KR20080087040A - Grease composition - Google Patents

Abstract

A grease composition comprising base oil, one or more urea thickeners, (A) in the range of from 0.1 to 5 weight% of tungsten disulphide and (B) in the range of from 0.1 to 5 weight% of one or more of zinc dithiophosphates and/or one or more molybdenum dialkyl dithiocarbamates, based on the total weight of the grease composition.

Description

Grease composition {GREASE COMPOSITION}

The present invention relates to a grease composition, in particular a low friction grease composition, whereby abrasions occurring in oil-coated parts such as bearings and gears can be reduced.

Greases with excellent friction wear characteristics are required, for example, in the bearings or gears of mechanical devices in the automotive, iron and steel, railway tracks and other industries. In particular, it is important in lubrication applications such as ball screw of constant velocity joints and injection molding machines of automobiles and drive devices of electric compression molding machines, where both rolling friction and sliding friction exist.

Typically, greases with excellent lubrication properties are prepared by adding molybdenum disulfide to the lithium soap thickener grease composition. Recently, greases are prepared by simultaneously adding an organic molybdenum compound and zinc dithiophosphate to the urea thickener grease. Such urea thickener greases are used for the purpose of reducing frictional wear characteristics. For example, published Japanese Patent Application No. 62-207397 discloses a grease composition comprising a sulfur-phosphorus type extreme pressure additive, wherein (a) molybdenum dialkyl dithiocarbamate sulfide (b) One or more ingredients selected from the group consisting of sulfurized oils, sulfurized olefins, tricresyl phosphates, trialkyl dithiophosphates, and zinc dialkyl dithiophosphates are combined with each other as essential ingredients.

Published Japanese Patent Application No. 63-046299 discloses a grease composition in which, as an additive, molybdenum dialkyldithiocarbamate sulfide and molybdenum dithiophosphate and optionally zinc dithiophosphate are simultaneously mixed with urea thickener grease.

However, in some jurisdictions, such as Japan, grease additives containing ordinary molybdenum such as those described above are defined as limiting substances. These chemicals are limited because of the risk of harmful effects on human health and ecosystems,

(E.g., Japanese PRTR Act: Pollutant Release Transfer Register; Law for promotion of Chemical Management) .For products containing more than a certain amount of this substance, the laws of these jurisdictions require the submission of an MSDS (Material Safety Data Sheet). Can be.

Lead and antimony compounds, also defined as PRTR limiting substances, have been used in grease compositions for many years. However, these components have almost been replaced by sulfur-free extreme pressure additives of this type or of this type.

However, the aforementioned molybdenum compounds, in particular molybdenum dialkyl dithiocarbamate sulfides, have an excellent effect on reducing friction and wear and are difficult to find replacements for. Moreover, even when these substitutes are added to the grease, significant amounts may be necessary to ensure a sufficiently low friction coefficient.

 Tungsten disulfide, known as solid lubricant, is a material that is not defined as a PRTR limiting material. Published Japanese Patent Application No. 2003-301188 discloses that a powder for density control is prepared by adding tungsten disulfide to lithium soap grease containing polyoxy propylene and glyceryl ether as a base oil, so that the used grease is used in water. When liberated, this grease floats or sinks.

 Avoiding the use of molybdenum compounds that are the subject of the previously mentioned PRTR limiting substances and / or reducing the amount of these components used in grease compositions improves safety, places little environmental burden with excellent friction and wear characteristics It is highly desirable to develop grease compositions.

Currently, grease compositions with low friction properties and excellent wear resistance have been surprisingly developed by mixing tungsten disulfide and zinc dithiophosphate and / or molybdenum dithiocarbamate with urea thickener grease.

Thus, the present invention relates to a base oil and at least one urea thickener, tungsten disulfide in the range of 0.1 to 5% by weight and (B) at least one zinc dithiophosphate in the range of 0.1 to 5% by weight, based on the total weight of the grease composition. And / or one or more molybdenum dithiocarbamates.

In a preferred specific example, the grease composition of the present invention may further comprise (C) one or more molybdenum dithiophosphates.

According to the present invention, the molybdenum compound designated as the PRTR limiting material may not be used or the usage may be relatively reduced, thereby obtaining a grease composition having excellent friction wear characteristics and high stability.

