JP6682271B2 - Grease composition - Google Patents

Description

  The present invention relates to a grease composition.

  Grease is a semi-solid lubricant in which a fibrous thickening agent is dispersed in a base oil, and is more likely to adhere to the lubricated part and less likely to flow out than the lubricating oil. Therefore, it is possible to make the lubrication system a simple structure, and it is mainly used for lubrication of rolling bearings, slide bearings, mechanical elements such as ball screws, linear motion guides, gears, etc., and is used for industrial machines and transportation machine systems. Widely used.

  In recent years, energy saving is required, and reduction of energy loss of various mechanical systems has become an urgent issue. In the case of automobile engine oil, in order to ensure fuel efficiency, the viscosity of the lubricating base oil should be as low as possible to reduce energy loss due to the viscous resistance of the lubricating oil and reduce the frictional resistance of sliding parts. Therefore, it is effective to optimally prescribe various additives such as friction reducing agents (Patent Document 1).

  On the other hand, in the case of grease which is a non-Newtonian fluid, it is necessary to consider not only the base oil viscosity but also the apparent viscosity including the structural viscosity caused by the fibrous thickener dispersed in the base oil. It is known that the apparent viscosity can be simply organized by the so-called consistency, and that the viscosity is high (soft) and the viscous resistance is low (Non-Patent Document 1).

JP 2012-102281 A

Fundamentals and Applications of Lubricating Greases, pp. 49-89, Japan Society of Tribology Grease Research Group, Yokendo, 2007

  However, it is not always easy to secure a proper consistency when applying it to a mechanical system while lowering the viscous resistance. In other words, if the grease is too soft, it scatters due to the centrifugal force that accompanies the rotational movement or flows out from the mechanical element. On the other hand, if it is too hard, it causes sliding resistance and hinders desired movement. In other words, in the case of the conventional grease, there was no choice but to practice the optimum prescription while balancing the base oil composition and the amount of the thickener.

  The problem to be solved by the present invention is to provide a grease composition having a low sliding resistance and capable of significantly reducing the power consumption of mechanical elements, particularly the power consumption during rotation of a bearing.

  As a result of intensive studies to solve the above problems, the present inventors used each of the base oils individually as a base oil of grease by mixing a predetermined amount of specific base oils having different properties. It was found that the power consumption during bearing rotation can be significantly reduced compared to grease.

To reduce the energy required to rotate the bearing and save energy, the rolling resistance and sliding resistance between the bearing rolling elements (balls, rollers) and the bearing rings (inner and outer rings) should be reduced as much as possible. It is important, and it is generally considered to be useful to lower the viscosity of the base oil of the lubricating oil (lubricating oil or grease), and to add an oily agent having a friction reducing effect as an additive. However, in the case of grease, it is necessary to expose the base oil to high temperature conditions in the process of manufacturing the thickener, and there is a limit to the reduction of viscosity in terms of evaporation of the base oil and safety. Further, there has been a problem that the effect of the friction-reducing additive decreases with the use time. On the other hand, the present inventors focused on the oil film forming ability of the bearing sliding portion and the viscosity change due to the temperature of the lubricating base oil, and formed a sufficient oil film between the bearing rolling element and the race to form a direct contact between them. to reduce energy loss, large molecular conformation to the components of the base oil, specifically be contained components (n-d-M ring analysis% C _a) containing an aromatic, and the temperature rise It has been found that it is effective to contain a paraffin component having a high viscosity index (% C _P by nd-M ring analysis) in a well-balanced manner in order to avoid a decrease in viscosity due to the above.

  The present invention has been made based on the above findings, and provides the grease composition described in [1] to [9] below.

