RU2570403C2 - Lubricating composition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: claimed invention relates to lubricating composition, containing plastic lubricant of natural and/or artificial origin and solid filler, represented by intercalated compounds of fluorinates graphite of general formula C_xFJ_0.14, wherein x=1÷6.

EFFECT: increased resource of operation of friction pairs.

2 cl, 4 ex, 1 tbl, 4 dwg

Description

Technical field

The invention relates to lubricants, and more particularly to the field of production of fillers for lubricating compositions that improve anti-wear and anti-friction properties of greases when used in friction units of various machines and mechanisms.

State of the art

The main purpose of lubrication is to separate hard surfaces moving relative to each other in order to minimize friction and wear. The choice of lubricant is determined largely by the particular application.

Grease (grease) is used where high pressures exist. Also, such lubricants are used to lubricate small gears and for many applications where sliding at low speed is required.

The composition of modern greases: liquid oil, solid thickener, additives, fillers. The latter is introduced into the base lubricant of natural and / or artificial origin in connection with the tightening of the operating conditions of friction units. As fillers are used highly dispersed, insoluble in oils substances that improve the performance of the lubricant. Most often, fillers with a low coefficient of friction are used: graphite, molybdenum disulfide, sulfides of certain metals, polymers, complex compounds of metals, etc.

Currently, the most promising are anti-friction anti-wear additives and fillers for fluoropolymer-based lubricants containing polytetrafluoroethylene (PTFE) or polycarbon monofluoride (CF) _n powders of various dispersion and / or fluorine-containing surfactants [see book: New in the technology of fluorine compounds / Ed. N. Ishikawa. - M., Mir, 1984. - S. 117, 129, 399].

In particular, a lubricating composition is known that contains, as an antifriction and antiwear additive to a grease, monofractional fine PTFE [patent RU 2100376, IPC C10M 169/04, C10M 169/04, C10M 147/02. Publ. 12/27/1997; Buznik V.M., Tsvetnikov A.K. Ultrafine polytetrafluoroethylene as a basis for promising new materials // Vestnik FEB RAS. - 1993. No. 3. - S.39-47] (analogues).

Operational experience shows that the disadvantage of PTFE as an additive is its high abrasion loss, poor mechanical properties, in particular creep, poor adhesion to a metal surface, limiting the use of such additives as an antifriction material.

A grease additive in the form of an anti-friction lubricant composition is also known [patent RU 2321620, IPC C10M 103/02, C10M 103/06, C10M 177/00. Publ. 04/10/2008] (analogue), including molybdenum disulfide and modified graphite. The latter consists of flake graphite powder particles no larger than 12 microns in size, coated with a thin film of an organofluorine surfactant (epilam) about 3 nm thick. After applying the epilam composition to the surface of the body to be modified, the solvent evaporates, and the fluorosurfactant itself reacts with the surface, while the fluorine-containing surfactant molecules create Langmuir structures (Langmuir stockade) in the form of spirals with axes normally directed to the surfaces, allowing not only reliable to hold lubricant media, but serve as a kind of buffer between contacting surfaces.

The disadvantage of the analogue lubricant composition is the presence of a fluorine-containing film only on the surface layer of the initial graphite particles, which makes its use ineffective to increase the wear resistance of friction units.

The closest analogue of the proposed technical solution is an antifriction lubricating composition for creating a lubricating coating [and.with. SU 601306, IPC C10M 7/04. Publ. 04/05/1978] (prototype), containing, wt.%: Fluorinated graphite (C _{1 + x} F) _n - 5 ÷ 60; molybdenum disulfide (MoS ₂ ) - 40 ÷ 95. In the lubricating composition, it is proposed to use particles of molybdenum disulfide and fluorographic graphite powders of a size not exceeding 15 microns, while fluorinated should contain from 10 to 40 wt.% Fluorine.

While natural and artificial MoS _{2 is} widely used in lubricant compositions, the use of (C _x F) _n in lubricants is very limited despite the fact that, unlike graphite and MoS _2, fluorinated graphite has good lubricating properties in an atmosphere of various compositions, as well as in a vacuum. It is believed that this material exhibits particularly high performance under high loads and high speeds. It has been found that when it is added to greases, their effectiveness sharply increases.