According to the invention, the base oil in the grease composition can conveniently be selected from synthetic oils such as ester oils, ether oils, hydrocarbon oils or mixtures thereof and mineral oils, vegetable oils.

One or more urea thickeners in the grease composition of the present invention may be selected from urea compounds such as monourea, diurea, triurea, tetraurea or other polyureas.

Diurea compounds are readily obtained by the reaction of diisocyanates with monoureas; Tetraurea compounds can be obtained by the reaction of diisocyanases, monoureas and diamines.

Examples of diisocyanates that can be used to make the urea compound include diphenylmethane diisocyanate, tolylene diisocyanate, totolylene diisocyanate and naphthylene diisocyanate.

In addition, examples of monoamines that may be used to make the urea compound include octylamine, dodecylamine, stearylamine, oleylamine, aniline, paratoluidine and cyclohexylamine. In addition, examples of the diamines that may be used to make the urea compound include ethylene diamine, propane diamine, butane diamine and phenylene diamine.

In a preferred specific example, the grease composition of the present invention may comprise one or more urea thickeners in a total amount ranging from 1 to 25% by weight, based on the total weight of the grease composition.

The grease compositions of the present invention comprise one or more additional thickeners such as metal soaps, organic materials, inorganic materials such as lithium soaps, lithium composite soaps, sodium terephthalate, urea / urethane components and clays.

The tungsten disulfide used as the component (A) mentioned above in the grease composition of the present invention is preferably a powder having an average particle size of 10 µm or less obtained by the Fisher Sub-sieve Sizer. More preferably, the tungsten disulfide used is a powder having an average particle size of about 0.6 μm obtained by the aforementioned method.

The one or more zinc dithiophosphates which can be used as the aforementioned component (B) in the grease composition of the present invention may conveniently be selected from zinc dialkyl dithiophosphates and / or zinc diaryl dithiophosphates. Preferably, said at least one zinc dithiophosphate may be selected from compounds of formula (I):

R 'in formula (I) represents a primary or secondary alkyl group or an aryl group, which may be the same or different. Preference is given to using primary or secondary alkyl groups as R '.

Specific examples of the above R 'methyl group, ethyl group, propyl group, isopropyl group, butyl group, secondary butyl group, isobutyl group, pentyl group, 4-methyl pentyl group, hexyl group, 2-ethyl hexyl group, heptyl group , Octyl group, nonyl group, decyl group, isodecyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, eicosyl group, docosyl group, tetracosyl group, cyclopentyl group, cyclohexyl group, methyl cyclohexyl Real group, ethyl cyclohexyl group, dimethyl cyclohexyl group, cycloheptyl group, phenyl group, tolyl group, xylyl group, ethyl phenyl group, propyl phenyl group, butyl phenyl group, pentyl phenyl group, hexyl phenyl group, heptyl phenyl group, octyl phenyl group, nonyl phenyl group, decyl phenyl group , Dodecyl phenyl group, tetradecyl phenyl group, hexadecyl phenyl group, octadecyl phenyl group, benzyl group and phenethyl group.

Specific examples of the above primary alkyl zinc dithiophosphate include zinc diisopropyl dithiophosphate, zinc diisobutyl dithiophosphate and zinc diisodecyl dithiophosphate.

In addition, specific examples of the above secondary dialkyl zinc dithiophosphate include zinc mono or di-sec-butyl dithiophosphate, zinc mono or di-sec-pentyl dithiophosphate and zinc mono and di-4-methyl-2-. Pentyl dithiophosphate.

 Specific examples of the above zinc aryl dithiophosphates include zinc di-para-dodecyl phenol dithiophosphate, zinc di-heptyl phenol dithiophosphate and zinc di-para-nonyl phenol dithiophosphate.

Preferred examples of one or more molybdenum dialkyl dithiocarbamates which may be used as component (B) in the grease composition of the present invention may be selected from the following formula (II) compounds.

(R ¹ R ² N-CS-S) ₂ Mo ₂ O _m S _n

R ¹ and R ² in formula (II) may each be independently selected from alkyl groups having carbon numbers ranging from 1 to 24, preferably carbon atoms ranging from 3 to 18, m is an integer ranging from 1 to 3, n is an integer ranging from 1 to 4 and m + n = 4.

