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Description  |
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FIELD OF THE INVENTION
This invention relates to fluorine-substituted hydrocarbon compounds, their
production, and their use for cleaning solid surfaces, and more
particularly to polyfluorooctanes, polyfluorooctenes, polyfluoroheptanes,
polyfluoroheptenes, and linear and cyclic polyfluorohexanes,
polyfluorohexenes, polyfluoropentanes, polyfluoropentenes,
polyfluorobutanes, and polyfluorobutenes, their production from linear and
cyclic polyfluoroalkane or polyfluoroolefin starting materials, and the
use of linear and cyclic polyfluoroalkanes as solvents.
BACKGROUND OF THE INVENTION
Various organic solvents have been used as cleaning liquids for the removal
of contaminants from contaminated articles and materials. Certain
fluorine-containing organic compounds such as
1,1,2-trichloro-1,2,2-trifluoroethane have been reported as useful for
this purpose, particularly with regard to cleaning organic polymers and
plastics which may be sensitive to other more common and more powerful
solvents such as trichloroethylene or perchloroethylene. Recently,
however, there have been efforts to reduce the use of certain compounds
such as trichlorotrifluoroethane which also contain chlorine because of a
concern over their potential to deplete ozone, and to thereby affect the
layer of ozone that is considered important in protecting the earth's
surface from ultraviolet radiation.
Boiling point, flammability and solvent power can often be adjusted by
preparing mixtures of solvents. For example, certain mixtures of
1,1,2,-trichloro-1,2,2-trifluoroethane with other solvents (e.g.,
isopropanol and nitromethane) have been reported as useful in removing
contaminants which are not removed by
1,1,2-trichloro-1,2,2-trifluoroethane alone, and in cleaning articles such
as electronic circuit boards where the requirements for a cleaning solvent
are relatively stringent, (i.e., it is generally desirable in circuit
board cleaning to use solvents which have low boiling points, are
non-flammable, have low toxicity, and have high solvent power so that flux
such as rosin and flux residues which result from soldering electronic
components to the circuit board can be removed without damage to the
circuit board substrate).
While boiling point, flammability, and solvent power can often be adjusted
by preparing mixtures of solvents, the utility of the resulting mixtures
can be limited for certain applications because the mixtures fractionate
to an undesirable degree during use. Mixtures can also fractionate during
recovery, making it more difficult to recover a solvent mixture with the
original composition. Azeotropic compositions, with their constant boiling
and constant composition characteristics, are thus considered particularly
useful.
Azeotropic compositions exhibit either a maximum or minimum boiling point
and do not fractionate upon boiling. These characteristics are also
important in the use of the solvent compositions in certain cleaning
operations, such as removing solder fluxes and flux residues from printed
circuit boards. Preferential evaporation of the more volatile components
of the solvent mixtures, which would be the case if the mixtures were not
azeotropes, or azeotrope-like, would result in mixtures with changed
compositions which may have less desirable properties (e.g., lower
solvency for contaminants such as rosin fluxes and/or less inertness
toward the substrates such as electrical components).
Azeotropic characteristics are also desirable in vapor degreasing
operations where redistilled material is usually used for final
rinse-cleaning. Thus, the vapor defluxing or degreasing system acts as a
still. Unless the solvent composition exhibits a constant boiling point
(i.e., is an azeotrope or is azeotrope-like) fractionation will occur and
undesirable solvent distribution may act to upset the safety and
effectiveness of the cleaning operation.
A number of azeotropic compositions based upon halohydrocarbons containing
fluorine have been discovered and in some cases used as solvents for the
removal of solder fluxes and flux residues from printed circuit boards and
for miscellaneous vapor degreasing applications. For example, U.S. Pat.
No. 2,999,815 discloses the azeotrope of
1,1,2-trichloro-1,2,2-trifluoroethane with acetone; U.S. Pat. No.
3,903,009 discloses a ternary azeotrope of
1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane and ethanol; U.S.
Pat. No. 3,573,213 discloses an azeotrope of
1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane; U.S. Pat. No.