[1] A grease composition containing a lubricating base oil and a thickener, wherein the lubricating base oil has a% C _{A of} n-d-M ring analysis value according to ASTM D3238 of 2 to 8, A first lubricating base oil having a% C _P of 50 to 75, and a% d C ring analysis% C _A according to ASTM D3238 of 1 or less, a% C _P of 70 or more, and a urea adduct value of 4 mass. % Of the second lubricating base oil, and the content of the first lubricating base oil is 5 to 90% by mass based on the total amount of the lubricating base oil. The grease composition, wherein the content of the lubricating base oil is 10 to 95% by mass.
[2] The grease composition according to [1], which has a consistency of 220 to 300.
[3] The grease composition according to [1] or [2], further containing an organic molybdenum compound.
[4] The grease composition according to [3], wherein the organic molybdenum compound contains at least one selected from molybdenum dithiocarbamate and molybdenum dithiophosphate.
[5] The grease composition according to any one of [1] to [4], wherein the first lubricating base oil has a kinematic viscosity at 40 ° C. of 10 to 700 mm ² / s and a viscosity index of 90 to 120. .
[6] The grease composition according to any one of [1] to [5], wherein the second lubricating base oil has a kinematic viscosity at 40 ° C. of 10 to 5000 mm ² / s and a viscosity index of 110 to 150. Stuff.
[7] The grease composition according to any one of [1] to [6], wherein the second lubricating base oil contains at least one selected from mineral oils and synthetic hydrocarbons.
[8] The grease composition according to any one of [1] to [7], wherein the thickener contains at least one selected from metal soap compounds and urea compounds.
[9] A grease composition containing a lubricating base oil, a thickener, and an organic molybdenum compound, wherein the lubricating base oil is% C of the n-d-M ring analysis value according to ASTM D3238. by _a 2 to 8,% _{C P} is the first and the lubricating oil base oil is 50~75, n-d-M ring analysis value of% _{C a} by ASTM D3238 of not more than 1,% _{C P} is 70 or more A second lubricating base oil, wherein the content of the first lubricating base oil is 5 to 90 mass% based on the total amount of the lubricating base oil, and the second lubricating oil is included. A grease composition having a base oil content of 10 to 95 mass% and a consistency of 220 to 300.

  The grease composition of the present invention has a special effect that the amount of electric power consumed for bearing rotation is small.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

The grease composition according to the embodiment of the present invention contains a lubricating base oil and a thickener. Lubricant base oil, the first and the lubricating oil base oil n-d-M ring analysis value of% _{C A} by ASTM D3238 there is 2 to 8,% _{C P} 50 to 75, according to ASTM D3238 n-d % of -M ring analysis value C _a is 1 or less,% C _P is 70 or more, containing a second lubricating base oil the urea adduct value is not more than 4 mass%, a. The mixing ratio of the first lubricating base oil and the second lubricating base oil is such that the content of the first lubricating base oil is 5 to 90% by mass based on the total amount of the lubricating base oil. The content of the lubricating base oil of No. 2 is 10 to 95% by mass.

In the present embodiment, focusing on the oil film forming ability of the bearing sliding portion and the viscosity change due to the temperature of the lubricating base oil, a sufficient oil film is formed between the bearing rolling element and the bearing ring to reduce energy loss due to direct contact between them. In order to reduce it, the "wedge effect" associated with rolling of the bearing ring and the bearing rolling element is used, and the component of the base oil has a large three-dimensional base oil constituent molecule, specifically, a component containing an aromatic (n- The first lubricating base oil is used based on the present inventors' finding that it is effective to include% C _A ) by dM ring analysis.

Regard n-d-M ring analysis value by ASTM D3238, the% _{C A} of the first lubricating base oil 2-8, preferably 2-6, more preferably 4-6. % Reduction in energy loss and C _A is less than 2 becomes insufficient, also tends low content of relatively paraffinic components exceeds 8, the viscosity reduction at a high temperature becomes large, the oil film forming ability Is insufficient in terms of.

% _{C P} of the first lubricating base oil is 50 to 75, preferably 60 to 70. If the% C _P is less than 50, the viscosity at high temperature is largely reduced and the oil film forming ability is poor, and if it exceeds 75, the content of the component containing an aromatic component tends to be relatively small, and the energy loss reducing effect is obtained. Is insufficient.

  The viscosity index of the first lubricating base oil is preferably 90 to 120, more preferably 95 to 115, and further preferably 100 to 110. When the viscosity index is 90 or more, the decrease in viscosity due to temperature rise can be suppressed, and the oil film forming ability is further improved.

The kinematic viscosity at 40 ° C. of the first lubricating base oil is not particularly limited, but from the viewpoint of safely preparing a grease having excellent lubricity, it is preferably 10 to 700 mm ² / s, more preferably 20 to 500 mm. ² / s, and more preferably 25 to 70 mm ² / s.

  The viscosity index and the kinematic viscosity at 40 ° C. in the present invention mean the viscosity index measured according to JIS K2283 and the kinematic viscosity at 40 ° C., respectively.

The first lubricating base oil is a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation or further vacuum distillation to obtain a distillate refined by various refining processes, and nd according to ASTM D3238. % _{C a} is 2 to 8,% _{C P} of -M ring analysis value can be mentioned those 50 to 75. The refining process includes hydrorefining, solvent extraction, solvent dewaxing and the like, and these can be combined and treated in an appropriate order to obtain the first lubricating base oil of the present embodiment. A mixture of two or more refined oils having different properties, which are obtained by different crude oils or distillate oils by different process combinations and sequences, is also useful. As long as the properties of the obtained first lubricating base oil are adjusted so as to satisfy the physical properties described above, the first lubricating base oil obtained by any method can be preferably used.

