The present invention relates to refrigerant compositions, particularly for use as replacements in air conditioning and refrigeration equipment currently employing, or designed to employ, chlorodifluoromethane (R22).
BACKGROUND OF THE INVENTION
Refrigerant is the substance which is used as working fluid in a thermodynamic cycle, undergoes a phase change from liquid to vapour and produces cooling. These are used in refrigeration, air conditioning, and heat pumping systems. They absorb heat from one area, such as an air conditioned space, and reject it into another, such as outdoors, usually through evaporation and condensation, respectively. These phase changes occur both in absorption and mechanical vapour compression refrigeration systems, but they do not occur in systems operating on a gas cycle using a fluid such as air.
Before the discovery of ozone hole in early 1970s, the refrigeration and air-conditioning industry was relying heavily on chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and their azeotropics.
HCFC refrigerant namely chlorodifluoromethane (R22) is widely used for residential and commercial air conditioning, as well as commercial refrigeration and has been commonly used with a mineral oil lubricant. R22 is the subject of a phase-out schedule under the Montreal Protocol as its chlorine content make it the largest ozone depleting substance in volumetric terms. R22 is prohibited from use in new equipment in some countries. After the discovery of ozone hole, the era for alternative refrigerants has started.
Refrigerant mixtures may be used as the alternative refrigerants. Refrigerant mixtures/blends can be classified based on the number of pure components, that is, binary/ternary/quaternary. A number of patents have suggested trinary refrigerant compositions as replacements for R22.

U.S. Patent no. 5,185,094 discloses a substantially constant boiling mixture consisting essentially of a ternary mixture of 5-59 % by weight pentafluoroethane (R125), 5-59 % by weight difluoromethane (R32) and 5-35 % by weight 1,1,1,2-tetrafluoroethane (R134a) having a vapor pressure of about 169 to about 207 psia. at 23.8° C and wherein the vapor pressure changes less than about 10%> after leakage of 50% of the initial mixture.
U.S. Patent no. 5,370,811 discloses a working fluid which consists essentially of 15 to 95%) by weight of tetrafluoroethane and two different fluorinated hydrocarbons having a boiling point not higher than -40° C under atmospheric pressure selected from the group consisting of 1 to 50% by weight of trifluoromethane, 1 to 60%> by weight of R32, 1 to 85% by weight of R125 and 1 to 80% by weight of 1,1,1-trifluoroethane which has a composition in a range between phase equilibrium lines.
U.S. Patent no. 5,438,849 discloses a heat pump or air conditioner containing a working fluid, said heat pump or air conditioner having a condenser and evaporator, which working fluid consists essentially of 15 to 95% by weight of tetrafluoroethane and two different fluorinated hydrocarbons having a boiling point not higher than -40° C under an atmospheric pressure selected from the group consisting of 1 to 50% by weight of trifluoromethane, 1 to 60% by weight of R32, 1 to 85% by weight of R125 and 1 to 80%) by weight of 1,1,1-trifluoroethane, which has a composition in a range between phase equilibrium lines.
U.S. Patent no. 5,643,492 discloses a substantially constant boiling mixture consisting essentially of a substantially constant boiling composition consisting of 5-90 % by weight of R125, 5-59 % by weight of R32, and 5-35 % by weight of R134a having a vapor pressure of about 186 to about 227 psia at 23.8 ° C, and wherein the vapor pressure changes less than about 10% after leakage of 50% of the initial mixture.
U.S. Patent no. 5,709,092 discloses a process for producing refrigeration in a refrigeration system designed to use R-502 comprising condensing a composition

