JP2014501292A - Grease composition - Google Patents

Abstract

A grease composition that can be used in a constant speed joint of an automobile drive train or other gear mechanism where a grease having a low coefficient of friction is desired.
The grease composition of the present invention is a grease composition comprising: at least one mineral base oil or synthetic base oil, individually or as a mixture; at least one as a thickener Fatty acid simple or complex metal soap; at least one molybdenum dithiocarbamate; and graphite. The present invention can be used for a constant velocity joint of an automobile power transmission device.
[Selection figure] None

Description

  The present invention relates to a grease composition that can be used in a constant speed joint of an automobile drive train or other gear mechanism where a grease having a low coefficient of friction is desired.

  A power transmission device or a mechanical coupling joint is a mechanical system consisting of several parts that are movable or deformable relative to one another, the mechanical system enabling the mutual driving of two rotating parts, The axis of rotation of the rotating part occupies a variable relative position during operation. In other words, it is an interlocking device that allows the rotation of one shaft to be transmitted to another shaft that is movable relative to the first shaft. A power transmission joint is said to be a constant speed joint if the rotational speeds of both shafts are equal at any point in time.

  The movement within the constant velocity joint is complex and has a combination of rolling, sliding and rotation. Not only wear on the contact surfaces of the components, but also large frictional forces between the surfaces occur. Wear can cause joint damage, and frictional forces can cause noise, vibration and shock in the drivetrain.

  Therefore, the grease used in constant velocity joints should have an anti-wear effect, preferably a low coefficient of friction, to reduce or prevent noise, vibration and shock.

Various known additives contribute to wear and / or friction reduction. Thus, known greases for constant velocity joints often contain the following: antiwear additives (eg, phosphorus containing compounds or phosphorus and sulfur containing compounds), and friction modifiers (eg, containing molybdenum) Organic compounds). The organic compound containing molybdenum has one or both properties of wear resistance and / or friction resistance. It is also known to use solid lubricants such as molybdenum bisulfide (MoS ₂ ) or tungsten bisulfide (WS ₂ ) or graphite as friction modifiers.

US Pat. No. 2,723,747 discloses a mineral and / or synthetic base oil, a polyurea thickener, and MoS ₂ as a solid lubricant, and graphite and at least one organomolybdenum compound (preferably molybdenum). A heat resistant grease for constant velocity joints comprising dithiocarbamate) is disclosed. Graphite is a solid lubricant, MoDTC, PTFE is able to reduce the content of expensive solid lubricant MoS _2, can not be substituted for fully taking it.

MoS type ₂ solid lubricants are expensive and result in high metal content in the formulation, which is undesirable for environmental reasons. This application does not suggest any reduction of the metal (Mo) content of the grease by completely replacing MoS ₂ with other solid lubricants. The molybdenum content of the disclosed composition is at least about 5,000 ppm.

  There is no mention of specific molybdenum and graphite content that allows optimization of grease performance with respect to wear and / or friction. This application does not suggest any use of lithium soap as a thickener instead of polyurea.

  Greases thickened with polyurea are technically more complicated to produce, especially because the components used in their production, such as isocyanates and amines, are highly toxic and less stable during storage Because it is not. The precautions to be taken make the manufacturing process more complex and more costly. The availability of raw materials is also lower than that of greases thickened with metal soaps (especially lithium and lithium composites). Polyureas are excellent in heat resistance, but their thixotropic properties also cause problems under mechanical stress and curing during storage. Therefore, technically easier and more economical greases for constant velocity joints are preferred for formulating greases from non-toxic and non-hazardous materials using fatty acid metal soaps as thickeners.

Certain commercial greases for constant velocity joints include, for example, mineral and / or synthetic base oils, lithium or lithium composite thickeners, and amounts of about 3% by weight (this means a Mo content of about 18,000 ppm) ) Molybdenum bisulfide MoS ₂ . Below this MoS ₂ content, the wear and friction performance is insufficient.

