CA2148698A1

CA2148698A1 - Azeotrope-like compositions of difluoromethane, pentafluoroethane and 1,1,1-trifluoroethane

Info

Publication number: CA2148698A1
Application number: CA002148698A
Authority: CA
Inventors: Rajiv Ratna Singh; Earl August Eugene Lund; Ian Robert Shankland
Original assignee: Individual
Current assignee: Honeywell International Inc
Priority date: 1992-11-10
Filing date: 1993-10-28
Publication date: 1994-05-26
Also published as: KR100218062B1; WO1994011459A1; KR950704438A; EP0668897A1; JPH08503461A

Abstract

The invention relates to azeotrope-like compositions of difluoromethane, pentafluoroethane and 1,1,1-trifluoroethane which are useful as refrigerants for heating and cooling applications and as blowing agents for the preparation of thermal plastic foam.

Description

wo94/ll4s9 PCT~US93/l0362 2~ 6~8 AZEOT~OP~L~ COMPOSmONS OF
D~LUOROMEI~ANE, ~ENTAFI,UOROliTlIANE

! Fluorocarbon bas~d fluids hav~ found widespread use in indu~try for refrigeration, air conditioning and heat pump application~.

Vapor co~pression is one form of refri.geration.
In its simplest form, vapor compre~ion in~olves ~`
changing the refrigerant from the liquid to the vapor phase through h~at ab~orption at a low pr~ssure and then from th~ ~apor ~o ~he liquid phase ~hrough heat removal at an elevated pressure. ~

While the primary purpose of refrigeration is to :`
20 remove energy at low temperatl~re, the primary purpose ;~
of a heat pump i9 to add energy at higher temperature.
Heat pump~ aro considered revers~ cycle systems because for heating, th~ operation of th6 cond~nser is inter-chang~d with that of the refrigeration evaporator.
~5 Certain fluorocarbons, and in particular :~
chlorofluorocarbons (CFC's), have gained widespread use ::~
in refrigeration applicationc including air conditioning and heat pump applications owing to their ~nique c~mbination of chemical and physical properties.
The majority of refrigerants utilized in ~apor ' compression systems are either single component fluids ¦ or azeotropic mixtures. Single component fluids and ¦ azeotropic mixtures are characterized as constant-1 35 boiling because they exhibit isothermal and isobaric I
:j , ,~ .

W094/~14~9 2 1 ~ PCT/US93/10362 ev~poration and condensation. The uQe of azeotropic mix~ure~ a~ refrigerant~ i~ known in the art. See, for ~, example, R.C. Downing, ~'Fluorocarbon Refrigerants -Handbook", pp. 139-158, Prentic~-Hall, 1988, and U.S.
Patent~ 2,101,993 and 2,641,579.
: .
. Azeotropic or azeotrope-lik~ compo itions are i d~ir~d b~c~use they do not fractionate upon boiling or evaporation~ This behavior is desirabl~ ~ecause in the previously described vapor compreQsion equipment with which these refrigerant~ are employed, condensed material is qenerated in preparation for cooling or for heating purposes, and unles~ the refrigerant co~po~ition is constant`boiling, i.~., is azeotrope-15 like, fractionation and segregation will occur upon -evaporation and condensation and undesirable ~--refrigerant distribution may act to upset cooling or heating.

The art is continually seeking new ~luorocarbon baYed azeotrope-like mixtures which offer alternatives `~
for r~frigeration and heat pump application~.
Currently, fluorocarbons which contain little or no chlorin~ ar~ of particular int~rQ~t becau~ they are con~id~red to bo environmentally acceptable ~ubstitutes for th~ ~ully halogenated CFC's which are suspected of c~u~ing ~nvironmental problems associated with the depletion o~ the earth's protectiv~ ozone layer.
~athematical model~ have substantiatsd that partially halogenated species, such as difluoromethane tHFC-32), penta-fluoroethane (125) and ~ trifluoroQthane ¦ (HFC-143a), will not adversely affect atmospheric I ~ ch~mistry since they contribute negligibly to ' stratospheric ozone depletion in comp~rison to the ¦ 35 fully halogenated species.

