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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to solvent mixtures formed of chlorinated
and/or fluorinated hydrocarbons and fluoroalcohols.
Besides pure chlorinated and/or fluorinated hydrocarbons, hereinafter
referred to as halogenated hydrocarbons or HHC, it is already known to use
mixtures of two or more halogenated hydrocarbons for diverse industrial
processes such as cleaning processes, vapor degreasing, and drying solid
surfaces, as well as working fluids for thermodynamic processes in which
thermal energy is transferred (heat pumps) or converted into higher value
forms of energy (Rankine processes). Such mixtures can be either
azeotropic or azeotrope-like in nature, or they can be non-azeotropic. The
term "azeotrope-like" is intended to refer to mixtures which throughout a
large range of concentrations boil at a substantially constant temperature
(variation in the boiling temperature of less than 5.degree. C.) and which
therefore behave for practical purposes similar to an azeotrope.
The known mixtures are still capable of improvement in their technical
characteristics, and there therefore exists a need for new solvent
mixtures with new, special characteristics.
SUMMARY OF THE INVENTION
It is the object of the invention to provide new solvent mixtures with
useful characteristics.
A further object of the invention is to provide processes for using such
new solvent mixtures.
These objects are achieved by providing a mixture comprising
2,2,2-trifluoroethanol and a halogenated hydrocarbon having from 1 to 3
carbon atoms selected from the group consisting of chlorinated
hydrocarbons, fluorinated hydrocarbons and chlorofluorohydrocarbons, or a
polyfluorinated aromatic hydrocarbon; the weight ratio of
2,2,2-trifluoroethanol to halogenated hydrocarbon or polyfluorinated
aromatic hydrocarbon being from 1:90 to 99:1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The invention relates to mixtures which are characterized by a content of
2,2,2-trifluoroethanol (TFE) and a halogenated hydrocarbon selected from
the group consisting of chlorinated and/or fluorinated hydrocarbons with 1
to 3 carbon atoms (HHC) and polyfluorinated, particularly perfluorinated,
aromatic hydrocarbons (AFHC) and by a weight ratio of
2,2,2-trifluoroethanol to halogenated hydrocarbon or polyfluorinated
aromatic hydrocarbon of 1:90 to 99:1.
In one subvariant of the invention, the mixtures are characterized by a
weight ratio of 2,2,2-trifluoroethanol to halogenated hydrocarbon or
polyfluorinated aromatic hydrocarbon of 1:50 to 1:1.5.
In another subvariant of the invention, the mixtures are characterized by a
weight ratio of 2,2,2-trifluoroethanol to halogenated hydrocarbon or
polyfluorinated aromatic hydrocarbon of 1:1 to 99:1.
Suitable halogenated hydrocarbons or polyfluorinated aromatic hydrocarbons
include those which boil at standard pressure in the temperature range
from +20.degree. C. to +150.degree. C. These are well known as such to
persons skilled in the art. For example, suitable materials are listed in
ISO/DIS 817 or other standard reference works.
Particularly preferred are mixtures, especially binary mixtures, which
contain 2,2,2-trifluoroethanol and a halogenated hydrocarbon selected from
the group consisting of dichloromethane, trichloromonofluoromethane (R11),
1,1,1-trichloroethane, tetrachloro-1,2-difluoroethane (R112),
1,1,2-trichloro-trifluoroethane (R113), tetrachloromonofluoroethane
(R121), and trichlorodifluoroethane (R122).
Another group of preferred mixtures comprises 2,2,2-trifluoroethanol and a
polyfluorobenzene, particularly hexafluorobenzene, as the polyfluorinated
aromatic hydrocarbon.
One group of special mixtures are those which contain
2,2,2-trifluoroethanol and trichloromonofluoromethane as a halogenated
hydrocarbon in a predetermined weight ratio. Mixtures are particularly
preferred which contain 2,2,2-trifluoroethanol and
trichloromonofluoromethane in a weight ratio from 1:90 to 1:10, since such
mixtures behave as azeotropes and boil in the range from about 21.degree.
to about 24.degree. C. A more narrow boiling range is exhibited by
mixtures which contain from 2 to 6 weight percent 2,2,2-trifluoroethanol
and correspondingly from 98 to 94 weight percent
trichloromonofluoromethane. The azeotropic mixture has a boiling point of
about 22.7.degree. C. and is characterized by the composition 4.+-.0.2
weight % 2,2,2-trifluoroethanol and correspondingly 96.+-.0.2 weight %
trichloromonofluoromethane.
