(PER)fluoropolyether polymer composition

Abstract

The present invention relates to a composition comprising at least one perfluoropolyether (PFPE) polymer and hydrogen-containing compounds, and to its use as lubricant in several industries, including vacuum systems.

Description

Description(Per)fluoropolyether polymer compositionPriority

[0001] This application claims priority filed on 2 July 2024 in Europe with Nr. EP24185891.9, the whole content of this application being incorporated herein by reference for all purposes.Technical field

[0002] The present invention relates to a composition comprising at least one perfluoropolyether (PFPE) polymer and hydrogen-containing compounds, and to its use as lubricant in several industries, including vacuum systems.Background

[0003] Synthetic lubricants containing fluorine atoms are traditionally used as lubricants, in particular for vacuum pumps, as they exhibit lubricating performance together with outstanding resistance to oxidation, to heat and to a variety of chemicals, and low vapor pressure. Indeed, a lubricant with low vapor pressure minimizes the risk of contamination in the vacuum system due to the lubricant vaporizing.

[0004] The primary role of perfluoropolyether (PFPE) lubricants in vacuum pumps is to reduce friction between moving parts, minimizing wear and extending the life of the pump. This is particularly important in rotary vane, piston, and other types of mechanical vacuum pumps where metal-to-metal contact occurs.

[0005] At the end of their life, when such lubricants have to be discarded, they are contaminated and incorporate various materials, such as abrasive powder of the vacuum pumps and other contaminants deriving from the use of the oil, such as hydrogen-containing compounds (e.g. paraffins, solvents, etc.). Such discarded lubricants usually have a brown-black appearance and have a modified viscosity compared to the starting lubricant.

[0006] Moreover, PFPE lubricants often contain additives for improving their performance, e.g. to improve anti-corrosion, anti-wear or low-friction properties, which may be PFPE-based additives. This makes the regeneration of exhausted PFPE oils challenging.

[0007] The issue of providing regenerated oils has been already faced in the art, for example in US 4,597,882 (in the name of Tokyo Denshi Kagaku Co., Ltd.), US 4,591,444, US 4,996,368, EP 0214672 and US 2010 / 126934.Summary of the invention

[0008] The Applicant dedicated many efforts to develop new perfluoropolyether (PFPE) polymers that can be advantageously used as lubricants, in particular for vacuum pumps.

[0009] Surprisingly, the Applicant developed a new composition comprising at least one (per)fluoropolyether (PFPE) polymer, preferably a perfluoropolyether (PFPE) polymer, and hydrogen-containing compounds in an amount from 10 ppm to 500 ppm, preferably from 10 ppm to 250 ppm, more preferably from 10 ppm to 150 ppm, even more preferably from 10 ppm to 75 ppm, expressed as ppm of hydrogen atoms, based on the total weight of the composition.

[0010] Even more surprisingly, the Applicant found that the above mentioned composition can be advantageously prepared using a process that can be easily put in place, with energy savings.

[0011] Advantageously, such composition can be used as lubricant, for example for vacuum pumps, without the need for further removal of the residual hydrogen content, which does not provide any drawback to the lubricated apparatus, such as a vacuum pump.

[0012] The Applicant has also found that the above composition can be prepared in an environmental-friendly way by adequately treating exhausted PFPE oils.Disclosure of the invention

[0013] In the present application:- the acronym ‘PFPE’ is intended to indicate (per)fluoropolyether polymer;- the expression “(per)fluoropolyether polymer” is intended to indicate partially and fully fluorinated polyether polymer;- the expression “perfluoropolyether polymer” is intended to indicate fully fluorinated polyether polymer;- the expression “(perfluorinated” referred to an entity is intended to indicate partially and fully fluorinated entity;- the expression “perfluorinated” referred to an entity is intended to indicate fully fluorinated entity;- the expression “hydrogen-containing compound” is intended to indicate a compound containing one or more C-H bonds; this expression includes both PFPE polymer containing C-H bonds, such as PFPE polymers having hydrogenated chain ends, and non-PFPE compounds containing C-H bonds.

