Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic sulfur compound – wherein the sulfur is single bonded...
Reexamination Certificate
2000-08-02
2002-06-11
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic sulfur compound, wherein the sulfur is single bonded...
C508S388000, C508S568000
Reexamination Certificate
active
06403539
ABSTRACT:
The present invention relates to perfluoropolyether lubricants having pendent sulphonylfluoride groups distributed from the polymeric backbone.
Specifically the invention relates to lubricants having an improved glass transition temperature (Tg) (up to −130° C.) combined with a high thermo-oxidative stability and obtainable by a process having improved Productivity with respect to the known lubricant process.
More specifically, the invention relates to lubricants based on perfluoropolyethers (PFPE) which, compared with the known commercial products in the lubricant field, show the following combination of properties:
Tg in the range from −130° to −60° C.;
Tg adjustable in function of the monomeric units present in the polymeric backbone, adjustable also when the molecular weight is the same;
high thermal stability also in oxidative conditions;
obtainable by a process in high productivity.
The preparation of perfluoropolyethers formed of oxyperfluoroalkylene sequences containing peroxidic groups in various amounts depending on the reaction conditions, is known in the prior art. These compounds can be obtained by oxidation of perfluoroolefins at low temperature (between −100° C. and −30° C.) with oxygen in the presence of UV radiations, or alternatively, by oxidation of perfluoroolefins at low temperature with oxygen in the presence of suitable polymerization initiators, for example F
2
, CF
3
OF. See EP 393,700 and EP 654,493. The elimination of the peroxidic groups from the perfluoropolyether chain can be carried out both by thermal and photochemical route. In these patents perfluoropolyethers having pendent functional groups from the polymeric backbone are not described.
Perfluoropolyethers having pendent functional groups from the polymeric backbone are described in EP 244,839. It is described the photooxidation of perfluorobutadiene, optionally with a perfluorinated olefin at low temperature in the presence of oxygen and subsequent photochemical decomposition of the peroxidic groups, allowing to obtain perfluoropolyethers formed by a backbone of oxyperfluoroalkylene units with pendent fluorinated epoxide groups. By converting the fluorinated epoxide groups polyfunctional derivatives having functional groups such as —COOH, —COOR, —CONHR (R═H or C
1
-C
12
alkyl), —CN, —CH
2
OH, —CH
2
NH
2
, etc. can be obtained which can be used for various applications depending on the functional groups pending along the polymeric backbone. The drawback of this patent is that the functional derivatives are obtained by complex reactions which require intermediate steps.
In U.S. Pat. No. 4,384,128 copolymers obtained from hexafluoropropene oxide (HFPO) and from perfluoroglycidyl-ethers epoxides, according to the following polymerization reaction, are described:
wherein: R
f
is selected from —CF
2
CF
2
SO
2
F, —(CF
2
)
4
COF, —CF
2
CF
2
CN, —C
6
F
5
, —CF
2
CF(CF
3
)OCF
2
CN, —CF
2
CF
2
OC
6
F
5
.
The polymerization carried out in the presence of a suitable solvent and anionic initiators at a temperature in the range −35° C. and 0° C. allows to obtain non peroxidic perfluoropolyethers. Subsequently, the copolymers contining the functional groups —COF, —COOH, —SO
2
F, reacted with suitable reactants can be converted into functionalized polymers containing the —COCl, —CONH
2
, —SO
2
OH, —SO
2
OM′, —CO
2
M′, —CN groups, wherein M′ is an alkaline metal or an ammonium group, which are endowed with hydrophilicity and have ionic exchange properties. The patent aim is the curing of these polymers in order to obtain moldable articles.
The use of PFPEs as lubricants is furthermore known, for example FOMBLIN® Y commercialized by AUSIMONT, having the following structure:
CF
3
—(O—CF(CF
3
)—CF
2
)
m
—(O—CFY)
n
—O—CF
3
(I)
wherein Y═F, CF
3
and the m
ratio ranges from 5 to 40.
