U.S. patent application number 11/449711 was filed with the patent office on 2006-12-14 for fluorinated greases having a low torque at low temperatures.
This patent application is currently assigned to SOLVAY SOLEXIS S.p.A.. Invention is credited to Patrizia MacCone.
Application Number | 20060281641 11/449711 |
Document ID | / |
Family ID | 36955255 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060281641 |
Kind Code |
A1 |
MacCone; Patrizia |
December 14, 2006 |
Fluorinated greases having a low torque at low temperatures
Abstract
Fluorinated greases comprising: (A) from 1% to 50% by weight of
a thickener; (B) from 99% to 50% by weight of a mixture of: (B1)
from 0, 1 to 100% by weight of a compound of structure:
X.sub.1--O(CF.sub.2O)n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.sub.2O-
).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q--X.sub.2 (I)
wherein: X.sub.1, X.sub.2 have formula --(CF.sub.2).sub.ZCF.sub.3
wherein z is an integer between 0 and 3; n is an integer between 1
and 200; m is an integer between 0 and 200; p, q are integers
between 0 and 10; with the proviso that: the
(p+q)/(p+q+m+n).ltoreq.0.05; m/n.ltoreq.0.7; the number average
molecular weight of (I) is between 1,000 and 10,000; the kinematic
viscosity at 40.degree. C. is lower than 20 cSt; and (B2) from
99.9% to 0% by weight of a perfluoropolyether oil having a
kinematic viscosity at 40.degree. C. higher than 15 cSt and
comprising repeating units of the type (CFXO) wherein X is F or
CF.sub.3; --CF.sub.2CF.sub.2O--, --C.sub.3F.sub.6O, --CF(CF.sub.3)
CF.sub.2O, --CF.sub.2CF (CF.sub.3) O--, statistically distributed
along the chain.
Inventors: |
MacCone; Patrizia; (Milano,
IT) |
Correspondence
Address: |
ARENT FOX PLLC
1050 CONNECTICUT AVENUE, N.W.
SUITE 400
WASHINGTON
DC
20036
US
|
Assignee: |
SOLVAY SOLEXIS S.p.A.
|
Family ID: |
36955255 |
Appl. No.: |
11/449711 |
Filed: |
June 9, 2006 |
Current U.S.
Class: |
508/182 |
Current CPC
Class: |
C10M 2201/1056 20130101;
C10M 2207/10 20130101; C10N 2020/06 20130101; C10N 2030/10
20130101; C10M 2217/06 20130101; C10N 2040/06 20130101; C10M 169/02
20130101; C10N 2040/30 20130101; C10M 2227/066 20130101; C10N
2030/04 20130101; C10M 2217/04 20130101; C10M 2227/06 20130101;
C10M 2201/062 20130101; C10M 107/38 20130101; C10N 2010/12
20130101; C10M 2207/123 20130101; C10M 2213/04 20130101; C10M
2213/043 20130101; C10N 2020/04 20130101; C10M 2201/041 20130101;
C10M 2217/00 20130101; C10N 2030/12 20130101; C10M 2219/08
20130101; C10M 2201/061 20130101; C10M 2223/08 20130101; C10M
2201/1026 20130101; C10M 2213/0626 20130101; C10N 2030/06 20130101;
C10M 2213/04 20130101; C10N 2060/09 20200501; C10M 2213/04
20130101; C10N 2060/09 20200501 |
Class at
Publication: |
508/182 |
International
Class: |
C10M 169/00 20060101
C10M169/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2005 |
IT |
MI2005 A 001080 |
Claims
1. Fluorinated greases comprising from (% by weight): (A) 1% to
50%, preferably from 10% to 40%, of one or more thickeners; (B) 99%
to 50%, preferably from 90% to 60%, of a mixture of the following
perfluoropolyethers: (B1) 0.1% to 100%, preferably from 5% to 100%,
of a perfluoropolyether having the following formula:
X.sub.1--O(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.s-
ub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q--X.sub.2 (I)
wherein: the repeating units --CF.sub.2O--, --CF.sub.2CF.sub.2O--,
--CF.sub.2CF.sub.2CF.sub.2O--,
--CF.sub.2CF.sub.2CF.sub.2CF.sub.2O-- are statistically distributed
along the backbone; --X.sub.1 and --X.sub.2 are perfluoroalkyl
chain end groups equal to or different from each other, having
formula --(CF.sub.2).sub.zCF.sub.3 wherein z is an integer from 0
to 3; n is an integer between 1 and 200, m is an integer between 0
and 200, p, q are integers between 0 and 10, preferably between 0
and 5, more preferably between 0 and 1; with the proviso that: the
ratio (p+q)/(p+q+m+n) is lower than or equal to 0.05, or also 0;
the ratio m/n, (when n is different from 0), is lower than or equal
to 0.7, preferably lower than 0.5, more preferably lower than 0.35;
the number average molecular weight of the compound of formula (I)
is between 1,000 and 10,000, preferably between 2,000 and 8,000,
more preferably between 2,400 and 5,000; the kinematic viscosity,
at 40.degree. C., is lower than 20 cSt; and the chlorine atoms,
determined by .sup.19F NMR, are substantially absent; (B2) 99.9% to
0%, preferably from 95% to 0%, of a perfluoropolyether oil having a
kinematic viscosity at 40.degree. C. higher than 15 cSt and
comprising repeating units of the type (CFXO) wherein X is F or
CF.sub.3; --CF.sub.2CF.sub.2O--, --CF (CF.sub.3) CF.sub.2O--,
--CF.sub.2CF(CF.sub.3)O--, statistically distributed along the
backbone; and optionally (C) 0% to 1.0% with respect to the total
weight of (A)+(B), preferably from 1% to 3%, of one or more
additives selected from anti-wear additives for high or low loads,
anti-rust, antioxidant additives, stabilizers.
