This invention relates to azeotropic compositions of 1,2-dichloro-1-fluoroethane or of 1,2-dichloro-1,2-difluoroethane with certain alcohols, ethers, or ketones.

FIELD OF THE INVENTION 
This invention relates to azeotropic compositions of 
chlorofluorohydrocarbons with alcohols, ethers, or ketones. In a further 
aspect, the invention relates to new solvent compositions. In another 
aspect, the invention relates to methods of removing excess solder flux 
from circuit boards. 
BACKGROUND OF THE INVENTION 
Azeotropic mixtures are liquid mixtures of two or more substances which 
mixtures behave like single substances in that the vapor produced by 
partial evaporation of the azeotropic liquid has the same composition as 
does the liquid. Azeotropic compositions exhibit either a maximum or 
minimum boiling point as compared with that of other but non-azeotropic 
mixtures of the same substances or components. 
Chlorofluorohydrocarbons have found usage for a variety of purposes. For 
some solvent purposes, however, the chlorofluorohydrocarbons in themselves 
have not exhibited adequate abilities. Particularly deficient have been 
the chlorofluorohydrocarbons in dissolving excess solder flux from printed 
circuits. Printed circuits are formed from a soft metal on a solid 
nonconducting surface such as a reinforced phenolic resin. During the 
manufacturing processes, the solid surface or support is coated with the 
soft metal. The particular desired portion or configuration of metal is 
coated with an acid-impervious protective coating, and the excess 
unprotected metal is removed by an acid etching process. 
The protective coating subsequently must be removed since solder joints 
must ultimately be made onto the printed circuit. After the impervious 
coating is removed, the circuits are coated with a rosin flux to permit 
the joints to be soldered, and after soldering the rosin flux itself must 
be removed. For removal of such coatings and fluxes, highly efficient 
uniform composition solvents are desirable. 
OBJECTS OF THE INVENTION 
It is an object of this invention to provide novel azeotropic compositions. 
It is a further purpose of this invention to provide new compositions of 
matter useful for dissolving solder flux. 
Other aspects, objects, and the several advantages of my invention will be 
readily apparent to one skilled in the art to which the invention most 
nearly pertains from the reading of my description and consideration of my 
appended claims. 
DESCRIPTION OF THE INVENTION 
I have discovered useful azeotropes of 1,2-dichloro-1-fluoroethane with 
each of the tetrahydrofuran, methyl ethyl ketone, methanol, ethanol, 
isopropanol; and of 1,2-dichloro-1,2-difluoroethane with each of 
tetrahydrofuran, methyl ethyl ketone, acetone, ethanol, and isopropanol. 
An azeotrope may be defined as a constant boiling mixture which distills 
without change in composition. Yet, at a differing pressure, the 
composition indeed may vary, at least slightly, with the change in 
distillation pressure, which also changes, at least slightly, the 
distillation temperature. An azeotrope of A and B may represent a unique 
type of relationship with a variable composition. 
Thus, it should be possible to fingerprint the azeotrope, which may appear 
under varying guises depending upon the conditions chosen, by any of 
several criteria: The composition may be defined as an azeotrope of A and 
B, since the very term azeotrope is at once definitive and limitative, 
requiring that A and B indeed form this unique composition of matter which 
is a constant boiling admixture. Or, the composition may be defined as a 
particular azeotrope of a weight percent relationship or mole percent 
relationship of A:B, but recognizing that such values point out only one 
such relationship, whereas a series of relationships of A:B may exist for 
the azeotrope, varied by influence of temperature and pressure. Or, 
recognizing that broadly speaking an azeotrope of A:B actually represents 
a series of relationships, the azeotropic series represented by A:B may in 
effect be fingerprinted or characterized by defining the composition as an 
azeotrope further characterized by a particular boiling point at a given 
pressure, thus giving identifying characteristics without unduly limiting 
the scope of the invention.

EXAMPLES 
The following data are presented in order to assist in disclosing and 
describing my invention, and, therefore, are not intended to be limitative 
of the reasonable scope thereof. 
