Patent Application
20210324291
This application claims priority to European application No. 17164462.8 filed on 3 Apr. 2017, the whole content of this application being incorporated herein by reference for all purposes.
The present invention relates to a composition suitable to be used as working fluid.
Working fluids are gases or liquids that, when pressurized, actuate a machine. Typical examples include steam in a steam engine, air in a hot air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder. More generally, in a thermodynamic system, the working fluid is a liquid or gas that absorbs or transmits energy.
The working fluid properties are essential for the full description of thermodynamic systems. Among the large number of suitable physical properties, their viscosity is of particular importance for use in applications such as hydrodynamic coupling, notably viscous couplings, and damping.
Working fluids that are suitable for the abovementioned applications and comprise organopolysiloxane as the base oil have been disclosed for example in U.S. Pat. No. 4,959,166 (COSMO OIL CP., LTD. ET AL.), EP 0397507 A (TONEN CORPORATION) and EP 0599251 A (COSMO OIL COMPANY, LTD. ET AL.).
More recently, WO 2016/150941 (SOLVAY SPECIALTY POLYMERS ITALY S.P.A.) disclosed a method for counteract vibrations and/or shocks in a device, wherein the method comprises:
providing an apparatus comprising a damper device, said damper device comprising at least one (per)fluoropolyether copolymer [polymer (P)] having a viscosity higher than 2,000 mm/s and comprising recurring units derived from (per)fluoropolyether and recurring units derived from at least one olefin, the viscosity being measured at 20° C. according to standard method ASTM D445, or with a dynamical mechanical spectrometer Anton Paar MCR 502 rheometer equipped with parallel plates 25 mm, at 1 rad/s and at 25° C.
This application teaches to provide a fluid suitable for use in a damper device, wherein the fluid is obtained by reacting a (per)fluoropolyether polymer and at least one olefin.
Compositions comprising a (per)fluoropolyether (PFPE) polymer as base oil and at least one perfluoropolymer, typically in the form of suspensions or dispersions, have been disclosed in the art.
For example, U.S. Pat. No. 6,100,325 (AUSIMONT S.P.A.) discloses a composition in the form of dispersion, which comprises 0.1-30 wt. % of a polytetrafluoroethylene or of tetrafluoroethylene (TFE) copolymers, 50-90 wt. % of a fluorinated liquid, 0.01-5 wt. % of a surfactant and a polar solvent (water and/or alcohol) in an amount complement to 100 wt. %. U.S. Pat. No. 6,025,307 (AUSIMONT S.P.A.) discloses a fluorinated grease, in the form of dispersions, comprising 15-50 wt. % of polytetrafluoroethylene or tetrafluoroethylene copolymers, 30-84.5 wt. % of perfluoropolyether oil having a viscosity comprised between 20 and 4000 cSt at 20° C.; 0.5-10 wt. % of surfactant or dispersant having perfluoropolyether or perfluoroalkylic chain; and optionally an anti-corrosion or anti-wear additive.
Lubricant compositions comprising a (per)fluoropolyether (PFPE) polymer characterized by high viscosity, for example in the form of paste, have been also disclosed in the art.
U.S. Pat. No. 5,032,302 (EXFLUOR RESEARCH CORPORATION) discloses a lubricant comprising perfluoropolyether oils containing perfluoropolyether solids as fillers, which can be prepared by mixing the perfluoropolyether solid and the perfluoropolyether oil. These compositions are said to be stable and to do not exhibit phase separation because the oil and the solid, being of the same chemical composition, are extremely compatible.
Also, JP H0673370 (NTN CORP.) discloses a damper sealant that is put in contact with a slidable member in order to prevent the leakage of an energy-absorbing fluid in a bumper or damper and is made of a lubricating rubber composition comprising (A) a thermoplastic fluororesin, (B) a fluororubber and (C) low molecular fluorine-containing polymer. In the description, as examples of component (C) the following are mentioned: tetrafluoroethylene polymer, fluoropolyether and polyfluoroalkyl. The fluoropolyethers have notably the following structures:
CF3O(C2F4)m(CF2O)n—CF3
CF3O(CF2CF(CF3)O)m(CF2O)n—CF3
CF3O(CF(CF3)CF2O)m(CF2O)n—CF3.