  U.S. Patent No. 5,078,172 describes greases for constant velocity joints having a low coefficient of friction comprising: base oil, simple or complex lithium soap thickener; MoDTC Or one or several organic components containing MoDTP-type molybdenum; at least one zinc dithiophosphate; phosphorus-free and sulfur-containing extreme pressure agent containing no metal; calcium salt of oxidized wax, calcium salt of petroleum sulfonate or aromatic Calcium salt of alkyl sulfonate. The disclosed composition examples have a high molybdenum content (about 8,500 ppm) and / or a high phosphorus content (about 2,000 ppm phosphorus), which creates environmental problems.

  This document describes these greases in terms of the possibility of partially replacing compounds containing molybdenum and / or phosphorus with other additives, or in particular with regard to wear and friction, in order to reduce the metal content of the composition. It does not describe the optimal molybdenum content that enables the protection or improvement of the properties of

  Non-Patent Document 1 (“Effect of graphite on friction and wear characteristics of molybdenum dithiocarbamate”, Y. Yamamoto et al., Tribology Letters, Vol 17, No. 1, July 2004) Discloses the effect of graphite on boosters. This improvement is particularly noticeable in the presence of the succinimide dispersant. This document is not related to the field of grease. This study is limited to one natural lubricant and does not address the grease field. There is no disclosure of specific combinations of base oil, graphite and MoDTC with other ingredients required for grease formulation in specific thickeners. It is therefore absolutely impossible to conclude from this publication whether the booster effect of graphite on the friction and wear performance of MoDTC is reproduced in greases containing specific thickeners. There has been no optimization of molybdenum and graphite content.

Patent Document 3 (International Patent Publication No. 2007/085643) is a constant velocity joint thickened with polyurea and comprising 0.1-5 wt% WS ₂ and 0.1-5 wt% zinc dithiophosphate and / or molybdenum dithiocarbamate A grease composition is disclosed. This application also discloses the possibility of using graphite or MoS ₂ as an additive in the grease. However, the use of graphite (or MoS ₂ ) in combination with MoDTC is not recommended because, according to this application, this combination has a detrimental effect on the wear resistance and friction coefficient of grease. It is.

  Thus, the present application contains non-toxic, available, low-cost raw materials, is easy to manufacture, has a reduced molybdenum (Mo) and phosphorus (P) content, and has sufficient wear resistance properties There is a need for greases for constant velocity joints having frictional properties (low coefficient of friction).

  Applicants have shown that greases for constant velocity joints that are thickened with fatty acid metal soaps and contain a combination of graphite and molybdenum dithiocarbamate can meet the above requirements.

  Such greases according to the invention have improved wear resistance properties compared to known greases for constant velocity joints based on lithium soap. The friction properties are comparable to known greases. Such greases can further achieve these performances with less molybdenum content and optionally less phosphorus content than prior art greases.

French Patent Application Publication No. 2723747 European Patent Specification No. 0708172 International Patent Publication No. 2007/085643

“Effect of graphite on friction and wear characteristics of molybdenum dithiocarbamate”, Y. Yamamoto et al., Tribology Letters, Vol 17, No. 1, July 2004

The present invention relates to a grease composition comprising:
one or several mineral or synthetic base oils, alone or as a mixture;
b. one or several simple or complex fatty acid metal salts as thickeners;
c. at least one molybdenum dithiocarbamate; and
d. Graphite.

  Preferably, the grease composition of the present invention has a molybdenum content of 100 to 2,800 ppm, preferably 1,500 to 2,500 ppm, preferably 1,700 to 2,300 ppm, preferably 2,000 to 2,200 ppm.

  Preferably, the grease composition of the present invention comprises 0.5 to 3.0% by weight of graphite, preferably 0.7 to 2.0% by weight.

  More preferably, the grease composition of the present invention has a Mo / [graphite] ratio between the molybdenum content (ppm) in the composition and the weight percentage of graphite of 1,250-1,550, preferably 1,300-1,500.

  In one embodiment, the grease composition of the present invention comprises phosphorus in a content of less than 1,500 ppm, preferably less than 1,200 ppm.

  In one embodiment, the grease composition of the present invention comprises zinc with a content of less than 1,500 ppm.