WO 94/1 14~9 PCr/US93/10362 ~ 9 8 w3_ Sub~titute refrigerantR mu~t al~o po~ tho propertie~ unique to the CFC ' ~ including chemica.l ' ~tabil ity, low toxic:ity, and ef f iciency in-uRe .
Ef~iciency in-us~ iE~ i~portant~ for ~x~mpla, in .7 ' 5 r~frig~ration application~ lika air condltioning where ', a lo~ in r~frigarant th~r~odyna~ic p~rfor~anc~ or ~
energy efficiRncy may produc~ ~condary en~ironmental : -ct~ due to incraa~d ~o~il fuQl u~ag~ arising from ~ :~
an im:xa3sed d~and f or ~lQctrical ~n~rgy . Further- ~
mor~, the ideal CFC refrigQrant sub~titute would not ::
requir~ major engineering ch~ng~ to conventional vapor ~:
co~nprs~sion technology currently us~d with CFC
r~frigerant~

~riptîon Qf the In~

Our solution to the need in th~ art for ; strAto~ph~rically ~f~r ~ubstitute~ for CFC-ba~ed ref~ig~rant compositions i8 mixtur~ compri~ing from - 20 about 90 to about 10 weight p~rc~nt difluoromQthane (HFC-32), fro~ about 1 to about 75 weight percent penta~luoro~th~ne (HFC-125) and rro~ about 10 to about 40 w~ight percent l,1,1-tri~lucroethano (HFC-143a) whlch ~oil at about -53~C + about 2'C at 760 mm Hg.
XFC-32 ha~ been proposed as an ~nvironmentally ~ccoptabl~ refrigerant however, it is not a p~rticularly efficient refrigerant e-~p~ci~lly at higher cond~n~ing temperatures, becaus~ it has a relatively , 30 low critical temperature. It is al~o ~lammabl~. HFC-:1 143a ~s a good refrigerant on a t~rmodyna~ic basis but ¦ has a lower vapor pressure than HFC-32. Thi~ results in a lower refrigeration capacity than HFC-32. HFC-- 143a is also flammable. HFC-125 also ha~ a lower capacity than HFC-32 but it is nonflammable. Applicants ,.
,, ,,...

W094/11459 PCT/US93~10362 ~14S~i98 .;

have ~urpri~ingly discovered that when the~a compounds .;
are combined in effective amounts, an azeotrope-like ; compo~ition results which ha~ a highar refrigeration capacity than ~FC-32, HFC-143a and HFC-l25 ~nd which i~
S non~lammable in certain proportions.

h~ lso discov~red that th~ azeotrope-like :~:
compositionn of the in~ention ara useful as blowing -~
agents for extruded thermal pl~stic foam~ such as 10 polyethylene and polystyrene foa~. When the .
compositions of the invention are used a~ blowing agents, they may be used ~lone or in combination with another liquid blowing ~gent such a~ dichloro-1-fluoroethane (HCFC-141b) or other hydrochloro-15 fluorocarbon or hydrofluorocar~on liquids. -~

The compo~itions of th~ preferred and mor~
prQferred azeotrope-like compo~ition~ of the invention ~
are summarized in Table I below. Note that the -composition ranges reported are in weight percent and the term "about" i8 understood to preface each range disclosed.

~:
~i, WO~4/114~9 PCT/US93/1036~
1~698 _5_ ~- ~
~;
-t :.:
Table I
. . .-,,, ," 1 __ :', . Boiling Point CoSponents HFC-32 HFC-125 ~FC- at 760 mm Hg 143a ~-C) ___. __ _ ,.
Preferred about -53 + I .
Composition 8S - lO 1 - 60 15 - 30 a~out 2 . - . . _, _ . __ .
More Preferred about -53 +
Composition 80 - 20 1 - 50 20 - 30 akout 2 ~nother . about -53 + I ~
Preferred S0 - 2035 - S0 15 - 30about 2 I -:
Compos ~tio`n ' ___ __ .

' Th~ precise or true azeotropa compo~ition~ have not ba~n determined but have b4en a~certained to be within the indicated range~. R~gardles~ of where the tru~ azootrop~ liQ, all co~position~ within the indicat~d rang~s, as well as certain co~positions out-id~ th~ indicated ranges, are azeotrope-like, as d-~ined mor~ particularly below.
.
For purpose~ of this discus~ion, by azeotrope-like composition i8 intended to mean that thQ compo~ition behave~ like a true a~eotrope in term~ of its constant i boiling characteristics or tendency not to ~ractionate ¦ upon boiling or evaporation. Thu~, in such a system, ' the composition of the vapor formed during evaporation is identical or substantially identical to the original liquid compo~ition. Hence, during boiling or ., ~, . ` .

WO94/11459 PCT/US93/10362 ~

X1~8698 ~:

- evaporation, the liquid composition, if it changes at all, change~ only slightly. This i~ contrasted with non-azeotrope-like composition~ in which the liquid and v~por compositions chang~ sub~tanti~lly during evaporation or condensation.
` .