The Applicant perceived that in working fluid comprising two different phases (typically a solid phase dispersed or suspended into a liquid phase), phase separation can occur when the working fluid is used in harsh conditions.
Also, the Applicant perceived that the highly viscous silicone oils currently used as damping fluids suffer from some disadvantages, such as sensitivity to acids, bases and moisture and in particular thermal instability. Indeed, as a result of prolonged exposure to high temperatures (200° C. or even higher) the highly viscous silicone oils gradually harden over time, until they become inoperable and must be replaced. Also, the Applicant noted that the thermal instability of the highly viscous silicone oils becomes more evident as the viscosity of the silicone oil increases.
Thus, the Applicant faced the problem to provide a composition intended for use as working fluid in several applications. To this aim, the Applicant faced the problem of providing a composition that can be prepared via a simple process, such that a wide range of viscosity can be provided depending on the final intended use.
The Applicant has surprisingly found that a composition in the form of a solution can be obtained by contacting at least one (per)fluoropolyether polymer and at least one amorphous polymer.
Advantageously, the Applicant found that the composition of the present invention is able to retain its viscous properties over a wide range of temperatures, without showing degradation even after use for long time in a harsh environment.
Thus, in a first aspect, the present invention relates to a composition [composition (C)] comprising at least one (per)fluoropolyether polymer [polymer (P)] and at least one amorphous polymer [polymer (F)], wherein said composition (C) is in the form of a solution.
Advantageously, said polymer (F) is selected in the group consisting of amorphous polymers characterized by a glass transition temperature (Tg) measured according to ASTM D3418, in the range from −100° C. to 250° C. It will be apparent to those skilled in the art that said polymer (F), being amorphous, does not show a melting temperature (Tm) when analysed by thermal analysis following ASTM D3418.
As mentioned above, the Applicant noted that composition (C) according to the present invention can be prepared having a wide range of viscosity, which can be modulated on the basis of the final use for which said composition (C) is intended.
Advantageously, said composition (C) is characterized by a viscosity in the range from 100 mm2/s and up to 2,000,000 mm2/s (measured at 20° C. according to standard methods, such as ASTM D445, or with a dynamical mechanical spectrometer Anton Paar MCR 502 rheometer equipped with parallel plates 25 mm, at 1 rad/s and at 25° C.).
As a consequence, said composition (C) can be used as working fluid in several applications, with the advantage that phase separation cannot occur in a homogeneous solution, even after exposure at high temperatures.
For the purpose of the present description and of the following claims:
Preferably, said polymer (P) is a (per)fluoropolyether polymer comprising a (per)fluoropolyether chain [chain (Rpf)] of formula:
—(CFX)aO(Rf)(CFX′)b—
wherein
a and b, equal or different from each other, are equal to or higher than 1, preferably from 1 to 10, more preferably from 1 to 3;
X and X′, equal or different from each other, are —F or —CF3, provided that when a and/or b are higher than 1, X and X′ are —F;
(Rf) comprises, preferably consists of, repeating units R∘, said repeating units being independently selected from the group consisting of:
(i) ˜CFXO—, wherein X is F or CF3;
(ii) —CFXCFXO—, wherein X, equal or different at each occurrence, is F or CF3, with the proviso that at least one of X is F;
(iii) —(CF2)j—CFZ—O— wherein j is an integer from 0 to 3 and Z is a group of general formula —O—R(f-a)-T, wherein R(f-a) is a fluoropolyoxyalkene chain comprising a number of repeating units from 0 to 10, said recurring units being chosen among the following: —CFXO—, —CF2CFXO—, with each of X being independently F or CF3 and T being a C1-C3 perfluoroalkyl group.