Limited use (C _x F) _n is associated with the complexity of its production and cost [see: Mitkin V.N. A review of the types of inorganic polymer fluorocarbon materials and the problems of the interaction of their structure and properties // Journal of Structural Chemistry. - 2003. V. 44, No. 1. - S.109-110].

On the other hand, as the tests of the lubricant composition shown in the prototype showed, the effect of extending the life of the friction pair from replacing natural flake graphite with fluorinated graphite is not very impressive. This is probably due to the distortion of the layered structure of natural flake graphite during high-temperature (500–600 ° C) synthesis (C _x F) _n [see: V. Mitkin A review of the types of inorganic polymer fluorocarbon materials and the problems of the interaction of their structure and properties // Journal of Structural Chemistry. - 2003. V. 44, No. 1. - S.104-105].

The problem solved by the invention

The present invention is directed to increasing the service life of friction pairs.

SUMMARY OF THE INVENTION

The above objectives are achieved by a technical solution, the essence of which is that in a lubricating composition containing a grease of natural and / or artificial origin and a solid filler, the solid filler is represented by intercalated fluorinated graphite compounds of the general formula C _x FJ _0.14 , where x = 1 ÷ 6.

The above tasks are also achieved by an additional technical solution, consisting in the fact that the content of the intercalated fluorinated graphite compound in the lubricant composition is from 0.001 to 0.5 wt.% By weight of the grease, although there may be other values in one direction or another.

The main distinguishing feature of the inventive lubricating composition is that the solid filler is represented by intercalated compounds of fluorinated graphite (ISFG) of the general formula C _x FJ _0.14 , where x = 1 ÷ 6. This feature is new and significant, as it eliminates the inherent prototype disadvantages.

It has been established that ISFG of the general formula C _x FJ _0.14 is a unique material, both in chemical composition and in terms of its complex of properties. First, ISFG is synthesized at a temperature that differs little from room temperature; therefore, the flat layered structure of graphite in it is completely preserved. Secondly, fluorine atoms in the graphite lattice are connected by strong covalent bonds with carbon atoms. Thirdly, the graphene planes in the ISFG are extended due to the introduction of iodine heptafluoride molecules JF ₇ so that the interplanar spacing is approximately two times higher than the similar parameter of unfunctionalized graphite. For this reason, the mobility of fluorinated graphene layers in the ISFG lattice is much greater. The surface films of the intercalated compound of fluorinated graphite create very slippery coatings and are comparable to polytetrafluoroethylene (teflon) in the antifriction characteristics of ISFG, and the presence of fluorine atoms on the graphene surface provides it with good adhesion to the surface to be protected, be it metal, dielectric, glass, ceramics, semiconductors, crystals etc. Moreover, the thickness of the protective film, depending on the composition of the ISPH (coefficient x in the formula), can reach from 6 to 1 atomic layer. Fourthly, the temperature of thermal decomposition of ISFG particles exceeds 400 ° C, which significantly exceeds the working temperature of polytetrafluoroethylene.

We found that the ISFG of the general formula C _x FJ _0.14 is stable for an unlimited time. The presence of iodine in the lattice of ISFG in the nanocrystalline state increases the antifriction properties of the filler, further reducing the friction coefficient in the reference pair (see, for example, patents SU 1087550; SU 1735346).

The optimal content of ISFG in a grease is from 0.001 to 0.5 wt.%, Which is determined, on the one hand, by the desire to create a cost-effective lubricant composition, on the other hand, with a high coating ability of ISFG. It is known that a monoatomic graphene layer is characterized by a very high specific surface - according to calculations, 2630 m ² / g [Graifer ED et al. Graphene: chemical approaches to the synthesis and modification / Advances in chemistry. - 80 (8). 2011. - P.785]. For this reason, even small additives of ISFG as a filler can create large areas of antifriction coatings on the friction surfaces of various mechanisms.

ISFG powders are easily mixed with greases of natural and / or artificial origin by all known mechanical methods.

Methods for the low-temperature synthesis of polyfluoride carbon with iodine heptafluoride of the general formula C _x FJ _0.14 , where x = 1 ÷ 6, preserving the layered structure of the starting graphite, are described in patents [RU 2404121. IPC C01B 31/04. Publ. 11/20/2010; RU 2419586. IPC C01B 31/04. Publ. 05/27/2011].

