided a method of retrofitting a heat transfer device comprising the step of removing an existing heat transfer fluid, and introducing a composition of the invention. Preferably, the heat transfer device is a refrigeration device, such as an ultra-low temperature refrigeration system. Advantageously, the method further comprises the step of obtaining an allocation of greenhouse gas (e.g. carbon dioxide) emission credit.

In accordance with the retrofitting method described above, an existing heat transfer fluid can be fully removed from the heat transfer device before introducing a composition of the invention. An existing heat transfer fluid can also be partially removed from a heat transfer device, followed by introducing a composition of the invention.

The compositions of the invention may also be prepared simply by mixing the R-1132a, CF<NUM>I, and the at least one additional compound of lower volatility than R-1132a (and optional components such as R-<NUM>, R-<NUM>, hydrocarbons, a lubricant, a stabiliser) in the desired proportions. The compositions can then be added to a heat transfer device (or used in any other way as defined herein).

In a further aspect of the invention, there is provided a method for reducing the environmental impact arising from operation of a product comprising an existing compound or composition, the method comprising replacing at least partially the existing compound or composition with a composition of the invention.

By environmental impact we include the generation and emission of greenhouse warming gases through operation of the product.

As mentioned above, this environmental impact can be considered as including not only those emissions of compounds or compositions having a significant environmental impact from leakage or other losses, but also including the emission of carbon dioxide arising from the energy consumed by the device over its working life. Such environmental impact may be quantified by the measure known as Total Equivalent Warming Impact (TEWI). This measure has been used in quantification of the environmental impact of certain stationary refrigeration and air conditioning equipment, including for example supermarket refrigeration systems.

The environmental impact may further be considered as including the emissions of greenhouse gases arising from the synthesis and manufacture of the compounds or compositions. In this case the manufacturing emissions are added to the energy consumption and direct loss effects to yield the measure known as Life-Cycle Carbon Production (LCCP). The use of LCCP is common in assessing environmental impact of automotive air conditioning systems.

In a preferred embodiment, the use of the composition of the invention results in the equipment having a lower Total Equivalent Warming Impact, and/or a lower Life-Cycle Carbon Production than that which would be attained by use of the existing compound or composition.

These methods may be carried out on any suitable product, for example in the fields of air-conditioning, refrigeration (e.g. low and ultra-low temperature refrigeration), heat transfer, aerosols or sprayable propellants, gaseous dielectrics, flame suppression, solvents (e.g. carriers for flavorings and fragrances), cleaners, topical anesthetics, and expansion applications. Preferably, the field is refrigeration.

Examples of suitable products include heat transfer devices, sprayable compositions, solvents and mechanical power generation devices. In a preferred embodiment, the product is a heat transfer device, such as a refrigeration device.

The existing compound or composition has an environmental impact as measured by GWP and/or TEWI and/or LCCP that is higher than the composition of the invention which replaces it. The existing compound or composition may comprise a fluorocarbon compound, such as a perfluoro-, hydrofluoro-, chlorofluoro- or hydrochlorofluoro-carbon compound or it may comprise a fluorinated olefin.

Preferably, the existing compound or composition is a heat transfer compound or composition such as a refrigerant. Examples of refrigerants that may be replaced include R-410A, R454B, R-452B and R-<NUM>, preferably R-410A.

Any amount of the existing compound or composition may be replaced so as to reduce the environmental impact. This may depend on the environmental impact of the existing compound or composition being replaced and the environmental impact of the replacement composition of the invention. Preferably, the existing compound or composition in the product is fully replaced by the composition of the invention.

The compositions of the present invention may find particular utility in vapour compression heat transfer systems, such as refrigeration, air-conditioning and heat pump systems.

The refrigerant compositions of the invention will typically be combined with a lubricant when used in a vapour compression heat transfer system. Suitable lubricants include polyol esters, such as neopentyl polyol esters, and polyalkylene glycols, preferably end capped at both ends with an alkyl, e.g. a C<NUM>-<NUM> alkyl, group.