  In the present embodiment, it is effective to add a chain hydrocarbon component having a low traction coefficient and a paraffin component to the base oil at the closest position between the bearing rolling element and the bearing ring, which are elastic fluid lubrication. Based on the knowledge of the present inventor, the second lubricating base oil is used.

On the other hand, the inventors of the present invention have found that, even if the amount of paraffin components in the lubricating base oil is large, if the paraffin components do not have appropriate branching, the viscosity increase in the low temperature range becomes large, and the torque at the start of the bearing at low temperatures becomes large. However, the urea adduct value was found to be effective as an index of the paraffin content that causes torque increase at low temperature bearing startup. I found it. Then, the present inventors mixed the second lubricating base oil with the urea adduct value,% C _P and% C _A satisfying specific conditions, respectively, into the first lubricating base oil to start at low temperature. It has been found that it is possible to reduce the torque of the bearing from room temperature to a high temperature range while suppressing a rapid increase in torque.

Regard n-d-M ring analysis value by ASTM D3238,% _{C A} of the second lubricating base oil, 1 or less, preferably 0.8 or less. When% C _A exceeds 1, it becomes impossible to adequately supply a suitable paraffin component having a low traction coefficient to the closest position between the bearing rolling element and the bearing ring, which is elastohydrodynamic lubrication.

The% C _P of the second lubricating base oil is 70 or higher, preferably 75 or higher, more preferably 80 or higher. If% C _P is less than 70, the effect of reducing the traction coefficient at the closest position between the bearing rolling element and the bearing ring, which becomes elastohydrodynamic lubrication, becomes insufficient.

  The urea adduct value of the second lubricating base oil is 4% by mass or less, and preferably 3.5% by mass, from the viewpoint of suppressing an increase in viscosity in a low temperature range and suppressing an increase in torque at bearing startup at a low temperature. % Or less, more preferably 3% by mass or less. The urea adduct value of the second lubricating base oil may be 0% by mass, but it is possible to obtain a lubricating base oil having a higher viscosity index while sufficiently suppressing the torque increase at bearing startup at low temperature. Further, from the viewpoint that the dewaxing condition is relaxed and the economy is excellent, the content is preferably 0.1% by mass or more, more preferably 0.5% by mass or more.

  The urea adduct value in the present invention is measured by the following method. 100 g of the weighed sample oil (lubricating base oil) is placed in a round bottom flask, 200 g of urea, 360 ml of toluene and 40 ml of methanol are added, and the mixture is stirred at room temperature for 6 hours. As a result, white granular crystals are formed as urea adducts in the reaction solution. The reaction solution is filtered through a 1-micron filter to collect the produced white granular crystals, and the obtained crystals are washed 6 times with 50 ml of toluene. The recovered white crystals are put in a flask, 300 ml of pure water and 300 ml of toluene are added, and the mixture is stirred at 80 ° C. for 1 hour. The aqueous phase is separated and removed with a separating funnel, and the toluene phase is washed 3 times with 300 ml of pure water. A desiccant (sodium sulfate) is added to the toluene phase for dehydration, and then toluene is distilled off. The ratio (mass percentage) of the urea adduct thus obtained to the sample oil is defined as the urea adduct value.

  In the measurement of the urea adduct value, as the urea adduct, a component of isoparaffin that causes a torque increase at low temperature bearing startup, and further normal paraffin when residual normal paraffin remains in the lubricating base oil. Since it can be accurately and reliably collected, it is an excellent index for the content ratio of normal paraffin and the specific isoparaffin. The inventors of the present invention have found that the main component of the urea adduct is normal paraffin and an isoparaffin urea adduct having a carbon number of 6 or more from the end of the main chain to the branching position by analysis using GC and NMR. Have confirmed.

  The viscosity index of the second lubricating base oil is 110-150, preferably 115-140, more preferably 125-140. When the viscosity index is 110 or more, the decrease in viscosity at high temperature can be suppressed, and the oil film forming ability is further improved. When the viscosity index is 150 or less, the production cost for obtaining the lubricating base oil is excellent.

The kinematic viscosity of 40 ° C. of the second lubricating base oil is preferably 10~5000mm ² / s, more preferably 20~3000mm ² / s, more preferably 25~70mm ² / s. When the kinematic viscosity at 40 ° C. is 10 mm ² / s or more, a decrease in flash point can be suppressed, and the grease can be manufactured safely. When the kinematic viscosity at 40 ° C. is 5000 mm ² / s or less, an increase in viscous resistance can be suppressed, and energy saving characteristics are further excellent.

