Azeotrope-like compositions comprising trichlorofluoromethane, a dichlorotrifluoroethane selected from the group consisting of 1,1-dichloro-2,2,2-trifluoroethane and 1,2-dichloro-1,1,2-trifluoroethane and isopentane are novel compositions particularly useful as blowing agents in the preparation of polyurethane and polyisocyanurate foams.

DESCRIPTION 
FIELD OF THE INVENTION 
This invention relates to azeotrope-like mixtures of 
trichlorofluoromethane, dichlorotrifluoroethane and isopentane. These 
mixtures are useful as blowing agents in the manufacture of rigid and 
flexible polyurethane foams and polyisocyanurate foams. 
BACKGROUND OF THE INVENTION 
Polyurethane and polyisocyanurate foams are manufactured by reacting and 
foaming a mixture of ingredients comprising in general an organic 
isocyanate, such as pure or crude toluene diisocyanate or a polymeric 
diisocyanate, with an appropriate amount of polyol or mixture of polyols, 
in the presence of a volatile liquid blowing agent, which vaporizes during 
the reaction, causing the polymerizing mixture of foam. The reactivity of 
these ingredients is enhanced through the use of various additives such as 
amine and/or tin catalysts and surfactant materials which serve to control 
and adjust cell size as well as to stabilize the foam structure during its 
formation. 
Flexible polyurethane foams are generally manufactured using an excess of 
diisocyanate which reacts with the water also included as a raw material, 
producing gaseous carbon dioxide, causing foam expansion. Flexible foams 
are widely used as cushioning materials in items such as furniture, 
bedding and automobiles. Auxiliary physical blowing agents such as 
methylene chloride and/or CFC-11 are required in addition to the 
water/diisocyanate blowing mechanism in order to produce low density, soft 
grades of flexible polyurethane foam. 
Rigid polyurethane and polyisocyanurate foams are almost exclusively 
expanded using CFC-11 as the blowing agent. Some rigid foam formulations 
do incorporate small amounts of water in addition to the CFC-11, but the 
CFC-11 is the major blowing agent component. Other formulations sometimes 
use small amounts of the more volatile dichlorodifluoromethane (CFC-12) in 
addition to CFC-11 for producing so-called froth-type foams. Rigid foams 
are closed-cell foams in which the CFC-11 vapor is trapped in the matrix 
of cells. These foams offer excellent thermal insulation characteristics, 
due in part to the low vapor thermal conductivity of CFC-11, and are used 
widely in thermal insulation applications such as roofing systems, 
building panels, refrigerators and freezers and the like. 
The fully halogenated chlorofluorocarbons such as CFC-11 are suspected of 
causing environmental problems in connection with the earth's protective 
ozone layer. Concern over the potential environmental impact of CFC 
emissions has prompted a phased reduction in fully halogenated CFC 
production and consumption. The azeotrope-like blowing agent blends 
described in this invention offer the potential of a 34 percent reduction 
in CFC-11 use. The other components of the blends, namely 
dichlorotrifluoroethane and isopentane, have very low ozone depletion 
potentials in comparison to CFC-11. 
Although methylene chloride is used as an auxiliary blowing agent in 
flexible polyurethane foam manufacture, it has found very little 
application as a blowing agent in the rigid urethane-type foams. Methylene 
chloride tends to remain dissolved in the polymeric back bone of the foam 
due to its greater solvency characteristics. The residual methylene 
chloride softens and plasticizes the polymer leading to foam collapse or 
excessive shrinkage as well as a reduction in the strength properties of 
the rigid foam. Some rigid foam formulations can tolerate small amounts of 
methylene chloride as a component of the blowing agent, for example, Taub 
and Ostrozynski in U.S. Pat. No. 4,055,521 demonstrate that a blend 
consisting of 83 parts CFC-11, 12 parts isopentane and 5 parts methylene 
chloride can be used to expand a rigid polyurethane foam with good 
properties. However, use of even these small amounts of methylene chloride 
in closed-cell foams may be objectionable due to the adverse toxicological 
properties of methylene chloride. 
