JP2006348292A - Fluorinated lubricant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an additive capable of substantially causing no change of lubrication characteristics of a perfluoropolyether oil, e.g. a dynamic viscosity, vaporization loss, chemical stability and a viscosity index, especially the viscosity index. <P>SOLUTION: The fluorinated lubricant contains a fluid point-decreasing additive of the structure: X<SB>1</SB>-O(CF<SB>2</SB>O)<SB>n</SB>(CF<SB>2</SB>CF<SB>2</SB>O)<SB>m</SB>(CF<SB>2</SB>CF<SB>2</SB>CF<SB>2</SB>O)<SB>p</SB>(CF<SB>2</SB>CF<SB>2</SB>CF<SB>2</SB>CF<SB>2</SB>O)<SB>q</SB>-X<SB>2</SB>(I) [wherein, X<SB>1</SB>and X<SB>2</SB>have each the formula: -(CF<SB>2</SB>)<SB>z</SB>CF<SB>3</SB>(wherein, z is an integer of 0-3); n is an integer of 1-200; m is an integer of 0-200; p and q are each an integer of 0-10; (p+q)/(p+q+m+n)≤0.05; m/n≤0.7; and the molecular weight of (I) is 1,000-10,000]. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to fluorinated derivatives that can lower the pour point temperature of a lubricating oil.
Specifically, the present invention relates to the use of a compound based on perfluoropolyether as an additive that lowers the pour point temperature of a fluorinated oil having a perfluoropolyether structure, and a lubricating composition comprising the additive About.

  In particular, the use of perfluoropolyether oils as lubricants over a wide temperature range is known in the prior art, for example in applications in the aerospace and refrigeration industries where excellent lubricity is required at very low temperatures. Among the commercially available lubricants having a perfluoropolyether structure, Solvay Solexis S. is used as a lubricant at a temperature lower than −80 ° C. Pee. A. Fomblin (FOMBLIN®) marketed by (Solvay Solexis S.p.A.). The low temperature lower limit for fluorinated and non-fluorinated lubricants is related to the temperature corresponding to the fluidity of the lubricant, where it is difficult to transfer the lubricant itself and is therefore powerful to use. Requires energy. In fact, in non-fluorinated oils, crystallization occurs in relation to the pour point, while in fluorinated oils, such as perfluoropolyether, a sudden increase in viscosity is observed.

  It is also known to use a pour point depressant additive to lower the pour point. For example, non-fluorinated additives have been developed for hydrogenated paraffins, mineral oils and petroleum. In general, such additives are hydrogenated polymers that are miscible with lubricating oils that prevent the oil from crystallizing as the temperature decreases without changing the lubricating properties. Examples of the additive are polyalkyl methacrylates, polyacrylates, and phthalates. For example, International Patent Application No. WO 89/01507 (Patent Document 1) discloses a polymethacrylate having a molecular weight in the range of 10,000 to 300,000 for lowering the pour point of paraffinic oil to about -35 ° C. It describes the use of "pour point depressing" additives consisting of rates.

International patent application WO 89/01507

However, the use of non-fluorinated additives in fluorinated oils, such as perfluoropolyether oils, is not feasible because the additive is immiscible with the fluorinated lubricant.
In the field of fluorinated oils, especially perfluoropolyether oils, “pour point depressing” additives that can lower the pour point are not available on the market.

Therefore, to extend the low temperature thermal rating of the fluorinated lubricant, preferably perfluoropolyether lubricant:
-Can lower the pour point of fluorinated lubricants, especially perfluoropolyether oils;
-Soluble in fluorinated oils, especially perfluoropolyether oils;
-Do not substantially change the lubricating properties of fluorinated oils, especially perfluoropolyether oils, such as kinematic viscosity, evaporation loss, chemical stability, viscosity index, in particular do not change the viscosity index;
There was an urgent need to be able to obtain an additive that could do this.

  The Applicant has unexpectedly and surprisingly made it possible for the addition of certain fluorinated compounds to perfluoropolyether oils to lower the pour point temperature of the oils described above. It has been found that it is possible to solve technical problems.