In a preferred embodiment, the grease composition of the present invention does not contain a MoS ₂ solid lubricant.

  In another preferred embodiment, the grease composition of the present invention does not contain a polytetrafluoroethylene solid lubricant.

  Preferably, the grease composition of the present invention comprises only one or several simple or complex fatty acid metal salts as thickeners.

  Preferably, the grease composition of the present invention comprises at least one simple, complex soap of lithium, sodium, calcium, barium or titanium, alone or as a mixture, as a thickener.

  Even more preferably, the grease composition of the present invention comprises one or several simple or complex lithium soaps as a thickener.

  In one embodiment, the grease composition of the present invention comprises a mineral base oil (a) and a synthetic base oil (a), preferably a synthetic base oil selected from polyalphaolefins.

  In a preferred embodiment, the grease composition of the present invention preferably further comprises a polymer (e) selected from polyisobutene, olefin copolymer, polymethacrylate, polyalphaolefin (preferably a polymer (e) selected from polyisobutene). Comprising.

  The grease composition of the present invention comprises one or several antiwear and / or extreme pressure additives (f) containing phosphorus and sulfur, preferably selected from zinc dithiophosphates (f ).

  Preferably, the grease composition of the present invention has a phosphorus content of 300 to 1,200 ppm, preferably 400 to 1,000 ppm, preferably 500 to 900 ppm.

  Preferably, the composition of the present invention has a zinc content of 500 to 1,400 ppm, preferably 600 to 1,300 ppm, preferably 800 to 1,000 ppm.

In one embodiment, the grease composition of the present invention comprises:
70-94% base oil (a);
• 5-25% thickener (b); and 1-5% MoDTC (c) and graphite (d) mixture.

In another embodiment, the grease composition of the present invention comprises:
70-94% base oil (a);
-5-25% thickener (b);
A mixture of 1-5% MoDTC (c) and graphite (d); and • one or several polymers (e) (preferably polyisobutenes) selected from polyisobutenes, olefin copolymers, polymethacrylates, polyalphaolefins Possible balance consisting of one or several polymers (e)) selected from

In a preferred embodiment, the grease composition of the present invention comprises:
70 to 93.9% base oil (a);
-5-23.5% thickener (b);
A mixture of 1-5% MoDTC (c) and graphite (d); and 0.1-1.5% of one or several antiwear and / or extreme pressure additives containing phosphorus and sulfur ( f) An additive preferably selected from zinc dithiophosphate.

In another preferred embodiment, the grease composition of the present invention comprises:
70 to 93.9% base oil (a);
-5-23.5% thickener (b);
A mixture of 1-5% MoDTC (c) and graphite (d);
0.1-1.5% of one or several anti-wear additives (f) containing phosphorus or containing phosphorus and sulfur, preferably selected from zinc dithiophosphate; and A possible remainder consisting of one or several polymers (e) selected from polyisobutenes, olefin copolymers, polymethacrylates, polyalphaolefins, preferably one or several polymers (e) selected from polyisobutenes.

  The present invention also relates to the use of the above-described grease composition as a grease for a constant velocity joint of an automobile power transmission device.

  The invention also relates to one of the constant velocity joints filled with said grease.

(Lubricating base oil (a))
The base oil used in the composition of the present invention may be a mineral or synthetic oil derived from groups I to V according to the classification specified in the API (American Petroleum Institute) taxonomy.

  The mineral base oil according to the invention can be obtained at atmospheric pressure and vacuum distillation of crude oil, followed by refining operations such as extraction with solvents, deasphalting, dewaxing with solvents, hydrotreating, hydrocracking and hydroisomerization. Include all types of base oils obtained by hydrofinishing.

  The base oil of the grease composition of the present invention may be a synthetic oil such as a specific ester, silicone, polyalkylene glycol, polybutene, polyalphaolefin (PAO), alkylbenzene, alkylnaphthalene.

  Base oils can also be naturally occurring oils such as alcohols and carboxylic acid esters that can be obtained from natural resources such as sunflower oil, rapeseed oil, palm oil and the like.