consisting essentially of a substantially constant boiling composition consisting of 5-90% by weight of R125, 5-59% by weight of R32, and 15-70 % by weight of R134a.
U.S. Patent no. 5,722,256 discloses an air conditioner or heat pump containing a non-flammable working fluid suitable as a substitute for a working fluid containing R-502, said air conditioner or heat pump having a condenser and evaporator for producing refrigeration in a refrigeration system designed to use R-502, which working fluid consists essentially of 5 to 90% by weight of a tetrafluoroethane, 5 to 60% by weight of R32 and 5 to 90% by weight of R125.
U.S. Patent no. 6,018,952 discloses a method for charging a refrigerant blend, when using as a refrigerant a non-azeotropic blend whose permissible range falls within 22 to 24% of R32, 23 to 27% of R125 and 50 to 54% of R134a.
U.S. Patent no. 6,187,219 discloses compositions of R32/R125/R134a by the weight % ratio of 20/20/60, 20/40/40 and 40/20/40.
U.S. Patent no. 6,669,862 discloses a refrigerant composition comprising a mixture of about 20% to 25% by weight of R32; about 20% to 28% by weight of R125; 48% to 54% by weight of R134a and about 0.008% to 1% by weight of a lower alkyl alcohol, formulated into a composition compatible with a refrigerating device.
European Patent no. 430169B1 discloses a working fluid can be used as substitute of R22 comprising tetrafluoroethane characterized in that said fluid comprises 15 to 90% by weight of tetrafluoroethane and at least two fluorinated hydrocarbons selected from the group consisitng of not more than 50% of trifluoromethane, not more than 60% of R32, not more than 85% of R125 and not more than 80%) of 1,1,1-trifluoroethane.
European Patent no. 509673B1 discloses a refrigerant composition for replacing refrigerant R22 comprising essentially of 55 to 65 % by weight of R134a, 25 to 35 % by weight of R32, 5 to 15 % by weight of R125.

European Patent no. 811670B1 discloses ternary mixture refrigerant in a composition range defined by a straight line A which connects a point al (R32/R134a = 43/57 wt%) and a point a2 (R125/R134a = 73/27 wt%), a line B which connects a point bl (R32/R134a = 21/79 wt%) and a point b2 (R125/R134a = 55/45 wt%), a line D which connects a point dl (R32/R125 = 60/40 wt%) and a vertex of R134a, and a line E which connects a point el (R32/R125 = 53/47 wt%) and a point e2 (R32/R134a = 19/81 wt%) in a ternary composition diagram of R32, R125 and R134a.
U.S. Patent no. 8,168,077 discloses a ternary refrigerant composition of R32, R125 and R134a (25-35%, 20-40% and 35-45% respectively) for the replacement of R22 refrigerant. However, ternary refrigerant composition is only utilized for heating and cooling application in low temperature refrigerant systems.
PCT publication no. WOO 1/23493 discloses R22 replacement binary refrigerant composition comprising R134a (50-20%); R125 (25-80%) and additive selected from saturated hydrocarbon. The use of saturated hydrocarbon as additives increases the flammability of the composition.
The above compositions have significant amount of R125 which contributes to the higher GWP of these compositions and defeats the purpose of using them as replacement for R22. There is an urgent need to develop nonflammable refrigerant compositions with lower GWP that can replace R22 and are compatible with the systems already in use for R22.
The present invention discloses refrigerant compositions as replacement for R22 comprising non chlorine containing refrigerants having low GWP and no deleterious effect on ozone layer.