The following structure:
X ₁ -O (CF ₂ O) _n (CF ₂ CF ₂ O) _m (CF ₂ CF ₂ CF ₂ O) _p (CF ₂ CF ₂ CF ₂ CF ₂ O) _q -X ₂ (I)
[Where:
- repeating structural unit _{-CF 2 O -, - CF 2} CF 2 O -, - CF 2 CF 2 CF 2 O -, - CF 2 CF 2 CF 2 CF 2 O- are distributed statistically along the chain And
-X ₁ and -X ₂ are equal or different from each other and are perfluoroalkyl chain end groups having the formula:-(CF ₂ ) _z CF _3, where z is an integer from 0 to 3. Yes;

-N is an integer between 1 and 200;
-M is an integer between 0 and 200;
-P and q are integers of 0-10, preferably 0-5, more preferably 0 or 1, even more preferably 0;

However;
The ratio (p + q) / (p + q + m + n) is less than or equal to 0.05 and may be 0, where (p + q + m + n) is different from 0;
The ratio m / n is less than or equal to 0.7 when n is different from 0, preferably lower than 0.5, more preferably lower than 0.35;
-The number average molecular weight of the compound (I) ranges from 1,000 to 10,000, preferably from 2,000 to 8,000, more preferably from 2,400 to 5,000.
It is an object of the present invention to use a compound having a pour point depressant additive for fluorinated oils, preferably perfluoropolyether oils.

^{In 19} F-NMR analysis, the additive of the present invention does not show a chlorine atom and is substantially absent.
For a compound of the formula (I) measured by ¹⁹ F-NMR and having substantially no chlorine atom, it means that the compound has a lower chlorine atom than the detection limit of the ¹⁹ F-NMR analysis method.

  The lubricating compositions of the present invention having a pour point below -95 ° C are particularly beneficial in aerospace and refrigeration industry applications; this low pour point is improved with respect to commercially available perfluoropolyether oils. ing.

Additives of formula (I) are fluorinated oils, preferably have a kinematic viscosity at 20 ° C. of 10 to 4,000 cSt, preferably 30 to 2,000 cSt, and one or more of the following repeating structural units : -CFXO- (where X is F or CF ₃ ; -CF ₂ CF ₂ O-,-(C ₃ F ₆ O)-, -CF ₂ CF ₂ CF ₂ O-, -CF ₂ CF ₂ CF Equal to ₂ CF ₂ O— and the structural units are statistically distributed along the main chain).

The perfluoropolyether oils are preferably selected from the following class:
_{(1) EO- (CF 2 CF} (CF 3) O) m '(CFXO) n' -E '
[Where:
X is equal to F or CF ₃
E and E ′ are equal to or different from each other and are selected from CF ₃ , C ₂ F ₅ or C ₃ F _7, and one fluorine atom of one or both terminal groups is substituted with Cl and / or H And
m ′ and n ′ are integers such that the ratio m ′ / n ′ is between 20 and 1,000; n ′ is different from 0; these building blocks are statistically along the main chain Distributed]
The kinematic viscosity of this substance is within the above range.

  These polymers can be obtained by perfluoropropene photooxidation as described in British Patent GB 1,104,432 and then by end group transformation as described in British Patent GB 1,226,566. .

(2) C ₃ F ₇ O (CF (CF ₃ ) CF ₂ O) _{o '} -D
[Where:
D is equal to —C ₂ F ₅ or —C ₃ F ₇ and one fluorine atom of one or both end groups is substituted with Cl and / or H;
o ′ is an integer such that the kinematic viscosity of the substance is within the above range].

  These polymers can be prepared by ionic oligomerization of perfluoropropylene oxide and subsequent treatment with fluorine as described in US Pat. No. 3,242,218.

(3) {C ₃ F ₇ O- (CF (CF ₃ ) CF ₂ O) _{p '} -CF (CF ₃ )-} ₂
[Where:
p ′ is an integer such that the kinematic viscosity of this material is within the above range, one F of one or both end groups C ₃ F ₇ is substituted with Cl and / or H].
These materials can be produced by ionic telomerization of perfluoropropylene oxide followed by photochemical dimerization as described in US Pat. No. 3,214,478.