Another group of special mixtures are those which contain
2,2,2-trifluoroethanol and 1,1,2-trichlorotrifluoroethane as a halogenated
hydrocarbon in a predetermined weight ratio. Mixtures are particularly
preferred which contain 2,2,2-trifluoroethanol and
1,1,2-trichlorotrifluoroethane in a weight ratio of from 1:90 to 1:5,
since such mixtures behave as azeotropes and boil in the range from about
42.degree. to about 45.degree. C. A more narrow boiling range is exhibited
by mixtures which contain 10 to 14 weight % 2,2,2-trifluoroethanol and
correspondingly 90 to 86 weight % 1,1,2-trichlorotrifluoroethane. The
azeotropic mixture has a boiling point of about 43.0.degree. C. and is
characterized by the composition 11.9.+-.0.2 weight %
2,2,2-trifluoroethanol and correspondingly 88.1.+-.0.2 weight %
1,1,2-trichlorotrifluoroethane.
Insofar as tetrachloro-1,2-difluoroethane is utilized as the halogenated
hydrocarbon, mixtures are preferred which contain up to about 5 weight %
2,2,2-trifluoroethanol. Mixtures with a higher 2,2,2-trifluoroethanol
content form a one-phase system only at temperatures which are elevated
with respect to room temperature.
The aforedescribed multicomponent mixtures or binary mixtures can be
utilized directly as such. But they also can be utilized in production of
more complex mixtures. The complex mixtures which then result, in which
the weight ratio of 2,2,2-trifluoroethanol to halogenated hydrocarbon lies
in the aforementioned predetermined ranges, are likewise considered to be
within the scope of the invention.
Hydrocarbons which are liquid at room temperature, preferably gasoline
fractions or heptanes such as n-heptane, are suitable as further
components of such complex mixtures. Mixtures of 2,2,2-trifluoroethanol
and halogenated hydrocarbon or polyfluorinated aromatic hydrocarbon with
up to 10 weight % (computed with respect to the total mixture) of liquid
hydrocarbon have proven to be very suitable. Mixtures according to the
invention based on tetrachloro-1,2-difluoroethane can contain up to about
7 weight % n-heptane in addition to up to about 6 weight %
2,2,2-trifluoroethanol, with the balance being
tetrachloro-1,2-difluoroethane.
Besides 2,2,2-trifluoroethanol and halogenated hydrocarbon or
polyfluorinated aromatic hydrocarbon, preferred complex mixtures
additionally contain one or more alcohols selected from the group
consisting of methanol, ethanol, i-propanol, n-propanol, n-butanol,
sec.-butanol, and tert.-butanol. The proportion of alcohol in complex
mixtures can vary within broad ranges. In the broadest form, the alcohol
can amount to from 0.1 to 50 weight % (computed with respect to the total
mixture). In one preferred embodiment the complex mixture contains 1 to 10
weight % alcohol. The addition of the aforementioned alcohols makes it
possible in particular to increase the concentration of
2,2,2-trifluoroethanol in the TFE/R112 system above the aforementioned
concentration limit without obtaining a two-phase system at room
temperature. For example, a mixture of about 12.5 weight % i-propanol, 50
weight % 2,2,2-trifluoroethanol and 37.5 weight %
tetrachloro-1,2-difluoroethane (computed with respect to the total
mixture) is a clear solution at room temperature.
Known additives can be incorporated into either the binary mixtures of
2,2,2-trifluoroethanol and halogenated hydrocarbons or also the complex
mixtures. One group of known additives are stabilizers. This group
includes such compounds which prevent an undesired reaction by components
of the mixture with each other or with other reactants, such as, for
example, atmospheric oxygen, water, metal, etc. Examples of known
stabilizers include nitroalkanes, particularly nitromethane or
nitroethane, alkylene oxides, preferably butylene oxide, or preferably
branched alkynol, such as for example 2-methyl-butyn-3-ol-2. These
stabilizers can be used alone or in combinations with each other, whereby
amounts from 0.01 to 6 weight %, in particular 0.05 to 1 weight %, are
very suitable.