  The second lubricating base oil is preferably one or more selected from mineral oils and synthetic hydrocarbon oils having the above properties. A base oil obtained by mixing a mineral oil and a synthetic hydrocarbon oil may be used as the second lubricating base oil.

The mineral oil of the second lubricating base oil is a lubricating oil distillate obtained by distilling a crude oil under atmospheric distillation or further distilling under reduced pressure, and refined by various refining processes according to ASTM D3238. The nd-M ring analysis has a% C _A of 1 or less, a% C _P of 75 or more, and a urea adduct value of 4% by mass or less. The refining process includes hydrocracking, hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, and the like, which are combined in an appropriate order to process the second lubricating base oil component of the present invention. Obtainable. A mixture of two or more refined oils having different properties, which are obtained by different crude oils or distillate oils by different process combinations and sequences, is also useful. As long as the properties of the obtained second lubricating base oil are adjusted so as to satisfy the above-mentioned physical properties, the second lubricating base oil obtained by any method can be preferably used.

Examples of the synthetic hydrocarbon oil of the second lubricating base oil include polyolefins such as poly-α-olefin, polybutene and copolymers of two or more kinds of various olefins, alkylbenzene, alkylnaphthalene, and the like, according to ASTM D3238. The nd-M ring analysis has a% C _A of 1 or less, a% C _P of 75 or more, and a urea adduct value of 4% by mass or less. Among these, poly-α-olefins are preferable in terms of availability, cost, viscosity characteristics, oxidation stability, and compatibility with system members. As the poly-α-olefin, a polymer such as 1-dodecene or 1-decene is more preferable in terms of cost.

  In the present embodiment, the second lubricating base oil may consist of only one of mineral oil and synthetic hydrocarbon oil, or may be a mixture of both. That is, as a preferable combination of the first lubricating base oil and the second lubricating base oil, the first lubricating base oil (mineral oil) and the second lubricating base oil (mineral oil), the first lubricating base oil (mineral oil), Lubricating oil base oil (mineral oil) and second lubricating base oil (synthetic hydrocarbon oil), or first lubricating base oil (mineral oil) and second lubricating base oil (mineral oil and synthetic carbon) A mixed base oil with hydrogen) can be exemplified. The first lubricating base oil (mineral oil), the second lubricating base oil (mineral oil), and the second lubricating base oil (synthetic hydrocarbon oil) may each be one kind or two or more kinds. It may be.

  The content of the first lubricating base oil is 5 to 90% by mass, preferably 10 to 80% by mass, and more preferably 30 to 60% by mass, based on the total amount of the lubricating base oil. The content of the second lubricating base oil is 10 to 95% by mass, preferably 20 to 90% by mass, and more preferably 40 to 70% by mass, based on the total amount of the lubricating base oil. If the contents of the first and second lubricating base oils are out of the above ranges, the desired power consumption reduction effect may not be obtained.

  The content of the lubricating base oil is, based on the total amount of the grease composition, preferably 70 to 98% by mass, and particularly preferably 80 to 97% by mass.

  The thickener preferably contains at least one selected from metal soap compounds (also referred to as “metal soap thickener”) and urea compounds (also referred to as “urea thickener”).

  Examples of the metal soap thickener include single soap and complex soap. The single soap is a metal soap obtained by saponifying a fatty acid or fat with an alkali metal hydroxide or an alkaline earth metal hydroxide. Complex soap is a compound obtained by combining a fatty acid used in a single soap and an organic acid having a different molecular structure. The fatty acid may be a fatty acid derivative having a hydroxy group or the like. The fatty acid may be an aliphatic carboxylic acid such as stearic acid or an aromatic carboxylic acid such as terephthalic acid. As the fatty acid, a monovalent or divalent aliphatic carboxylic acid, for example, an aliphatic carboxylic acid having 6 to 20 carbon atoms is used, and particularly, a monovalent aliphatic carboxylic acid having 12 to 20 carbon atoms or 6 to 14 carbon atoms is used. The divalent aliphatic carboxylic acid of is preferably used. As the fatty acid, a monovalent aliphatic carboxylic acid containing one hydroxyl group is preferable. As the organic acid to be combined with the fatty acid in the complex soap, acetic acid, dibasic acids such as azelaic acid and sebacic acid, and benzoic acid are preferable.