_{(4) EO- (CF 2 CF} (CF 3) O) q '(C 2 F 4 O) r' (CFX) s '-E'
[Where:
X is equal to F or CF ₃ ;
E and E ′ are equal to or different from each other and are as described above;
q ′, r ′, and s ′ are integers such that 0 is included and the kinematic viscosity of the material is within the above range].
These materials can be produced by photooxidation of a mixture of C ₃ F ₆ and C ₂ F ₄ and subsequent treatment with fluorine as described in US Pat. No. 3,665,041.

(5) EO- (C ₂ F ₄ O) _{t '} (CF ₂ O) _u' -E '
[Where:
E and E ′ are equal to or different from each other and are as described above;
t ′ and u ′ are integers such that the ratio t ′ / u ′ is between 0.1 and 5, u ′ is different from 0]. The kinematic viscosity of this substance is within the above range.
These polymers can be made by photooxidation of C ₂ F ₄ as described in US Pat. No. 3,715,378 and subsequent treatment with fluorine as described in US Pat. No. 3,665,041. .

(6) EO- (CF ₂ CF ₂ CF ₂ O) _{v '} -E'
[Where:
E and E ′ are equal to or different from each other and are as described above;
v ′ is a number such that the kinematic viscosity of the substance is within the above range].
These polymers are obtained as described in EP 148,482.

(7) DO- (CF ₂ CF ₂ O) _{z '} -D'
[Where:
D and D ′ are equal to or different from each other and are selected from C ₂ F ₅ and C ₃ F ₇ , wherein one fluorine atom of one or both end groups is substituted with Cl and / or H;
z ′ is an integer such that the kinematic viscosity of the substance is within the above range].
These polymers can be obtained as described in US Pat. No. 4.523,039.

(8) E ₁ -O- (CF ₂ O) _n (CF ₂ CF ₂ O) _m- (CF ₂ CF ₂ CF ₂ O) _p- (CF ₂ CF ₂ CF ₂ CF ₂ O) _q -E ₂
[Where:
E ₁ and E ₂ are equal to or different from each other and are perfluoroalkyl end groups having the formula — (CF ₂ ) _z CF _3, where z is an integer from 0 to 3;
n, m, p, and q are integers that are equal to or different from each other and included between 0 and 100, and are selected such that the kinematic viscosity of the oil is within the above range, and the ratio m / n Is an integer such that it is between 2 and 20, n is different from 0; (p + q) / (n + m + p + q) is between 0.05 and 0.2, and (n + m + p + q) is different from 0; n / (N + m + p + q) is between 0.05 and 0.40, and (n + m + p + q) is different from 0].

These polymers can be obtained according to EP 1,454,938.
Preferred perfluoropolyether oils are of class (1), (4), (5), (8) or mixtures thereof and are marketed as Fomblin® marketed by Solvay Solexis. Available and of class (2), (6).

  The additives according to the invention are used in amounts ranging from 0.1 to 30% by weight, preferably from 1 to 20% by weight, more preferably from 5 to 10% by weight, with respect to the final composition.

Further objects of the invention are:
A) at least one fluorinated oil, preferably having a kinematic viscosity at 20 ° C. of between 10 and 4,000 cSt, preferably between 30 and 2,000 cSt, and one or more of the following repeating structural units: —CFXO - (wherein, X is, F or _{CF 3); - CF 2 CF} 2 O -, - (C 3 F 6 O) -, - CF 2 CF 2 CF 2 O -, - CF 2 CF 2 CF 2 CF 70 to 99.9% by weight of a perfluoropolyether oil comprising ₂ O-, the building blocks statistically distributed along the main chain; and

B) 0.1-30% by weight of at least the additive of formula (I);
A lubricating composition comprising

  In the composition mixtures of these perfluoropolyether oils, mixtures of additives of general formula (I) can be used.