2. Greases according to claim 1, wherein the thickener (A) is
selected from the known thickeners of the prior art, for example
talc, silica, polytetrafluoroethylene (PTFE), or their
mixtures.
3. Greases according to claim 1, wherein the thickener is silica,
in amounts ranging from 1 to 10% by weight with respect to the
total weight of (A)+(B).
4. Greases according to claim 1, wherein the thickener is talc or
PTFE, in amounts ranging from 5% to 40% by weight, more preferably
from 5% to 35%, with respect to the total (A)+(B).
5. Greases according to claim 4, wherein the thickener is PTFE,
more preferably PTFE having an average particle size between 0.01
.mu.m and 0.3 .mu.m.
6. Greases according to claim 1, wherein component (B2) is selected
from the following classes (1) E-O--
(CF.sub.2CF(CF.sub.3)O).sub.m'(CFXO).sub.n'-E' wherein: X is equal
to F or CF.sub.3; E and E', equal to or different from each other,
are selected from CF.sub.3, C.sub.2F.sub.5 or C.sub.3F.sub.7, one
fluorine atom of one or both the end groups being replaceable with
Cl and/or H; m' and n' are integers such that the m'/n' ratio is
between 20 and 1,000, n' being different from zero; the units being
statistically distributed along the backbone, the viscosity of the
product being as above; (2) C.sub.3F.sub.7O(CF (CF.sub.3)
CF.sub.2O).sub.o'-D wherein: D is equal to --C.sub.2F.sub.5 or
--C.sub.3F.sub.7, one fluorine atom of one or both the end groups
being replaceable with C1 and/or H; o' is an integer such that the
viscosity of the product is as above; (3)
{C.sub.3F.sub.7O--(CF(CF.sub.3)
CF.sub.2O).sub.p'--CF(CF.sub.3)--}.sub.2 wherein: p' is an integer
such that the viscosity of the product is as above, one F atom of
one or both the end groups C.sub.3F.sub.7 being replaceable with Cl
and/or H; (4) E-O-- (CF.sub.2CF(CF.sub.3)O).sub.q,
(C.sub.2F.sub.4O).sub.r, (CFX).sub.s, -E' wherein: X is equal to F
or CF.sub.3; E and E', equal to or different from each other, are
as above; q', r' and s' are integers including 0, and such that the
viscosity of the product is as above; (5)
E-O--(C.sub.2F.sub.4O).sub.t'(CF.sub.2O).sub.u'-E' wherein: E and
E', equal to or different from each other, are as above; t' and u'
are integers such that the ratio t'/u' is between 0.1 and 5, u'
being different from 0, and the viscosity of the product is as
above; (6) E-O--(CF.sub.2CF.sub.2CF.sub.2O).sub.v'-E' wherein: E
and E', equal to or different from each other, are as above; v' is
a number such that the viscosity of the product is as above; (7)
D-O--(CF.sub.2CF.sub.2O).sub.z, -D' wherein: D and D', equal to or
different from each other, are selected from C.sub.2F.sub.5 or
C.sub.3F.sub.7, one fluorine atom of one or both the end groups
being replaceable with C1 and/or H; z' is an integer such that the
viscosity of the product is as above; (8)
E.sub.1-O(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m--(CF.sub.2CF.sub.2CF.-
sub.2O).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q-E.sub.2
wherein: E.sub.1 and E.sub.2 are perfluoroalkyl end groups, equal
to or different from each other, having formula
--(CF.sub.2).sub.zCF.sub.3 wherein z is an integer from 0 to 3; n,
m, p, q are integers equal to or different from each other between
0 and 100 and selected so that the viscosity of the oil is as above
and such that the ratio m/n is between 2 and 20, n being different
from 0; (p+q)/(n+m+p+q) is between 0.05 and 0.2, (n+m+p+q) being
different from 0; n/(n+m+p+q) is between 0.05 and 0.40, (n+m+p+q)
being different from 0.
7. Greases according to claim 6, wherein component (B2) is selected
from the classes (1), (4), (5), (8) or their mixtures, more
preferably from the classes (5) and (8) or their mixtures.
8. Greases according to claim 1 comprising additives commonly used
in the lubrication field, preferably anti-wear additives for high
and low loads, anti-rust, antioxidant additives and/or stabilizers,
in an amount not higher than 10% by weight with respect to the
total composition.