A further group of additives includes known compounds such as corrosion
inhibitors, non-ionic or ionic emulsifiers, coloring agents, etc.
The aforedescribed compositions have numerous possibilities for use. One
large area of use in the cleaning and/or vapor degreasing sector. In these
known processes, the object to be cleaned is immersed in one or more
stages in a liquid and/or vaporized cleaning mixture or is sprayed with a
liquid cleaning mixture. In known processes, the cleaning effect can be
increased by utilizing elevated temperatures and/or ultrasonic energy
and/or agitation. Likewise, an improvement in the cleaning effect through
mechanical means, for example brushes, is known.
For example, the electronics industry utilizes primarily organic resin
fluxes for soldering operations. Excess amounts of these organic compounds
must be removed from circuit boards after the soldering operation. This is
done with organic solvents which are compatible with the circuit boards
and the electronic components, i.e. the solvent may not react therewith.
The resin fluxes are mixtures of polar and non-polar compounds and often
contain special activators. Fluorinated hydrocarbons alone, which are
non-polar, are not effective to remove the polar components of the resin.
Known mixtures which in addition to fluorinated hydrocarbons contain an
alcohol are similarly not in a position to completely remove particular
special fluxed with high activator contents. Mixtures according to the
invention, however, can remove both polar and also non-polar components
and are therefore more widely effective as removing agents for resin
fluxes, particularly those with high activator contents. Binary mixtures
or complex mixtures which contain 2,2,2-trifluoroethanol and at least one
halogenated hydrocarbon selected from the group dichloromethane,
trichloromonofluoromethane and 1,1,2-trichlorotrifluoroethane, and
optionally additionally alcohol and/or additive, are particularly suitable
for this application. Mixtures having a 2,2,2-trifluoroethanol to
halogenated hydrocarbon weight ratio of from 1:90 to 1:1.5 are preferably
utilized for this type of application.
Thus circuit boards with or without attached circuit components
(particularly SMD-equipped boards) can be cleaned without any problem with
the binary or complex mixtures according to the invention even when fluxes
with a high activator content are used, without formation of the "white
spots" which may occur when conventional cleaning agents are used.
Another area in which the mixtures according to the invention are
particularly useful is the removal of water from solid surfaces. For this
purpose a large number of processes are also known in the art which
envision a one-stage or multi-stage treatment of the objects to be dried,
similar in principle to those described above for cleaning.
The compositions according to the invention displace the water with a
solvent film which evaporates without leaving a residue on the objects to
be dried. The mixtures mentioned above as particularly well suited for
cleaning processes are also preferentially suitable for drying.
The new azeotropic or azeotrope-like mixtures of 2,2,2-trifluoroethanol and
trichloromonofluoromethane or 2,2,2-trifluoroethanol and
1,1,2-trichlorotrifluoroethane according to the invention are also desired
systems for refrigerants and lubricants, since the compositions have a low
surface tension, a low viscosity and a high density of about 1.4 to 1.7
g/cm.sup.3 at 20.degree. C. The foregoing physical characteristics are
those which are desired for lubricant uses. For example, compositions
according to the invention are desired when the mixtures are used as
lubricants in metalworking machines, for example, in boring, milling,
turning, cutting threads, stamping or the like, where a residue-free
surface is necessary. For these uses in particular known lubricant
additives can also be incorporated. For example, suitable additives are
described in DE-OS 33 42 852 or DE-OS 33 35 870, the disclosures of which
are incorporated herein by reference.
The low surface tension of the compositions according to the invention
makes them particularly suitable for cleaning of capillary systems. The
high wetting capacity and density of the binary mixtures of the invention,
optionally in admixture with isopropanol, ethanol or mixtures of the same,
makes these compositions good cleaning agents for capillary systems.