Other volatile liquids such as hydrocarbons have not found acceptance as 
blowing agents for polyurethane-type foams due to their extreme 
flammability and poor thermal conductivity properties. These aspects 
outweigh the economic advantages that hydrocarbons have over 
fluorocarbons. Although the blends described in this invention do contain 
a hydrocarbon, it is present as a minor component and overall the blends 
are nonflammable as evidenced by flash point tests. Furthermore, as the 
present blends are azeotrope-like in nature, their vapor and liquid 
compositions are identical and the flammable hydrocarbon component will 
not fractionate or segregate from the mixture during boiling or 
evaporation. 
U.S. Pat. Nos. 3,940,342 and 4,002,573 discloses binary constant boiling 
compositions of 1,2-dichloro-1,1,2-trifluoroethane with 
trichlorofluoromethane, with diethyl ether and with dichloromethane and 
also ternary constant boiling compositions comprising 
1,2-dichloro-1,1,2-trichloroethane, diethyl ether and 
1,2-dibromo-1,1,2,2-tetrafluoroethane. 
U.S. Pat. No. 4,624,970 discloses the use of mixtures of CFC-11 and 
HCFC-123 or HCFC-123a to blow urethane type foams. Such blowing agent 
mixtures were found to permit greater amounts of low cost aromatic 
polyester polyols to be used in rigid foam formulations without serious 
degredation in foam properties. 
It is accordingly an object of this invention to provide novel 
azeotrope-like compositions based on a fluorocarbon which is not fully 
halogenated, which can be used as blowing agents to produce rigid and 
flexible polyurethane foams and polyisocyanurate foams with good 
properties. 
Other objects and advantages of the invention will become apparent from the 
following description of the invention. 
In accordance with the invention, novel azeotrope-like compositions are 
provided comprising trichlorofluoromethane, a dichlorotrifluoroethane 
selected from the group consisting of 2,2-dichloro-1,1,1-trifluoroethane 
ethane (HCFC-123) and 1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a) and 
isopentane which are useful as blowing agents in the manufacture of rigid 
and flexible polyurethane foams as well as polyisocyanurate foams. Such 
azeotropic compositions are formed when either of the above recited 
isomers of dichlorotrifluoroethane is employed in about the same 
proportions. 
In a preferred embodiment of the invention, azeotrope-like compositions 
comprise from about 66 to about 80 weight percent trichlorofluoromethane 
(CFC-11), from about 17 to 15 weight percent of the recited 
dichlorotrifluoroethane isomers and from about 17 to 5 weight percent 
isopentane. The dichlorotrifluoroethane isomers, not being perhalogenated, 
are considered to be stratospherically safe. Both of the recited isomers 
form azeotrope-like compositions with trichlorofluoromethane and 
isopentane. Our best estimate of the minimum boiling azeotropic 
composition is about 79 weight percent CFC-11, about 15 weight percent of 
the recited dichlorofluoroethane isomers and about 6 weight percent 
isopentane. These mixtures are nonflammable liquids, do not fractionate 
upon evaporation or boiling and provide about 20 to 34 percent reduction 
in the amount of fully halogenated CFC-11 required to expand the foam. 
Their expansion efficiency (gas volume generated per unit weight) is 
better than CFC-11 alone and they also produce foams with similar thermal 
insulation characteristics to foams expanded with CFC-11. 
DESCRIPTION OF THE INVENTION 
The novel azeotrope-like compositions of the invention comprise CFC-11, 
dichlorotrifluoroethane (HCFC-123 or HCFC-123a) and isopentane. 
For ease of reference the HCFC-123 or HCFC-123a isomers will sometimes be 
referred to collectively as "dichlorotrifluoroethane". 
In a preferred embodiment of the invention, the azeotrope-like compositions 
comprise from about 66 to about 80 weight percent CFC-11, from about 17 to 
about 15 weight percent dichlorotrifluoroethane and from about 17 to about 
5 weight percent isopentane. 
Our best estimate of the true azeotrope containing HCFC-123 is about 79 
weight percent CFC-11, about 15 weight percent HCFC-123 and about 6 weight 
percent isopentane. The azeotropic composition of the isomeric system is 
very similar, about 78 weight percent CFC-11, about 15 weight percent 
HCFC-123a and about 7 weight percent isopentane. 