[0014] In the first aspect, the present invention relates to a composition [composition (C)] comprising:(a) at least one (per)fluoropolyether polymer [polymer (P)] having a partially or fully fluorinated backbone, preferably a fully fluorinated backbone, comprising at least recurring units of formula -[CF(CF3)CF2O]- and two chain ends, located at the opposite sides of said backbone, each of said chain ends comprising a (perfluorinated group, preferably a perfluorinated group; and(b) hydrogen-containing compounds, in an amount of from 10 ppm to 500 ppm of hydrogen atoms based on the total weight of composition (C), as measured via1H- NMR.

[0015] Preferably, said polymer (P) has a backbone complying with the following formula: -[(CFX1O)g1(CFX2CFX3O)g2(CF2CF2CF2O)g3(CF2CF2CF2CF2O)g4]- wherein- X1is independently selected from -F and -CF3,- X2, X3, equal or different from each other and at each occurrence, are independently -F, -CF3, with the proviso that at least one of X is -CF3;- g2 is an integer > 0 and- g1 , g3, and g4, equal or different from each other, are independently integers >0, such that g1+g2+g3+g4 is in the range from 2 to 1000, wherein when at least one of g1 , g3 and g4 are different from zero, the recurring units are statistically distributed along the backbone.

[0016] Preferably, said two chain ends comprise a perfluorinated (also referred to as “fully fluorinated”) group, more preferably selected from a perfluorinated linear or branched alkyl chain having from 1 to 3 carbon atoms.

[0017] Preferably, said polymer (P) has a weight average molecular weight of from 1500 to 8000 amu, more preferably from 1800 to 5000 amu, as determined by NMR analysis.

[0018] Preferably, said polymer (P) has a kinematic viscosity at 20°C of from 40 to 8000 cSt, more preferably from 50 to 5000 cSt and even more preferably from 60 to 1000 cSt, as measured according to ASTM D445.

[0019] Preferably, composition (C) of the present invention is obtained via a method comprising the following steps:(I) providing an exhausted composition [composition (c1)] comprising at least one polymer (P) as defined above and at least one hydrogen-containing compound, the composition (c1) having an amount higher than 500 ppm of hydrogen atoms based on the total weight of composition (c1) as determined by1H-NMR;(II) filtering said composition (c1), thus obtaining a first composition;(III) contacting said first composition with activated carbon, thus obtaining a second composition;(IV) contacting said second composition with an ion exchange resin, thus obtaining composition (C).

[0020] Preferably, said step (II) is performed in a pressure filter.

[0021] More preferably, said step (II) is performed using a filter having a pore size from 15 to 0.7 micrometers.

[0022] Preferably, said step (II) of filtering is performed at least once, more preferably at least twice.

[0023] More preferably, when step (II) is performed at least twice, two filters are used having a decreasing pore size. For example, the first step of filtration is performed using a filter having a pore size from 15 to 3 micrometers and the at least second filtration is performed using a filter having a pore size from 10 to 0.7 micrometers.

[0024] Preferably, step (III) is performed at a temperature from about 10°C, more preferably from about 20°C, to about 90°C, more preferably to about 80°C.

[0025] According to a preferred embodiment, step (III) is performed under heating, for example at a temperature from about 40°C to about 80°C.

[0026] Suitable activated carbon for use in the process of the represent invention is for example an internally porous microcrystalline, non-graphitic forms of carbon, having surface area higher than 200, more preferably higher than 500 m2 / g.

[0027] Preferably, such activated carbon is in the form of powder, granules or crystals. More preferably, it is in the form of powder.

[0028] Optionally, step (III) is followed by a step (lll-b) comprising at least one filtration of the composition obtained in step (III).

[0029] Preferably, such step (lll-b) is performed in a pressure filter.

[0030] Preferably, such a filter has a pore size from 15 to 0.7 micrometers, more preferably from 5 to 0.7 micrometers.

[0031] Preferably, step (IV) is performed at a temperature from room temperature, eg. 20°C to about 60°C for example under heating. More preferably, step (IV) is performed at a temperature from 35°C to 60°C.

[0032] Step (IV) can be performed with an anionic or a cationic exchange resin.

[0033] For example, good results were obtained performing step (IV) once using an anionic exchange resin.