The binary or complex mixtures according to the invention can also be used,
for example, as follows:
for cleaning small parts or particulate material (preferably in a closed
installation)
for removing or stripping coatings or lacquers
as a solvent and/or additive for solvents for chemical cleaning
as a special solvent, extraction agent and/or recrystallization medium in
the chemical and pharmaceutical industries
as a medium for dissolving, softening, surface treating, such as, for
example, etching or delustering of synthetic materials such as, for
example, polyamides, polymethacrylates, polyformaldehydes,
polyacrylonitriles etc.
A further significant area of utilization for binary or complex mixtures
according to the invention is as working fluids in thermodynamic
processes, in which thermal energy is transferred or converted into higher
value energy forms.
In the processes known as Rankine processes, for example, electrical energy
is generated by means of expansion turbines or piston machines. In such
processes, mixtures according to the invention can be utilized with
advantage--without incorporation of alcohol however--particularly mixtures
formed of 2,2,2-trifluoroethanol and trichloromonofluoromethane, mixtures
formed of 2,2,2-trifluoroethanol and 1,1,2-trichlorotrifluoroethane, and
mixtures formed of 2,2,2-trifluoroethanol and polyfluorinated aromatic
hydrocarbon. For this application, mixtures are preferred which the weight
ratio of 2,2,2-trifluoroethanol to halogenated hydrocarbon or
polyfluorinated aromatic hydrocarbon is preferably from 1:1 to 99:1, in
particular from 9:1 to 50:1. For mixtures of 2,2,2-trifluoroethanol and
polyfluorinated aromatic hydrocarbon, polyfluorinated aromatic hydrocarbon
rich mixtures having a 2,2,2-trifluoroethanol to polyfluorinated aromatic
hydrocarbon ratio of 1:1 to 1:90 are suitable.
For utilization as the working fluid in heat pumps, preferably high
temperature heat pumps or absorption heat pumps or thermal converters as
well as cooling media in absorption coolers, the just mentioned mixtures
are likewise preferred.
European patent no. EP-A-0 120 319 discloses general mixtures of (a) a
fluoroalcohol corresponding to the general formula X(C.sub.n
F.sub.2n)C.sub.m H.sub.2m OH wherein X is F or H, m is 1 to 3, n is 1 to
10, together with (b) a halogenated or non-halogenated hydrocarbon.
Further, U.S. Pat. No. 3,509,061 discloses mixtures for drying solid
surfaces which in addition to a perhalogenated alkane contain 0.02 to 1
weight % of a fluoroalcohol corresponding to the formula F(CF.sub.2).sub.m
CHROH wherein m is 1 to 11, and R is H and C.sub.1 - to C.sub.11
-perfluoroalkyl. As concrete examples of compounds which fall under the
given general formula for fluoroalchols, a whole series of fluorine
containing alcohols are mentioned, but not 2,2,2-trifluoroethanol. The
mixtures according to the invention are therefore novel. It was also
surprising that the mixtures according to the invention are very well
suited for the aforementioned uses, since the mixtures disclosed in
European patent no. EP-A-0 120 319 are used only for removal of wax. By
means of the mixtures according to the invention, new solutions are made
possible for problems in a wide variety of fields of use. In particular,
mixtures of 2,2,2-trifluoroethanol and trichloromonofluoromethane or
1,1,2-trichlorotrifluoroethane do not exhibit any flash point according to
the closed crucible method at 2,2,2-trifluoroethanol concentrations up to
that of the azeotrope throughout the entire temperature range up to the
boiling point. The mixtures disclosed in U.S. Pat. No. 3,509,061 are, for
example, not suitable for the removal of activator-containing fluxes,
since when they are used and 2,2,2-trifluoroethanol is selected as the
fluoroalcohol, "white spots" arise.
The following examples are intended to further describe the invention
without limiting its scope. Unless otherwise indicated, percentages are
always weight percent.
EXAMPLE 1
Cleaning of Circuit Boards
Cleaning tests were carried out in a conventional, commercial, two- or
three-chamber cleaning installation with circuit boards which were
contaminated with strong activator containing soldering flux. The test
conditions are reproduced in Table 1.