The precise or true azeotrope compositions have not been determined but 
have been ascertained to be within the indicated ranges. Regardless of 
where the true azeotrope lies, all compositions within the indicated 
ranges, as well as certain compositions outside the indicated ranges, are 
azeotrope-like, as defined more particularly below. 
The compositions of the invention are capable of expanding 
polyurethane-type foams possessing very good characteristics in comparison 
to foams expanded with CFC-11 alone. An advantage of using the 
compositions of the invention to blow urethane-type foams is that foams 
produced with such compositions consume less CFC-11 and will therefore 
emit less CFC-11. The expansion efficiency of the blends, that is gas 
volume generated per unit weight of blowing agent, is greater than that of 
CFC-11. 
Compositions within the azeotrope-like region do not exhibit flash points 
and are classified as nonflammable liquids. At the low isopentane 
composition the vapor phase does not possess flame limits while at the 
high isopentane composition it does exhibit very narrow flame limits in 
air. This narrow range of vapor flammability will not inhibit the use of 
these blends as urethane foam blowing agents. 
From fundamental principles, the thermodynamic state of a fluid is defined 
by four variables: pressure, temperature, liquid composition and vapor 
composition, or P-T-X-Y, respectively. An azeotrope is a unique 
characteristic of a system of two or more components where X and Y are 
equal at the stated P and T. In practice, this means that the components 
of a mixture cannot be separated during evaporation or boiling and hence 
simultaneous vaporization in a constant proportion of all the components 
of the azeotrope-like mixture will occur during the foam forming process. 
An additional consequence of the azeotrope-like behavior is that it is not 
possible to separate the flammable isopentane component from the blend by 
evaporation, which could happen if the blend were not azeotrope-like 
leading to a potentially hazardous situation. 
For the purpose of this discussion, by azeotrope-like composition is 
intended to mean that the composition behaves like a true azeotrope in 
terms of its constant boiling characteristics or tendency not to 
fractionate upon boiling or evaporation. Such composition may or may not 
be a true azeotrope. Thus, in such compositions, the composition of the 
vapor formed during boiling or evaporation is identical or substantially 
identical to the original liquid composition. Hence, during boiling or 
evaporation, the liquid composition, if it changes at all, changes only to 
a minimal or negligible extent. This is to be contrasted with 
non-azeotrope-like compositions in which during boiling or evaporation, 
the liquid composition changes to a substantial degree. 
Thus, one way to determine whether a candidate mixture is "azeotrope-like" 
within the meaning of this invention, is to distill a sample thereof under 
conditions (i.e. resolution-number of plates) which would be expected to 
separate the mixture into its separate components. If the mixture is 
non-azeotropic or non-azeotrope-like, the mixture will fractionate, i.e. 
separate into its various components with the lowest boiling component 
distilling off first, and so on. If the mixture is azeotrope-like, some 
finite amount of a first distillation cut will be obtained which contains 
all of the mixture components and which is constant boiling or behaves as 
a single substance. This phenomenon cannot occur if the mixture is not 
azeotrope-like i.e., it is not part of an azeotropic system. If the degree 
of fractionation of the candidate mixture is unduly great, then a 
composition closer to the true azeotrope must be selected to minimize 
fractionation. 
It follows from the above that another characteristic of azeotropic-like 
compositions is that there is a range of compositions containing the same 
components in varying proportions which are azeotrope-like. All such 
compositions are intended to be covered by the term azeotrope-like as used 
herein. As an example, it is well known that at differing pressures, the 
composition of a given azeotrope will vary at least slightly as does the 
boiling point of the composition. Thus, an azeotrope of A and B represents 
a unique type of relationship but with a variable composition depending on 
temperature and/or pressure. 
In the process embodiment of the invention, the azeotrope-like compositions 
of the invention may be used as blowing agents for the preparation of 
flexible and rigid polyurethane foams as well as rigid polyisocyanurate 
foams by reacting and foaming a mixture of ingredients which will form the 
polymeric foam in the presence of said blowing agent compositions.

EXAMPLE 1 
This example confirms the existence of an azeotrope between CFC-11, 
HCFC-123 and isopentane as well as confirming the existence of an 
azeotrope between CFC-11, HCFC-123a and isopentane. The method of 
distillation is employed in this example. 