The Tg values obtained with these PFPEs are of the order −65° C.-85° C. and depends on the PFPE number average molecular weight. The molecular weight being fixed, the Tg has a well determined value. Therefore the only way to furtherly decrease the Tg is to reduce the molecular weight. This implies products having high vapour pressure. They have the drawback to require frequent lubricant re-fillings since there are substantial losses of product in the use at high temperatures. This phenomenon is even more evident in specific applications, for example in aerospace field, wherein the lubricant is used in temperature cycles varying from very high temperature values to very low temperature values.
To overcome this drawback, an alternative is the use of FOMBLIN® Z commercialized by AUSIMONT, having the following structure:
CF
3
—(O—CF
2
—CF
2
)
m
—(O—CF
2
)
n
—O—CF
3
(II)
wherein the m
ratio ranges from 0.3 to 5.
The Tg obtained with these PFPEs are of the order of −130° C. and −120° C. and depend on the PFPE number average molecular weight and on the m
ratio.
The perfluoropolyether FOMBLIN® Z have however the drawback to be obtained with a process having low productivity. In fact for their obtainment it is necessary to polymerize the tetrafluoroethylene monomer in the presence of a solvent. This involves a high production cost of FOMBLIN® Z compared with that of FOMBLIN® Y. Furthermore FOMBLIN® Z compared with FOMBLIN® Y shows a reduced thermal stability in oxidative conditions.
The need was felt to have available a perfluoropolyether lubricant overcoming the drawbacks of commercial products.
The Applicant has surprisingly and unexpectedly found a class of lubricants which solves the above technical problem showing the following combination of properties:
Tg in the range −130° and −60° C.;
Tg adjustable in function of the monomeric units present in the polymeric backbone, adjustable also when the molecular weight is the same;
high thermal stability also in oxidative conditions;
obtainable by a process in high productivity.
An object of the invention are perfluoropolyether lubricants containing sequences of oxyperfluoroalkylene units, characterized by the presence of sulphonylfluoride groups pending from the polymeric backbone and having the following formula (III):
wherein:
T are end groups selected from —CF
2
X (X═F,CF
3
,Cl), —C
3
F
7
, —COF, —CF(CF
3
)COF, —CF
2
COF, —CF
2
COCF
3
;
d,e,f,h are integers; a,b,c can be zero or integers; said units are statistically distributed along the chain, being a+b+c+d+e+f+h such that the number average molecular weight ranges from 500 to 5×10
5
, preferably from 1,000 to 50,000.
Generally the units d,e,f,h are present in most polymeric chains; of course some chains can contain only some of these units.
The perfluoropolyether lubricants of the invention are homopolymers of the perfluoro 3-oxa 5-fluorosulphonyl 1-pentene (CF
2
═CFOCF
2
CF
2
SO
2
F) or copolymers of this sulphonic monomer with perfluoroolefins.
The perfluoroolefins are preferably tetrafluoroethylene and/or perfluoropropene.
Other optional units which can be present are those derived from comonomers, such as for example perfluoroal-kylvinylethers CF
2
═CF
2
OR
f
, wherein R
f
is a perfluoroalkyl group —CF
3
, —C
2
F
5
, —C
3
F
7
, or perfluorinated conjugated dienes, in particular perfluorobutadiene.
The perfluoropolyether lubricants of the present invention can therefore contain perfluorinated units of the type —(CF
2
CF(CF
3
)O)—, —(CF(CF
3
)O)—, —(CF
2
CF
2
O)—, —(CF
2
O)—, —(CF
2
CF(OCF
2
CF
2
SO
2
F)O)—, —(CF(OCF
2
CF
2
SO
2
F)O)— statistically distributed along the chain and in an amount variable depending on the operating conditions.
The sulphonic functional perfluoropolyethers of the invention contain in variable amounts, depending on the operating polymerization process conditions, the above units. Besides the sulphonic pendent group is linked to the backbone through an oxygen atom (C—O—C bond). According to a not binding theory, the Applicant considers that these structural characteristics bring a greater flexibility degree and therefore a greater co
De Patto Ugo
Marchionni Giuseppe
Arent Fox Kintner Plotkin & Kahn
Ausimont S.p.A.
McAvoy Ellen M.
LandOfFree
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