  Particularly preferred are additives of formula (I) and at least one oil of class (1) and (5); a composition comprising class (5) oils having a kinematic viscosity at 20 ° C. of between 30 cSt and 300 cSt. Further preferred.

  The lubricating composition of the present invention exhibits a lower pour point than that of the non-added oil.

  Lubricating compositions of the present invention having a pour point below -95 ° C are particularly beneficial in aerospace applications; this low pour point is an improvement over commercially available perfluoropolyether oils.

  The compositions of the present invention exhibit a pour point temperature, preferably a pour point temperature that is at least 4 ° C. lower with respect to one of the perfluoropolyether lubricants contained therein, and at least 5% with respect to the pour point temperature of the non-added oil. (See comparative example).

  Furthermore, the composition of the present invention is clear as it has been found that the additive of formula (I) is completely soluble in perfluoropolyether oils, and therefore the composition is thermodynamic. Stable. This is particularly advantageous as there are no phase separation problems during storage.

  The lubricating composition of the present invention can also contain additives commonly used in perfluoropolyether oils such as, for example, rust inhibitors, antiwear agents, antioxidant additives and heat stabilizers.

  As noted above, the use of the lubricating composition of the present invention can be applied where lubrication capacity is required at very low operating temperatures, for example in aerospace applications, in refrigeration, and in equipment under vacuum used at low temperatures. It is especially beneficial.

  Moreover, the Applicant believes that the additive of the present invention is liquid at a temperature of 20 ° C., has a low vapor pressure, and has a high viscosity index and lower than −90 ° C., preferably lower than −95 ° C. It has also been found that the pour point is preferably lower than -100 ° C. Thus, the additive can itself be used as a lubricating oil.

  A further object of the present invention is the use of compound (I) as a lubricating oil having a low pour point.

A compound of formula (I) can be prepared, for example, according to the following method comprising the following steps:
a) Synthesis of perfluoropolyether peroxide obtainable by one of the following reactions:

a1) at a temperature between −40 ° C. and −100 ° C., which is liquid under the reaction conditions, the formula:
C _y F _{(2y + 2-x)} H _x (II)
(Wherein y is an integer from 2 to 4 and x is an integer equal to 0 or 1)
Photo-oxidation of tetrafluoroethylene (TFE) in the presence of UV light in the presence of elemental fluorine as a chain transfer agent diluted with an inert gas in a solvent of
Or

a2) Fluorine or formula by operation in a temperature range of −40 ° C. to −100 ° C. in an inert solvent at a pressure between 0 and 12 bar.
R _f OF (III)
(Wherein R _f is a perfluoroalkyl group having 1 to 3 carbon atoms)
TFE oxidation using the following hypofluorites as radical initiators.
Preferably a2) is used;

b) the peroxide obtained in step a) at a temperature of 150 ° C. to 250 ° C. in the presence of any element of fluorine and a chain transfer agent selected from one or more hypofluorites of the formula (III) Processing;

c) Treatment of the polymer obtained in step b) with elemental fluorine at a temperature between 100 ° C. and 250 ° C. or with fluorine by operating at a temperature between −50 ° C. and 120 in the presence of UV irradiation. processing.

Generally in step a1), fluorine, the molar ratio fluorine / tetrafluoroethylene is between ^{1.2 × 10 -3 ~2 × 10 -2} , preferably 1.7 × 10 ^-3 ~1.2 × 10 ^- It is added in such an amount that is between ² , and diluted with an inert gas having a volume ratio of 1 / 1.000 to 1/50.

In step a1), preferred solvents are: perfluoropropane (C ₃ F ₈ ), hydropentafluoroethane (C ₂ F ₅ H) and 2-hydroheptafluoropropane (CF ₃ CFHCF ₃ ), C ₄ F ₉ H (for example, CF ₃ CFHCF ₂ CF ₃ , (CF ₃ ) ₃ CH, HCF ₂ CF ₂ CF ₂ CF ₃ ).