Specific examples of one or more molybdenum dialkyl dithiocarbamates mentioned above include molybdenum diethyl dithiocarbamate sulfide, molybdenum dipropyl dithiocarbamate sulfide, molybdenum dibutyl dithiocarbamate sulfide, molybdenum dipentyl dithiocarbamate sulfide , Molybdenum dihexyl dithiocarbamate sulfide, molybdenum dioctyl dithiocarbamate sulfide, molybdenum didecyl dithiocarbamate sulfide, molybdenum didodecyl dithiocarbamate sulfide, molybdenum di (butylphenyl) dithiocarbamate sulfide, molybdenum Di (nonylphenyl) dithiocarbamate disulfide, oxy-molybdenum diethyl dithiocarbamate sulfide, oxy-molybdenum dipropyl dithiocarbamate sulfide, oxy-molybdenum dipentyl dithiocarbamate sulfide, oxy-molybdenum dihexyl dity Orca Mate sulfide, oxy-molybdenum dioctyl dithiocarbamate sulfide, oxy-molybdenum didecyl dithiocarbamate sulfide, oxy-molybdenum dididodecyl dithio carbamate sulfide, oxy-molybdenum (butylphenyl) dithiocarbamate sulfide, oxy -Molybdenum di (nonylphenyl) dithiocarbamate sulfide and mixtures thereof.

The aforementioned components (A) tungsten disulfide and (B) at least one zinc dithiophosphate and / or at least one molybdenum dithiocarbamate are each mixed in the grease composition of the invention in amounts ranging from 0.1 to 5% by weight. Preferably, the aforementioned components (A) and (B) are each mixed in the grease composition of the invention in amounts ranging from 0.2 to 3% by weight, based on the total weight of the grease composition. If the aforementioned components (A) and (B) are each mixed in an amount of less than 0.1% by weight based on the total weight of the grease composition, a low coefficient of friction cannot be obtained and the frictional wear is not sufficiently improved. Moreover, if the aforementioned components (A) and (B) are mixed in an amount exceeding 5% by weight based on the total weight of the grease composition, no further improvement is observed in terms of beneficial effects.

In the grease composition of the present invention, one or more molybdenum dithiophosphates (C) may be included in amounts ranging from 0.1 to 5% by weight, more preferably from 0.2 to 3% by weight.

The grease compositions of the present invention may be formulated with antioxidants such as amine and / or phenolic antioxidants, extreme pressure additives such as olefin sulfides and / or oil sulfides, viscosity increasing agents such as polybutene and / or Or polymethacrylates, solid lubricants such as molybdenum disulfide and / or boron nitride, metal salts that can be used as waterproofing or structural stabilizers, such as sulfonates, salicylates and / or phenates and extreme pressures. It may include various types of known additives such as phosphites and / or phosphates which may be used as abrasion reducers.

The invention further provides a method for reducing friction and / or wear in bearings, gears and / or joints in a mechanical device, the method comprising lubricating the bearings, gears and joints with the grease composition described above.

The present invention also provides bearings, gears and joints wherein the grease composition described above is used as a lubricant.

The invention also proposes the use of the grease composition described above for lubricating bearings, gears and / or joints.

The invention has been described below with respect to the following examples, which are not intended to limit the scope of the invention in any way.

The following base grease and additives were treated in a three-roll mill with the mixed compositions shown in Tables 1 to 4 to obtain grease compositions Examples 1 to 7 and Comparative Examples 1 to 8.

[1] base greases

[1-1] Diurea Greece

Diphenyl methane-4,4'-diisocyanate (295.2 g) and octylamine (304.8 g) were refined mineral oil (5400 g) having a kinematic viscosity of about 15 mm ² / s at 100 ° C.

       In the reaction mixture, the produced diurea compound was uniformly dispersed to obtain a base grease. The content of urea compound in the base grease was 10% by weight. The concentration (25 ° C., 60 W) of the diurea grease according to JS-K2220 was 283 and the dropping point was 263 ° C.

[1-2] tetraurea grease

       Diphenyl methane-4,4'-diisocyanate (382.7 g), stearylamine (411.4 g)

And ethylene diamine (46.0 g) were reacted in purified mineral oil (5160 g) having a kinematic viscosity of about 15 mm ² / s at 100 ° C., and the resulting urea compound was uniformly dispersed to obtain base grease. The content of urea compound in the base grease was 14% by weight. The concentration of tetraurea grease according to JS-K2220 was 285 (25 ° C., 60 W), and the dropping point was 202 ° C.