[0034] Optionally, step (IV) is followed by a step (IV-b) comprising at least one filtration.

[0035] Preferably, such step (IV-b) is performed in a pressure filter.

[0036] Preferably, such a filter has a pore size from 15 to 0.7 micrometers, more preferably from 5 to 0.7 micrometers.

[0037] According to another embodiment, step (IV) can be performed twice. For example, step (IV) can be performed a first time using an anionic exchange resin and a second time using a cationic exchange resin. Alternatively, step (IV) can be performed a first time using a cationic exchange resin and a second time using an anionic exchange resin.

[0038] When step (IV) is performed twice, each step (IV) can be followed by a filtration step. Such filtration step can be performed using the pressure filter disclosed above.

[0039] Composition (C) of the present invention can be used as such as lubricant.

[0040] Alternatively, composition (C) can be added with suitable additives, for example additives having anti-rust properties, thus obtaining a re-formulated composition [composition (C-r)].

[0041] More preferably, each of said additives is added in an amount from about 0.5 to about 20 wt.% based on the total weight of the composition (C-r).

[0042] Such composition (C-r) can be advantageously used as lubricant, in particular in vacuum pumps.

[0043] Without being bound by any theory, it is believed that the composition (C) according to the present invention contains at least one hydrogen-containing compound deriving from the use of oil, for example as lubricant in the vacuum pumps. The at least one hydrogen-containing compound may also be a PFPE polymer chain containing hydrogen atoms; such species may derive from PFPE-based additives, which are normally polymers having chain ends terminating with functional groupsthat may react and, thus, deteriorate forming C-H bonds during the use of the composition (e.g. as lubricant).

[0044] Thus, in a further aspect, the present invention relates to a method for purifying an exhausted composition comprising at least one polymer (P) as defined above and at least one hydrogen-containing compound, which is a contaminant for said composition or said polymer (P).

[0045] Preferably, said method comprises the steps of:(i) providing an exhausted composition [composition (c1)] comprising at least one polymer (P) as defined above, and at least one hydrogen-containing compound such that the amount of hydrogen is higher than 500 ppm based on the total weight of composition (c1) as determined by1H-NMR;(ii) filtering said composition (c1), thus obtaining a first composition;(iii) contacting said first composition with activated carbon, thus obtaining a second composition;(iv) contacting said second composition with an ion exchange resin, thus obtaining a composition [composition (C)] comprising:(a) a (per)fluoropolyether polymer [polymer (P)] having a partially or fully fluorinated backbone, preferably a fully fluorinated backbone, comprising at least recurring units of formula -[CF (CF3)CF2O]- and two chain ends, at the opposite sides of said backbone, comprising a (perfluorinated group, preferably a perfluorinated group; and(b) at least one hydrogen-containing compound in an amount of from 10 ppm to 500 ppm of hydrogen atoms based on the total weight of composition (C), as measured via1H-NMR.

[0046] Preferably, such exhausted composition is obtained as discharge from at least one pump, more preferably at least one vacuum pump.

[0047] Composition (c1) contains an amount of hydrogen-containing compounds at least higher than 500 ppm, expressed as ppm of hydrogen atoms, based on the weight of the composition as determined by1H-NMR. The upper amount of the hydrogen in composition (c1) is not limited, although it is preferably at most 10000 ppm, preferably at most 5000 ppm.

[0048] Preferably, said step (ii) of filtering is performed at least once, more preferably at least twice.

[0049] Preferably, said step (ii) is performed in a pressure filter.

[0050] More preferably, said step (ii) is performed using a filter having a pore size from 15 to 0.7 micrometers.

[0051] Even more preferably, when step (ii) is performed at least twice, two filters are used having a decreasing pore size. For example, the first step of filtration is performed using a filter having a pore size from 15 to 3 micrometers and the at least second filtration is performed using a filter having a pore size from 10 to 0.7 micrometers.

[0052] Preferably, step (iii) is performed at a temperature from about 10°C, more preferably from about 20°C, to about 90°C, more preferably to about 80°C.

[0053] According to a preferred embodiment, step (III) is performed under heating, for example at a temperature from about 40°C to about 80°C.