A 15-plate Oldershaw distillation column with a cold water cooled automated 
liquid dividing head was used for this example. The distillation column 
was first charged with approximately 580 grams of 79.5 weight percent 
CFC-11, 14.5 weight percent HCFC-123 and 6.0 weight percent isopentane. 
The mixture was heated under total reflux for a period of about one and 
half hours to ensure equilibration. A 10:1 reflux ratio was used in this 
distillation. About 60 percent of the original charge was collected in 7 
overhead fractions. The composition of these fractions as well as the 
composition of the residue in the distillation column were determined by 
gas chromatography. Table I shows that the compositions of the starting 
material, the compositions of the 7 distillate fractions, and the 
composition of the column residue are identical within the uncertainty 
associated with the analytical technique. The equivalent liquid and vapor 
compositions indicate that the mixture is an azeotrope. The composition of 
the azeotrope is in the region of about 79 weight percent CFC-11, about 15 
weight percent HCFC-123 and about 6 weight percent isopentane. 
TABLE I 
______________________________________ 
CFC-11, HCFC-123 & Isopentane Distillation Data 
Vapor Mixture Composition 
Temperature 
(parts by weight) 
Mixture (.degree.C.) 
HCFC-123 CFC-11 Isopentane 
______________________________________ 
Original 14.4 79.8 5.8 
Charge 
Distillate 
23.3 14.9 79.0 6.1 
Fraction #1 
Distillate 
23.3 14.6 79.5 5.9 
Fraction #2 
Distillate 
23.3 15.0 79.0 6.0 
Fraction #3 
Distillate 
23.6 15.0 79.0 6.0 
Fraction #4 
Distillate 
23.7 14.6 79.6 5.8 
Fraction #5 
Distillate 
23.6 14.5 79.8 5.7 
Fraction #6 
Distillate 
23.6 14.4 79.8 5.8 
Fraction #7 
Liquid 14.2 80.2 5.6 
Residue 
Barometric pressure = 754.6 mm Hg 
______________________________________ 
A similar distillation, this time starting with a mixture in which the 
isomer HCFC-123a is used in place of HCFC-123 also provides evidence of an 
azeotrope. These distillation results are summarized in Table II. The 
azeotropic composition for this mixture is about 78 weight percent CFC-11, 
about 15 weight percent HCFC-123a and about 7 weight percent isopentane. 
TABLE II 
______________________________________ 
CFC-11, HCFC-123a & Isopentane Distillation Data 
Vapor 
Temper- 
Mixture Composition 
ature (parts by weight) 
Mixture (.degree.C.) 
HCFC-123a CFC-11 Isopentane 
______________________________________ 
Original 16.3 76.7 7.0 
Charge 
Distillate 
22.9 14.6 78.2 7.2 
Fraction #1 
Distillate 
22.9 14.7 78.1 7.2 
Fraction #2 
Distillate 
22.9 14.9 77.9 7.2 
Fraction #3 
Distillate 
22.9 14.8 78.1 7.1 
Fraction #4 
Distillate 
22.9 15.3 77.5 7.2 
Fraction #5 
Liquid 17.5 75.6 6.9 
Residue 
Barometric pressure = 735.5 mm Hg 
______________________________________ 
Although in the present case the two isomers, HCFC-123 and HCFC-123a, 
behave very similarly with respect to azeotrope formation with CFC-11 and 
isopentane, this, as is well known, is not always the case with isomers. 
For example, when the distillation of Table I is repeated using n-pentane 
in place of the isopentane, the mixture is observed to fractionate, 
indicating that the CFC-11/HCFC-123/n-pentane system is not an azeotrope 
or azeotrope-like. 
EXAMPLE 2 
This example describes additional distillations of 
CFC-11/HCFC-123/isopentane mixtures which are used to determine the 
constant boiling or azeotrope-like composition range. 
The distillations were performed using a 5-plate Oldershaw distillation 
column at a 3:1 reflux ratio. The mixtures were heated at total reflux for 
about an hour and a half to ensure equilibration before collecting 50 
percent of the original charge in 4 distillate fractions. 
The vapor and liquid compositions were analyzed using gas chromatography. 
CFC-11/HCFC-123/isopentane blends with compositions (by weight) of 
64.6/15.3/20.1 and 69.7/15.4/14.9 were distilled in order to map the 
azeotrope-like region. The distillation date are shown in Table III. 