3,789,006 discloses the ternary azeotrope of
1,1,2-trichloro-1,2,2-trifluoroethane with nitromethane and isopropanol;
U.S. Pat. No. 3,728,268 discloses the ternary azeotrope of
1,1,2-trichloro-1,2,2-trifluoroethane with acetone and ethanol; U.S. Pat.
No. 2,999,817 discloses the binary azeotrope of
1,1,2-trichloro-1,2,2-trifluoroethane and methylene chloride (i.e.,
dichloromethane); and U.S. Pat. No. 4,715,900 discloses ternary
compositions of trichlorotrifluoroethane, dichlorodifluoroethane, and
ethanol or methanol.
As noted above, many solvent compositions which have proven useful for
cleaning contain at least one component which is a halogen-substituted
hydrocarbon containing chlorine, and there have been concerns raised over
the ozone depletion potential of halogen-substituted hydrocarbons which
contain chlorine. Efforts are being made to develop compositions which may
at least partially replace the chlorine containing components with other
components having lower potential for ozone depletion. Azeotropic
compositions of this type are of particular interest.
Means of synthesizing various fluorine-substituted alkanes have been
reported.
U.S. Pat. No. 2,917,559 discloses a vapor phase process for the production
of 2-fluoropropane by the reaction of HF and propylene over an activated
carbon catalyst.
U.S. Pat. No. 2,975,220 discloses compounds of the general formula
R(CH.sub.2 CF.sub.2)nQ, where n is an integer and Q is halogen or hydrogen
and R is a halogenated radical. These compounds (e.g., CF.sub.3 CH.sub.2
CF.sub.2 CF.sub.2 CF.sub.3) may be prepared by reacting vinylidene
fluoride with certain telogens.
U.S. Pat. No. 3,520,786 discloses a process for the preparation of
cycloalkanes by electrolyzing a solution of halocarbons having 3-6 ring
carbons of the general composition
C(R.sub.1)RR-C(.sub.1-4)RR-C(R.sub.2)RR, where R may be an alkyl group,
hydrogen, or a halogen; R.sub.1 is halogen; and R.sub.2 may be a halogen,
quarternary ammonium salt or a tosylate; and isolating the corresponding
cycloalkane.
U.S. Pat. No. 4,902,838 discloses a process for the isomerization of
C.sub.2 to C.sub.6 hydrofluorocarbons having lesser thermodynamic
stability to hydrofluorocarbons having greater thermodynamic stability by
isomerization in the vapor phase of at least one C.sub.2 to C.sub.6
saturated hydrofluorocarbon with a catalyst comprising aluminum fluoride.
The isomerization of 1,1,2,2-tetrafluoroethane, a vicinal-dihydro
fluorocarbon, to 1,1,1,2-tetrafluoroethane, a geminal-dihydro
fluorocarbon, is exemplified.
Eur. Pat. Appln. No. 365,296 discloses a process for the preparation of
1,1,1,2-tetrafluoroethane by the isomerization of
1,1,2,2-tetrafluoroethane over a fluorination catalyst. The only catalyst
examplified is chromia.
C. Zhanxun et al., Proc. Annu. Int. Conf. Plasma Chem. Technol., 4th,
Meeting Date 1987, 173-9 (1989) and C. Zhanxun et al., Adv. Low-Temp.
Plasma Chem., Technol., Appl., 2, 265-73 (1988) disclose the formula
CF.sub.3 CF.sub.2 CH.sub.2 CF.sub.2 CF.sub.3 as a theoretical product from
the degradation of plasma-polymerized tetrafluoroethylene.
There are also means of synthesizing various fluorine-substituted alkenes.
For example, U.S. Pat. Nos. 4,820,883 and 4,820,884 disclose the use of
activated carbon for the preparation of unsaturated fluorocarbons by
defluorinating perfluoro compounds.
SUMMARY OF THE INVENTION
In accordance with this invention, novel saturated compounds are provided
which contain no chlorine and which may be used alone or in combination
with various other miscible solvents as agents for cleaning solid
surfaces. Novel unsaturated compounds, which may be used for preparation
of the corresponding saturated compounds, are also provided in accordance
with this invention.