  The solvent used in step a1) is liquid at the synthesis temperature (−40 ° C. to −80 ° C.) and dissolves even polymeric polymer peroxides forming a homogeneous solution. This represents a notable advantage since there is no separation of the polymer peroxide. This allows the industrial use of the method since there is no clogging of the factory piping due to uncontrolled increase in viscosity. In addition, heat exchange is very effective, which prevents the occurrence of unutilized degradation of the polymer peroxide.

  Furthermore, the solvent used in step a1) allows high reaction kinetics and high production coupled with a low content of peroxide in the polymer lower than (active oxygen 4-5 g) / (product 100 g). It is possible to maintain the sex and avoid the danger of explosion.

  As mentioned above, the fluorine used in step a1) must be diluted with gas. In general, an inert gas such as nitrogen or helium is used. Oxygen can also be used as a diluent. In fact, when undiluted fluorine is used, the fluorine will cause uncontrolled local reactions and gaseous decomposition products. The latter results in process termination due to reactor and optical system (UV lamp) deposits in the case of polymerization in the presence of UV radiation. Moreover, in these cases, an uncontrolled increase in P.O. higher than (active oxygen 4-5 g) / (product 100 g) can occur, resulting in an explosion risk for the system. If it is used diluted, fluorine in step a1) acts as a chain transfer agent with a very high selectivity on the order of 90%. Further, in step a1), fluorine avoids the use of reactive activators, shortens the reaction induction time and is substantially eliminated.

In step a2), the TFE oxidation is carried out without using UV light, and the solvent can be the one described above or a chlorinated solvent. For example, CF ₂ Cl ₂ which may optionally be in a mixture with COF ₂ may be mentioned.

  In step a2), the molar ratio TFE / chemical initiator ranges from 10 to 200, preferably from 40 to 120.

  In step a2), the use of a chain transfer agent can be omitted if control of the molecular weight is not necessary. This occurs, for example, when the peroxidized product has a kinematic viscosity at 20 ° C. of less than 5,000 cSt.

In step b), in general, the fluorine or hypofluorite of formula (III), if present, is 1 × 10 ^{−2 to} 3 mol · hour / Kg polymer, preferably 2 × 10 ⁻² to 2 Used at a flow rate of mole · hour / Kg polymer.

  Steps a) and b) of the process according to the invention can be carried out in a discontinuous, semi-continuous or continuous manner.

  Step b) ends when there is substantially no peroxide content in the polymer. This has a P.O. value below the detection limit (1 ppm) of the analytical method used which exists in the titration of iosulfate with iodine generated by the reaction of polymer peroxide with sodium iodide. In general, the heat treatment time is 10 to 30 hours, depending on P.O. and the temperature used in this step.

Step c) is usually performed in a discontinuous manner. This reaction is terminated in ¹⁹ F-NMR analysis when functional end groups (mainly -OCF ₂ COF and -OCOF) are converted to perfluoroalkyl end groups (method detection limit: 1 meq ( eq) / Kg polymer).

In step c), the fluorine is generally supplied in an amount such that it has a concentration in the perfluoropolyether corresponding to the solubility limit of fluorine. At the temperature used in this process, it is on the order of (10 ⁻² mol of fluorine) / liter of polymer.

Optionally, the product can be distilled to obtain a fraction having a given number average molecular weight and the molecular weight distribution determined.
Several illustrative but non-limiting examples of the present invention continue.

Characterize :
-Pour point temperature measurement:
Performed using the ASTM D 97 method.
The results listed are the average of 5 tests.

-Kinematic viscosity measurement:
Performed according to ASTM D 445 method.
-Measurement of the viscosity index:
Performed according to ASTM D 2270 method. The higher the viscosity index, the lower the viscosity change with respect to the temperature change.

Example 1
A perfluoropoly of class (5), known for commercial use under the name Fomblin® Z25, having a kinematic viscosity at 20 ° C. of 255 cSt, a viscosity index equal to 356 and a pour point of −74 ° C. To 95 g of ether was added 5 g of an additive of formula (I) having a number average molecular weight of 2,467, m / n = 0.33 and p + q / (p + q + m + n) = 0.016.