The azeotropes of my invention were prepared by distilling mixtures of the 
chlorofluorohydrocarbon and the other component until the overhead 
temperature reached a constant value and the composition of the distillate 
remained unchanged as verified by GLC analysis, thereby establishing the 
existence of a minimum boiling azeotrope in each case. 
The azeotropes were tested as solvents for solder flux on printed circuits. 
EXAMPLE I 
Azeotropic compositions were prepared and characterized by the properties 
tabulated below: 
TABLE I 
__________________________________________________________________________ 
Composition 
of Azeotrope 
Azeotrope.sup.(a) 
Chlorofluoro- Chlorofluoro- 
B.P. (Pressure) 
hydrocarbon 
Alcohol hydrocarbon/Alcohol 
__________________________________________________________________________ 
56.degree. 
C (742 mm) 
141.sup.(b) 
Methanol 
(73.5/ 
26.5 
wt. % 
(64.4/ 
35.6 
area % 
65.degree. 
C (749 mm) 
141 Ethanol 
81.2/ 
18.8 
wt. % 
68.degree. 
C (740 mm) 
141 Isopropanol 
81.3/ 
16.6.sup.(d) 
wt. % 
52.degree. 
C (741 mm) 
132.sup.(c) 
Methanol 
90.4/ 
9.6 wt. % 
56-57.degree. 
C (748 mm) 
132 Ethanol 
94.9-95/ 
5-5.1 
wt. % 
47.degree. 
C (744 mm) 
132 Isopropanol 
98.7/ 
1.3 wt. % 
__________________________________________________________________________ 
.sup.(a) B. P. is the boiling point for the azeotropic composition at 
substantially atmospheric in each case. The pressure showing was the 
atmospheric barometric pressure taken from daily laboratory readings. 
.sup.(b) 141 represents 1,2-dichloro-1-fluoroethane 
.sup.(c) 132 represents 1,2-dichloro-1,2-difluoroethane 
.sup.(d) Remaining 2.1 weight per cent not identified. 
The azeotropes were tested as solvents for removal of solder flux from 
commercial circuit boards, with results as shown below, along with 
comparative runs: 
TABLE II 
______________________________________ 
Wt. % of Flux 
Runs Solvent Systems Dissolved 
______________________________________ 
1 141/methanol 97.0 
2 141/ethanol 91.5 
3 141/isopropanol 95.7 
4 132/methanol 98.7 
5 132/ethanol 94.0 
6 132/isopropanol 98.0 
7 113.sup.(e) 28.4 
8 1,1,1-trichloroethane 
82.6 
9 113/ethanol azeotrope 
66.5 
10 113/ethanol/acetone azeotrope 
57.0 
11 113/isopropanol azeotrope 
69.5 
12 141 51.3 
13 132 74.2 
______________________________________ 
.sup.(e) 113 represents 1,1,2-trichloro-1,2,2-trifluoroethane. 
The data in Table II show that the novel azeotropic compositions of this 
invention were more effective than several commercially available solvents 
or of 141 or 132 alone in removing solder flux from printed circuit 
boards. 
EXAMPLE II 
Azeotropic compositions were prepared and characterized by the properties 
tabulated below: 
TABLE III 
______________________________________ 
Approximate 
Weight Per Cent 
Composition 
of Azeotrope 
Azeotrope Chlorofluoro- Chlorofluoro- 
B.P. (Pressure) 
hydrocarbon 
Ether hydrocarbon/Ether 
______________________________________ 
74.degree. C 
(739 mm) 141 THF.sup.(f) 
61.8/38.2 
70.degree. C 
(739 mm) 132 THF 45.9/54.1 
______________________________________ 
.sup.(f) THF represents tetrahydrofuran. 
The azeotropes were tested as solvents for removal of solder flux from 
commercial circuit boards, with results as shown below, along with 
comparative runs with other similar materials. 
TABLE IV 
______________________________________ 
Runs Solvent Systems Wt. % of Flux Dissolved 
______________________________________ 
14 141/THF 100 
15 132/THF 100 
16 1,1,1-Trichloroethane 
82.6 
17 113/ethanol azeotrope 
66.5 
18 141 51.3 
19 132 74.2 
______________________________________ 
The data in Table IV above show that the novel azeotropic compositions of 
this invention were more effective in removing solder flux from printed 
circuit boards than several commercially available solvents or 141 or 132 
alone. 