In one process e~bodiment of the invention, the azeotrope-like composition of the invention ~y be u~ed in ~ method for producing refrige~ation which co~pri~es condensing a refrigerant comprising the azeotrope-like compositions and thereafter evaporating th~ refrigerant in the vicinity o~ the body to be cooled.
..
~' In another process embodiment o~ th~ invention, the azeotrope-like composition~ of ~he invention may be used in a method for producing heating which compriseR
conden~ing a re~rigerant in the vicinity of tha body to be heated and thereafter evaporating the refrigerant.
In still another prosess embodiment of the inYention, the azeotrope-like co~po~itions of the invention may be used as a blowing agent in a process f or making extruded thermal plastic foams comprising blending hoat plasticized polyolefin resin with a blowing agent and introducing the resin/blowing agent bl~nd ~nto a zone of lower pressure to cause foaming.
Generally, about l - 15 parts of blowing agent are utilized per lO0 parts resin.
The difluoromethane, pentafluoroet~ane and l,l,l-'' trifluoroethane components of the novel azeotrope-like compositions of the invention are known materials.
Preferably they should be used in sufficiently high -~
purity so a-~ to avoid the introduction of adverse i~ :

; . .

WO 94/114~9 Pcr/us93/10362 ~

_7_ 698 ~:
inrluence~ upon the constant boiling properties of the ~yste~.

S
This example conf i~llQ the existence of constant boiling or azeotrope-like co~aposition~ of HFC-32/HFC~
125,~HFC-14~ ria the ~ethod of di~tillation. It ~ls~ `:
illustrate~ that the~Q mixture~ do not fractionate during distillationD :~

A lS0-plate packed di~tillation colu~n with a liquid nitrogen condensed vapor dividing h~!ad was used for thi~ ex~ple. The distillation column was charqed w~th a 29~43.8/27~2 weight percent blPnd o~ HFC-32/HFC-12S/HFC-143a respectively. The composition wa~ heated under total reflux for about an hour to en~ure equilibr~tion. Vapor ~a~plQ6~ wQre taken fro~ the top of the condQnser and analyzed u~ing gas chromatography.
20 Tho average~ of the vapor ~a~ple compositions and the overhead t~peratures were quite con~tant within the - uncerta~nty a~aociated wit~ deter~ining the compo~ition~, indicating that thQ ~ixtures are ron~tant-}~oiling or azeotrope-like.
Exam~l~

The expariment outlined in Exampl8 1 above is repeated fc~r aach of the following compo~itions:
a) 90-10/1-75/10-40 weight perc~nt blend of HFC- :
32/HFC-125/HFC-143a respectively;

b) 10-85/1-60/15-30 weight perc:ent blend of HFC-32/HFC-125/HFC-143a respectively;
:-!

WO94/11459 æ 1 4 ~ 6 9 ~ PCT/US93/~036 .

. -8~
- c) 20-80/1-50/20-30 weight percent blend of HFC-32~HFC-125/HFC-143a respectively;
., ,~
d) 20-50/35-50/15-30 weight percent blend of HFC-32/HFC-125/HF~-143a respectiv~ly.

The average~ of th~ vapor ~a~pl~ co~po~ition and ~ th~ overhead temperatur~ ar~ quitQ con~tant with the. ~-i uncer~ainty a~80ciated with deterQining th~
co~position, indicating that th~ composition~ ar~
constant-boiling or azeotropQ-like.

E~D~I&

~ his ex~mple shows that aæ~otrope-like compo~itions o~ H~C-32, ~FC-125 and HFC-143a have cQrtain pQrformanc~ advantage~ when co~pared to HFC-32, HFC-125 and HFC-143a individually.
Th~ theoretical performance of a refrigerant at sp~ci~ic oparating conditions can be ~timated ~rom the thermodynamic properties of the refrigerant using standard refrigeration cycle analy~i~ techniques. See, for ex~pl~, "Fluorocarbons Refrigerant~ Handbook", ch.

3, Pr~ntice-Hall, (1988) by R.C. Downing. The coe*~icient of performance, COP, i8 a univer~ally ~;
accsptQd m~asure, especially useful in reprQsenting the ~;
relztive thermodynamic efficiency of a refrigerant in a specific he~ting or cooling cycle involving ~vaporation or conden~ation of the refriger~nt. In refrigeration ! engineering this term expresses the ratio of useful ~, refrigeration to the energy applied by the compressor in compressing the vapor. The capacity of a refrigerant represents the volumetric efficiency of the . i W0~4/11459 PCT~US93/10362 21 ~698 _g~
r~friger~nt. To a compres~or engineer thiR value expres~e~ the capability of a compressor to pump guan~itie~ o~ hea~ for a given volu~etric flow rate o~ :
refrigerant. In other word~, given a ~peci~ir ::~
. 5 co~pr~sor, a refrigerant wit~ a high~r capacity will deliver more cooling or heating power.
3 w~ have performed thi~ type of calculation for `~ a mediu~ to low temperature refrigeration cycl~ where 10 the conden~er temperature i3 typ~cally 115-F and the ~vapora~or temperature is typically 40F. We have furth~r assumed isentropic compre~Rion and la compressor inlst temp~rature of 65-F. Such calculatio:n~ were p~r~or~ed for a 75/4/21 weight per~Qnt blend o~ HFC-lS 32/HFC-125/HFC-143a respectively and for HFC-32 and HFC-125 alone. `~
':
Und~r th~ conditions specified above, the COP ::
of the 7S/4/21 weight percent HFC-32/HFC-125/HFC-143a blend wa~ 1.66. The COP for each of HFC-32 and HFC-125 was 1. 63 and 1. 57 respectively. Thus, the energy efficiency of th~ mixture wa~ higher than that of pure HFC-32 and HFC-125. Similarly, th~ capacity of the azQotropic blend was higher ~han that of HFC-32, HFC-12S and HFC-143a by 4%, 15% and 17% re~pectively.