The pour point of the resulting composition is determined according to the method described above and is equal to -82 ° C. The viscosity index of the composition is equal to 348.
Thus, the resulting lubricating composition exhibits a pour point 8 ° C. lower than that of the base perfluoropolyether oil, corresponding to a pour point temperature decrease of about 11%.

  The addition of the additive (I) of the present invention to the perfluoropolyether oil does not change the lubricating properties, because the viscosity index of the resulting lubricating composition is substantially equal to that of the base oil, It should be noted.

Example 2
Example 1 was repeated using an additive of formula (I) having a number average molecular weight of 3,777, m / n = 0.31 and p + q / (p + q + m + n) = 0.016.
The pour point of the resulting mixture is determined according to the method described above and is equal to −80 ° C.
The resulting lubricating composition thus exhibits a pour point 6 ° C. lower than that of the base perfluoropolyether oil, corresponding to a pour point temperature reduction of about 8%.

Example 3 (comparison)
Example 1 was repeated using a compound having the formula (I) and a number average molecular weight of 4,000 but having m / n = 0.8 as an additive.
The pour point of the resulting mixture is determined according to the method described above and is equal to -76 ° C.
Thus, the resulting lubricating composition exhibits a pour point that is 3 ° C. lower than that of the base perfluoropolyether oil. Such temperature fluctuations correspond to a reduction of about 3%.

Example 4
It has a kinematic viscosity of 30 cSt at 20 ° C., a pour point of −93 ° C., and is known for commercial use under the name of Fomblin (registered trademark) Z03. 10 g of additive having the formula (I) with a molecular weight of 2,467, m / n = 0.33 and p + q / (p + q + m + n) = 0.016 were added.
The pour point of the resulting mixture is determined by the above method and is equal to -102 ° C.
The resulting lubricating composition thus exhibits a pour point that is 11 ° C. lower than that of the base perfluoropolyether oil, corresponding to a pour point temperature reduction of about 10%.

Example 5
Example 1 was repeated using an additive having the formula (I) where the number average molecular weight was 3,777, m / n = 0.31 and p + q / (p + q + m + n) = 0.016.
The pour point of the resulting mixture is determined by the above method and is equal to -99 ° C.
Thus, the lubricating composition of this example exhibits a pour point 6 ° C. lower than that of the base perfluoropolyether oil, corresponding to a pour point temperature reduction of about 6%.

Example 6
Perfluoropolyether oil of structure (6) having a kinematic viscosity of 53 cSt and a pour point of −75 ° C. determined by the method described above, known commercially as Demnum® S-20 Example 1 was repeated using as a lubricant.
The pour point of the resulting mixture is determined by the above method and is equal to -79 ° C.
The resulting lubricating composition thus exhibits a pour point 4 ° C. lower than that of the base perfluoropolyether oil, corresponding to a reduction of about 6%.

Example 7 (comparison)
Example 6 was repeated using as a additive a compound having the formula (I) and a number average molecular weight of 4,000 but m / n = 0.8.
The pour point of the resulting mixture is determined by the above method and is equal to -75 ° C.
Thus, the resulting lubricating composition exhibits a pour point equal to that of the base perfluoropolyether oil.

Example 8
A perfluoropolyether oil of structure (6) having a kinematic viscosity of 500 cSt and a pour point of −53 ° C. determined by the above method and known for commercial use as demnum (registered trademark) S-200 is a lubricating oil. Example 4 was repeated using
The pour point of the resulting mixture is determined by the above method and is equal to −63 ° C.
The resulting lubricating composition thus exhibits a pour point 10 ° C. lower than that of the base perfluoropolyether oil, corresponding to a reduction of about 19%.

Example 9
Lubricate perfluoropolyether oil of structure (2) having a kinematic viscosity of 60 cSt and a pour point of −47 ° C. determined by the above method and known commercially as Krytox® 1506 Example 1 was repeated using as an agent.
The pour point of the resulting mixture is determined by the above method and is equal to -51 ° C.
The resulting lubricating composition thus exhibits a pour point 4 ° C. lower than that of the base perfluoropolyether oil, corresponding to a 9% reduction.