Preferably, said chain (Rf) is selected from chains of formula:
—[(CF2CF2O)b1(CF2O)b2(CF(CF3)O)b3(CF2CF(CF3)O)b4]— (Rf-I)
wherein:
b1, b2, b3, b4, are independently integers ≥0 such that the number average molecular weight is between 400 and 20,000, preferably between 1,000 and 10,000; preferably b1 is 0, b2, b3, b4 are >0, with the ratio b4/(b2+b3) being ≥1;
—[(CF2CF2O)c1(CF2O)c2(CF2(CF2)cwCF2O)c3]— (Rf-II)
wherein:
cw=1 or 2;
c1, c2, and c3 are independently integers ≥0 chosen so that the number average molecular weight is between 400 and 20,000, preferably between 1,000 and 10,000; preferably c1, c2 and c3 are all >0, with the ratio c3/(c1+c2) being generally lower than 0.2;
—[(CF2CF(CF3)O)d]— (Rf-III)
wherein:
d is an integer >0 such that the number average molecular weight is between 1,000 and 20,000, preferably between 400 and 10,000;
—[(CF2O)c2(CF2(CF2)cwCF2O)c3]— (Rf-IV)
wherein:
cw=1 or 2;
c2 and c3 are independently integers ≥0 chosen so that the number average molecular weight is between 400 and 20,000, preferably between 1,000 and 10,000; preferably the ratio c3/c2 is generally lower than 0.2;
—[(CF2CF2C(Hal*)2O)e1—(CF2CF2CH2O)e2—(CF2CF2CH(Hal*)O)e3]— (Rf-V)
wherein:
Good results have been obtained when said chain (Rf) comprises at least one recurring unit comprising 3 carbon atoms.
According to a particularly preferred embodiment, said chain (Rf) complies with formulae (Rf-VI-a) to (Rf-VI-c):
—[(CF2CF(CF3)O)f1—(CF2O)f2]— (Rf-VI-a)
wherein
f1 and f2, are independently integers ≥0 such that the number average molecular weight is between 400 and 20,000, preferably between 1,000 and 10,000; preferably both f1 and f2 are integers higher than 0, with the ratio f1/f2 being 1, more preferably higher than 1;
—(CF(CF3)CF2O)f3— (Rf-VI-b)
wherein
f3 is an integer higher than 0, such that the number average molecular weight is between 400 and 20,000, preferably between 1,000 and 10,000;
—(CF2CF2CF2O)f4— (Rf-VI-c)
wherein
f4 is an integer higher than 0, such that the number average molecular weight is between 400 and 20,000, preferably between 1,000 and 10,000.
According to a preferred embodiment, said chain (Rpf) has two chain ends comprising perfluorooxyalkyl groups, more preferably comprising from 1 to 3 carbon atoms.
Suitable polymers (P) are commercially available under the trade name Fomblin® from Solvay Specialty Polymers Italy S.p.A., Krytox® from Chemours Co., and Demnum® from Daikin Ind., Ltd.
Preferably, said polymer (F) is selected in the group comprising, more preferably consisting of:
Good results have been obtained by selecting said polymer (F) among perfluoropolymers.
In the present description and in the following claims:
Suitable perfluoropolymers according to the present invention comprise at least one recurring units comprising at least one perfluorinated monomer selected in the group comprising, preferably, consisting of:
(A) cyclic monomers complying with one of the following formulae (A1) to (A3):
wherein each of Rf4, Rf5, Rf6, equal of different each other, is independently a fluorine atom, a C1-C6 perfluoroalkyl group, optionally comprising one or more oxygen atom, e.g. —CF3, —C2F5, —C3F7, —OCF3, —OCF2CF2OCF3;
wherein n is 1 or 2;
wherein n is 1 or 2;
(B) C2-C8 perfluoroolefins, such as tetrafluoroethylene (TFE) and hexafluoropropene (HFP);
(C) CF2═CFORf1, wherein Rf1 is selected from:
(Rf1*) C1-C6 perfluoroalkyl group, such as —CF3, —C2F5, —C3F7; or
(Rf1**) —CF2O(CF2)tORf2
wherein t is an integer equal to 1 or 2 and Rf2 is a linear or branched C1-C6 perfluoroalkyl group, e.g. —CF3, —C2F5, —C3F7; a cyclic C5-C6 perfluoroalkyl group, or a linear or branched C1-C12 (per)fluorooxyalkyl group comprising one or more ether groups, such as —CF2CF2OCF3 and —CF(CF3)OCF3.