The novel compounds of this invention include the group of
dihydropolyfluoropentanes, dihydropolyfluorohexanes,
dihydropolyfluoroheptanes and dihydropolyfluorooctanes represented by the
formula R.sup.1 CH.sub.2 CF.sub.2 R.sup.2 wherein R.sup.1 is selected from
the group consisting of --CF.sub.2 CF.sub.3 and --CF.sub.2 CF.sub.2
CF.sub.3 and R.sup.2 is selected from the group consisting of --CF.sub.3,
--CF.sub.2 CF.sub.3 and --CF.sub.2 CF.sub.2 CF.sub.3 or wherein R.sup.1
and R.sup.2 together are --(CF.sub.2).sub.3 --; and the group of
monohydropolyfluoroolefins represented by the formula R.sup.3 X.sup.1
C.dbd.CX.sup.2 R.sup.4 wherein R.sup.3 is selected from the group
consisting of --CF.sub.3 and --CF.sub.2 CF.sub.3, R.sup.4 is selected from
the group consisting of --CF.sub.2 CF.sub.2 CF.sub.3, --CF.sub.2 CF.sub.2
CF.sub.2 CF.sub.3 and --CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3, and
X.sup.1 and X.sup.2 are different and are selected from the group
consisting of hydrogen and fluorine, provided that when R.sup.3 is
--CF.sub.2 CF.sub.3 R.sup.4 is --CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3.
A process is provided in accordance with this invention for preparing
compounds selected from the group consisting of
gem-dihydropolyfluoroalkanes of the formulae R.sup.5 CH.sub.2 CF.sub.2
R.sup.6 and R.sup.5 CF.sub.2 CH.sub.2 R.sup.6 and
monohydropolyfluoroolefins of the formulae R.sup.5 CH.dbd.CFR.sup.6 and
R.sup.5 CF.dbd.CHR.sup.6 wherein R.sup.5 and R.sup.6 are each
independently selected from the group consisting of --CF.sub.3, --CF.sub.2
CF.sub.3 and --CF.sub.2 CF.sub.2 CF.sub.3, or wherein R.sup.5 and R.sup.6
together are --(CF.sub.2).sub.2 --, --(CF.sub.2).sub.3 -- or
--(CF.sub.2).sub.4 --, which comprises the step of contacting a saturated
starting material of the formula R.sup.5 CHFCHFR.sup.6 wherein R.sup.5 and
R.sup.6 are as above, at an elevated temperature with a carbon catalyst or
a catalyst containing at least one compound of a metal selected from the
group consisting of sodium, potassium, rubidium, cesium, yttrium,
lanthanum, cerium praseodymium, neodymium, samarium, chromium, iron,
cobalt, rhodium, nickel, copper, zinc, and mixtures thereof, supported on
carbon.