9. Greases according to claim 8, wherein the stabilizing additives
are selected from the perfluoropolyether dinitro derivative
compounds and the perfluoropolyether pyridine derivatives.
10. Greases according to claim 8, wherein the anti-wear additives
are selected from molybdenum sulphide, molybdenum organic
compounds, boron nitride, graphite, phosphazene derivatives,
preferably phosphazene derivatives containing perfluoropolyether
chains.
11. Greases according to claim 8, wherein the anti-rust additives
are selected from disodic sebacate, sodium carbonate,
functionalized derivatives of carboxylic acids containing
perfluoro-polyether chains.
12. A process for preparing the greases of claim 1, comprising the
following steps: feeding of the oil and/or mixture of lubricating
oils (B1), (B2), in a mixer and degassing under vacuum at
60.degree. C. for 2 hours at 0.1 mbar; gradual addition of
component (A) (thickener) until reaching the desired composition;
optional addition of component (C) (additive): when the additive is
liquid it is premixed with the basic oil or in the mixture before
adding the thickener; when the additive is solid, it is premixed
with the thickener powder before the gradual addition to the basic
oil or to the mixture; constant stirring for at least 8 hours under
vacuum; discharge of the obtained grease and its refining by
passage on tri-roller refiner.
13. Use of the greases of claim 1 for the lubrication at
temperatures lower than -40.degree. C., preferably lower than
-60.degree. C., for applications in the aerospace and refrigeration
industry.
14. Use according to claim 13 at temperatures from -40.degree. C.
to -80.degree. C., wherein component B) is formed of an oil
mixture, wherein the oil (B1) is present up to at most 50% by
weight with respect to the oil (B2), preferably up to 30%, and the
kinematic viscosity of the mixture is preferably lower than 40 cSt,
more preferably lower than 35 cSt.
15. Use according to claim 13 at temperatures lower than
-80.degree. C. wherein component (B) of the grease is formed of the
oil (B.sub.1).
16. Use of the greases of claim 6 for the lubrication in
applications having temperature ranges between -100 and
+180.degree. C. wherein the oil (B2) is that of the class (8).
Description
[0001] The present invention relates to fluorinated greases having
a low torque.
[0002] The invention specifically relates to
perfluoropolyether-based greases having lower torques at low
temperatures, in particular at temperatures lower than -40.degree.
C.
[0003] The invention more specifically relates to
perfluoropolyether grease compositions having improved torques at
-40.degree. C., in particular at temperatures lower than
-40.degree. C., and to the use of said compositions in the
lubrication in a wide temperature range, preferably between
-100.degree. C. and +180.degree. C.
[0004] It is known in the prior art to use perfluoro-polyether oils
as lubricants in a wide temperature range, in particular at very
low temperatures, for example in the aerospace and refrigeration
industry. Among these lubricants, those used for the low
temperatures have a typically linear structure, as for example
FOMBLIN.RTM. marketed by Solvay Solexis S.p.A. These oils are used
alone or formulated with particular thickeners, for example
polytetrafluoroethylene (PTFE), to obtain greases.
[0005] In case of greases to be used at low temperatures, the
lowering of the torques is essential to reduce the energy for the
handling of mechanical parts, for example bearings, in contact with
the grease. In particular in aerospace applications fluorinated
greases having lubricating properties at -40.degree. C., and even
at much lower temperatures -40.degree. C., are required.
[0006] Fluorinated greases having a low torque at -40.degree. C.,
are known. For example, U.S. Pat. No. 6,329,326 describes greases
for ball-bearings for cars containing linear perfluoropolyether
oils having a kinematic viscosity, measured at 40.degree. C.,
between 40 and 160 cSt, and PTFE having an average diameter lower
than 0.1 micron. These greases are characterized by a low torque at
-40.degree. C., and a good durability at 180.degree. C. and can
therefore be used in a temperature range from -40.degree. C., to
200.degree. C. In this patent, applications at temperatures lower
than -40.degree. C., are not mentioned, the behaviour of the
greases at temperatures lower than -40.degree. C., is described
neither.
[0007] U.S. Pat. No. 6,723,684 describes greases for bearings in
the automotive field and planes, having the following composition:
a perfluoro-polyether oil having a linear structure and viscosity,
at 40.degree. C., equal to or lower than 25 cSt; a
perfluoro-polyether oil having a linear structure and viscosity, at
40.degree. C., equal to or higher than 250 cSt; PTFE as thickener.
The two oils used to prepare the grease are mixed so as to have a
total viscosity, measured at 40.degree. C., from 40 to 150 cSt.
These greases are used in a temperature range from -40.degree. C.,
to +180.degree. C. Torques at -40.degree. C., are given, however
values and/or applications at temperatures lower than -40.degree.
C., are not reported.
[0008] The need was therefore felt to have available fluorinated
greases having low torques at temperatures lower than or equal to
-40.degree. C., in particular values lower than those of the
greases based on linear perfluoropolyether oils of the prior
art.