  Examples of the metal of the metal soap thickener include alkali metals such as lithium and sodium, alkaline earth metals such as calcium, and amphoteric metals such as aluminum. Among these, alkali metal, especially lithium is preferably used.

  The metal soap thickeners may be used alone or in combination of two or more. The content of the metal soap thickener is, for example, preferably 2 to 30% by mass, more preferably 3 to 20% by mass, and further preferably 10 to 20% by mass based on the total amount of the grease composition.

  As the urea-based thickener, for example, a diurea compound obtained by the reaction of diisocyanate and monoamine, a polyurea compound obtained by the reaction of diisocyanate, monoamine, or diamine can be used.

  Examples of the diisocyanate include aliphatic diisocyanate and aromatic diisocyanate. Examples of the aliphatic diisocyanate include diisocyanates having saturated and / or unsaturated linear, branched, or alicyclic hydrocarbon groups. For example, phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate, diphenylmethane diisocyanate, octadecane diisocyanate, decane diisocyanate, hexane diisocyanate and the like are preferable. Examples of monoamines include aliphatic monoamines and aromatic monoamines. Examples of the aliphatic monoamines include monoamines having a saturated and / or unsaturated linear, branched, or alicyclic hydrocarbon group. For example, octylamine, dodecylamine, hexadecylamine, stearylamine, oleylamine, aniline, p-toluidine, cyclohexylamine and the like are preferable. Examples of the diamine include aliphatic diamine and aromatic diamine. Examples of the aliphatic diamine include diamines having a saturated and / or unsaturated linear, branched, or alicyclic hydrocarbon group. For example, ethylenediamine, propanediamine, butanediamine, hexanediamine, octanediamine, phenylenediamine, tolylenediamine, xylenediamine, diaminodiphenylmethane and the like are preferable.

  The urea thickener may be used alone or in combination of two or more. The content of the urea thickener is, for example, based on the total amount of the grease composition, preferably 2 to 30% by mass, more preferably 3 to 20% by mass, and further preferably 10 to 20% by mass.

  The grease composition preferably contains an organic molybdenum compound. As a result, the life of the bearing can be extended. Examples of the organic molybdenum compound include molybdenum dithiocarbamate, molybdenum dithiophosphate, amine complex of molybdenum, succinimide complex of molybdenum, molybdenum salt of organic acid, molybdenum salt of alcohol and the like. Among these, molybdenum dithiocarbamate and molybdenum dithiophosphate are preferable from the viewpoint of extending the life of the bearing.

As the molybdenum dithiocarbamate, for example, a compound represented by the following general formula (1) can be used.

In the formula (1), R ¹ , R ² , R ³ and R ⁴ may be the same or different and each has 2 to 24 carbon atoms, preferably an alkyl group having 4 to 13 carbon atoms or 6 to 24 carbon atoms, Preferably, it represents a hydrocarbon group such as an aryl group having 8 to 15 carbon atoms (including an alkylaryl group). X ¹ , X ² , X ³ and X ⁴ may be the same or different and each represents a sulfur atom or an oxygen atom. The alkyl group mentioned here includes a primary alkyl group, a secondary alkyl group and a tertiary alkyl group. These may be linear or branched.

  Preferred examples of the alkyl group are ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, Hexadecyl group, heptadecyl group, octadecyl group and the like can be mentioned. These may be primary alkyl groups, secondary alkyl groups or tertiary alkyl groups, and may be linear or branched. Preferred examples of the (alkyl) aryl group include a phenyl group, a tolyl group, an ethylphenyl group, a propylphenyl group, a butylphenyl group, a pentylphenyl group, a hexylphenyl group, an octylphenyl group, a nonylphenyl group, a decylphenyl group, and an unphenyl group. Examples thereof include a decylphenyl group and a dodecylphenyl group. The alkyl group in the (alkyl) aryl group may be a primary alkyl group, a secondary alkyl group or a tertiary alkyl group, and may be linear or branched. The (alkyl) aryl group includes all substitution isomers having different substitution positions of the alkyl group with respect to the aryl group.