The invention is illustrated by the following non-limiting examples.

The invention is now illustrated by theoretical cycle modelling of performance of selected compositions of the invention in a cooling cycle (Examples <NUM>-<NUM>).

R-410A was chosen as the reference refrigerant for all modelling experiments. The following conditions were assumed:.

The modelling was carried out in Microsoft Excel using NIST REFPROP10 as the thermodynamic data source. The phase equilibria of binary mixtures of R-1132a with R-134a, R-1234yf, R-<NUM>, R-152a, R-<NUM>, CF<NUM>I and R-<NUM>; and of binary mixtures of CF3I with R-<NUM> and R-152a were first studied using a constant-volume apparatus to measure the vapour pressure of the mixtures at a temperature range of from -<NUM> to +<NUM>. This data was then regressed to yield interaction parameters for use in REFPROP that reproduced the experimental data.

The cycle modelled was a standard air-conditioning vapour compression cycle comprising evaporator, compressor, condenser and expansion device.

Mixtures of the invention can offer capacity and energy efficiency (COP) close to those obtainable with R-410A and thus are suitable for use in air-conditioning applications. Certain preferred mixtures of the invention offer capacity and COP within <NUM>% of the values obtainable with R-410A with temperature glides of less than <NUM> in evaporator and/or condenser. It is anticipated that such mixtures would be usable with minor adaptation of existing designs of equipment (intended for R-410A). Other compositions offer higher capacity but with higher temperature glide; such mixtures could nonetheless offer promise for new designs of equipment.

Examples <NUM> to <NUM> demonstrate the theoretical cycle modelling of performance of selected compositions of the present invention in a heat pump cycle. R-1234yf was chosen as the reference refrigerant for the heat pump cycle.

The modelling was carried out in Microsoft Excel using NIST REFPROP10 as the thermodynamic data source. The phase equilibrium of mixtures of R-1132a with R-<NUM> and R-1234yf was first studied using a constant-volume apparatus to measure the vapour pressure of binary mixtures of R-1132a/R-<NUM> or R-1132a/R-1234yf over a range of temperatures from - 70C to +40C. This data was then regressed to yield binary interaction parameters for use in REFPROP that reproduced the experimental data.

The cycle modelled included intermediate pressure vapour injection of refrigerant vapour to improve cycle performance. For each composition the optimum injection pressure was determined so as to maximise the Coefficient of Performance (COP) for heating.

For the heat pump cycle the following conditions were assumed:.

Claim 1:
A ternary or higher refrigerant composition comprising from <NUM> to <NUM>% by weight trifluoroiodomethane (CF<NUM>I), from <NUM> to <NUM>% by weight <NUM>,<NUM>-difluoroethylene (R-1132a), and at least one additional compound of lower volatility than <NUM>,<NUM>-difluoroethylene selected from the group consisting of <NUM>,<NUM>,<NUM>-trifluoroethylene (R-<NUM>), difluoromethane (R-<NUM>), propane (R-<NUM>), propylene (R-<NUM>), fluoroethane (R-<NUM>), pentafluoroethane (R-<NUM>), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroethane (R-134a), <NUM>,<NUM>,<NUM>,<NUM>-tetrafluopropene (R-1234yf), isobutane (R-600a), n-butane (R-<NUM>), trans-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluopropene (R-1234ze(E)), <NUM>,<NUM>,<NUM>-trifluoropropene (R-1243zf), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropene (R-1225ye), <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-heptafluoropropane (R-227ea), <NUM>,<NUM>-difluoroethane (R-152a), cis-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluopropene (R-1234ze(Z)), <NUM>-chloro-<NUM>,<NUM>,<NUM>-trifluoropropene (R-1233zd(E/Z)) and <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoro-<NUM>-butene (R-1336mzz(E/Z)).