[0009] The Applicant has surprisingly and unexpectedly found
fluorinated greases comprising particular linear
perlfuoropolyethers usable in applications at temperatures lower
than -40.degree. C., showing torques lower than those of the prior
art greases.
[0010] It is therefore an object of the present invention
fluorinated greases comprising from (% by weight): [0011] (A) 1% to
50%, preferably from 10% to 40%, of one or more thickeners; [0012]
(B) 99% to 50%, preferably between 90% and 60%, of a mixture of the
following perfluoropolyethers: [0013] (B1) 0.1% to 100%, preferably
from 5% to 100%, of a perfluoropolyether having the following
formula:
X.sub.1--O(CF.sub.2).sub.n(CF.sub.2CF.sub.2O).sub.m(CF.sub.2CF.sub.2CF.su-
b.2).sub.p(CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.qX.sub.2 (I)
[0014] wherein: [0015] the repeating units --CF.sub.2O--,
--CF.sub.2CF.sub.2O--, --CF.sub.2CF.sub.2CF.sub.2O--,
--CF.sub.2CF.sub.2CF.sub.2CF.sub.2O-- are statistically distributed
along the backbone; [0016] --X.sub.1 and --X.sub.2 are
perfluoroalkyl chain end groups equal to or different from each
other, having formula --(CF.sub.2).sub.zCF.sub.3 wherein z is an
integer from 0 to 3; [0017] n is an integer between 1 and 200,
[0018] m is an integer between 0 and 200, [0019] p, q are integers
between 0 and 10, preferably between 0 and 5, more preferably
between 0 and 1; [0020] with the proviso that: [0021] the ratio
(p+q)/(p+q+m+n) is lower than or equal to 0.05, or also equal to 0;
[0022] the ratio m/n, (when n is different from 0), is lower than
or equal to 0.7, preferably lower than 0.5, more preferably lower
than 0.35; [0023] the number average molecular weight of the
compounds of formula (I) is between 1,000 and 10,000, preferably
between 2,000 and 8,000, more preferably between 2,400 and 5,000;
[0024] the kinematic viscosity, at 40.degree. C., is lower than 20
cSt; and [0025] the chlorine atoms, determined by .sup.19F NMR, are
substantially absent. [0026] (B2) 99.9% to 0%, preferably from 95%
to 0%, of a perfluoropolyether oil having a kinematic viscosity, at
40.degree. C., higher than 15 cSt and comprising repeating units of
the type (CFXO) wherein X is F or CF.sub.3; [0027]
--CF.sub.2CF.sub.2O--, --CF(CF.sub.3)CF.sub.2O--,
--(F.sub.2CF(CF.sub.3)O--, statistically distributed along the
backbone; and optionally [0028] (C) 0% to 10% with respect to the
total weight of (A)+(B), preferably from 1% to 3%, of one or more
additives selected from anti-wear additives for high or low loads,
anti-rust, antioxidant additives, stabilizers.
[0029] The thickener (A) can be selected from the known thickeners
of the prior art, for example talc, silica, polytetrafluoroethylene
(PTFE), or their mixtures. When silica is used as thickener, the
amounts range from 1 to 10% by weight with respect to the total
weight of (A)+(B); when talc or PTFE are used, the amounts range
from 5% to 40% by weight, more preferably from 5% to 35%, with
respect to the total (A)+(B).
[0030] Preferably, as thickener, PTFE is used, more preferably PTFE
having an average particle size between 0.01 .mu.m and 0.3 .mu.m.
PTFE, used as thickener, can be obtained by the known
polymerization techniques, in particular by microemulsion, emulsion
or dispersion polymerization. Furthermore the PTFE can also be
subjected to irradiation. Known processes for preparing PTFE are
described in patents EP 1,520,906, U.S. Pat. No. 4,864,006, U.S.
Pat. No. 6,297,334, U.S. Pat. No. 6,576,703.
[0031] Compounds (B1) of formula (I), wherein the chlorine atoms,
determined by .sup.19F NMR, are substantially absent, are compounds
wherein the chlorine atoms are lower than the sensititivy limit of
the analytical .sup.19F NMR method.
[0032] Component (B1) is liquid at 20.degree. C., shows a low
vapour pressure, a high viscosity index and therefore it can be
considered a lubricating oil. Besides it shows pour point values
preferably lower than -90.degree. C.
[0033] Component (B2) can be selected from the following
classes:
(1) E-O--(CF.sub.2CF(CF.sub.3)O).sub.m'(CFXO).sub.n'-E'
[0034] wherein: [0035] X is equal to F or CF.sub.3; [0036] E and
E', equal to or different from each other, are selected from
CF.sub.3, C.sub.2F.sub.5 or C.sub.3F.sub.7, one fluorine atom of
one or both the end groups being replaceable with Cl and/or H;
[0037] m' and n' are integers such that the ratio m'/n' is between
20 and 1,000, n' being different from zero; the units being
statistically distributed along the backbone, the viscosity of the
product being as above.