  As more preferable molybdenum dithiocarbamate, specifically, molybdenum sulfide diethyldithiocarbamate, molybdenum sulfide dipropyldithiocarbamate, molybdenum dibutyldithiocarbamate sulfide, molybdenum dipentyldithiocarbamate sulfide, molybdenum dihexyl dithiocarbamate, molybdenum dioctyldithiocarbamate sulfide, sulfide molybdenum Molybdenum didecyl dithiocarbamate, molybdenum sulfide didodecyl dithiocarbamate, molybdenum sulfide di (butylphenyl) dithiocarbamate, molybdenum sulfide di (nonylphenyl) dithiocarbamate, oxymolybdenum diethyldithiocarbamate sulfide, oxymolybdenum dipropyl dithiocarbamate, oxymolybdenum dibutyl dithiocarbamate sulfide, Sulfurization Xymolybdenum dipentyl dithiocarbamate, oxymolybdenum dihexyl dithiocarbamate, oxymolybdenum dioctyl dithiocarbamate, oxymolybdenum didecyl dithiocarbamate, oxymolybdenum didodecyl dithiocarbamate, oxymolybdenum di (butylphenyl) dithiocarbamate, oxymolybdenum di (nonylphenyl) ) Dithiocarbamate, a mixture thereof and the like can be exemplified. The alkyl group in these molybdenum dithiocarbamates may be linear or branched, and the bonding position of the alkyl group in the alkylphenyl group is arbitrary. As these molybdenum dithiocarbamates, compounds having hydrocarbon groups having different carbon numbers and / or structures in one molecule can also be preferably used.

  As molybdenum dithiophosphate, a commercially available lubricant additive can be used, and for example, a compound represented by the following general formula (2) can be used.

In the formula (2), R ⁵ and R ⁶ may be the same or different and each represents a hydrocarbon group having 1 or more carbon atoms. X ⁵ , X ⁶ , X ⁷ , X ⁸ and X ^{9, which} may be the same or different, each represents an oxygen atom or a sulfur atom. a, b, and c each represent an integer of 1 to 6. However, at least one of X ⁵ , X ⁶ , X ⁷ , X ⁸ and X ⁹ represents a sulfur atom. Examples of the hydrocarbon group represented by R ⁵ and R ⁶ include an alkyl group having 1 to 24 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an alkylcycloalkyl group having 6 to 11 carbon atoms, and 6 carbon atoms. To C18 aryl groups, C7-24 alkylaryl groups, and C7-12 arylalkyl groups.

  From the viewpoint of extending the life of the bearing, the content of the organic molybdenum compound is preferably 300 mass ppm or more, more preferably 500 mass ppm or more, still more preferably 600 mass, as the molybdenum element amount conversion based on the total amount of the grease composition. ppm or more, particularly preferably 700 mass ppm or more. The content of the organic molybdenum compound is preferably 50,000 mass ppm or less, more preferably 40,000 mass ppm or less, in terms of molybdenum element amount, based on the total amount of the grease composition, from the viewpoint of the effect of addition to the bearing performance and the manufacturing cost. It is preferably 30,000 mass ppm or less. The content of the organic molybdenum compound is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, based on the total amount of the grease composition, as the weight of the molybdenum compound. . The content of the organic molybdenum compound is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 10% by mass or less as the weight of the molybdenum compound based on the total amount of the grease composition, from the viewpoint of the effect of addition to the bearing performance and the manufacturing cost. Is 5% by mass or less.

  In addition to the above components, the grease composition can contain additives generally used in lubricating oils and greases, if necessary. Such additives include, for example, detergents, dispersants, antiwear agents, viscosity index improvers, antioxidants, extreme pressure agents, rust inhibitors, corrosion inhibitors, metal deactivators, solid lubricants, etc. Can be mentioned. The content of these additives is preferably 10% by mass or less, and more preferably 5% by mass or less, based on the total amount of the grease composition.

  The consistency of the grease composition is preferably 220 to 300, more preferably 225 to 295, further preferably 230 to 290, and particularly preferably 230 to 285. When the consistency of the grease composition is within the above range, the amount of electric power consumed for bearing rotation can be significantly reduced. As the method for adjusting the consistency of the grease composition, the types and mixing ratios of the above-mentioned first lubricating base oil, second lubricating base oil and thickener, and the grease composition described below are produced. In this case, a method of adjusting the mixing method of each component (for example, the number of times of mixing, heating temperature, cooling rate, roll condition) and the like can be mentioned.

  In the present invention, the consistency refers to the miscibility measured according to JIS K2220. The specific measurement conditions are as follows. After filling the sample in the consistency measuring pot and keeping it at 25 ° C., it is mixed 60 times in 1 minute using a specified mixer. Then, after removing the excess sample with a spatula and flattening the surface of the sample, a prescribed cone is dropped into the sample for 5 seconds, and a value 10 times as deep as the penetration depth (mm) is defined as the mixing consistency. .