OBJECT OF THE INVENTION
A first aspect of the present invention provides refrigerant composition comprising difluoromethane (R32); 1,1,1,2-tetrafluoroethane (R134a) and pentafluoroethane (R125) as a drop-in replacement for R22.
A second aspect of the present invention provides a nominal refrigerant composition comprising about 23% by weight to about 29% by weight of R32 and about 71% by weight to about 77% by weight of R134a as a drop-in replacement for R22.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, a refrigerant is defined as a heat transfer fluid that undergoes a phase change from liquid to gas and back again during a cycle used to transfer of heat.
Drop-in refrigerant is a refrigerant which can replace the other refrigerant without any change in the existing system.
As used herein, non-absorbable gases are the gases which cannot be compressed predominately include air.
Non-azeotropic composition is a mixture of two or more substances that behaves as a simple mixture rather than a single substance. One way to characterize a non-azeotropic composition is that the vapor produced by partial evaporation or distillation of the liquid has a substantially different composition as the liquid from which it was evaporated or distilled, that is, the admixture distills/refluxes with substantial composition change.
The refrigeration capacity is a measure of the ability of a refrigerant or heat transfer composition to produce cooling. Therefore, the higher the capacity, the greater the cooling that is produced. Cooling rate refers to the heat removed by the refrigerant in the evaporator per unit time.
Coefficient of performance (COP) is the amount of heat removed divided by the required energy input to operate the cycle. The higher the COP, the higher is the
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energy efficiency. COP is directly related to the energy efficiency ratio (EER) that is the efficiency rating for refrigeration or air conditioning equipment at a specific set of internal and external temperatures.
Discharge temperature is a temperature of the refrigerant gas at the discharge of the compression.
Flammability is a term used to mean the ability of a composition to ignite and/or propagate a flame. Determination of whether a refrigerant compound or mixture is flammable or non-flammable can be done by testing under the conditions of ASTM-681.
Global warming potential (GWP) is an index for estimating relative global warming contribution due to atmospheric emission of a kilogram of a particular greenhouse gas compared to emission of a kilogram of carbon dioxide. GWP can be calculated for different time horizons showing the effect of atmospheric lifetime for a given gas. The GWP for the 100-year time horizon is commonly the value referenced. For mixtures, a weighted average can be calculated based on the individual GWPs for each component. The standard GWP values for R22, 32, 125 and 134a has been taken from IIPCC 5th Assessment report 2014 (AR5). The GWP of the refrigerant mixture has been derived from mass fraction and the corresponding GWP values.
Ozone depletion potential (ODP) is a number that refers to the amount of ozone depletion caused by a substance. The ODP is the ratio of the impact on ozone of a chemical compared to the impact of a similar mass of CFC-11 (fluorotrichloromethane). Thus, the ODP of CFC-11 is defined to be 1.0. Other CFCs and HCFCs have ODPs that range from 0.01 to 1.0. HFCs have zero ODP because they do not contain chlorine or other ozone depleting halogens.
A first aspect of the present invention provides refrigerant composition comprising R32, R125 and R134a as replacement of refrigerant R22.
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In one embodiment of this aspect of the present invention, the refrigerant composition comprises of about 20% by weight to about 30% by weight of R32; about 65% by weight to about 77% by weight of R134a and more than 0 to less than 15% by weight of R125.
In another embodiment of this aspect of the present invention, the refrigerant composition comprises of about 20% by weight to about 30% by weight of R32, about 65% by weight to about 77% by weight of R134a and more than 0 to less than 10% by weight of R125.
In one embodiment of this aspect of the present invention, the refrigerant composition comprises of about 20% by weight to about 30% by weight of R32, about 65% by weight to about 77% by weight of R134a and more than 0 to less than 7% by weight of R125.
In another embodiment of this aspect of the present invention, the refrigerant composition comprises of about 20% by weight to about 30% by weight of R32, about 65% by weight to about 77% by weight of R134a and more than 0 to less than 5% by weight of R125.
Another embodiment of this aspect of the present invention, provides a nominal refrigerant composition comprising of about 22% by weight to about 27% by weight of R32, about 70% by weight to about 75% by weight of R134a and more than 0 to less than 5% by weight of R125.
In one embodiment of this aspect of the present invention, the refrigerant composition has GWP of less than 1500.
In another embodiment of this aspect of the present invention, the refrigerant composition has GWP of less than 1300.
In another embodiment of this aspect of the present invention, the refrigerant composition additionally comprises of about less than 0.5% of non-absorbable gases.
