R22/R124/R142b refrigerant blends

Abstract: Refrigerant mixtures of the HCFCs monochlorodifluoromethane, 2-chloro-1,1,1,2-tetrafluoroethane, and 1-chloro-1,1-difluoroethane whose composition falls within the area of polygon KLTS of the FIGURE.

Description: This invention concerns refrigerant mixtures of the hydrochlorofluorocarbons ("HCFCs") monochlorodifluoromethane ("R22"), 2-chloro-1,1,1,2-tetrafluoroethane ("R124"), and l-chloro-l,l-difluoroethane ("R142b"), which mixtures are particularly useful as a replacement for the chlorofluorocarbon ("CFC") dichlorodifluoromethane ("R12"). R12 has been the refrigerant of choice for, for example, auto air conditioning and domestic refrigerators, but has been found to have unacceptably high ozone depletion potential ("ODP") and global warming potential ("GWP"). Several replacements have been proposed for R12, but all have been found wanting. For example, 1,1,1,2-tetrafluoroethane ("R134a") is more acceptable environmentally, but cannot be used in most existing equipment owing to incompatibility with common refrigeration oils. Blends of R22 and R142b have better oil solubility, but in the event of a prolonged leak from the vapor phase can become flammable owing to fractionation causing a shift to over about 70% R142b. A blend of R22 and R124 has also been proposed (US-PS 4 303 536), but does not offer the solubility and cost-effectiveness of the subject ternary blend. What is needed is a refrigerant blend which offers a combination of high energy efficiency (as indicated by a high "COP" or coefficient of performance), good oil solubility, and low cost, while remaining essentially nonflammable throughout a leak. Such blends would be useful as replacements for R12 in auto air conditioning, domestic refrigerators, commercial refrigeration units, and the like. EP-A-299 614 relates to a refrigerant containing three or more halocarbons, each halocarbon after the first having a successively higher boiling point. The refrigerant has a temperature/pressure relation substantially equal to FC-12. However, EP-A-299 614 teaches the use of one or more components having a high ozone depletion potential, a high global warming potential or low solubility. EP-A-402 937 relates to a refrigerant composition comprising dichloromonofluoromethane and one or more fluoroalkyl compounds selected from trifluoromethane, pentafluoroethane, monochlorodifluoromethane, and 1-chloro-1,1-difluoroethane. Dichloromonofluoromethane, however, a component in all of the blends of EP-A-402 937, has a threshold limit value ("TLV") of only 10 parts per million (compared to a TLV of about 1000 for most refrigerants) and thus is seldom used. EP-A-402 937, in disclosing an R22/R142b/R21 blend, also takes the same approach as EP-A-299 614 in that it shows that the flammable R142b component must have a boiling point intermediate that of the other components. The FIGURE is a ternary diagram showing the region of the compositions of the present invention (in weight percent). It has now been unexpectedly found that R22/R124/R142b ternary blends falling within area KLTS of the FIGURE meet the foregoing objectives of efficiency, solubility, cost, and nonflammability. Lines KS and LT in the FIGURE represent outer compositional bounds because mixtures within these limits are calculated to have pressures within plus or minus 25% of the pressure of R12 over the temperature range of -20°C to 70°C. Compositions in the region below line KL are nonflammable (or essentially so) and remain so in the event of a leak from the vapor phase. At least 5% R142b is desired (represented by line ST) to enhance solubility of the blend since R142b is found to be more soluble than R22 or R124 in conventional oils such as alkyl benzene oils, to increase efficiency (COP increases in accordance with the amount of R142b present for a given amount of R22), and to lower the cost of the blend. Preferred mixtures of this invention fall within the area of polygon PQNM defined by points P (57, 18, 25), Q (40, 26, 34), N (40, 50, 10), and M (47.5, 42.5, 10) in the FIGURE. The compositional limits are determined by a desire to maximize the COP (thus a content of at least 10% R142b as represented by line MN), to achieve a cooling capacity at least about equal to that of R12 (thus a content of at least 40% R22 as represented by line QN), to achieve a pressure in the condenser (which is the highest pressure in a refrigeration system) which is about equal to or less than 1.1 times that of R12 (achieved by mixtures in the region to the right of line PM), and to provide an added margin of nonflammability (by operating in the region below line PQ). Most preferred are those blends having a condenser pressure about equal to that of R12 (achieved by blends in the area to the right of line VW) so that the most preferred embodiment is represented by compositions in the area of triangle VQW defined by points V (45.5, 23, 31.5), Q (40, 26, 34), and W (40, 38.5, 21.5) in the FIGURE. The boiling points of R22, R124, and R142b, in degrees C, are -40.75, -11.95, and -9.15, respectively. Their saturated vapor pressures (at 20°C) in MPa (psia) are 1.011, 0.436 and 0.402 (132.1, 48.8, and 43.8), respectively. Parameters calculated by the steady-state thermodynamic analysis for R12 and various R22/R124/R142b mixtures in a typical automobile air conditioner (with compressor, condenser, and evaporator) are reported in the Table below:

Claims: A refrigerant mixture containing a ternary blend of halocarbons, a component of which is monochlorodifluoromethane (R22), characterized in that the refrigerant mixture consists essentially of monochlorodifluoromethane (R22), 2-chloro-1,1,1,2-tetrafluoroethane (R124) and 1-chloro-1,1-difluoroethane (R142b), said mixture having a composition falling within the area of a three phase diagram in the form of a triangle the apices of which correspond to the pure components R22, R124 and R142b, said area being defined by lines KL (corresponding to the line as represented in the figure), LT, TS and KS, said lines connecting the points K, L, T and S having the following coordinates in said three phase diagram: K (64 wt.% R22, 7 wt.% R124, 29 wt.% R142b), L (10 wt.% R22, 33 wt.% R124, 57 wt.% R142b), T (5.5 wt.% R22, 89.5 wt.% R124, 5 wt.% R142b), S (58 wt.% R22, 37 wt.% R124, 5 wt.% R142b). The refrigerant mixture according to claim 1, characterized in that said mixture has a composition falling within the area of the three phase diagram defined in claim 1, said area being defined by lines PQ, QN, NM and MP, said lines connecting the points P, Q, N and M, having the following coordinates in said three phase diagram: P (57 wt.% R22, 18 wt.% R124, 25 wt.% R142b), Q (40 wt.% R22, 26 wt.% R124, 34 wt.% R142b), N (40 wt.% R22, 50 wt.% R124, 10 wt.% R142b), M (47.5 wt.% R22, 42.5 wt.% R124, 10 wt.% R142b). The refrigerant mixture according to claim 1, characterized in that said mixture has a composition falling within the area of the three phase diagram defined in claim 1, said area being a triangle, the corners of which are defined by the points V, Q and W having the following coordinates in said three phase diagram: V (45.5 wt.% R22, 23 wt.% R124, 31.5 wt.% R142b), Q (40 wt.% R22, 26 wt.% R124, 34 wt.% R142b), W (40 wt.% R22, 38.5 wt.% R124, 21.5 wt.% R142b).

Inventors: MCMASTER CROOKER RICHARD, MCMASTER CROOKER, RICHARD
Applicants: ATOCHEM NORTH AMERICA ELF, ELF ATOCHEM NORTH AMERICA, INC.
Application year: 1992
Main classification: C09K5
IPC codes: C09K5, C09K3