According to a first preferred embodiment, said polymer (F) is a copolymer of tetrafluoroethylene (TFE), i.e. it comprises recurring units derived from TFE and recurring units derived from at least one perfluorinated monomer different from TFE [co-monomer (F)].
The term “copolymer” is intended to indicate also TFE terpolymer and TFE tetrapolymer, comprising recurring units derived from TFE and from two and three perfluorinated monomers different from TFE, respectively.
According to a first variant of the first preferred embodiment, said at least one co-monomer (F) is selected from the group consisting of:
wherein each of Rf4, Rf5, Rf6, equal of different each other, is independently a fluorine atom, a C1-C6 perfluoroalkyl group, optionally comprising one or more oxygen atom, e.g. —CF3, —C2F5, —C3F7, —OCF3, —OCF2CF2OCF3; more preferably, Rf4 is —OCF3 or F and Rf5 and Rf6 are both a fluorine atom or both a methyl group;
wherein n is 1 or 2;
wherein n is 1 or 2; and
According to this first variant, polymer (F) preferably comprises more than 50% by moles, more preferably more than 75% by moles of recurring units derived from said at least one co-monomer selected from those of formula (A1) to (A3) above.
According to this first variant, polymer (F) preferably comprises up to 99% by moles, more preferably up to 95% by moles of recurring units derived from said at least one co-monomer selected from those of formula (A1) to (A3) above.
According to this first variant, polymer (F) preferably comprises from 77% by moles to 95% by moles of recurring units derived from said at least one co-monomer selected from those of formula (A1) to (A3) above and recurring units derived from TFE, such that the sum of the percentages of recurring units from said monomer and from TFE is equal to 100% by moles.
According to a second variant of the first preferred embodiment, said at least one co-monomer (F) is selected in the group consisting of:
(C) CF2═CFORf1, wherein Rf1 is selected from:
According to this second variant, polymer (F) preferably comprises more than 5% by moles, more preferably more than 15% by moles of recurring units derived from said at least one co-monomer selected from those of formula (C).
According to this second variant, polymer (F) preferably comprises up to 50% by moles, more preferably up to 45% by moles of recurring units derived from said at least one co-monomer selected from those of formula (C) above.
According to this second variant, polymer (F) preferably comprises from 15% by moles to 45% by moles of recurring units derived from said at least one co-monomer selected from those of formula (C) above and recurring units derived from TFE, such that the sum of the percentages of recurring units from said co-monomer and from TFE is equal to 100% by moles.
According to a second preferred embodiment, said polymer (F) is a homopolymer, i.e. it essentially consists of recurring units of formula (A1)
wherein each of Rf4, Rf5, Rf6, equal of different each other, are as defined above; more preferably, Rf4 is —OCF3 or F and Rf5 and Rf6 are both a fluorine atom or both a methyl group.
According to a third preferred embodiment, said polymer (F) is a homopolymer or copolymer comprising recurring units of formula:
CF2═CFO—CF2O—CF2CF3 (MOVE1); (C**i)
CF2═CFO—CF2O—CF2CF2OCF3(MOVE2); (C**ii)
CF2═CFO—CF2O—CF(CF3)OCF3(MOVE2a); (C**iii)
CF2═CFO—CF2O—CF3 (MOVE3); (C**iv)
and combinations thereof.
Unexpected results have been obtained in the present invention selecting said polymer (F) from polymers commercially available under the trade name of HYFLON® AD, Tecnoflon® PFR-LT (both commercially available from Solvay Specialty Polymers Italy S.p.A.), Teflon® AF (commercially available from Chemours Co.) and Cytop® (commercially available from Cytec Ind. Inc.).
Composition (C) can be prepared according to known techniques of the prior art. Preferably, the composition according to the present invention is prepared by solvent mixing or dry mixing.
According to a first preferred embodiment, at least one polymer (F) is dissolved in at least one solvent [solvent (S)], preferably a (per)fluorinated solvent, and mixed with a stirrer machine.