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In another embodiment of this aspect of the present invention, the refrigerant composition may contain optional components selected from the group consisting of lubricants, dyes (including Ultra Violet dyes), solubilizing agents, compatibilizers, stabilizers, tracers, perfluoropolyethers, anti-wear agents, extreme pressure agents, corrosion and oxidation inhibitors, metal surface energy reducers, metal surface deactivators, free radical scavengers, foam control agents, viscosity index improvers, pour point depressants, detergents, viscosity adjusters, and mixtures thereof. Indeed, many of these optional other components fit into one or more of these categories and may have qualities that lend themselves to achieve one or more performance characteristic.
In another embodiment of this aspect of the present invention, the refrigerant mixture may additionally contain other refrigerants selected from the group consisting of HFOs including HFO1234yf, HFO1234ze, HFO1233, HFO1234ze, HFO1233zd, HFO1336mzz and the like.
In another embodiment of this aspect of the present invention, the refrigerant composition is a drop in replacement for R22.
In another embodiment of this aspect of the present invention, the refrigerant composition is a non-azeotropic mixture.
In another embodiment of this aspect of the present invention, the refrigerant composition can be either charged as liquid composition or full vapor composition.
In another embodiment of this aspect of the present invention, the refrigerant composition is preferably charged in liquid form.
In another embodiment of this aspect of the present invention, the refrigerant composition has lower discharge temperature compared to R22 thus the use of this composition increases life of the compressor.
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In another embodiment of this aspect, the present invention provides a refrigeration process using the refrigerant composition of the present invention comprising the steps of:
a) condensing the refrigerant composition;
b) evaporating the refrigerant composition.
A second aspect of the present invention provides a nominal refrigerant composition comprising difluoromethane (R32) and 1,1,1,2-tetrafluoroethane (R134a) as replacement of refrigerant R22.
In one embodiment of this aspect of the present invention, the nominal composition comprises of about 23% by weight to about 29% by weight of R32 and about 71% by weight to about 77% by weight of R134a.
In another embodiment of this aspect of present invention, the nominal composition comprises 24% by weight of R32 and 76% by weight of R134a.
In another embodiment of this aspect of present invention, the nominal composition comprises 26% by weight of R32 and 74% by weight of R134a.
In another embodiment of this aspect of present invention, the nominal composition comprises 27% by weight of R32 and 73% by weight of R134a.
In another embodiment of this aspect of present invention, the nominal composition comprises 29% by weight of R32 and 71% by weight of R134a.
In another embodiment of this aspect of the present invention, the nominal composition comprises 23.5% by weight of R32 and 76.5% by weight of R134a.
In another embodiment of this aspect of the present invention, the refrigerant composition has GWP of less than 1500.
In another embodiment of this aspect of the present invention, the refrigerant composition has GWP of less than 1300.
In another embodiment of this aspect of the present invention, the refrigerant composition additionally comprises of about less than 0.5% of non-absorbable gases.
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In another embodiment of this aspect of the present invention, the refrigerant composition may contain optional components selected from the group consisting of lubricants, dyes (including UV dyes), solubilizing agents, compatibilizers, stabilizers, tracers, perfluoropolyethers, anti-wear agents, extreme pressure agents, corrosion and oxidation inhibitors, metal surface energy reducers, metal surface deactivators, free radical scavengers, foam control agents, viscosity index improvers, pour point depressants, detergents, viscosity adjusters, and mixtures thereof. Indeed, many of these optional other components fit into one or more of these categories and may have qualities that lend themselves to achieve one or more performance characteristic.
In another embodiment of this aspect of the present invention, the refrigerant composition is a drop-in replacement for R22.
In another embodiment of this aspect of the present invention, the refrigerant composition is a non-azeotropic mixture.
In another embodiment of this aspect of the present invention, the refrigerant composition can be either charged as liquid composition or full vapor composition.
In another embodiment of this aspect of the present invention, the refrigerant composition has lower discharge temperature as compared to R22 thus results in increasing the life of the compressor.
In another embodiment of this aspect, the present invention provides a refrigeration process using the refrigerant composition of the present invention comprising the steps of:
a) condensing the refrigerant composition;
b) evaporating the refrigerant composition.
The refrigerant compositions of the present invention may be used in stationary or mobile air conditioning systems or heat exchanger systems. Preferably, the refrigerant compositions would be utilized in domestic room air conditioning systems.
