Processes for making polyfluorfullerene and compositions comprising same

The invention relates to a process for making polyfluorofullerene as well as polyfluorofullerene itself made according to the process. In the process according to the invention, a fullerene solution is mixed with a polytetrafluoroethylene dispersion, and the reaction mixture is irradiated with fluorescent light to form polyfluorofullerene. The polyfluorofullerene thus made can be used as oiling agent, lubricant, or as additive for lubricants.

BACKGROUND OF THE INVENTION 
This invention relates to a process for making polyfluorofullerene and to 
compositions comprising polyfluorofullerene. 
This application is based on German Patent Application File No. 195 18 
005.4, hose disclosure is incorporated herein in its entirety. 
Polyfluorofullerenes are derived from the fullerenes. 
This new substance class consisting of C.sub.60, C.sub.70 fullerenes was 
documented as existing for the first time in 1985 by means of mass 
spectroscopy investigations (H. W. Kroto, J. R. Heath, S. C. O'Brien, R. 
F. Curl, R. E. Smalley, Nature 1985, 318, 162), and the first macroscopic 
quantities were made in 1990 (W. Kratschmer, L. D. Lamb, K. Fostiropoulos, 
D. R. Huffman, Nature 1990, 347, 354). 
Until the present invention, polyfluorofullerenes were obtained from solid 
ftlllerene by treating a solution of fullerene in dichloromethane with 
XeF.sub.2 or due to the action of F.sub.2 gas at low pressure (D. A. 
Dixon, N. Matsuzawa, T. Fukunaga, F. N. Tebbe, J. Phys. Chem. 1992, 96, 
6107, J. H. Holloway, E. G. Hope, R. Taylor, G. L. Langley, A. G. Advent, 
T. J. Dennis, J. H. Hare, H. W. Kroto, D. M. Walton, J. Chem. Soc. Chem. 
Commun. 1991, 966; H. Selig, C. Lifshitz, T. Peres, J. E. Fischer, A. R. 
McGhie, W. J. Romanov, J. P. McCauley Jr., A. B. Smith III, J. Am. Chem. 
Soc. 1991, 113, 5476) 
In the process, polyfluorofullerenes were obtained with a varying degree of 
fluorination having the empirical formula C.sub.m F.sub.2n, where m, n are 
natural numbers with m=60 or 70 and n=15-35, but can vary both below and 
above the given range. For example, a hyperfluorinated fullerene with n=51 
and the general empirical formula C.sub.60 F.sub.102 has already been 
documented by way of mass spectroscopy. Fullerenes with m&gt;70 and the 
corresponding fluorinated compounds are also possible. 
Fullerene Sci. Technol. (1993), 1 (4), 499-535 discloses comprehensive 
investigation results pertaining to the manufacture of polyfluorofullerene 
due to the action of F.sub.2 gas upon solid fullerene with reaction times, 
temperature and the F.sub.2 being varied. Both pure C.sub.60 fullerene and 
a mixture of C.sub.60 /C.sub.70 fullerene were used as initial compounds. 
With relation to the use of the new substance class of 
polyfluorofullerenes, Derwent Abstr. No. 94-071 652/09 discloses that in 
JP 060 24720-A, polyfluorofullerene is made by means of the action of 
F.sub.2 gas on fullerene in the presence of hydrogen fluoride and the 
resulting polyfluorofullerene is suitable as a lubricant or as additive 
for lubricants. 
OBJECTS AND SUMMARY OF THE INVENTION 
A principal object of the present invention is to provide an improved 
method for making polyfluorofullerenes. 
Another object of the present invention is to provide compositions 
comprising polyfluorofullerenes for lubricants or as lubricant additives. 
Other objects and advantages will become apparent from the disclosures 
which follow. 
In the process according to the present invention, fullerene is dissolved 
in an apolar solvent and mixed with a polytetrafluoroethylene dispersion. 
The reaction mixture is irradiated with fluorescent light having a 
wavelength in the range of about 380-780 nm during the mixing period. 
Fluorescent light is used as activation energy, because fullerene is 
photosensitive and in the visible range spectrum absorbs from about 200 to 
600 nm. 
Benzene or toluene are preferred as apolar solvents, however, other 
solvents, e.g., hexane, can also be used as well as mixtures of two or 
more solvents. Although the mixing time of the fullerene solution with the 
polytetrafluoroethylene dispersion should be at least about 10 minutes, 
increasing the mixing time does not have a disadvantageous effect on the 
result of the reaction. 
The temperature is generally kept at about 30.degree. to 40.degree. C., or 
more (e.g., greater than 100.degree. C.) during mixing. Care must be taken 
to make sure that the temperature remains below the decomposition 
temperature of the polytetrafluoroethylene. 
The resulting polyfluorofullerene can be recovered by sublimation at about 
350.degree. C. under a protective gas atmosphere. Or, it can be extracted 
using an apolar solvent, preferably benzene or toluene. The latter is 
possible because the constituents of the reaction mixture--that are not 
converted into polyfluorofullerene--are not soluble in the solvent 
mentioned. Here again, other conventional solvents such as, for example, 
hexane, can be used as well as two or more suitable solvents. 
If desired, extraction can be followed by sublimation in order to provided 
highly pure, polyfluorofullerene. 
The polyfluorofullerene made according to the invention can have many uses. 
For example, it can be used as oiling agent in the chemical industry or as 
lubricant or as additive to lubricants.