  Preferably, in the composition of the invention, a polyalphaolefin (PAO) type synthetic oil is present in combination with a mineral oil. Polyalphaolefins are obtained, for example, from monomers having 4 to 32 carbon atoms (eg octene, decene). Their weight average molecular weight is generally between 250 and 3,000.

  The base oil mixture is adjusted such that its viscosity at 40 ° C. according to ASTM D445 standard is 30 to 140 cSt, preferably 50 to 100 cSt. For this purpose, a wide range of light polyalphaolefins such as PAO 6 (31 cSt at 40 ° C.), PAO 8 (48 cSt at 40 ° C.), or heavy polyalphaolefins such as PAO 40 (400 cSt at 40 ° C.) Or PAO 100 (1,000 cSt at 40 ° C.) can be used.

(Thickener (b))
The grease of the present invention is thickened with a fatty acid metal soap.

  Fatty acid metal soaps may be prepared separately or manufactured in situ during the manufacture of the grease (in the latter case, the fatty acid is dissolved in the base oil and then the appropriate metal hydroxide Add). Such thickeners are readily available and inexpensive products commonly used in the grease field. They exhibit the best technical compromise because they have both good mechanical properties, good heat resistance and good water resistance.

  Fatty acids having a long chain which generally has 10 to 28 carbon atoms and is saturated or unsaturated and ultimately hydroxylated are preferably used.

  Long chain fatty acids (generally having 10 to 28 carbon atoms) are, for example, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, linoleic acid, erucic acid and those Is a hydroxylated derivative of 12-hydroxystearic acid is the best known derivative of this type and is preferred.

  These long chain fatty acids are generally derived from vegetable oils such as palm oil, castor oil, rapeseed oil, sunflower oil, etc., or animal fats (tallow, whale oil, etc.).

  So-called simple soaps can be formed by using one or several long chain fatty acids.

  One or several long chain fatty acids and one or several carboxylic acids with short hydrocarbon chains containing up to 8 carbon atoms can also be combined to form so-called complex soaps.

  The saponifying agent used in the manufacture of soap is a metal compound of lithium, sodium, calcium, barium, titanium, aluminum (preferably a metal compound of lithium and calcium), preferably a hydroxide or oxide of these metals Or it may be carbonate. With the exception of simple or complex aluminum soaps having a spherical gel structure, especially metal soaps of lithium, sodium, calcium, barium, titanium form a fiber structure.

  One or several metal compounds with or without the same metal cation can be used in the grease of the present invention. Accordingly, lithium soap can be combined with a lower proportion of calcium soap. This has the advantage of improving the water resistance of the grease.

  Metal soap is used in the grease of the present invention in a content of about 5-20 wt%, preferably 8-15 wt%, preferably 10-12 wt%, generally 11 wt%. The amount of metal soap is generally adjusted to obtain grade 00, grade 0, grade 1 or grade 2 greases according to the NLGI classification.

  Preferably, the grease of the present invention mainly contains fatty acid metal soap as a thickener. This means that the total amount of simple or complex fatty acid metal soap is the highest weight percent in the grease of the present invention compared to the weight percent of other thickening materials.

  Preferably, the grease of the present invention contains primarily simple or complex lithium soap as a thickener. This means that the total amount of simple or composite lithium soap will be the highest weight percent in the grease of the present invention compared to the weight percent of other thickening materials.

  Preferably, the amount of simple or complex fatty acid metal soap is at least 50 wt%, more preferably at least 80 wt%, based on the total weight of the thickening material in the grease composition of the present invention.

  Preferably, the amount of simple or complex lithium soap is at least 50 wt%, more preferably at least 80 wt%, based on the total weight of the thickening material in the grease composition of the present invention.

  According to one embodiment, the greases of the present invention can contain simple or complex metal soaps of fatty acids as the main thickener, and smaller amounts of other thickeners such as polyurea or bentonite. Or an aluminosilicate type inorganic thickener can be contained.

  Preferably, the greases according to the invention do not contain polyurea type thickeners, which are technically more difficult to produce, especially because the components used in their production, such as isocyanates and Since amines are highly toxic and not very stable on storage).