[2] additives

[2-1] Tungsten disulfide (denoted WS ₂ in the table): Tungsten disulfide powder having an average particle size of 0.6 µm was used under the trade name "Tanmik B" from Nippon Lubricants Ltd. .

[2-2] Zinc dithiophosphate (denoted Zn-DTP in the table): An additive sold under the trade name "Lubrizol 1395" by Lubrizol Inc. was used.

[2-3] Molybdenum dithiocarbamate (denoted Mo-DTC in the table): An additive sold under the trade name "Molyvan A" by Vanderbilt Inc. was used.

[2-4] Molybdenum dithiophosphate (denoted as Mo-DTP in the table): An additive sold under the trade name "Sakuralube 300" by Asahi Electrochemical Industries Ltd. was used.

[2-5] Molybdenum disulfide (denoted as MoS ₂ in the table): Molybdenum disulfide having an average particle size of 0.7 μm manufactured by CLIMAX MOLYBDENUM UK Ltd was used.

[2-6] Graphite (marked graphite in the table): Graphite produced under the trade name "FAHN" by Fuji Graphite Ltd was used.

Falex Abrasion Resistance Test

In order to confirm the performance of the grease compositions obtained according to the examples and the comparative examples, the Falex wear resistance test was carried out and the evaluation of the wear coefficient and wear resistance (surface roughness of the test sample) for the grease composition was carried out.

The Falex wear resistance test was based on IP 241 (IP: Institute of Petroleum, UK); After the test was completed, this test was conducted under the following conditions to obtain a wear coefficient. Moreover, Rmax (micrometer) (maximum surface roughness) of the control test sample was measured.

Exam conditions

Rotational Speed: 290 ± 10 rpm

Temperature: room temperature (about 25 ℃)

Load: 890 N (200 lbf)

Time: 15 minutes

Amount of grease used: Approximately 1 g was used for the test sample.

Test result

The results of the Falex wear resistance test are shown in Tables 1-4.

Table 1

 Example One 2 3 4   Composition (wt%) Bass grease Diurea greece 96.0 98.0 96.0 95.0 Tetraurea greece - - - - additive WS ₂ 3.0 1.0 2.0 2.0 Zn-DTP 1.0 - - 1.0 Mo-DTC - 1.0 1.0 1.0 Mo-DTP - - 1.0 1.0 gun 100.0 100.0 100.0 100.0  Falex Exam Friction coefficient, μ 0.081 0.082 0.056 0.057 Surface roughness, Rmax (μm) 9.3 10.1 6.6 5.9

TABLE 2

 Example 5 6 7  Composition (wt%) Bass grease Diurea greece - - - Tetraurea greece  96.0  96.0  96.0 additive WS ₂  2.0  2.0  3.0 Zn-DTP  1.0  1.0  - Mo-DTC  1.0  -  1.0 Mo-DTP  -  1.0  - gun  100.0  100.0  100.0  Falex test  Friction coefficient, μ  0.060  0.070  0.083  Surface Roughness, Rmax (㎛)  7.8  5.9  8.1

TABLE 3

 Comparative example One 2 3 4   Composition (wt%) Bass grease Diurea greece  97.0  97.0  97.0  97.0 Tetraurea greece  -  -  -  - additive WS ₂  3.0  -  -  - Zn-DTP  -  3.0  -  - Mo-DTC  -  -  3.0  - Mo-DTP  -  -  -  3.0 Mo-S ₂  -  -  -  - black smoke - -  -  - gun  100.0  100.0  100.0  100.0  Falex Exam Friction coefficient, μ  0.116  0.090  0.079  0.072 Surface roughness, Rmax (μm)  36.2  21.9  35.0  17.2

Table 4

 Comparative example  5  6  7  8   Composition (wt%) Bass grease Diurea greece  98.0  -  96.0  - Tetraurea greece  -  98.0  -  96.0 additive WS ₂  -  -  -  - Zn-DTP  1.0  1.0  -  1.0 Mo-DTC  1.0  1.0  1.0  - Mo-DTP  -  -  1.0  - Mo-S ₂  -  -  2.0  - black smoke - -  -  3.0 gun  100.0  100.0  100.0  100.0 Falex Exam Friction coefficient, μ  0.094  0.103  0.090  0.123 Surface roughness, Rmax (μm)  12.1  11.3  14.0  31.2

As clearly shown in Tables 1 and 2, Examples 1 to 7 exhibit low frictional properties with coefficients of friction of approximately 0.056 to 0.083 in the Palex test and values of approximately 5.9 to 10.1 μm at the maximum surface roughness of the test specimen. It shows abrasion resistance.