[0038] These polymers can be obtained by perfluoropropene
photo-oxidation as described in GB 1,104,432, and by subsequent
conversion of the end groups as described in GB 1,226,566;
(2) C.sub.3F.sub.7O(CF(CF.sub.3)CF.sub.2O).sub.o'-D
[0039] wherein: [0040] D is equal to --C.sub.2F.sub.5 or
--C.sub.3F.sub.7, one fluorine atom of one or both the end groups
being replaceable with Cl and/or H; [0041] o' is an integer such
that the viscosity of the product is as above.
[0042] These polymers can be prepared by ionic oligomerization of
the perfluoropropylenoxide and subsequent treatment with fluorine
as described in U.S. Pat. No. 3,242,218;
(3)
{C.sub.3F.sub.7O--(CF(CF.sub.3)CF.sub.2O).sub.p--CF(CF.sub.3)--}.sub-
.2
[0043] wherein: [0044] p' is an integer such that the viscosity of
the product is as above, one F atom of one or both the end groups
C.sub.3F.sub.7 being replaceable with Cl and/or H.
[0045] These products can be prepared by ionic telomerization of
[0046] the perfluoropropylenoxide and subsequent photochemical
dimerization as reported in U.S. Pat. No. 3,214,478;
[0047] (4)
E-O--(CF.sub.2CF(CF.sub.3)O).sub.q'(C.sub.2F.sub.4O).sub.r'(CFX).sub.s'E'
[0048] wherein: [0049] X is equal to F or CF.sub.3; [0050] E and
E', equal to or different from each other, are as above; [0051] q',
r' and s' are integers including 0, and such that the viscosity of
the product is as above.
[0052] These polymers are obtainable by photooxidation of a mixture
of C.sub.3F.sub.6 and C.sub.2F.sub.4 and subsequent treatment with
fluorine as described in U.S. Pat. No. 3,665,041;
(5) E-O-(c.sub.2F.sub.4O).sub.t'(CF.sub.2O).sub.u'E'
[0053] wherein: [0054] E and E', equal to or different from each
other, are as above; [0055] t' and u' are integers such that the
ratio t'/u' is between 0.1 and 5, u' being different from 0, and
the viscosity of the product is as above. [0056] These polymers are
obtained by photooxidation of C.sub.2F.sub.4 as reported in U.S.
Pat. No. 3,715,378 and subsequent treatment with fluorine as
described in U.S. Pat. No. 3,665,041; (6)
E-O--(CF.sub.2CF.sub.2CF.sub.2O).sub.v'-E' [0057] wherein: [0058] E
and E' equal to or different from each other, are as above; [0059]
v' is a number such that the viscosity of the product is as above.
[0060] These polymers are obtained as described in EP 148,482; (7)
D-O--(CF.sub.2CF.sub.2O).sub.z'-D' [0061] wherein: [0062] D and D',
equal to or different from each other, are selected from
C.sub.2F.sub.5 or C.sub.3F.sub.7, one fluorine atom of one or both
the end groups being replaceable with Cl and/or H; [0063] z' is an
integer such that the viscosity of the product is as above. [0064]
These polymers can be obtained as reported in U.S. Pat. No.
4,523,039; (8)
E.sub.1-O(CF.sub.2O).sub.n(CF.sub.2CF.sub.2O).sub.m-(CF.sub.2CF.sub.2-
CF.sub.2O).sub.p (CF.sub.2CF.sub.2CF.sub.2CF.sub.2O).sub.q-E.sub.2
[0065] wherein: [0066] E.sub.1 and E.sub.2 are perfluoroalkyl end
groups, equal to or different from each other, having formula
--(CF.sub.2).sub.zCF.sub.3 wherein z is an integer from 0 to 3;
[0067] n, m, p, q are integers equal to or different from each
other between 0 and 100 and selected so that the viscosity of the
oil is as above and such that the ratio m/n is between 2 and 20, n
being different from 0; (p+q)/(n+m-+p+q) is between 0.05 and 0.2,
(n+m+p+q) being different from 0; n/(n+m+p+q) is between 0.05 and
0.40, (n+m+p+q) being different from 0.
[0068] These polymers can be obtained according to EP
1,454,938.
[0069] The classes (1), (4), (5), (8) or their mixtures are
preferred, the classes (5) and (8) or their mixtures are more
preferred.
[0070] The mixture of oils (B1)+(B2) preferably has a kinematic
viscosity lower than 40 cSt at 40.degree. C.
[0071] Optionally, as said, additives commonly used in the
lubrication field, f.i. anti-wear additives for high and low loads,
anti-rust, antioxidant additives and/or stabilizers can be present
in the lubricating composition of the present invention, in an
amount not higher than 10% by weight with respect to the total
composition. As stabilizing additives, the perfluoropolyether
dinitro derivative compounds, described in patent application US
2003/0203,823; the pyridine derivatives obtained according to
patent application US 2004/235,685, can be mentioned. As anti-wear
additives, it can be mentioned molybdenum sulphide, molybdenum
organic compounds, boron nitride, graphite, phosphazene
derivatives, in particular phosphazene derivatives containing
perfluoro-polyether chains, for example as those described in
patent application US 2003/176.738. As anti-rust additives, the
disodic sebacate, sodium carbonate, functionalized derivatives of
carboxylic acids containing perfluoropolyether chains, for example
as those described in U.S. Pat. No. 5,000,864 or in U.S. Pat. No.