Said at least one solvent (S) is preferably selected from (per)fluoropolyethers having chemical formula different from the chemical formula of polymer (P) (such as, those commercially available from Solvay Specialty Polymers Italy S.p.A. under the trade name Galden®), perfuoroalkanes (such as, perfuorohexane, perfuoroheptane and the like), hydrofluoroethers, and mixtures thereof.
Then, a heating step is performed at a temperature lower than the solvent (S) boiling point. More preferably, said heating step is performed at a temperature between 20 and 100° C. Even more preferably, said heating step is performed for at least 1 hour.
Then, a cooling step to room temperature is performed, thus obtaining a composition [composition (C)] in the form of a solution comprising said polymer (F) and said at least one solvent (S).
Then, said composition (CA) and at least one polymer (P) are contacted, to form a composition [composition (CAA)] and a mixing step is performed. Preferably, said mixing step is performed at room temperature, more preferably for about 1 hour. Then, said composition (CAA) is heated to remove said at least one solvent (S), preferably by treatment under vacuum, to obtain the composition (C) according to the present invention.
According to a second preferred embodiment, at least one polymer (P) and at least one polymer (F) are first contacted and then mixed together with a stirrer machine. Then, a heating step is performed, at a temperature of about 150-200° C., preferably for more than 1 hour, even more preferably from 2 to 5 hours.
Preferably, said composition (C) comprises at least one polymer (P) in an amount higher than 50 wt. % and up to 99.99 wt. %, more preferably from 60 wt. % to about 99.95 wt. %, even more preferably from 70 to 99.90 wt. % based on the total weight of said composition (C).
Preferably, said composition (C) comprises at least one polymer (F) in an amount of from 0.01 to less than 50 wt. %, more preferably from 0.05 to 40 wt. %, even more preferably from 0.10 to 30 wt. % based on the total weight of said composition (C).
According to a particular preferred embodiment, said composition (C) comprises at least one polymer (F) in an amount of from 0.1 to 20 wt. % based on the total weight of said composition (C).
Composition (C) according to the invention has a viscosity in the range from 100 mm2/s to 2,000,000 mm2/s—measured at 20° C. according to standard methods, such as ASTM D445, or with a dynamical mechanical spectrometer Anton Paar MCR 502 rheometer equipped with parallel plates 25 mm, at 1 rad/s and at 25° C.
Compositions (C) according to the present invention can further comprise additional ingredients, selected in the group comprising heat-resistance improving agents, anti-oxidant agents, anti-wear agents and the like.
Typically, each of the additional ingredients is added to the composition in an amount from 0.0001 wt. % and up to 5 wt. % based on the total weight of composition (C).
Advantageously, composition (C) according to the present invention can be used as hydraulic fluid in viscous couplings, shock absorbers, pumps, brake cylinders; damping media in speed regulators, fluid clutches (e.g., for fans), nautical and aero-nautical instruments, gyro-compasses, shock-absorbing struts, recording instruments, time regulators, pneumatic valves, overload relays, sound pickups; lubricants; release agents
According to a preferred embodiment, composition (C) is used as working fluid within a viscous coupling.
Viscous couplings are mechanical devices typically composed of a housing, a hub and several tens of thin annular plates attached to each of the housing and the hub. When composition (C) according to this invention is used, a viscous coupling is provided also comprising said composition (C) within the housing.
According to a preferred embodiment, composition (C) is used as working fluid within a damper device.
Suitable damper devices are selected in the group comprising dash pots; shock absorbers such as twin-tube or mono-tube shocks absorbers, positive sensitive damping (PSD) shock absorbers, acceleration sensitive damping (ASD); rotary dampers; tuned mass dampers; viscous couplings; viscous fan clutches and torsional viscous dampers.
Typical apparatus wherein the damper devices can be used are selected in the group comprising: mechanical or electric device for wheeled vehicles (such as suspensions installations, carburettors, internal combustion devices, engines, transmissions, crankshafts), for work boats (such as engines), for aircrafts and spacecraft (such as aircraft carrier decks), for power transmission lines, for wind turbine, for consumer electronics (such as mobile phones and personal computers), for off-shore rig, for oil & gas distribution systems (such as pumps); compressors (such as reciprocating compressors for gas pipelines); devices for buildings and civil structures (such as bridges, towers, elevated freeways).