Another embodiment of the present invention is a grease composition containing a lubricating base oil, a thickener, and an organic molybdenum compound, wherein the lubricating base oil is ndM according to ASTM D3238. the first and the lubricating oil base oil% _{C a} is 2 to 8,% _{C P} of the ring analysis value of 50~75, n-d-M ring analysis value of% _{C a} by ASTM D3238 is 1 or less,% C _P is contained, and a second lubricating base oil is 70 or more, based on the lubricating base oils the total amount, the content of the first lubricating base oil is 5 to 90 wt%, The grease composition has a content of the second lubricating base oil of 10 to 95 mass% and a consistency of 220 to 300. This embodiment has a special effect that both reduction of power consumption during rotation of the bearing and extension of the life of the bearing can be achieved at the same time.

  The method for producing a grease composition according to this embodiment includes a step of mixing a first lubricating base oil, a second lubricating base oil, and a thickener to obtain a grease composition. The first lubricating base oil and the second lubricating base oil have a content of the first lubricating base oil of 5 to 90 mass% and a second lubricating base oil based on the total amount of the lubricating base oil. It is mixed so that the content of oil is 10 to 95% by mass.

  In the present embodiment, a thickener prepared in advance may be mixed with the first and second lubricating base oils, or the first lubricating base oil or the second lubricating base oil or these You may mix | blend the raw material of a thickener with a mixed base oil, and make the said raw material react in base oil, and you may obtain a thickener. For example, when a metal soap-based thickener is used, it may be added to the lubricating base oil in the form of metal soap, but the carboxylic acid and the metal source (metal salt, metal salt hydroxide, etc.) are separately added to the lubricating oil. It may be blended with a base oil and reacted with a carboxylic acid and a metal source at the time of grease production to obtain a metal soap thickener. When a urea-based thickener is used, it may be added to the lubricating base oil in the form of a urea compound, but diisocyanate and amines (monoamine, diamine, etc.) may be added to the lubricating base oil to prepare the diisocyanate at the time of grease preparation. It may be reacted with an amine to form a urea thickener.

  The grease composition obtained by mixing the first lubricating base oil, the second lubricating base oil, and the thickener can be subjected to a dispersion treatment with a roll or a mill, if necessary. .

  Hereinafter, the present invention will be described more specifically based on Examples, but the present invention is not limited to the following Examples.

[Base oil A]
As a base oil A, a lubricating base oil having the following properties, which was obtained by solvent-refining a distillate oil obtained by distilling an atmospheric distillation residue under reduced pressure, was used.
Kinematic viscosity at 40 ° C .: 37.6 mm ² / s
Viscosity index: 107
Flash point: 220 ° C
% _CP : 66
% _C A: 5.2

[Base oil B]
The bottom fraction obtained from the fuel oil hydrocracker was used as a raw material for the lubricating base oil, and hydrotreated using a hydrotreating catalyst. At this time, the reaction temperature and the liquid hourly space velocity were adjusted so that the decomposition rate of normal paraffin in the feed oil was 10% by mass or less. Furthermore, for the object to be treated obtained by the hydrotreatment, a zeolite-based hydrodewaxing catalyst whose noble metal content is adjusted to 0.1 to 5% by mass is used to hydrodewax in the temperature range of 315 to 325 ° C. To obtain dewaxed oil. Further, the dewaxed oil was hydrorefined using a hydrorefining catalyst. Then, a lubricating base oil having the following properties obtained by distillation was used as base oil B.
Kinematic viscosity at 40 ° C .: 36.8 mm ² / s
Viscosity index: 130
Flash point: 240 ° C
% _CP : 79
% _C A: 0
Urea adduct value: 2% by mass

[Base oil C]
Poly-α-olefin (Durasyn 166, manufactured by INEOS), which is a synthetic hydrocarbon having the following properties, was used as the base oil C.
Kinematic viscosity at 40 ° C .: 30.8 mm ² / s
Viscosity index: 135
Flash point: 250 ° C
% C _P : 91
% _C A: 0
Urea adduct value: 0 mass%

[Base oil D]
The fraction separated by vacuum distillation of the solvent-refined base oil was solvent-extracted with furfural, hydrotreated, and then dewaxed with a mixed solvent of methyl ethyl ketone-toluene. The wax component removed during the solvent dewaxing and obtained as a slack wax was used as a raw material for the lubricating base oil, and hydrotreated. At this time, the reaction temperature and the liquid hourly space velocity are adjusted, and the temperature condition for hydrodewaxing the object to be treated obtained by the hydrotreatment is adjusted as low as about 300 ° C. to hydrorefining the dewaxed oil obtained. did. Then, a lubricating base oil having the following properties and a urea adduct value of 5 mass% obtained by distillation was used as a base oil D.
Kinematic viscosity at 40 ° C .: 32.0 mm ² / s
Viscosity index: 130
Flash point: 240 ° C
% _CP : 75
% _C A: 0
Urea adduct value: 5% by mass