  More preferably, the grease of the present invention contains only a simple or complex fatty acid metal soap as a thickener.

  More preferably, the grease of the present invention contains only a simple or complex fatty acid metal soap of lithium as a thickener.

(Molybdenum dithiocarbamate and graphite)
The grease composition of the present invention contains graphite and molybdenum dithiocarbamate, which gives the composition improved wear resistance properties compared to known commercial greases. These properties can be reached with less molybdenum content than known greases.

  Preferably, the molybdenum content of the grease of the present invention is 1,000-2,800 ppm.

  Preferably, the Mo / [graphite] ratio of molybdenum content (ppm) and weight percent of graphite in the composition is from 1,250 to 1,550. Indeed, it can be seen that when these compounds are present in the aforementioned ratios, the grease composition also has very good wear and friction properties comparable to known commercial greases. Furthermore, these good properties are reached at less molybdenum content and optionally other metal element content such as zinc or phosphorus element content than known greases.

These performances can be achieved without the need to add solid lubricant additives such as MoS ₂ or polytetrafluoroethylene (PTFE) powder to the grease composition of the present invention. The possible content of phosphorus-containing additives, in particular anti-wear additives, can also be reduced.

Molybdenum dithiocarbamate (MoDTC) (c)
The composition of the present invention contains molybdenum dithiocarbamate, a friction modifying additive well known to those skilled in the art.

  These molybdenum dithiocarbamate organometallic friction modifiers can be, for example, molybdenum dialkyldithiocarbamates corresponding to formula (I):

[Wherein X ₁ , X ₂ , X ₃ , X ₄ are preferably alkyl chains having 2 to 13 carbon atoms, preferably 2 to 6 carbon atoms].

  The amount of MoDTC in the composition of the present invention is adjusted so that their molybdenum content is 1,000-2,800 ppm, preferably 1,500-2,500 ppm, preferably 1,700-2,300, preferably 2,000-2,200 ppm.

  This content can be measured by a usual method (plasma, atomic absorption, fluorescent X-ray).

  In grease compositions, it is not desirable to use MoDTC as a single additive (antiwear). In fact, MoDTC is known to require the presence of a minimum activation temperature and other additives (antiwear, extreme pressure additives) to be effective.

  Greases comprising MoDTC without the use of any other wear resistance and / or extreme pressure additive are not particularly effective at low temperatures. Thus, in prior art greases, MoDTC is combined with a phosphorus-containing additive such as dithiophosphate.

  In the grease of the present invention, MoDTC is combined with graphite, which enables the production of greases with very good properties with regard to wear and friction at low molybdenum and phosphorus levels.

  If the Mo content is too low, the wear resistance properties (especially under high loads) will be insufficient for application to constant velocity joints.

  It can be seen that if the MoDTC content is too high (at the expense of graphite), the friction performance of the grease decreases.

  Furthermore, for environmental reasons, a too high content of Mo element in the grease is undesirable. When the Mo threshold is exceeded, no significant increase in wear is observed.

[Graphite (d)]
The grease composition of the present invention contains graphite. The presence of graphite, known for its properties as a solid lubricant, eliminates the use of molybdenum (and optionally, while maintaining the wear and friction properties suitable for constant speed joint applications without the use of any metallic elements. The content of the friction modifier and the antiwear additive containing phosphorus can be reduced.

  However, it is not desirable to completely replace such molybdenum additives with graphite because graphite is not very effective under heavy loads and wear problems can occur with such greases. Furthermore, increased wear is also seen when the amount of graphite is too high to sacrifice molybdenum.

  Preferably, the graphite used in the composition of the present invention is a micrometer sized powder and is characterized by a particle size of about 1-15 μm and a diameter D50 of, for example, 3-8 μm, preferably 5-7 μm. Has a particle size distribution.

  The grease composition of the present invention preferably contains 0.5 to 3.0% by mass of graphite, preferably 0.7 to 2.0% by mass, preferably 0.75 to 1.7% by mass, preferably 1.0 to 1.5% by mass.