Brief Description of the Drawings:

- figure 1 shows a photograph of particles of a powder of natural coarse crystalline flake graphite;

- figure 2 shows a photograph of the particles of powder intercalated compounds of fluorinated graphite;

- figure 3 shows the change in the coefficient of friction in the reference pair during antifriction tests of the lubricant composition based on the standard LITOL-24 grease;

- figure 4 shows the change in the coefficient of friction in the reference pair during antifriction tests of a lubricant composition based on LITOL-24 grease with the addition of 0.01 wt.% ISFG.

The following examples are provided for illustrative purposes and should not be construed as limiting the scope of the present invention.

Example 1. A lubricating composition for lubricating bearings operating under vacuum is prepared on the basis of mineral vacuum oil VM-12 (TU 38.1011237-89). As a precursor for the synthesis of intercalated compounds of fluorinated graphite, natural large-crystalline flake graphite of the GT-1 brand is used (crucible graphite in accordance with GOST 4596-75), additionally chemically purified to an ash content of no more than 0.1 wt.% (See figure 1) . A portion of graphite is treated with the gas or liquid phase of iodine heptafluoride at a mass ratio of reactants 1: 4 for 24 hours at 20 ° C, as a result of which a fluoroxidant is introduced into the layered graphite lattice with the formation of the so-called intercalated fluorinated graphite compound of the general formula C _x FJ _{0, 14} , where x = 1 ÷ 6 (see figure 2).

The powder of intercalated compounds of fluorinated graphite is mixed with BM-12 oil in a ratio of 1: 100000 and 1: 1000, which corresponds to the content of ISPH in the lubricating fluid of 0.001 wt.% And 0.1 wt.%, And is subjected to ultrasonic dispersion for 30 minutes with ultrasonic frequency of 40 kHz in an ultrasonic bath model VASCA ULTRASUONI.

It was found that ultrasonic dispersion of ISPH in vacuum oil in an amount of up to 0.1 wt.% Allows to obtain homogeneous dispersions, the separation of which does not occur, at least for a month.

Tests of lubricating compositions are carried out on the automated tribotechnical complex “High Temperature TRIBOMETER” of the Swiss company “CSM Instruments” in accordance with international standards ASTM G99-959 and DIN 50324. The installation uses standard balls of aluminum oxide Al ₂ O _{3 with a} diameter of 3 mm, a special holder model samples (plates made of polished steel 12X18H10T) for conducting a test in a lubricating fluid and a heating system for samples to maintain a constant temperature of 60 ° C of the model sample during the test. During the tribological test, the dynamic coefficient of friction is measured and the wear resistance of the material of the model sample is evaluated.

For a model sample (st. 12X18H10T) it was measured and accepted that the hardness of the material is 2.05 GPa, the elastic modulus is 171 GPa, and the Punch coefficient is 0.3.

The average coefficient of friction µ in the reference pair during one test for all lubricant compositions relative to the coefficient of friction of the base oil (pure BM-12) decreased slightly. The wear of model samples is much more reduced (see table, items 1-3): for a lubricant composition with the addition of ~ 0.001 wt.% ISPH, a decrease of 38% occurs.

Table No. p / p The composition of the lubricating composition Wear of a model sample, 10 ^-5 mm ² / Nm) Note one BM-12 oil 6.78 ± 0.62 2 Oil VM-12, 0.001 wt.% ISFG 4.22 ± 0.62 38% less wear 3 Oil VM-12, 0.1 wt.% ISFG 5.46 ± 1.51 20% less wear four LITOL greasing 2.24 ± 0.56 5 LITOL lubricant, 0.01 wt.% ISFG 1.10 ± 0.09 51% less wear 6 LITOL lubricant, 0.1 wt.% ISFG 0.97 ± 0.16 57% less wear 7 LITOL lubricant, 0.5 wt.% ISFG 1.84 ± 0.25 18% less wear

Table continuation No. p / p The composition of the lubricating composition Wear of a model sample, 10 ^-5 mm ² / Nm) Note 8 UPI grease 0.43 ± 0.07 9 Lubricant UPI, 0.01 wt.% ISFG 0.34 ± 0.04 21% less wear 10 Lubricant UPI, 0.1 wt.% ISFG 0.42 ± 0.08 2.4% less wear eleven KST grease 1.71 ± 0.70

Example 2. A lubricating composition for the lubrication of bearing bearings of rotors of electric motors is prepared on the basis of Litol-24 grease (GOST 21150-87).