Exa~n~le 4 ~

A small 304 grade stainle~s steel pressure Ye~sel is constructed using schedule 40 pipe which is 4 inches in length and 2 inches in diameter. The vessel ,. . .
:j has top and bottom flanges which ar~ used to close the :~
ends of the cell. A pressure tight seal i5 maintained . between the ends of the pipe and the flanges using . 35 Teflon o-rings. The vessel is closed by tightening 4 :.,, ., 1 ,,,,,.

~Os4/ll4s9 '~ 1 4~6 98 PCT/US93/10362 -10- ~"~, ; bolt~ which run the length of the cRll through the top and ~o~to~ flanges. ~h~ ds~ign pre~sur~ limit for the ! apparatu~ is 1700 psi at 200C; the operation~l limit s i~ sat at lOoo psi.

ThreR gra~.~ of v~ry finely ground Dow Styrene 685D is placed into ~ 3 inch x ~.5 inch op~n gla~s jar.
Th~ gla~ jar is then pl~c~d in th~ pre~ure ve~el and thQ pr~ur~ ve~el i8 clo~ed and evacuated.
Tw~nty two and one half gra~ of the co~po~tion o~ Exa~ple 1 i~ charged into 'thQ ~ealed ve ~el. Th2 vessel i~ placed in a 250F oven overnight. The ves~ remoYed fro~ t~e oven, `;~-rapidly depr~urized and th~n immGr~ed in watsr. The gla~.~ jar i~ removed fro~ th~ ves~el. The resulting foa~ ha~ ~ den~ity of 3 - 4 lb~ Y indicating that the - eo~po~ition oY Example 1 ia a good blowing agent for thermal pla~tie foam.
In ~ummary, we have diseovered that eompositions o~ HFC-32, HFC-125 and HFC-143a are ~zeotrop~-lik~, useful ~ blowing agent~ rOr thermal pla~tie rO~o ~nd polyurethanQ fo~m and ~xhibit improved 25 r~r~g~r~tion properties.

~ Th~ ~xperiment outlined in Example 4 above is 30 r~peated using eaeh of compo~ition~ a)- d) of Example ~ 2. In e~eh C~8~ ~ the resulting foam has a dQnsity of 3; s - 4 lb~/ft3 indicating that eaeh of eomposition~ a) - -~ d) is a good blowing agent for thermal pla~tic foam.
.,;~ ~.

, I
'-:
. ~. -.

Claims

What is Claimed:

1. Azeotrope-like compositions consisting essentially of from about 90 to about 10 weight percent difluoromethane, from about 1 to about 75 weight percent pentafluoroethane and from about 10 to about 40 weight percent 1,1,1-trifluoroethane which boil at about -53°C at 760 mm Hg.

2. The azeotrope-like compositions of claim 1 wherein said compositions boil at -53°C ? about 2°C at 760 mm Hg.

3. The azeotrope-like compositions of claim 1 consisting essentially of from about 85 to about 10 weight percent difluoromethane, from about 1 to about 60 weight percent pentafluoroethane and from about 15 to about 30 weight percent 1,1,1-trifluoroethane.

4. The azeotrope-like compositions of claim 1 consisting essentially of from about 80 to about 20 weight percent difluoromethane, from about 1 to about 50 weight percent pentafluoroethane and from about 20 to about 30 weight percent 1,1,1-trifluoroethane.

5. The azeotrope-like compositions of claim 1 consisting essentially of from about 50 to about 20 weight percent difluoromethane, from about 35 to about 50 weight percent pentafluoroethane and from about 15 to about 30 weight percent 1,1,1-trifluoroethane.

6. A method for producing refrigeration which comprises condensing a composition of claim 1 and thereafter evaporating said composition in the vicinity of a body to be cooled.

7. A method for producing heating which comprises condensing a composition of claim 1 in the vicinity of a body to be heated and thereafter evaporating said composition.

8. A process for making extruded thermal plastic foams comprising blending heat plasticized polyolefin resin with a composition of claim 1 and introducing the blend into a zone of lower pressure to cause foaming.