[0054] Optionally, step (iii) is followed by a step (iii-b) comprising at least one filtration of the composition obtained in step (iii).

[0055] Preferably, such step (iii-b) is performed in a pressure filter.

[0056] Preferably, such a filter has a pore size from 15 to 0.7 micrometers, more preferably from 5 to 0.7 micrometers.

[0057] Preferably, step (iv) is performed at a temperature from room temperature, eg. 20°C to about 60°C for example under heating. More preferably, step (IV) is performed at a temperature from 35°C to 60°C.

[0058] Optionally, step (iv) is followed by a step (IV-b) comprising at least one filtration.

[0059] Preferably, such step (iv-b) is performed in a pressure filter.

[0060] Preferably, such a filter has a pore size from 15 to 0.7 micrometers, more preferably from 5 to 0.7 micrometers.

[0061] 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.

[0062] The present invention will be now described in more detail with reference to the following examples, whose purpose is merely illustrative and not intended to limit the scope of the disclosure.

[0063] EXAMPLES

[0064] Materials

[0065] Several samples of exhaust PFPE oil used as lubricant in vacuum pumps in different market sectors and industries were obtained, mixed together and treated as follows.The content of hydrogen-containing compounds in the mixture was higher than 500 ppm of hydrogen atoms based on the total weight of the mixture.

[0066] 1 kg of mixture was filtered in a pressure filter on 5 pm PTFE membrane filter and further filtered on 1.2 pm PTFE membrane.

[0067] The oil thus obtained was loaded into a glass flask, equipped with a stirrer, heating oil bath and thermocouple. 10 g of activated carbon in powder form (Norit(R)RX1 ,5 Extra) were added. The mixture was heated at 60°C and kept under stirring for 4 hours. After this time, the flask was cooled at 40°C and the mix was filtered on a 1 .2 pm PTFE membrane in a pressure filter.

[0068] The oil thus obtained was loaded into a glass flask equipped with a stirrer, heating oil bath and thermocouple. The reactor bath was heated to 45°C and stirred at 650 rpm. Once the temperature was reached, 14 g of ion exchange resin (Amberjet(R)4400; - OH form) were added and the mixture was stirred for 5 hours. After that time, the mixture was cooled at about 35°C and the oil was separated by filtration on 1 .2 pm PTFE membrane, thus obtaining 800 g of Composition 1.

[0069] The PFPE oil of Composition 1 complied with the following chemical formula: F3C - { [O-CF(CF3)-CF2]m- [OCF2]n} - OCF3with Mw = 3629 amu (as determined by NMR) and kinematic viscosity at 20°C in the range 200-300 cSt (determined according to ASTM D445).

[0070] Methods

[0071] Kinematic viscosity was determined according to ASTM D445 at the temperatures listed in Table 1.

[0072] Weight loss was measured according to ASTM D2595 at 149°C for 22 hours

[0073] Vapor pressure at 20°C and 100°C was determined according to ASTM D2595.Vapor pressure at a temperature of 200°C and higher was determined using the method reported in M. Bassi; Thermochimica Acta v. 521 (2011) pp. 197-2011.

[0074] The hydrogen content (as ppm of H) was determined by comparing the integrals of all the peaks in the proton spectrum with the integral of an internal standard that was a coaxial capillary tube containing a known concentration in ppm as well as molarity of a known, calibrated hydrofluorinated compound, namely either hexafluoro xylene or 2,2,2-trifluoro ethanol. The capillary tubes employed for the PFPE hydrogen content determination were calibrated against a known concentration of a known compound contained in a 5 mm NMR tube. Namely, the hexafluoroxylene capillary was determined against a known weighed amount of 2,2,2-trifluoroethanol. 2,2,2-trifluoroethanol capillary was determined against a known weighed amount of hexafluoroxylene. In both cases, the calibration was carried out by comparing the respective integrals. The NMR instrument employed for the hydrogen content was a Varian Mercury 300 spectrometer, operating at 282.14 MHz for1H and equipped with a 5-mm auto switchable probe with a single axis (Z) gradient coil configured as 4-nuc mode (1H / 19F / 13C / 31P).

[0075] The results are summarized in the following Table 1 .