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The refrigerant compositions of the present invention work well in existing R22 air conditioning and refrigeration systems that use mineral oil and alike lubricants. The refrigerant compositions of the present invention work well in existing R22 air conditioning and refrigerant systems used today with only minor adjustments.
The present invention thus provides an R22 replacement refrigerant compositions that are compatible with existing mineral oil and alike lubricants and do not require replacement of the expensive devices in the legacy system.
The refrigerant compositions of the present inventions also work well with if R134 is replaced with R134a.
The AHR1210/240 standard uses several different temperatures to derive the “Seasonal” component of the rating. The highest ambient air temperature used in the AHR1210/240 standard is 95F (35°C), and this may result in condensing temperatures for the refrigerant inside the condenser of between 105F and 110F (40°C to 43°C) because the refrigerant inside the system has to be warmer than the outside air temperature in order for the heat to move from the refrigerant to the outside air. Conventional operation conditions for the legacy R22 systems include these standards and their conditions.
Each of the components of the cooling system is sensitive to the composition and amount of refrigerant flowing through it, and the legacy R22 systems are no exception. Large changes in refrigerant flow rate as compared to the designed flow rates will cause the amount of heat absorbed by the system to change adversely. For example, if the refrigerant absorbs too much heat from the evaporator because the expansion device cannot adequately slow down the flow rate of refrigerant, the compressor will pump too much refrigerant and overload the electric motor which could either trigger associated electrical protection circuits or permanently damage the motor. On the other hand, if the refrigerant absorbs too little heat because the expansion device cannot pass
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enough refrigerant, the system will lose the ability to absorb enough heat to keep the cooled area at the selected temperature.
Fortunately, legacy refrigeration systems were all designed at a time when there were far fewer refrigerants and lubricant options. This fact caused design engineers to use substantially the same refrigerant and lubrication performance criteria when specifying the expansion devices, motors, etc. that were used in these legacy systems. As a result, those systems tended to be fairly close in terms of the tolerable range of adjustments that each could employ and still achieve acceptable performance. The present invention is specifically designed to be a retrofit refrigerant for R22 systems that can be used in the legacy R22 equipment with the legacy mineral oil and alike lubricants. This latter property thus eliminates the need to replace the existing lubricant for a polyol ester or alkylbenzene lubricant and avoids the introduction of a lubricant solvent that can dislodge debris deposits in older systems and absorb ambient moisture more readily.
The formulation according to the invention exhibits cooling and condensation properties that make it well suited as a retrofit for R22 refrigerants without the need to replace the expansion devices and flow valves of the existing legacy equipment. Specifically, the inventor has found that the existing flow control devices in legacy equipment for R22 refrigeration systems has the ability to deliver the correct refrigerant flow rate without affecting the continuity of the refrigerating cycle. The refrigerant formulation of the invention exhibits cooling capacities and mass flow rates that are within the flow adjustment tolerances of such equipment. Thus, the refrigerant formulation of the present invention can replace the legacy R22 refrigerant using the same lubricant and the same expansion valves with only adjustments that are within acceptable ranges of such legacy equipment.
R32 is commercially available or may be prepared by methods known in the art, such as by dechlorofluorination of methylene chloride.
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R125 is commercially available or may be prepared by methods known in the art, such as dechlorofluorination of 2,2-dichloro-1,1,1-trifluoroethane as described in US Patent No. 5,399,549, incorporated herein by reference.
R134a is commercially available or may be prepared by methods know in the art, such as by the hydrogenation of 1 ,1 -dichloro-1 ,2,2,2-tetrafluoroethane (i.e., CCI2FCF3 or CFC-114a) to 1 ,1 ,1 ,2-tetrafluoroethane.
It is against this and other backgrounds, which shall be filed in a detailed manner in complete specifications, in due course, the present invention is brought out and explained in following non-limiting examples.
EXAMPLES Example 1
The refrigerant compositions according to the invention having composition of R125:R134a:R32 were prepared and tested with standard ASHRAE modeling program maintaining indoor at 27ºC dry bulb temperature (DBT) and 19ºC wet bulb temperature (WBT) and outdoor at 35 DBT and 24 WBT.
The refrigerant compositions of the present invention are enlisted in Table 1 and the results are shown below in Table 2
Table 1