6,025,307, can be mentioned.
[0072] Component (B1) can be prepared, for example, according to
the following process comprising the following steps: [0073] a)
synthesis of a peroxidic perfluoropolyether, obtainable by one of
the following reactions: [0074] a1) tetrafluoroethylene (TFE)
photooxidation, in the presence of UV light, at a temperature
between -40.degree. C. and -100.degree. C., in solvents liquid
under the reaction conditions, of formula:
C.sub.yF.sub.(2y+2-x)H.sub.x (II) [0075] wherein y is an integer
from 2 to 4; x is an integer equal to 0 or 1; [0076] in the
presence of elemental fluorine as chain transfer agent, diluted
with an inert gas; [0077] or [0078] a2) TFE oxidation by using as
radical initiator fluorine or hypofluorites of formula R.sub.fOF
(III) [0079] R.sub.f being a perfluoroalkyl radical from 1 to 3
carbon atoms, [0080] by operating in the temperature range from
-40.degree. C. to -100.degree. C. at a pressure between 0 and 12
bar, in an inert solvent; [0081] preferably a2) is used; [0082] b)
thermal treatment of the peroxidic product obtained in step a) at a
temperature from 150.degree. C. to 250.degree. C., optionally in
the presence of chain transfer agent selected from elemental
fluorine and one or more hypofluorites of formula (III); [0083] c)
treatment with elemental fluorine of the polymer obtained in b) at
temperatures from 100.degree. C. to 250.degree. C., or by treatment
with fluorine in the presence of UV radiations, by operating at
temperatures between -50.degree. C. and 120.degree. C. In step a1)
the fluorine is generally added in amounts such that the molar
ratio fluorine/tetrafluoroethylene is between 210.sup.-2 and
1.210.sup.-3, preferably between 1.210.sup.-2 and 1.710.sup.-3 and
is diluted with an inert gas in ratios by volume from 1/50 to
1/1,000.
[0084] In step a1) preferably the solvents are the following:
perfluoropropane (C.sub.3F.sub.8), hydropentafluoroethane
(C.sub.2F.sub.5H) and 2-hydroheptafluoropropane
(CF.sub.3CFHCF.sub.3), C.sub.4F.sub.9H (for example
CF.sub.3C--FHCF.sub.2CF.sub.3, (CF.sub.3).sub.3CH,
HCF.sub.2CF.sub.2CF.sub.2CF.sub.3).
[0085] The solvent used in step a1) is liquid at the synthesis
temperatures (-40.degree./-80.degree. C.) and solubilizes the
peroxidic polymer even in high molecular weights forming a
homogeneous solution. This represents a remarkable advantage since
there is no separation of the peroxidic polymer. This makes
possible the industrial use of said process as no cloggings of the
industrial plant piping due to uncontrolled viscosity increase take
place. Further the thermal exchanges are extremely effective and
this avoids uncontrolled degradation of the peroxidic polymer.
[0086] Besides, the solvents used in step a1) allow a high reaction
kinetics, so to maintain high productivities combined with a low
peroxidic content in the polymer, lower than 4-5 g of active
oxygen/100 g of product, to avoid explosion risks.
[0087] As said, the fluorine used in step a1) must be diluted with
a gas. Generally an inert gas, as nitrogen or helium is used.
Oxygen can also be used as diluent. In fact, when undiluted
fluorine is used, the fluorine produces uncontrolled local
reactions and gaseous decomposition products. The latter cause
stopping of the process due to fouling of the reactor and of the
optical system (UV lamp) in case of polymerization in the presence
of UV radiations. Besides, in these cases, there can be an
uncontrolled increase of the peroxidic content P.O., higher than
4-5 g of active oxygen/100 g of product, bringing to explosion
risks in the system. When it is used diluted, the fluorine acts in
step a1) as chain transfer agent with a very high selectivity, of
the order of 90%.
[0088] The fluorine furthermore, in step a1), reduces and
substantially eliminates the reaction induction times avoiding the
use of reaction activators.
[0089] In step a2), wherein the TFE oxidation is carried out
without using the UV light, the solvents can be those above
mentioned, or chlorinated solvents. For example CF.sub.2Cl.sub.2,
optionally in admixture with COF.sub.2 can be mentioned.
[0090] In step a2) the molar ratio TFE/chemical initiator ranges
from 10 to 200, preferably from 40 to 120.
[0091] In step b) the use of chain transfer agent can be omitted
when the control of the molecular weight is not necessary. This
happens, for example, when the viscosity of the peroxidic product
is lower than 5,000 cSt.
[0092] In step b) generally fluorine or hypofluorites of formula
(III), when present, are used with a flow-rate from 110.sup.-2 to
3, preferably from 210.sup.-2 to 2 molesh/Kg polymer.
[0093] Step a) and step b) of the process of the present invention
can be carried out in a discontinous, semicontinuous or continuous
way.