(Compound containing phosphorus and sulfur (f))
The grease of the present invention optionally contains antiwear and extreme pressure additives containing phosphorus and sulfur that are commonly used in grease and lubricant formulations.

  These are, for example, without limitation, thiophosphoric acid, thiophosphorous acid, esters of these acids, their salts, and dithiophosphates, in particular zinc dithiophosphate.

  Particularly preferred are zinc dithiophosphates of the formula (II):

[Wherein R ₁ , R ₂ , R ₃ , R ₄ are each independently a linear or branched alkyl group having 1 to 24, preferably 3 to 14 carbon atoms, or 6 An optionally substituted aryl group having ˜30, preferably 8 to 18 carbon atoms].

  These various compounds can be used in the grease composition of the present invention alone or as a mixture. Their mass percentage in the compositions of the present invention is preferably 0.5-5 wt%, preferably 0.7-2 wt%, or even 0.8-1.5 wt%, based on the total weight of the composition. Their amounts are adjusted to observe the limited content of molybdenum and phosphorus elements in the composition of the present invention.

  The molybdenum (Mo) content of the composition of the present invention is preferably 1,000 to 2,800 ppm, preferably 1,500 to 2,500 ppm, preferably 1,700 to 2,300, preferably 2,000 to 2,200 ppm.

  The phosphorus (P) content of the composition of the present invention is preferably less than 1,500 ppm, preferably less than 1,200 ppm, preferably 300-1,200 ppm, preferably 400-1,000 ppm, preferably 500-900 ppm.

  This content can be measured by a usual method (plasma, atomic absorption method).

  Preferably, when the composition contains zinc dithiophosphate, the zinc content of the composition of the invention is less than 1,500 ppm, preferably 500-1,400 ppm, preferably 600-1,300 ppm, preferably 700-1,200 ppm, Preferably it is 800-1,000 ppm.

  Lubricating compositions of the present invention comprise antiwear and extreme pressure additives containing phosphorus, such as alkyl phosphate esters or alkylphosphonate esters; phosphoric acid; phosphorous acid; phosphorous acid and phosphoric acid mono-, di- And triesters; and their salts.

  The lubricating composition of the present invention can also contain antiwear and extreme pressure additives containing sulfur, such as dithiocarbamates, thiadiazoles and benzothiazoles, sulfur-containing olefins.

(Other additives)
The greases of the present invention can be any type of additive suitable for their use, for example, an antioxidant, eg, an oxygen-containing compound such as an amino or phenolic antioxidant, ester. A rusting agent and a copper deactivator can also be contained.

  These various compounds are generally present in the grease in a content of less than 1% by weight or even less than 0.5% by weight.

  The grease of the present invention further comprises a polymer (e) such as polyolefin, polyisobutene (PIB), polyethylene, polypropylene, heavy PAO, olefin copolymer (OCP) (eg hydrogenated diene-styrene), polymethacrylate (PMA). May generally be contained in a content of 1 to 35%. For example, a PIB with a molar mass of 15,000-25,000 daltons is generally used at a content of 2-15% or 5-10% by weight.

  These polymers are used to improve the tackiness of the grease so that the grease better resists centrifugation. These polymers further result in better adhesion of the grease to the surface, increasing the viscosity of the base oil fraction and thus increasing the thickness of the oil film between the parts subject to friction.

(Grease manufacturing method)
The grease of the present invention is preferably produced by forming a metal soap in situ.

  One or several fatty acids are dissolved in a fraction of the base oil or base oil mixture at room temperature. This fraction is generally about 50% of the total amount of oil contained in the final grease. The fatty acid can be a long chain acid having 14 to 28 carbon atoms to form a simple soap, and a short chain fatty acid having 6 to 12 carbon atoms to form a composite soap and Any combination is possible.

  The metal compound (preferably metal hydroxide type metal compound) is added at a temperature of about 60-80 ° C.

  Thus, a single metal or a combination of multiple metals can be added. A preferred metal for the composition of the present invention is calcium, optionally combined with calcium in a proportion less than lithium.