The invention will now be described in greater detail by way of the 
following examples. 
DESCRIPTION OF THE EMBODIMENTS (BEST MODE) 
Example I: Method of Making Polyfluorofullerene 
40 mg fullerene was dissolved in 5 ml of benzene and 2 g dispersed 
polytetrafluoroethylene was added. The fullerene used for this purpose was 
produced at the "Ruder Boskovic" Institute in Zagreb where it was procured 
from Hoechst. The degree of purity of the fullerene procured from Hoechst 
was 99.9%, according to manufacturer's information. The fullerene which is 
used can consist of C.sub.60, C.sub.&gt;60, C.sub.70 and C.sub.&gt;70 as well as 
mixtures of these fullerenes. The temperature was set at between 
30.degree. and 40.degree. C., and the components were mixed by means of 
ultrasound with stirring, over a period of 10 minutes. In addition, 
activation energy in the form of fluorescent light was applied while 
stirring. The emitted radition is in the visible or near the visible range 
of the spectrum, roughly in the range from 380 to 780 nm. The reaction 
vessel used for this fluorination reaction is made of 
polytetrafluoroethylene. 
During the mixing process, a reaction mixture is obtained having a bright 
to dark yellow color from the white dispersion of the 
polytetrafluoroethylene and the violet solution of fullerene. 
Example I(A): Varying the Mixing Times 
The method of Example I was followed except that the mixing time was varied 
and increased incrementally up to a mixing time of three days. 
Compared to the mixing time of 10 minutes of Example I, increasing the 
mixing time did not change the reaction results. The yield remained 
essentially constant. 
Example I(B): Varying the Fullerene Concentration 
The procedure of Example I was followed except that the fullerene 
concentration as varied. It was determined that up to 2 g of fullerene 
could be dissolved in 5 ml of enzene. The quantity of dispersed 
polytetrafluoroethylene was kept constant. The best mixture was achieved 
when 60 mg of fullerene was used with the same solvent volume of 5 ml and 
2 g of dispersed polytetrafluoroethylene. 
Example I(C): Varying the Temperature 
At first, the procedure of Example I was used. To achieve greater 
saturation, the reaction mixture was then heated to about 100.degree. C. 
over a period of up to five days. By achieving greater saturation, it was 
desired to obtain a higher yield and, then, a higher degree of 
fluorination in the direction n =30 of the general empirical formula, 
which would correspond to perfluorinated fullerene. However, when compared 
to the reaction of Example I, no ascertainable change in the reaction 
result was observed. In particular, the yield remained essentially 
constant. Nevertheless, an increased temperature is advantageous for 
isolating and recovering polyfluorofullerene by means of sublimation--as 
will be described hereinafter--because, when benzene is used as the 
solvent, evaporation occurs at the temperature mentioned, and sublimation 
can readily occur. 
Example I(D): Varying the Solvents 
The procedure of Examples I(A)-I(C) were followed except that instead of 
enzene, toluene was used. No ascertainable changes in the reaction 
behavior were observed compared to benzene. 
Generally, any apolar solvent is suitable. The more polar a solution is, 
however, the less suitable is it for use as a solvent in the context of 
the present invention. Accordingly, solvents such as THF and acetone can 
still be used whereas, for example, water is unsuitable as a solvent. 
Comparative Example I(E) 
The procedure of Example I was employed except that instead of using the 
fullerene solution, a powdery fullerene was used. The temperature was also 
raised to about 400.degree. C. No conversion to polyfluorofullerene was 
observed. 
Example II: Isolating Polyfluorfullerene by Sublimation 
After the mixture was made and the reaction occurs in the manner described 
in Example I, the temperature was raised to permit the solvent to 
evaporate. The temperature was kept below the decomposition temperature of 
polytetrafluoroethylene, i.e., at a temperature somewhat over 100.degree. 
C. The temperature was then raised to about 350.degree. C., and the 
polyfluorofullerene was sublimated under a protective gas atmosphere. 
Alternatively, sublimation can also be carried out in a vacuum. Both 
sublimation under a protective gas atmosphere and in a vacuum are suitable 
for essentially preventing the development of byproducts such as 
oxy-compounds of polyfluorofullerene by at least partial reaction with 
oxygen. 
Example III: Isolating Polyfluorofullerene by Extraction 
The procedure of Example I was employed to form polyfluorofullerene. 
Polyfluorofullerene was then recovered from the reaction mixture by means 
of extraction sing benzene or toluene as the extraction agent. The 
unreacted polytetrafluoroethylene contained in the reaction mixture is 
insoluble in benzene, whereas polyfluorofullerene is dissolved in benzene. 
Other apolar solvents, such as, for example, hexane or mixtures of at 
least two suitable apolar solvents, can be used. 
Example IV 
The recovered polyfluorofullerene was analyzed by means of mass 
spectrometry. It was found that polyfluorofullerene having the general 
empirical formula C.sub.m F.sub.2n was formed where m=60, 70 and n=20-35. 
Although certain presently preferred embodiments of the present invention 
have been specifically described herein, it would be apparent to those 
skilled in the art to which the invention pertains that variations and 
modifications of the various embodiments shown and described herein maybe 
made without departing from the spirit and scope of the invention. 
Accordingly, it is intended that the invention be limited only to the 
extent required by the appended claims and the applicable rules of law.