[0094] Step b) ends when the peroxidic content in the polymer is
substantially absent. This means that the P.O. value is equal to or
lower than the sensitivity limit of the analytical method used (1
ppm), by titration with thiosulphate of the iodine developed by the
reaction of the peroxidic polymer with sodium iodide. Generally the
thermal treatment times are from 10 to 30 hours, depending on the
P.O. and the temperature used in this step.
[0095] Step c) is usually carried out in a discontinuous way. The
reaction ends when, at .sup.19F NMR analysis, the functional end
groups (mainly --OCF.sub.2COF and --OCOF) have been transformed
into perfluoroalkyl end groups (method sensitivity limit: 1 meq/Kg
polymer).
[0096] In step c) the fluorine is fed in amounts so to have a
concentration in the perfluoropolyether generally corresponding to
the fluorine solubility limit. At the temperature used in the step,
it is of the order or 10.sup.-2 moles of fluorine/litre of
polymer.
[0097] Optionally, the product can be distilled to obtain fractions
having a given number average molecular weight and a determined
distribution of the molecular weights.
[0098] The fluorinated greases of the present invention can be
obtained according to the mixing procedures described in the prior
art, for example comprising the following steps: [0099] feeding of
the oil and/or mixture of lubricating oils (B1), (B2), in a mixer
and degassing under vacuum at 60.degree. C. for 2 hours at 0.1
mbar; [0100] gradual addition of component (A) (thickener) until
reaching the desired composition; [0101] optional addition of
component (C) (additive): when the additive is liquid it is
premixed with the basic oil or the mixture before adding the
thickener; when the additive is solid, it is premixed with the
thickener powder before the gradual addition to the basic oil or to
the mixture; [0102] constant stirring for at least 8 hours under
vacuum; [0103] discharge of the obtained grease and its refining by
passage on tri-roller refiner.
[0104] The consistency of the greases of the present invention
depends on the total concentration of the thickener used in the
composition; in particular by increasing the thickener content, the
penentration value decreases. The amounts of thickener (A) reported
above allow to obtain all the penetration NLGI classes defined by
the ASTM D 217 method, from degree 000, corresponding to a
penetration value of 475 mm/10', to degree 6, corresponding to 85
mm/10'. This allows to satisfy the various requirements in a wide
application range.
[0105] The lubricating compositions of the present invention show a
torque lower than those of the prior art. (see the comparative
Examples). Furthermore said compositions can be used even at
temperatures lower than -40.degree. C., preferably lower than
-60.degree. C., for applications at very low temperatures as for
example in the aerospace and refrigeration industry. In
applications wherein one operates at temperatures from -40.degree.
C. to -80.degree. C., component B) is preferably formed of an oil
mixture, wherein the oil (B1) is present up to at most 50% by
weight with respect to (B2), preferably up to 30%, and the
kinematic viscosity of the mixture is preferably lower than 40 cSt,
more preferably lower than 35 cSt. In applications at temperatures
lower than -80.degree. C., component (B) is preferably formed of
the oil (B1) alone.
[0106] It is surprising and unexpected that the invention greases
comprising compounds of formula (I) show at -60.degree. C. starting
torque values much lower than those of the greases prepared
according to the prior art, the penetration and the viscosity of
the basic oils being substantially the same (see the comparative
Examples).
[0107] The lubricating compositions of the present invention show
furthermore the advantage to be usable in applications having wide
temperature ranges, for example -100/+180.degree. C. It has indeed
been found that the compositions wherein the oil (B2) belongs to
the class (8) show a high thermal stability at 180.degree. C.
combined with a low torque value. Therefore said compositions can
be used as lubricants in applications where wide temperature ranges
are present.
[0108] Some illustrative but not limitative Examples of the present
invention follow.
EXAMPLES
Characterization
Determination of the Torque at Low Temperature
[0109] The torque measurements have been carried out at different
temperatures (-40.degree. C., -60.degree. C. and -70.degree. C.) by
using a ball-bearing according to what described in the ASTM D 1478
method. The measured parameters are the "starting torque",
representing the initial starting point of the bearing, and the
"running torque", which represents the working stress after 1 test
hour. The measure unit is the gcm.
Determination of the Kinematic Viscosity
[0110] The kinematic viscosity at a given temperature has been
determined by using capillary Cannon-Fenske type viscometers
according to the ASTM D 445 method.
Determination of the Penetration (or Grease Consistency)
[0111] The penetration value has been evaluated according to the
ASTM D 217 method. The higher the penetration value and the lower
the grease consistency.
Example 1
[0112] 70 g of a perfluoropolyether oil of structure (I) having
number average molecular weight 2,467, m/n 0.33, (p+q)/-(p+q+m+n)
0.016 and kinematic viscosity at 20.degree. C. of 13 cSt, were
additioned with 30 g of PTFE, commercially known as Algoflon.RTM.
L206. A grease having a penetration of 309 mm/10' was obtained.
[0113] The starting torque and running torque values were measured,
at the temperature of -70.degree. C., and resulted equal to 578 gcm
and 44 gcm, respectively.