Intercalated compounds of fluorinated graphite are obtained according to the technology described in example 1. The ISPH powder is mixed in a paddle mechanical mixer with Litol-24 lubricant in a ratio of 1: 10000, 1: 1000 and 1: 500, which corresponds to the content of ISPH in the lubricating composition of 0.01 wt. %, 0.1 wt.% And 0.5 wt.%.

Tests of lubricant compositions at the tribotechnical complex are carried out according to the conditions of example 1. It is established that the introduction of Litol-24 "from 0.01 to 0.5 wt.% ISFG powder allows to reduce the friction coefficient for the rubbing pair" aluminum oxide - steel 12X18H10T " by 17% (see figure 3 and figure 4), while the wear of model samples is reduced by 57% (see table, items 4-7).

It is typical that, for a standard lubricant sample, the value of the friction coefficient increases during tests, while for grease samples modified with ISFH additive, μ decreases, approaching the value 0.12.

Example 3. A lubricating composition for lubricating bearings operating in an aggressive environment is prepared on the basis of UPI synthetic plastic fluorocarbon grease (TU 95.2289-91). The chemical formula of the lubricant is C _n F _{2n + 2} , where n is from 15 to 25. UPI grease is widely used in the nuclear industry in the technology of separation of uranium isotopes, for the lubrication of the rubbing parts of machines and devices operating in aggressive environments, for filling the seals of rotating shafts.

Intercalated compounds of fluorinated graphite are obtained according to the technology described in example 1. The powder of intercalated compounds of fluorinated graphite is mixed with UPI oil in a ratio of 1: 10000 and 1: 1000, which corresponds to the content of ISPH in the lubricating fluid of 0.01 wt.% And 0.1 wt. %, and subjected to ultrasonic dispersion at a temperature of 60 ° C according to the conditions of example 1.

It was found that ultrasonic dispersion of ISFG in UPI lubricant at 60 ° C in an amount of up to 0.1 wt.% Allows to obtain uniform dispersions, the separation of which does not occur, at least for a month.

Tests of the lubricant composition at the tribotechnical complex are carried out according to the conditions of example 1. It was found that the introduction of 0.01 to 0.1 wt.% ISFG powder into the lubricant UPI does not reduce the friction coefficient in the fluorocarbon grease for the reference pair “aluminum oxide - steel 12X18H10T”, but at the same time, the wear of the model sample decreases by 21% (see table, items 8-10).

Example 4. Lubricating compositions based on UPI lubricant according to the conditions of Example 3 were compared with industrial lubricant KST (TU 95.2289-91) - UPI lubricant filled with finely dispersed fluoroplastic powder in the range of 2.8–3.6 wt.%. The chemical formula of the grease is C _n F _{2n + 2} , where n is from 15 to 25. The KST grease is widely used in the nuclear industry to lubricate the rubbing parts of machines and devices operating in aggressive environments, to fill the seals of rotating shafts.

Tests of the KST lubricant composition in the tribotechnical complex are carried out according to the conditions of Example 1. The friction coefficient of the support pair “aluminum oxide - steel 12X18H10T” on the KST lubricant composition corresponded to UPI fluorocarbon grease and UPI-ISFG lubricant compositions, however, the model specimen is 4 times worn higher than the UPI lubricant, and 5 times higher than the lubricant composition "UPI - 0.01% ISFG" (see table, item 11).

In conclusion, we note that greases modified with powders of intercalated compounds of fluorinated graphite demonstrate excellent tribological and rheological characteristics that cannot be achieved in the corresponding lubricating compositions containing other particles of fluorocarbon materials - fine fluoroplastic powders, fluorinated graphite powders, epilated graphite powders, etc. Inspection of the mechanisms after operation showed that the friction surfaces are covered with durable translucent fluorocarbon films that reliably protect them from wear. The method of preparation of the lubricating composition ensures the implementation of environmentally friendly processes without the release and formation of harmful and toxic substances.

Claims (2)

1. A lubricating composition containing a grease of natural and / or artificial origin and a solid filler, characterized in that the solid filler is represented by intercalated fluorinated graphite compounds of the general formula C _x FJ _0.14 , where x = 1 ÷ 6. 2. The lubricating composition according to claim 1, characterized in that the content of intercalated compounds of fluorinated graphite in the lubricating composition is from 0.001 to 0.5 wt.% By weight of the grease.

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