EXAMPLE III 
Azeotropic compositions were prepared and characterized by the properties 
tabulated below: 
TABLE V 
__________________________________________________________________________ 
Approximate Wt. % 
Composition 
of Azeotrope 
Azeotrope Chlorofluoro- Chlorofluoro- 
B.P. (Pressure) 
hydrocarbon 
Ketone 
hydrocarbon/Ketone 
__________________________________________________________________________ 
80.degree. C 
(atmospheric) 
141 MEK.sup.(g) 
54.1/45.9 
80.degree. C 
(743 mm) 
132 MEK 39.8/60.2 
66.degree. C 
(736 mm) 
132 Acetone 
72.3/27.7 
__________________________________________________________________________ 
.sup.(g) MEK represents methyl ethyl ketone. 
The azeotropes were tested as solvents for removal of excess solder flux 
from commercial circuit boards, with the results as shown below, along 
with comparative runs with other materials. 
TABLE VI 
______________________________________ 
Runs Solvent Systems Wt.% of Flux Dissolved 
______________________________________ 
20 141/MEK 100 
21 132/MEK 98 
22 1,1,1-Trichloroethane 
82.6 
23 113/ethanol azeotrope 
66.5 
24 113/ethanol/acetone azeotrope 
57.0 
25 141 51.3 
26 132 74.2 
______________________________________ 
The data in Table VI above show that the novel azeotropic compositions of 
this invention were more effective in removing solder flux from printed 
circuit boards than several commercially available solvents or 141 or 132 
alone. 
EXAMPLE IV 
Flash point data were obtained for azeotropic compositions of my discovery: 
TABLE VII 
______________________________________ 
Flash Point of 
alcohol, ether 
Run Azeotrope or ketone.sup.(i) 
No. Azeotrope Flash Point, .degree. F.sup.(h) 
Component Alone 
______________________________________ 
27 141/methanol 46.degree. F 51.degree. F 
28 141/ethanol 75.degree. F.sup.(j) 
56.degree. F 
29 141/isopropanol 
-- 53.degree. F 
30 132/methanol 46.degree. F 51.degree. F 
31 132/ethanol 75.degree. F.sup.(k) 
56.degree. F 
32 132/isopropanol 
75.degree. F.sup.(l) 
53.degree. F 
33 141/THF 40.degree. F 6.degree. F 
34 132/THF 36.degree. F 6.degree. F 
35 141/MEK -- 23.degree. F 
36 132/MEK 42.degree. F 23.degree. F 
37 132/Acetone 45.degree. F 15.degree. F 
______________________________________ 
.sup.(h) Flash point determination in accordance with ASTM Method D-56. 
.sup.(i) Flash point data obtained from Shell Chemical Co. Brochure 
IC-71-18. 
.sup.(j) Burned at 75.degree. F, not self-extinguishing. 
.sup.(k) Did not burn at 75.degree. F; supported combustion of vapors and 
air, but was self-extinguishing. 
.sup.(l) Did not burn at 75.degree. F; did not support combustion, but wa 
self-extinguishing. 
Data on two azeotropes were not obtained as indicated by the dashes above. 
The flash point data in general show that the inventive azeotropes are 
less hazardous in most cases than the alcohol, ether, or ketone 
non-chlorofluorohydrocarbon component alone. The azeotropes in most cases 
have higher flash points than does the second component alone. 
It will be understood that the description given hereinabove of the use of 
azeotropic compositions of my invention in cleaning or dissolving solder 
flux is given for illustrative purposes only, that the invention itself is 
not restricted to such specific embodiments, and that other techniques may 
be employed. These unique azeotropic compositions will have applications 
as solvents for greases, oils, waxes, aerosol propellants, and the like; 
and in cleaning electric motors, compressors, photographic film, oxygen 
storage tanks, lithographic plates, typewriters, precision instruments, 
gauges, sound tape, cloth, clothing, and the like. It will be readily 
apparent that the novel azeotropic compositions can be used for a variety 
of purposes as indicated by my general description and suggestions.