TABLE III 
______________________________________ 
Constant Boiling Characteristics 
Vapor Mixture Composition 
Temperature 
(parts by weight) 
Mixture (.degree.C.) 
HCFC-123 CFC-11 Isopentane 
______________________________________ 
Original 15.3 64.6 20.1 
Charge 
Distillate 
23.0 17.4 65.6 17.0 
Fraction #1 
Distillate 
23.0 17.2 65.2 17.6 
Fraction #2 
Distillate 
24.0 17.1 64.8 18.1 
Fraction #3 
Distillate 
24.0 15.8 65.9 18.3 
Fraction #4 
Liquid 12.8 63.4 23.9 
Residue 
Barometric pressure = 744.6 mm Hg 
______________________________________ 
Original 15.4 69.7 14.9 
Charge 
Distillate 
22.9 16.9 70.0 13.1 
Fraction #1 
Distillate 
22.9 17.2 69.2 13.6 
Fraction #2 
Distillate 
23.0 16.4 70.1 13.5 
Fraction #3 
Distillate 
23.1 16.1 70.0 13.9 
Fraction #4 
Liquid 14.3 68.7 17.0 
Residue 
Barometric pressure = 744.6 mm Hg 
______________________________________ 
These data, along with the data shown in Table I show that the region where 
vapor and liquid compositions are essentially identical, that is, the 
region where the mixture is azeotrope-like, includes the region of about 
66 to 80 weight percent CFC-11, about 17 to 15 weight percent HCFC-123 and 
about 17 to 5 weight percent isopentane. 
EXAMPLE 3 
Flammability characteristics of various CFC-11/HCFC-123/isopentane blends 
are assessed in this example. The flammability of the liquids was 
determined using both Tag open cup (ASTM D 1310-86) and Tag closed cup 
(ASTM D 56-82) methods. Vapor flammability was measured using a eudiometer 
apparatus similar to that described by Zabetakis et al. in Industrial and 
Engineering Chemistry, Vol. 43, No. 9 p. 2120 (1951). 
The flash point data (see Table IV) show that the 
CFC-11/HCFC-123/isopentane blends begin to exhibit a flash point when the 
isopentane composition is increased to about 20 weight percent. Mixtures 
with compositions within the azeotrope-like region defined in the previous 
example were shown not to exhibit a flash point, that is, they are 
nonflammable liquids. 
TABLE IV 
______________________________________ 
Flash Point Data 
CFC-11/HCFC-123/Isopentane 
Flash Point (.degree.F.) 
Composition Open Cup Closed Cup 
______________________________________ 
78/15/7 None None 
75/15/10 None None 
70/15/15 None None 
65/15/20 -27 None 
______________________________________ 
Vapor flammability data are summarized in Table V. The isopentane rich end 
of the azeotrope-like composition range does exhibit a narrow range of 
vapor flammability. This behavior would not, however, preclude use of 
these blends as a foam blowing agent. 
TABLE V 
______________________________________ 
Vapor Flammability Data 
CFC-11/HCFC-123/Isopentane 
Lower Limit Upper Limit 
Composition Volume % Mixture 
______________________________________ 
79/15/6 None None 
75/15/10 14.6 15.6 
70/15/15 8.0 15.8 
______________________________________ 
EXAMPLE 4 
This example describes an evaluation of the properties of rigid 
polyurethane and polyisocyanurate foams prepared using a 79/15/6 blend of 
CFC-11/HCFC-123/isopentane. Foams of similar density were prepared using 
100 percent CFC-11 for comparison purposes. 
Free-rise rigid polyurethane foams were prepared from the formulations 
specified in Table VI using a Martin Sweets Co. Modern Module III urethane 
foam machine at a delivery rate of 15 lbs./min. This polyurethane 
formulation is one example of a pour-in-place rigid polyurethane 
formulation which might be used as an appliance insulation. 
The foams were characterized (Table VII) according to initial thermal 
conductivity (K-factor), density, dimensional stability, porosity (% 
closed-cells) and reactivity. Urethane foam produced using the 
azeotrope-like blend possesses almost identical properties to the CFC-11 
expanded foams. 