Another process is provided in accordance with this invention for preparing
gem-dihydropolyfluoroalkanes of the formula R.sup.7 CH.sub.2 CF.sub.2
R.sup.8 wherein R.sup.7 and R.sup.8 are each independently selected from
the group consisting of --CF.sub.3, --CF.sub.2 CF.sub.3 and --CF.sub.2
CF.sub.2 CF.sub.3 or wherein R.sup.7 and R.sup.8 together are
--(CF.sub.2).sub.2 --, --(CF.sub.2).sub.3 or --(CF.sub.2).sub.4 --, which
comprises the step of reacting an olefinic starting material of the
formula R.sup.7 CH.dbd.CFR.sup.8 wherein R.sup.7 and R.sup.8 are as above,
with HF at an elevated temperature in the presence of a carbon catalyst or
a catalyst of at least one compound of a metal selected from the group
consisting of sodium, potassium, rubidium, cesium, yttrium, lanthanum,
cerium praseodymium, neodymium, samarium, chromium, iron, cobalt, rhodium,
nickel, copper, zinc, and mixtures thereof, supported on carbon. The
gem-dihydropolyfluoroalkanes may be used in combination with other
miscible solvents (e.g., alcohols, ethers, esters, ketones,
nitrogen-containing organic compounds such as acetonitrile and
nitromethane, and halogenated hydrocarbons) as agents for cleaning solid
surfaces.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides novel saturated linear polyfluorohydrocarbons which
contain two hydrogen atoms per molecule which are attached to the same
carbon atom (i.e., gem-dihydropolyfluoroalkanes). The novel
gem-dihydropolyfluoroalkanes of this invention have the formula R.sup.1
CH.sub.2 CF.sub.2 R.sup.2 wherein R.sup.1 is selected from the group
consisting of --CF.sub.2 CF.sub.3 and --CF.sub.2 CF.sub.2 CF.sub.3 and
R.sup.2 is selected from the group consisting of --CF.sub.3, --CF.sub.2
CF.sub.3 and --CF.sub.2 CF.sub.2 CF.sub.3 or wherein R.sup.1 and R.sup.2
together are --(CF.sub.2).sub.3 --, and include the
dihydropolyfluorooctanes CF.sub.3 CF.sub.2 CH.sub.2 CF.sub.2 CF.sub.2
CF.sub.2 CF.sub.2 CF.sub.3 and CF.sub.3 CF.sub.2 CF.sub.2 CH.sub.2
CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 ; the dihydropolyfluoroheptanes
CF.sub.3 CF.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 and
CF.sub.3 CF.sub.2 CF.sub.2 CH.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 ; the
dihydropolyfluorohexane CF.sub.3 CF.sub.2 CH.sub.2 CF.sub.2 CF.sub. 2
CF.sub.3 ; the dihydropolyfluoropentane CF.sub.3 CF.sub.2 CH.sub.2
CF.sub.2 CF.sub.3 ; and the compound
##STR2##
This invention also provides novel polyfluoroolefins which contain one
hydrogen atom per molecule which is attached to one of the carbons forming
the olefinic bond. The novel monohydropolyfluoroolefins of this invention
have the formula R.sup.3 X.sup.1 C.dbd.CX.sup.2 R.sup.4 wherein R.sup.3 is
selected from the group consisting of --CF.sub.3 and --CF.sub.2 CF.sub.3,
R.sup.4 is selected from the group consisting of --CF.sub.2 CF.sub.2
CF.sub.3, --CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 and --CF.sub.2 CF.sub.2
CF.sub.2 CF.sub.2 CF.sub.3, and X.sup.1 and X.sup.2 are different and are
selected from the group consisting of hydrogen and fluorine, provided that
when R.sup.3 is --CF.sub.2 CF.sub.3 R.sup.4 is --CF.sub.2 CF.sub.2
CF.sub.2 CF.sub.3, and include the monohydropolyfluorohexenes CF.sub.3
CH.dbd.CFCF.sub.2 CF.sub.2 CF.sub.3 and CF.sub.3 CF.dbd.CHCF.sub.2
CF.sub.2 CF.sub.3 ; the monohydropolyfluoroheptenes CF.sub.3
CH.dbd.CFCF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 and CF.sub.3 CF.dbd.
CHCF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 ; and the monohydropolyfluorooctenes
CF.sub.3 CH.dbd.CFCF.sub.2 CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3, CF.sub.3
CF.dbd.CHCF.sub.2 CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3, CF.sub.3 CF.sub.2
CH.dbd.CFCF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 and CF.sub.3 CF.sub.2
CF.dbd.CHCF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3.