  The reaction of saponification of fatty acid with a metal compound is performed at a temperature of about 100 to 110 ° C.

  The water formed is then evaporated by baking the mixture at a temperature of about 200 ° C. The grease is then cooled by adding the remaining fraction of base oil.

  The additive is then incorporated at about 80 ° C.

  Next, kneading is performed for a sufficient time in order to obtain a homogeneous grease composition.

(Grease grade)
The consistency of a grease is a measure of its hardness or its fluidity at rest. It is quantified by the penetration depth of a cone having a predetermined size and mass. The grease is subjected to kneading in advance. Conditions for measuring the consistency of grease are specified in the ASTM D217 standard.

  Greases are classified according to their consistency into nine NLGI (National Lubricating Grease Association) classes or grades commonly used in the grease field. These grades are shown in the table below.

  The grease of the present invention is preferably a grease having a consistency of 265 to 430, preferably 265 to 385, preferably 265 to 340 millimeters / 10 according to ASTM D217. Preferably they are NLGI grade 00, 0, 1 or 2, i.e. their consistency is 400 to 430, or 335 to 385, or 310 to 340, or 265 to 295 millimeters per ASTM D217, respectively. 10.

1. Manufacture of grease composition Various additives from the same base grease thickened with simple lithium soap prepared from litin (LiOH.H ₂ O) and 12-hydroxystearic acid and containing mineral and synthetic base oil In particular, a grease composition containing graphite and molybdenum dithiocarbamate is prepared.

  The composition of the base grease is shown in Table 1 below. The term “base grease” generally means, for those skilled in the art, a grease composition that contains only base oil and thickener and no additives.

From the base grease, the addition of various additives: polymers for improving the tack and adhesion (PIB), antiwear agents (DTPZn), as well as various solid lubricants: MoS _2, graphite, MoDTC:
The graphite used is a micrometer powder with a diameter D50 = 6 μm;
The MoDTC used is molybdenum di-n-butyldithiocarbamate containing 28% by weight molybdenum;
The MoS ₂ used is a micrometer powder consisting of particles with a particle size of 0.5-8 μm and a D50 of about 2 μm.

  All greases prepared are grade 2 according to the NLGI classification.

  Grease A is a commercially available grease for constant velocity joints, and greases E, I and J are according to the present invention.

  Table 2 shows the mass composition of the greases and their wear and friction properties.

  The wear properties were evaluated by measuring the wear diameter (millimeter) after a 4-ball wear test according to ASTM D 2266 standard (1 hour, 40 kg load, 75 ° C.). According to the STL S71 3100 standard, the grease for constant velocity joints should produce a wear diameter of less than 50 mm.

Friction properties were evaluated by measuring the average coefficient of friction with a Cameron printed cylinder-plane tribometer under the following conditions:
-Movement pin: SKF100C6 cylinder (diameter 7mm x length 7mm)
-Fixed plane: XC38 without THT, circular polishing (Ra 0.8μm)
-Movement distance: 2.5mm
-Frequency: 5 levels from 2.5 to 40Hz, + 1/20 reducer
-Load: 3 levels, 10, 50, 110N
-Duration: 20 consecutive, 1,786 seconds total-16 plateaus stabilized for 80 seconds, calculating average friction for the last 40 seconds-2 quick acquisitions in 3 instantaneous friction cycles-2 functional stages (initial run-in Period + temperature change)
-Temperature: 2 phases: low temperature phase (50 ° C), then high temperature phase (100 ° C)
-Grease amount: 1 g, applied as a thin continuous film before testing

  All greases containing MoDTC in combination with graphite have a much lower molybdenum content than commercial grease A for improved wear performance.

  Greases E and I have the additional advantage of having a coefficient of friction as low as that of commercial grease A.