An advantage of the azeotrope-like blends over CFC-11 is their expansion 
efficiency. The above example shows that about 3% less blowing agent blend 
is required to achieve the same density. 
Polyisocyanurate foams were produced in a similar manner to the 
polyurethane foams using the formulation described in Table VIII. Foam 
properties are summarized in Table IX. Again the foam expanded with the 
azeotrope-like blend possesses essentially identical properties to the 
CFC-11 expanded foam while the blend exhibits greater expansion efficiency 
over that of CFC-11. 
TABLE VI 
______________________________________ 
Rigid Polyurethane Formulation 
Parts by Weight 
Component (a) (b) 
______________________________________ 
Pluracol 1114.sup.1 (420-OH#) 
100. 100. 
Silicone L-5340.sup.2 1.5 1.5 
Thancat TD-33.sup.3 0.5 0.5 
Thancat DME.sup.4 0.2 0.2 
Catalyst T-12.sup.5 0.1 0.1 
CFC-11 35. -- 
CFC-11/HFC-123/Isopentane 
-- 34.1 
(79/15/6) 
Lupranate M20S.sup.6 (1.29 Index) 
129. 129. 
______________________________________ 
.sup.1 BASF Wyandotte Corp. polyether polyol 
.sup.2 Union Carbide Corp. silicone surfactant 
.sup.3 Texaco Inc. 33% triethylene diamine in propylene glycol 
.sup.4 Texaco Inc. N,N--dimethylethanolamine 
.sup.5 Metal & Thermit Co. dibutyl dilaurate 
.sup.6 BASF Wyandotte Corp. polymethylene polyphenylisocyanate 
TABLE VII 
______________________________________ 
Rigid Urethane Foam Properties 
Formulation 
Formulation 
Physical Properties 
(a) (b) 
______________________________________ 
Density (lb/cu.ft.) 
2.0 2.0 
K-factor* 0.130 0.136 
(Btu in/hr ft.sup.2 .degree.F.) 
Dimensional Stability* 
% Vol. Change (-40.degree. C. 24 hr) 
-0.4 0.0 
% Vol. Change (70.degree. C. 16 hr) 
0.4 0.0 
Porosity (% Closed-Cells) 
90.7 91.4 
Reactivity 
Cream Time (sec) 14. 9. 
Gel Time (sec) 38. 30. 
Tack Free Time (sec) 
52. 41. 
______________________________________ 
*5 day old foam 
TABLE VIII 
______________________________________ 
Polyisocyanurate Formulation 
Parts by Weight 
Component (c) (d) 
______________________________________ 
Foamol 250.sup.1 (448-OH#) 
60. 60. 
Silicone L-5340.sup.2 2.0 2.0 
DMP-30.sup.3 1.3 1.3 
Foamcat 70.sup.4 4.0 4.0 
PEG 200.sup.5 6.7 6.7 
CFC-11 55.2 -- 
CFC-11/HCFC-123/Isopentane 
-- 52.8 
(79/15/6) 
Mondur MR200.sup.6 (3.68 Index) 
240. 240. 
Percent Isocyanurate 18. 18. 
______________________________________ 
.sup.1 Jim Walter Resources Inc. 
.sup.2 Union Carbide Corp. 
.sup.3 Rohm and Hass Co. 
.sup.4 Jim Walter Resources Inc. 
.sup.5 Union Carbide Corp. 
.sup.6 Mobay Chemical Corp. 
TABLE IX 
______________________________________ 
Polyisocyanurate Foam Properties 
Formulation 
Formulation 
Physical Properties 
(c) (d) 
______________________________________ 
Density (lb/cu.ft.) 
1.83 1.83 
K-factor* 0.141 0.141 
(Btu in/hr ft.sup.2 .degree.F.) 
Dimensional Stability* 
% Vol. Change (-40.degree. C. 24 hr) 
0.0 0.0 
% Vol. Change (70.degree. C. 16 hr) 
-0.1 0.0 
Porosity (% Closed-Cells) 
92.8 92.6 
Reactivity 
Cream Time (sec) 10 13.7 
Gel Time (sec) 34. 23.2 
Tack Free Time (sec) 
46. 30. 
______________________________________ 
*5 day old foam