According to another embodiment, the present invention relates to a method for increasing the viscosity of at least one polymer (P) as defined above, said method comprising contacting said at least one polymer (P) with at least one polymer (F) as defined above.
Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.
The invention will be herein after illustrated in greater detail by means of the Examples contained in the following Experimental Section; the Examples are merely illustrative and are by no means to be interpreted as limiting the scope of the invention.
Materials
Base oils 1 to 3, Polymers A to E and Galden®HT55 perfluoropolyether polymer were obtained from Solvay Specialty Polymers Italy S.p.A.
Base oil (P1): Fomblin®Y06 PFPE branched PFPE oil having the following chemical formula:
CF3O—[(CF2CF(CF3)O)m—(CF2O)n]—CF3
with m/n=40/1 and average molecular weight of about 1,800 Da.
Base oil (P2): Fomblin®YPL1500 PFPE branched PFPE oil having the following chemical formula:
CF3O—[(CF2CF(CF3)O)m—(CF2O)n]—CF3
with m/n=40/1 and average molecular weight of about 6,600 Da.
Base oil (P3): Fomblin® PFPE branched PFPE oil having the following chemical formula:
CF3O—[(CF2CF(CF3)O)m—(CF2O)n]—CF3
with m/n=40/1 and average molecular weight of about 8,500 Da.
Polymer (FA): Tecnoflon® PFR LT
low temperature perfluoroelastomer
Polymer (FB): Hyflon® AD 40L
amorphous perfluorinated copolymers of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxide(TTD) and tetrafluoroethylene (TFE)
having glass transition temperature (measured according to ASTM D3418) of 95° C. and intrinsic viscosity (measured according to ASTM D2857) of 0.40 dl/g at 30° C.
Polymer (FC): Hyflon® AD 40H
amorphous perfluorinated copolymers of 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxide (TTD) and tetrafluoroethylene (TFE)
having glass transition temperature (measured according to ASTM D3418) of 95° C. and intrinsic viscosity (measured according to ASTM D2857) of 1.3 dl/g at 30° C.
Polymer D: Algofon® L203
PTFE powder
Polymer E: Hylar® 5000
PVDF powder
Methods
The kinematic viscosity at a given temperature was determined according to ASTM D445 using a Cannon-Fenske capillary viscosimeter.
Viscosity index (VI) was determined according to ASTM D2270.
The compositions according to the invention were prepared according to the following procedure.
Each of Polymer FA, FB and FC in the amount provided in the following
Table was weighed and dissolved in a glass flask, with 40 g of Galden®HT55 as solvent. The mixture was put under stirring at 40° C. for one hour. At the end of the stirring, the mixture was analysed by visual inspection. The solution was homogeneous.
Then, 98 g of Base Oil P3 were added and the mixture was heated to the solvent reflux under stirring (700 rpm) for one hour. The solution thus obtained, which appeared clear and homogeneous, was heated up to 150° C. under vacuum in order to remove the solvent.
The final composition consisted of a single phase clear, viscous and sticky.
This compositions was submitted to further characterization and analysis.
All the compositions according to the invention were prepared following the procedure described above, by using the Base Oils, the Polymers provided in the following Table 1.
As comparison, Table 1 also shows the properties of each of the Base Oils.
As further comparison, compositions comprising Base Oil (P3) and each of polymer D and polymer E were prepared following the same procedure described above for the compositions according to the invention.
The compositions thus obtained were analysed by visual inspection and found to be completely opalescent.
The compositions thus obtained were centrifuged for about 5 minutes in order to improve their mixing. After this centrifugation, two phases appeared showing a separation between the solid polymer and the Base Oil.
Due to this phase separation, the kinematic viscosities could not be measured and viscosity index could not be calculated.
Further analysis demonstrated that the two phases comprised the raw components.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17164462.8 | Apr 2017 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/058288 | 3/30/2018 | WO | 00 |