[0076] Table 1

[0077] The above results showed that Composition 1 according to the present invention had clear aspect, and properties in terms of kinematic viscosity and weight loss suitable for use as lubricants in vacuum pumps.

[0078] Composition 1 was added with 5 wt.% of Fomblin(R) DA306 / VAC as antirust, thus obtaining Composition (1-r).The tribological properties were measured according to ASTM D6425, at 300N and 50°C. The results are summarized in Table 2.

[0079] Table 2

[0080] The above results showed that Composition (1 -r) had optimal behavior in terms of Coefficient of Friction (CoF) and wear.

Claims

Claims1 . A composition [composition (C)] comprising:(a) at least one (per)fluoropolyether polymer [polymer (P)] having a partially or fully fluorinated backbone, preferably a fully fluorinated backbone, comprising at least recurring units of formula -[CF(CF3)CF2O]- and two chain ends, located at the opposite sides of said backbone, each of said chain ends comprising a (perfluorinated group, preferably a perfluorinated group; and(b) hydrogen-containing compounds, in an amount of from 10 ppm to 500 ppm of hydrogen atom, based on the total weight of composition (C), as measured via1H- NMR.

2. The composition (C) according to Claim 1 , wherein said polymer (P) has a backbone complying with the following formula:-[(CFX1O)g1(CFX2CFX3O)g2(CF2CF2CF2O)g3(CF2CF2CF2CF2O)g4]- wherein- X1is independently selected from -F and -CF3,- X2, X3, equal or different from each other and at each occurrence, are independently-F, -CF3, with the proviso that at least one of X is -CF3;- g2 is an integer > 0 and- g1 , g3, and g4, equal or different from each other, are independently integers >0, such that g1+g2+g3+g4 is in the range from 2 to 1000, wherein when at least one of g1 , g3 and g4 are different from zero, the recurring units are statistically distributed along the backbone.

3. The composition according to Claim 1 or 2, wherein said chain ends of said polymer (P) comprise a perfluorinated group.

4. The composition according to Claim 3, wherein said perfluorinated group is selected from a perfluorinated linear or branched alkyl chain having from 1 to 3 carbon atoms.

5. The composition according to any one of Claims 1 to 4, wherein polymer (P) has a weight average molecular weight of from 1500 to 8000 amu, as determined by NMRanalysis.

6. The composition according to any one of Claims 1 to 5, wherein polymer (P) has a kinematic viscosity at 20°C of from 40 to 8000 cSt, as measured according to ASTM D445.

7. A method for manufacturing composition (C) comprising:(a) at least one (per)fluoropolyether polymer [polymer (P)] having a partially or fully fluorinated backbone, preferably a fully fluorinated backbone, comprising at least recurring units of formula -[CF(CF3)CF2O]- and two chain ends, located at the opposite sides of said backbone, each of said chain ends comprising a (perfluorinated group, preferably a perfluorinated group; and(b) hydrogen-containing compounds, in an amount from 10 ppm to 500 ppm of hydrogen atoms based on the total weight of composition (C), as measured via1H- NMR, said method comprising the steps of:(I) providing an exhausted composition [composition (c1 )] comprising at least one polymer (P) as defined above and at least one hydrogen-containing compound, the composition (c1) having an amount higher than 500 ppm of hydrogen atoms based on the total weight of composition (c1) as determined by1H-NMR;(II) filtering said composition (c1), thus obtaining a first composition;(III) contacting said first composition with activated carbon, thus obtaining a second composition;(IV) contacting said second composition with an ion exchange resin, thus obtaining composition (C).

8. The method according to Claim 7, wherein said step (II) is performed in a pressure filter.

9. The method according to Claim 7 or 8, wherein said step (II) is performed at least twice, with two filters having a decreasing pore size.

10. The method according to any one of Claims 7 to 9, wherein step (III) is performed at a temperature from 10°C to 90 °C.

11. The method according to any one of Claims 7 to 10, wherein said step (III) is followed by a step (lll-b) of filtration of the composition obtained in step (III).

12. The method according to any one of claims 7 to 11 , wherein the exhausted composition [composition (c1 )] is an exhausted pump oil, preferably an exhausted vacuum pump oil.

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