On the contrary, as clearly shown in Tables 3 and 4, the products of Comparative Examples 1 to 8 show unsatisfactory results with respect to both the friction coefficient and the wear resistance characteristics in each case.

Specifically, the products of Comparative Examples 1, 2, 5, 7 and 8 show high values at high coefficient of friction and maximum surface roughness of the test sample. The products of Comparative Examples 3 and 4 exhibit relatively low coefficient of friction values but the maximum surface roughness of the test sample has a high value; The low coefficient of friction in this case is presumed to be due to the lower pressure on the contact surface due to the increased wear. In the case of the product of Comparative Example 6, the maximum surface roughness of the test sample is relatively close to that of the example, but this product has a high coefficient of friction value.

In addition, as can be seen by comparing the Examples with Comparative Examples 7, 8, in the case of molybdenum disulfide or graphite, which is a lattice layer structure material such as tungsten disulfide used in the present invention, excellent low coefficient of friction and good wear resistance as in the actual examples are obtained. Results that satisfy all of the conditions provided are not obtained even when the above materials are used, for example with Mo-DTC, Mo-DTP or Zn-DTP.

Therefore, with the grease composition according to the present invention, excellent lubricating effect can be obtained without using a molybdenum compound such as molybdenum dialkyl dithiocarbamate sulfide, or the amount of the molybdenum compound can be reduced.

Claims (10)

One or more zinc dithiophosphates and / or one or more of (A) 0.1 to 5% by weight tungsten disulfide and (B) 0.1 to 5% by weight based on the total weight of the base oil, one or more urea thickeners, grease composition A grease composition comprising molybdenum dialkyl dithiocarbamate. The grease composition of claim 1, further comprising (C) at least one molybdenum dithiophosphate. The grease composition of claim 2, wherein the at least one molybdenum dithiophosphate (C) is present in an amount ranging from 0.1 to 5 wt% based on the total weight of the grease composition. The grease composition of claim 1, wherein the at least one urea thickener is present in an amount ranging from 1 to 25 wt% based on the total weight of the grease composition. The grease composition according to any one of claims 1 to 3, wherein the tungsten disulfide (A) is a powder having an average particle size of less than 10 m obtained by the Fisher method. 6. The grease composition of claim 1, wherein at least one zinc dithiophosphate is selected from compounds of formula (I): 7. [ Formula I ]

R ′ in formula (I) refers to a primary or secondary alkyl group or an aryl group, which may be the same or different. The method of claim 1, wherein the one or more zinc dithiophosphates are zinc diisopropyl dithiophosphate, zinc diisobutyl dithiophosphate, zinc diisodecyl dithiophosphate, zinc mono or di- sec-butyl dithiophosphate, zinc mono or di-sec-pentyl dithiophosphate, zinc mono or di-4-methyl-2-pentyl dithiophosphate, zinc di-para-dodecyl phenol dithiophosphate, zinc di- A grease composition selected from heptyl phenol dithiophosphate and zinc di-para-nonylphenol dithiophosphate. 8. The grease composition of claim 1, wherein at least one molybdenum dithiocarbamate is selected from compounds of formula (II): [ Formula II ] (R ¹ R ² N-CS-S) ₂ Mo ₂ O _m S _n R ¹ and R ² in formula (II) may each be independently selected from alkyl groups having 1 to 24 carbon atoms, m is an integer from 0 to 3, n is an integer from 1 to 4, and m + n = 4. A method of reducing friction and / or wear in bearings, gears and / or joints of a mechanical device, comprising lubricating the bearings, gears and / or joints with the grease composition according to any one of claims 1-8. How to include. Use of the grease composition according to any one of claims 1 to 9 used for lubricating bearings, gears and / or joints.