Example 10
Example 9 was repeated using 90 g of oil and 10 g of additive, changing the mixture composition.
The pour point of the resulting mixture is determined by the above method and is equal to -56 ° C.
The resulting lubricating composition thus exhibits a pour point 9 ° C. lower than that of the base perfluoropolyether oil, corresponding to a 19% reduction.

Example 11
The additive of Example 1 was characterized and the following properties were obtained:
-Kinematic viscosity at 20 ° C: 13 cSt;
Kinematic viscosity at −60 ° C .: 344 cSt;
-Viscosity index: 381;
Pour point: −111 ° C .;

  From the above data it is clear that the compounds of formula (I) can themselves be used as lubricating oils in applications where lubrication is required at very low temperatures.

  Lubricating compositions of the present invention having a pour point below -95 ° C are particularly beneficial in aerospace applications; this low pour point is an improvement over commercially available perfluoropolyether oils. The compounds of formula (I) can also be used as lubricating oils in applications that themselves require lubrication at very low temperatures.

Claims (11)

The following structure:
X ₁ -O (CF ₂ O) _n (CF ₂ CF ₂ O) _m (CF ₂ CF ₂ CF ₂ O) _p (CF ₂ CF ₂ CF ₂ CF ₂ O) _q -X ₂ (I)
[Where:
- repeating structural unit _{-CF 2 O -, - CF 2} CF 2 O -, - CF 2 CF 2 CF 2 O -, - CF 2 CF 2 CF 2 CF 2 O- are distributed statistically along the chain And
-X ₁ and -X ₂ are equal or different from each other and are perfluoroalkyl chain end groups having the formula:-(CF ₂ ) _z CF _3, where z is an integer from 0 to 3. Yes;
-N is an integer between 1 and 200;
-M is an integer between 0 and 200;
-P and q are integers of 0-10, preferably 0-5, more preferably 0 or 1, even more preferably 0;
However;
The ratio (p + q) / (p + q + m + n) is less than or equal to 0.05 and may be 0, where (p + q + m + n) is different from 0;
The ratio m / n is less than or equal to 0.7 when n is different from 0, preferably lower than 0.5, more preferably lower than 0.35;
-The number average molecular weight of the compound (I) ranges from 1,000 to 10,000, preferably from 2,000 to 8,000, more preferably from 2,400 to 5,000.
And a compound substantially free of chlorine atoms in the compound of formula (I) measured by ¹⁹ F-NMR analysis as a pour point depressant additive for fluorinated oils. The fluorinated oils have a kinematic viscosity at 20 ° C. between 10 and 4,000 cSt, preferably between 30 and 2,000 cSt, and one or more of the following repeating structural units: —CFXO— (where X is , F or CF ₃ ; -CF ₂ CF ₂ O-,-(C ₃ F ₆ O)-, -CF ₂ CF ₂ CF ₂ O-, -CF ₂ CF ₂ CF ₂ CF ₂ O- The use according to claim 1, wherein the units are perfluoropolyether oils comprising (the units are statistically distributed along the main chain). Perfluoropolyether oils have the following classes:
_{(1) EO- (CF 2 CF} (CF 3) O) m '(CFXO) n' -E '
[Where:
X is equal to F or CF ₃
E and E ′ are equal to or different from each other and are selected from CF ₃ , C ₂ F ₅ or C ₃ F ₇ , wherein one fluorine atom of one or both terminal groups is substituted with Cl and / or H There;
m ′ and n ′ are integers such that the ratio m ′ / n ′ is between 20 and 1,000; n ′ is different from 0; these building blocks are statistically along the main chain Distributed]
The kinematic viscosity of this substance is within the above range;
(2) C ₃ F ₇ O (CF (CF ₃ ) CF ₂ O) _{o '} -D
[Where:
D is equal to —C ₂ F ₅ or —C ₃ F ₇ and one fluorine atom of one or both end groups is substituted with Cl and / or H;
o ′ is an integer such that the kinematic viscosity of the substance is within the above range];
(3) {C ₃ F ₇ O- (CF (CF ₃ ) CF ₂ O) _{p '} -CF (CF ₃ )-} ₂