TABLE 1
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No. Mixture Cleaning Conditions
Result
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1. R113 + TFE 2-bath, 3 min. ultrasonic
+
88.1% + 11.9% 1 min. vapor degreasing
2 Azeotrope as in Test 1 -
R113 + MeOH*
3 Azeotrope as in Test 1 -
R113 + EtOH*
4 Azeotrope as in Test 1 -
R113 + i-PrOH*
5 R113 + i-PrOH* 3-bath, 3 min. ultrasonic
-
65% + 35% in 1 min. ultrasonic
Bath 1; R113 1 min. vapor degreasing
in Bath 2 & 3
6 R113 + EtOH* as in Test 5 -
65% + 35%
7 R11 + TFE as in Test 1 +
96.0% + 4.0%
8 R113 + TFE as in Test 5 +
60% + 40% in
Bath 1; Bath
2 & 3 as in No. 1
9 R113 + TFE + as in Test 1 +
EtOH* + CH.sub.3 NO.sub.2
83.4% + 11.3% +
5.0% + 0.3%
10 R112 + TFE + as in Test 1 +
i-PrOH,* 85% +
5.0% + 10%
11 R113 + TFE as in Test 1 -
99% + 1%
12 R11 + TFE as in Test 1 -
99% + 1%
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*MeOH = methanol, EtOH = ethanol, iPrOH = isopropanol
In the tests characterized with a "+" in the results column, a very good
cleaning result was achieved and "white spots" were not formed. In the
tests characterized with a "-", "white spots" were formed.
It can clearly be seen that the mixtures according to the invention (Test
Nos. 1 and 7 through 10) are superior to mixtures according to the state
of the prior art (Test Nos. 2 through 6). Also the Tests 11 and 12, in
which mixtures were utilized, the composition of which was chosen in
accordance with U.S. Pat. No. 3,509,061, did not yield satisfactory
results.
EXAMPLE 2
Cleaning of Loose Material
Loose material (transistor caps) was cleaned with
1,1,2-trichlorotrifluoroethane and 2,2,2-trifluoroethanol (88.1%+11.9%) in
a two chamber installation (3 minutes ultrasonic, 1 minute vapor
degreasing) to remove drawing oils. After the treatment, the loose
material was unobjectionably clean.
EXAMPLE 3
Drying of Solid Surfaces
Optical lenses were treated with 1,1,2-trichlorotrifluoroethane and
2,2,2-trifluoroethanol (88.1%+11.9%) in a two chamber dry installation (1
minute spraying, 1 minute vapor). Fully dry lenses resulted which
exhibited no residues on their surfaces.
EXAMPLE 4
Etching of Synthetic Material
Molded pieces of (a) polymethacrylate (Plexiglass) or (b) polyamide
(Ultramid.RTM.) were immersed in a mixture of
1,1,2-trichlorotrifluoroethane and 2,2,2-trifluoroethanol (88.1%+11.9%).
In test (a) a clearly noticeable attack was apparent after 5 minutes, and
a strong clouding of the surface after 2 hours. The originally transparent
molded article was completely matt. In test (b) a strong surface attack
appeared after only 3 minutes.
EXAMPLE 5
Kaury-Butanol Number
The following Kaury-Butanol numbers were determined in the conventional
manner:
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Mixture Kaury-Butanol Number
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R113 + TFE 17
88.1% + 11.9%
R11 + TFE 37
96.0% + 4.0%
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It is surprising that the mixtures according to the invention, in spite of
their low Kaury-Butanol numbers in comparison to the azeotropes
trichloromonofluoromethane/ethanol (KB=70),
1,1,2-trichlorotrifluoroethane/ethanol (KB=29),
1,1,2-trichlorotrifluoroethane/isopropanol (KB=28), or
trichloromonofluoromethane/isopropanol (KB=68)show an improved solvent
action.
The foregoing description and examples have been set forth merely to
illustrate the invention and are not intended to be limiting. Since
modifications of the described embodiments incorporating the spirit and
substance of the invention may occur to persons skilled in the art, the
scope of the invention should be limited solely with respect to the
appended claims and equivalents.
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