A process provided in accordance with this invention for preparing
compounds selected from the group consisting of
gem-dihydropolyfluoroalkanes of the formulae R.sup.5 CH.sub.2 CF.sub.2
R.sup.6 and R.sup.5 CF.sub.2 CH.sub.2 R.sup.6 and
monohydropolyfluoroolefins of the formulae R.sup.5 CH.dbd.CFR.sup.6 and
R.sup.5 CF.dbd.CHR.sup.6 wherein R.sup.5 and R.sup.6 are each selected
from the group consisting of --CF.sub.3, --CF.sub.2 CF.sub.3 and
--CF.sub.2 CF.sub.2 CF.sub.3 or wherein R.sup.5 and R.sup.6 together are
--(CF.sub.2).sub.2 --, --(CF.sub.2).sub.3 -- or --(CF.sub.2).sub.4 --,
comprises the step of contacting a saturated starting material of the
formula R.sup.5 CHFCHFR.sup.6, wherein R.sup.5 and R.sup.6 are as above,
at an elevated temperature with a carbon catalyst or a catalyst of at
least one compound of a metal selected from the group consisting of
sodium, potassium, rubidium, cesium, yttrium, lanthanum, cerium
praseodymium, neodymium, samarium, chromium, iron, cobalt, rhodium,
nickel, copper, zinc, and mixtures thereof, supported on carbon. The
carbon which is used as a catalyst can be either unwashed or acid washed.
The washed carbon is normally prepared by treating the carbon with acid
containing neither phosphorus nor sulfur, to remove impurities. Preferably
a subsequent treatment is done with hydrofluoric acid to further reduce
impurities, especially silicon. After such treatment the washed carbon
typically contains less than about 0.1% ash. Commercially available
carbons useful in the process of this invention include those sold under
the following trademarks: Darco.TM., Nuchar.TM., Columbia SBV.TM.,
Columbia MBV.TM., Columbia MBQ.TM., Columbia JXC.TM., Columbia CXC.TM.,
Calgon PCB.TM., and Barnaby Cheny NB.TM.. The carbon catalyst can be in
the form of powder, granules, or pellets, etc. High surface area carbons
such as Calgon.RTM. PCB and Carbosieve G.RTM. are preferred over low
surface area carbons. Examples of acids which may be used in the first
acid wash of this process include organic acids such as acetic acid and
inorganic acids, e.g., HCl or HNO.sub.3. Preferably hydrochloric acid or
nitric acid is used. The acid treatment may be accomplished in several
ways. A preferred embodiment is described below.
A carbon catalyst is soaked overnight with gentle stirring in a 1M solution
of the acid prepared in deionized water. The carbon catalyst is separated
and washed with deionized water until the pH of the washings is about 3.
The carbon catalyst is then soaked again, with gentle stirring in a IM
solution of the acid prepared in deionized water, for about 12 to 24
hours. The carbon catalyst is then finally washed with deionized water
until the washings are substantially free of the anion of the acid (e.g.,
Cl.sup.- or NO.sub.3.sup.-), when tested by standard procedures. The
carbon catalyst is then separated and dried at about 120.degree. C. A
sample of this washed carbon is then soaked, if desired, in 1M HF prepared
in deionized water for about 48 hours at room temperature with occasional
stirring in an HF-resistant container. The carbon catalyst is separated
and washed repeatedly with deionized water until the pH of the washings is
greater than 4. The carbon catalyst is then dried at about 150.degree. C.,
followed by calcination at about 300.degree. C. Suitable carbons include
acid washed carbons (e.g., carbons essentially free of K.sup.+) or
unwashed carbons (e.g., carbons containing from about 0.1 to about 2
percent by weight K.sup.+). Metal compounds supported on carbon may also
be used for either the rearrangement of vicinal-dihydropolyfluoroalkanes
to geminal-dihydropolyfluoroalkanes or the dehydrofluorination of
vicinal-dihydropolyfluoroalkanes to mixtures of
monohydropolyfluoroolefins. The metals of the compounds may be selected
from the group consisting of sodium, potassium, rubidium, cesium, yttrium,
the lanthanide series especially, lanthanum, cerium, praseodymium,
neodymium, and samarium, chromium, iron, cobalt, rhodium, nickel, copper,
zinc, and mixtures thereof. Example compounds include the acetates,
nitrates, chlorides and/or fluorides of said metals. The carbon supported
metal compounds may be prepared from soluble metal salts by known art
procedures. Generally, where carbon-supported metal compounds are used,
the metals comprise from about 0.5 to 30 percent by weight of the
catalyst.
HF may be added during the isomerization. Thr | | |