Example 1A (Comparative)
[0114] The Example 1 was repeated but by using as component B) a
perfluoropolyether oil of class (5) wherein m/n=1.1, having a
kinematic viscosity at 40.degree. C. between 40 cSt and 160 cSt and
equal to 151 cSt.
[0115] A grease having a penetration of 290 mm/10' was
obtained.
[0116] The starting torque and running torque values were measured,
at the temperature of -70.degree. C., and resulted equal to 3,667
gcm and 1,581 gcm, respectively.
[0117] The comparison of the data of the Example 1 with those of
the Example 1A (comparative) shows that the invention greases show
torque values at -70.degree. C. much lower than those of the
greases obtained according to the prior art teachings, the
oil/thickener content being equal.
Example 2
[0118] 70 g of a perfluoropolyether oil of structure (I) wherein
m/n=0.31, (p+q)/(p+q+m+n)=0.016 and having number average molecular
weight of 3,985 and a kinematic viscosity at 20.degree. C. of 19
cSt, were additioned with 30 g of PTFE, commercially known as
Algoflon.RTM. L206. A grease having a penetration of 315 mm/10' was
obtained.
[0119] The grease starting torque and running torque values were
measured at the temperature of -60.degree. C., and resulted equal
to 358 gcm and 34 gcm, respectively.
Example 3 (Comparative)
[0120] The Example 2 was repeated but by replacing the oil of
formula (I) with 70 g of a linear perfluoropolyether oil of class
(5), wherein m/n 0.8, having a number average molecular weight
equal to 4,000, commercially known as Fomblin.RTM. Z03.
[0121] A grease having a penetration of 312 mm/10' was
obtained.
[0122] The starting torque and running torque values of the grease
were measured at the temperature of -40.degree. C., and resulted
equal to 455 gcm and 198 gcm, respectively.
[0123] The starting torque and running torque values of the grease
were measured also at the temperature of -60.degree. C., and
resulted equal to 676 gcm and 181 gcm, respectively.
[0124] The comparison of the data of the Example 2 with those of
the Example 3 (comparative) shows that the greases obtained from
the perfluoropolyether oils of structure (I) of the present
invention show a torque value at temperatures lower than
-40.degree. C. reduced by 50% in comparison with greases obtained
by using a commercial oil as basic oil, the grease penetration and
substantially the basic oil viscosity being equal. It results
furthermore that the greases of the invention show starting torque
and running torque values at -60.degree. C. lower than those of the
greases obtained from commercial linear perfluoro-polyether oils
measured at -40.degree. C.
[0125] Furthermore also the comparison of the data of the Example 1
with those of the Example 3 (comparative) shows the same behaviour
described above.
Example 4
[0126] A mixture B) of oils was prepared formed of: [0127] (B1) 76
g of the oil of structure (I) of the Example 1; [0128] (B2) 24 g of
an oil of class (5) having viscosity at 40.degree. C. of 320
cSt.
[0129] The kinematic viscosity of the so obtained mixture, measured
at 40.degree. C., is lower than 40 cSt and is equal to 23.1
cSt.
[0130] 30 g of PTFE, commercially known as Algoflon.RTM. L206, were
added to 70 g of the previously prepared mixture.
[0131] A grease having a penetration of 317 mm/10' was obtained.
The starting torque and running torque values of the grease were
measured, at the temperatures of -40.degree. C., and -60.degree.
C., and the following results were obtained: TABLE-US-00001 T
(.degree. C.) Starting torque (g cm) Running torque (g cm) -40 286
126 -60 338 92
Example 5 (Comparative)
[0132] The Example 4 was repeated but by replacing the oil of
formula (I) with a perfluoropolyether oil of class (5) having a
substantially equal kinematic viscosity and lower than 25 cSt.
[0133] The mixture of basic oils B) was prepared so as to obtain a
mixture having a kinematic viscosity substnatially equal to that of
the Example 4, by mixing: [0134] 96 g of a perfluoropolyether oil
of class (5) wherein m/n=0.8 and having kinematic viscosity
measured at 40.degree. C. lower than 25 cSt and equal to 17 cSt;
[0135] 4 g of a perfluoropolyether oil of class (5) having
kinematic viscosity at 40.degree. C. higher than 250 cSt and equal
to 320 cSt.
[0136] The kinematic viscosity of the so obtained mixture, measured
at 40.degree. C., is 25.5 cSt.
[0137] A grease having a penetration of 311 mm/10' was then
obtained.
[0138] The starting torque and running torque values of the grease
were measured at the temperatures of -40.degree. C. and -60.degree.
C., and the following results were obtained: TABLE-US-00002 T
Starting torque Running torque (.degree. C.) (g cm) (g cm) -40 299
162 -60 819 153
[0139] The comparison of the data of the Example 4 with those of
the Example 5 (comparative) shows that, the grease penetration and
substantially the viscosity of the basic oil mixture (component B)
being equal, the greases of the invention, even showing a torque
value at -40.degree. C., substantially equal to that of the greases
containing linear perfluoropolyether oils according to U.S. Pat.
No. 6,723,684, show at -60.degree. C. a twice lower starting torque
value.
* * * * *