Claims (22)

Grease composition comprising:
(A) one or several mineral or synthetic base oils, alone or as a mixture;
(B) one or several simple or complex fatty acid metal soaps as thickeners;
(C) at least one molybdenum dithiocarbamate; and (d) graphite.   2. The grease composition according to claim 1, wherein the molybdenum content is 1,000 to 2,800 ppm (preferably 1,500 to 2,500 ppm, preferably 1,700 to 2,300 ppm, preferably 2,000 to 2,200 ppm).   The grease composition according to any one of claims 1 to 2, comprising 0.5 to 3.0% by mass (preferably 0.7 to 2.0% by mass) of graphite.   The grease according to any one of claims 1 to 3, wherein the Mo / [graphite] ratio of the molybdenum content (ppm) in the composition to the mass percentage of graphite is 1,250 to 1,550 (preferably 1,300 to 1,500). Composition.   The grease composition according to any one of claims 1 to 4, comprising phosphorus in a content of less than 1,500 ppm (preferably less than 1,200 ppm).   6. The grease composition according to any one of claims 1 to 5, comprising zinc in a content of less than 1,500 ppm. The grease composition according to any one of claims 1 to 6, which does not contain a MoS ₂ solid lubricant.   The grease composition according to any one of claims 1 to 7, which does not contain a polytetrafluoroethylene solid lubricant.   9. Grease composition according to any one of claims 1 to 8, comprising only one or several simple or complex fatty acid metal soaps as thickener.   10. Grease composition according to any one of claims 1 to 9, comprising at least one simple, complex soap of lithium, sodium, calcium, barium or titanium, alone or as a mixture, as a thickener.   11. Grease composition according to any one of claims 1 to 10, comprising one or several simple or complex lithium soaps as a thickener.   12. Grease composition according to any one of claims 1 to 11, comprising a mineral base oil (a) and a synthetic base oil (a), preferably a synthetic base oil selected from polyalphaolefins.   Grease according to any one of claims 1 to 12, further comprising a polymer (e) selected from polyisobutene, olefin copolymer, polymethacrylate, polyalphaolefin (preferably a polymer (e) selected from polyisobutene). Composition.   14. One or several antiwear and / or extreme pressure additives (f) containing phosphorus and sulfur (f), preferably selected from zinc dithiophosphates, according to any one of claims 1-13 The additive further comprises a grease composition.   15. The grease composition according to claim 14, wherein the phosphorus content is 300 to 1,200 ppm (preferably 400 to 1,000 ppm, preferably 500 to 900 ppm).   The grease composition according to any one of claims 14 to 15, wherein the zinc content is 500 to 1,400 ppm (preferably 600 to 1,300 ppm, preferably 800 to 1,000 ppm). The grease composition according to any one of claims 1 to 16, comprising:
70-94% base oil (a);
• 5-25% thickener (b); and 1-5% MoDTC (c) and graphite (d) mixture. The grease composition according to any one of claims 1 to 4 or 7 to 13, comprising:
70-94% base oil (a);
-5-25% thickener (b);
A mixture of 1-5% MoDTC (c) and graphite (d); and • one or several polymers (e) (preferably polyisobutenes) selected from polyisobutenes, olefin copolymers, polymethacrylates, polyalphaolefins Possible balance consisting of one or several polymers (e)) selected from The grease composition according to any one of claims 14 to 17, comprising:
70 to 93.9% base oil (a);
-5-23.5% thickener (b);
A mixture of 1-5% MoDTC (c) and graphite (d); and 0.1-1.5% of one or several antiwear and / or extreme pressure additives containing phosphorus and sulfur ( f) Additives selected from (and preferably zinc dithiophosphate). The grease composition according to any one of claims 14 to 17, comprising:
70 to 93.9% base oil (a);
-5-23.5% thickener (b);
A mixture of 1-5% MoDTC (c) and graphite (d);
From 0.1 to 1.5% of one or several antiwear and / or extreme pressure additives (f) containing phosphorus or containing phosphorus and sulfur (preferably zinc dithiophosphate) One or several polymers (e) selected from polyisobutenes, olefin copolymers, polymethacrylates, polyalphaolefins (preferably one or several polymers selected from polyisobutenes (e Possible remainder consisting of)).   Use of the grease composition according to any one of claims 1 to 20 as a grease for a constant speed joint of an automobile power transmission device.   A constant velocity joint filled with the grease according to any one of claims 1 to 20.