Compositions R32* R134a* R125*
Composition 1 24 72 4
Composition 2 26 73 1
Composition 3 25 73 2
Composition 4 23 70 7
*all quantities are calculated as % by weight
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Table 2

Refrigerant compositions Cooling Capacity Quantity Charged Power Consumption COP ODP GWP
R22 100 100 100 100 1760
Composition 1 91.6 100 99.3 94.7 0 1225
Composition 2 90.6 100 99.3 90.8 0 1157
Composition 3 89.7 100 97.9 91.2 0 1182
Composition 4 88.8 100 101 87.8 0 1288
As depicted in Table 2, the refrigerant compositions of the present invention exhibit good cooling capacity and will operate in substantially the same manner as the legacy R22 refrigerant under the same conditions. The performance factor is almost close to R22. Example 2
The refrigerant compositions according to the invention having composition of R134a:R32 were prepared and tested with standard ASHRAE modeling program maintaining indoor at 27°C dry bulb temperature (DBT) and 19°C wet bulb temperature (WBT) and outdoor at 35 DBT and 24 WBT.
The refrigerant compositions of the present invention are enlisted in Table 3 and the results are shown below in Table 4.
Table 3

Compositions R32* R134a*
Composition 1 29 71
Composition 2 27 73
Composition 3 23.5 76.5
*all quantities are calculated as % by weight

Table 4

Refrigerant compositions Cooling Capacity Quantity Charged Power Consumption COP ODP GWP
R22 100 100 100 100 1760
Composition 1 90.7 100% 99.3 91.6 0 1119
Composition 2 87.9 100 99.3 89.7 0 1132
Composition 3 78.5 100 100 78.6 0 1154
As depicted in Table 4, the refrigerant compositions of the present invention exhibit a cooling capacity close to that of R22 refrigerant and would operate in substantially the same manner as the legacy R22 refrigerant under the same conditions. The performance factor is almost close to R22.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention and specific examples provided herein without departing from the spirit and scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention that come within the scope of any claims and their equivalents.

We Claim:

A refrigerant composition comprising difluoromethane (R32); 1,1,1,2-tetrafluoroethane (R134a) and pentafluoroethane (R125).
2. The refrigerant composition as claimed in claim 1, comprises from about 20% by weight to about 30% by weight of R32; about 65% by weight to about 77% by weight of R134a and more than 0 to less than 15% by weight of R125.
3. The refrigerant composition as claimed in claim 1, comprises from about 23%
by weight to about 26% by weight of R32, about 70% by weight to about 73% by
weight of R134a and 1 to 7% by weight of R125.
4. A nominal refrigerant composition comprising difluoromethane (R32) and 1,1,1,2-tetrafluoroethane (R134a).
5. The nominal refrigerant composition as claimed in claim 4, comprising from about 23% by weight to about 29% by weight of R32 and about 71% by weight to about 77% by weight of R134a.

6. The refrigerant composition as claimed in claim 1-5, wherein the composition is to be used as a drop-in replacement for R22.
7. The refrigerant composition as claimed in claims 1 and 4, wherein the said refrigerant composition has GWP of less than 1500.

8. The refrigerant composition as claimed in claims 1 and 4, wherein the refrigerant composition is a non-azeotropic mixture.