[Where:
p ′ is an integer such that the kinematic viscosity of the substance is within the above range, one F of one or both end groups C ₃ F ₇ is substituted with Cl and / or H];
_{(4) EO- (CF 2 CF} (CF 3) O) q '(C 2 F 4 O) r' (CFX) s '-E'
[Where:
X is equal to F or CF ₃ ;
E and E ′ are equal to or different from each other and are as described above;
q ′, r ′ and s ′ are integers including 0 and the kinematic viscosity of the substance being within the above range];
(5) EO- (C ₂ F ₄ O) _{t '} (CF ₂ O) _u' -E '
[Where:
E and E ′ are equal to or different from each other and are as described above;
t ′ and u ′ are integers such that the ratio t ′ / u ′ is between 0.1 and 5, u ′ is different from 0]. The kinematic viscosity of this substance is within the above range.
(6) EO- (CF ₂ CF ₂ CF ₂ O) _{v '} -E'
[Where:
E and E ′ are equal to or different from each other and are as described above;
v ′ is a number such that the kinematic viscosity of the substance is within the above range].
(7) DO- (CF ₂ CF ₂ O) _{z '} -D'
[Where:
D and D ′ are equal to or different from each other and are selected from C ₂ F ₅ and C ₃ F ₇ , wherein one fluorine atom of one or both end groups is substituted with Cl and / or H;
z ′ is an integer such that the kinematic viscosity of the substance is within the above range];
(8) E ₁ -O- (CF ₂ O) _n (CF ₂ CF ₂ O) _m- (CF ₂ CF ₂ CF ₂ O) _p- (CF ₂ CF ₂ CF ₂ CF ₂ O) _q -E ₂
[Where:
E ₁ and E ₂ are equal to or different from each other and are perfluoroalkyl end groups having the formula — (CF ₂ ) _z CF _3, where z is an integer from 0 to 3;
n, m, p, and q are integers that are equal to or different from each other and included between 0 and 100, and are selected such that the kinematic viscosity of the oil is within the above range, and the ratio m / n Is an integer such that it is between 2 and 20, n is different from 0; (p + q) / (n + m + p + q) is between 0.05 and 0.2, and (n + m + p + q) is different from 0; n / (N + m + p + q) is between 0.05 and 0.40, and (n + m + p + q) is different from 0];
Use according to claim 2, selected from.   The perfluoropolyether oils are of class (1), (4), (5), (8) or mixtures thereof, and those of classes (2) and (6). use.   5. The pour point depressant additive is used in an amount ranging from 0.1 to 30% by weight, preferably 1 to 20% by weight, more preferably 5 to 10% by weight with respect to the final composition. Use according to one.   6. Use according to any one of claims 1 to 5, wherein a mixture of additives of general formula (I) and a mixture of perfluoropolyether oils is used. A) at least one fluorinated oil, preferably having a kinematic viscosity at 20 ° C. of between 10 and 4,000 cSt, preferably between 30 and 2,000 cSt, and one or more of the following repeating structural units: —CFXO - (wherein, X is, F or _{CF 3; -CF 2 CF 2 O} -, - (C 3 F 6 O) -, - CF 2 CF 2 CF 2 O -, - CF 2 CF 2 CF 2 CF 2 Equal to O-, and the structural units are statistically distributed along the main chain) containing 70-99.9 wt% perfluoropolyether oil; and B) at least one addition of formula (I) 0.1-30% by weight of agent;
A lubricating composition comprising:   3. At least one additive of formula (I) and at least one oil of class (1) and (5); preferably class (5) oils having a kinematic viscosity between 30 cSt and 300 cSt. 9. The composition according to 8.   9. Lubricating composition according to claim 7 or 8, comprising rust inhibitors, antiwear agents, antioxidant additives and suitable heat stabilizers for perfluoropolyether oils.   Use of the compound (I) according to claim 1 as a lubricating oil having a low pour point.   The perfluoropolyether lubricant according to claim 10.