Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic halogen compound
Reexamination Certificate
2000-05-24
2001-07-31
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic halogen compound
C524S462000, C524S463000, C524S464000
Reexamination Certificate
active
06268321
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates to an improved method of preparing a grease, and to the grease produced thereby.
2. Description of Related Arts
The use of grease to lubricate fittings is well known to persons skilled in the art. Grease is essentially thickened oil, and because of its viscosity is well suited for lubricating surfaces where oil might run off or drip.
Polychlorotrifluoroethylene polymer of controlled molecular weight has been used by the assignee of this application as a thickening agent, which is then incorporated into polychlorotrifluoroethylene oil for the preparation of a grease. The grease produced is characterized by excellent properties.
In the process of making this grease, the molecular weight of the polymer must be carefully controlled in order to achieve acceptable results, and for this purpose use had been made previously of carbon tetrachloride as a telogen.
However, carbon tetrachloride, because it is harmful to the ozone layer and the environment, is no longer a desirable telogen. Therefore, a search was made to find a suitable substitute for carbon tetrachloride.
From other work in the telomerization field, one would expect that chloroform could be used as a substitute for carbon tetrachloride. It is well known that chloroform in large ratios to chlorotrifluoroethylene [R-1113] was used to make chlorotrifluoroethylene oils of the type used here. See, for example,
Preparation, Properties, and Technology of Fluorine and Organic Fluoro Compounds
, edited by Charles Slesser and Stuart R. Schram, McGraw-Hill Book Company, Inc., 1951, page 607. However, the results that we have achieved using chloroform to make higher controlled molecular weight polymers have been disappointing.
The use of 2,2-dichloro-1,1,1-trifluoroethane [R-123] as polymerization medium in the preparation of fluorine polymers having fluoroolefin units as building blocks is known from Japanese Unexamined Patent Publication No. 6-340718, which was laid open on Dec. 13, 1994. R-1113 is listed as an example of a fluoroolefin monomer useful in the process disclosed therein. However, there is no mention therein of its use as a thickening agent for incorporation into polychlorotrifluoroethylene oil for the preparation of a grease.
Moreover, the Japanese application actually teaches away from the use of R-123 as a telogen. The Japanese application teaches that R-123 provides “some” chain transferring. However, the Japanese application expressly teaches that chain transfer compounds usually must be added to the reaction medium to control the molecular weight of the polymer. Therefore, the use of R-123 as an acceptable telogen per se cannot be gleaned from the Japanese application. The clear suggestion is that telogen additives must be employed; the R-123 alone is insufficient.
Further, the examples of the Japanese application lead to the use of very high amounts of R-123 as solvent. The amounts of R-123 employed are approximately 2.5 and 10 times the amount of monomers employed.
U.S. Pat. No. 5,182,342 describes a process for the free radical polymerization of fluoromonomers, including R-1113, in selected hydrofluorocarbon solvents. The teachings of the patent purport to be very broad, and appear to embrace also the use of R-123 as the polymerization solvent. However, R-123 is not specifically mentioned as an example. Moreover, there is no teaching therein that R-123 is an acceptable telogen per se, nor is there any teaching therein of the use of the resulting polymer in the preparation of a grease.
Accordingly, there remained a need to find an acceptable substitute for carbon tetrachloride, which would be useful to make chlorotrifluoroethylene polymer of controlled molecular weight, which, in turn, could then be combined with polychlorotrifluoroethylene oil to make a grease.
SUMMARY OF THE INVENTION
It has now been found that R-123 is an excellent telogen per se, and is useful alone as a telogen for polymerizations of chlorotrifluoroethylene monomer, leading to the production of chlorotrifluoroethylene polymer of controlled molecular weight. For this use, R-123 is superior to carbon tetrachloride and chloroform, both well regarded telogens. The chlorotrifluoroethylene polymer produced may then be combined with polychlorotrifluoroethylene oil to make a grease, which, we have discovered, has excellent properties.
In view of the successful use of R-123 as a telogen, we expected that closely related homologs thereof should be useful in a similar manner.
Accordingly, the invention, in a first embodiment, relates to an improved process for preparing polychlorotrifluoroethylene polymer comprising polymerizing chlorotrifluoroethylene monomer in the presence of a telogen, wherein the improvement comprises using as the telogen a compound of the formula CF
3
—(CF
2
)
n
—CHCl
2
, wherein n is 0, 1, 2 or 3.
A second embodiment of the present invention relates to a process for preparing a grease comprising combining this polychlorotrifluoroethylene polymer with polychlorotrifluoroethylene oil in amounts and under conditions resulting in the production of a grease.
DETAILED DESCRIPTION OF THE INVENTION
Telomerization processes are well known to persons skilled in the art, and, accordingly, the details thereof will not be repeated here. The essence of the present invention resides in the discovery that R-123 has surprising abilities as a telogen. We have discovered that R-123 is a superior telogen to carbon tetrachloride not only because it has less ozone depletion potential, but also because smaller amounts of R-123 than carbon tetrachloride are required to produce useful telomers.
Further on this point, it is well known that telomer chain length is regulated by the amount and nature of the telogen. The telogen occasionally reacts with the growing reactive polymer to terminate the existing polymer chain while creating a new reactive molecule, which will start a new chain. This new chain will grow by addition of new monomer until the new chain is terminated by telogen, and the process continues.
This phenomena of “chain transfer” is dependent upon two primary factors: the strength of the bond broken in the telogen, and the stability of the resultant reactive telogen radical. Thus, different telogens have different abilities to chain transfer. These abilities are often expressed as a chain transfer coefficient, C∞, which is a ratio of the probabilities a growing polymer will react with telogen or with more monomer.
Extrapolating from data for other telogens and monomers, C∞ for R-123 would have been expected to be smaller than for carbon tetrachloride. Thus, R-123 would have been expected to be less likely to chain transfer, and, in converse, would have been expected to give longer telomers, having higher molecular weight.
However, quite contrary to what would have been expected, we discovered that R-123 is much more likely to chain transfer than carbon tetrachloride. Had R-123 been less likely to chain transfer a greater amount of R-123 would have been needed to achieve the desired molecular weight. However, we discovered that approximately 90% less R-123 than carbon tetrachloride was required.
In view of the results achieved with R-123, it would be readily apparent to persons skilled in the art that the closely related homologs CF
3
—CF
2
—CHCl
2
, CF
3
—CF
2
—CF
2
—CHCl
2
, and CF
3
—CF
2
—CF
2
—CF
2
—CHCl
2
should be useful in a similar manner. In this regard, the “CHCl
2
” portion of the molecule is the most important structural feature as far as the telomerization reaction is concerned since it is this portion of the molecule that undergoes change to form the reactive species that initiate, chain transfer, or terminate the reaction. Accordingly, it should be possible to lengthen the perfluoroalkyl portion of the molecule without adversely affecting the reaction. However, the use of R-123 is the preferred embodiment.
In general, the amount of R-123 or homolog used is, in terms of weight, less than the amount of R-1113 monomer employe
Halocarbon Products Corporation
Medley Margaret
Norris & McLaughlin & Marcus
LandOfFree
Grease prepared from chemically inert oil and thickening... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Grease prepared from chemically inert oil and thickening..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Grease prepared from chemically inert oil and thickening... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2502857