[Sample oil 1-1 to 1-10]
Base oils A, B, C and D were put in a stainless steel container in the blending amounts shown in Tables 1 and 2 (shown by mass%). When a urea compound is used as a thickener, amine and isocyanate, which are raw materials for the urea compound, are added to a lubricating base oil in a container, heated to 150 ° C. and stirred with a magnetic stirrer to remove the amine and diisocyanate. It was made to react. Then, after dehydration, it was cooled to room temperature to obtain a semi-solid composition. When a metal soap compound is used as a thickener, lithium stearate is added to a lubricating base oil, heated to 200 ° C., and then cooled to obtain a semisolid composition. Furthermore, di-t-butyl-p-cresol, which is a phenolic antioxidant, was added to each of the obtained semi-solid compositions, and the mixture was subjected to a dispersion treatment with a three-roll mill to have the compositions shown in Tables 1 and 2. A grease composition was obtained.

[Evaluation test 1]
The power consumption during bearing rotation when each grease composition was used was measured by the following method. As the bearing, double row tapered roller bearing 4T-CRI-0868 manufactured by NTN was used. Before the test, the inside of the bearing was thoroughly washed with an organic solvent, and then the experimental oil (grease composition) was injected into the gap between the bearing roller, the bearing ring, and the cage with a syringe. In the experiment, a total of 4 bearings (2 bearings × 2 sets) filled with the same oil agent were used. The bearing inner ring is fixed and rotated in a certain direction with an electric motor (TYPE: FEQ, made by Yasukawa Electric Co., Ltd., 2.2 kW) through a pulley, and the power consumption of the electric motor is measured by a wattmeter (CE3169, manufactured by HIOKI, CLAMP ON POWER). HiTESTER). The bearing rotation speed was 1300 rpm, the temperature was room temperature, and the integrated power consumption (kW) in continuous rotation for 2 hours was compared. The number of repeated experiments was 3 times. The obtained results are shown in Tables 1-2. The bearing power consumption and power reduction rate (%: sample oil 1-6 standard) in Tables 1 and 2 are average values of three experiments. The power reduction rate in this embodiment indicates a negative value when the power consumption is less than the standard.

[Sample oil 2-1 to 2-12]
The base oils A, B, C and D, and the thickener were put in a stainless steel container in the blending amounts (shown by mass%) shown in Tables 3 to 5. When a metal soap compound (single soap) is used as a thickener, lithium stearate is added to a lubricating base oil, heated to 200 ° C. and then cooled to obtain a semi-solid composition. . When a metal soap compound (complex soap) is used as a thickener, 12-hydroxystearic acid, azelaic acid, and lithium hydroxide are added to a lubricating base oil and heated to 200 ° C to react to form a complex soap. A semi-solid composition was obtained by cooling. When a urea compound is used as a thickener, amine and isocyanate, which are the raw materials of the urea compound, are added to the lubricating base oil in the container, heated to 150 ° C., stirred with a magnetic stirrer to remove the amine and The diisocyanate was reacted. Then, after dehydration, it was cooled to room temperature to obtain a semi-solid composition. Furthermore, di-t-butyl-p-cresol, which is a phenolic antioxidant, was added to each of the obtained semi-solid compositions, and the mixture was subjected to a dispersion treatment with a three-roll mill, and the compositions shown in Tables 3 to 5 were obtained. A grease composition was obtained. Further, the obtained grease composition was measured for penetration (blending consistency) according to JIS K2220.

[Evaluation test 2-1]
The power consumption during bearing rotation when each grease composition was used was measured by the following method. The bearing used was a double-row ball bearing 7008A-DF manufactured by NSK. Before the test, the inside of the bearing was thoroughly washed with an organic solvent, and then the experimental oil (grease composition) was injected into the gap between the bearing ball, the bearing ring, and the cage with a syringe. In the experiment, a total of 4 bearings (2 bearings × 2 sets) filled with the same oil agent were used. The bearing inner ring is fixed and rotated in a certain direction with an electric motor (TYPE: FEQ, made by Yasukawa Electric Co., Ltd., 2.2 kW) through a pulley, and the power consumption of the electric motor is measured by a wattmeter (CE3169, manufactured by HIOKI, CLAMP ON POWER). HiTESTER). The bearing rotation speed was 1300 rpm, the temperature was room temperature, and the integrated power consumption (kW) in continuous rotation for 2 hours was compared. The number of repeated experiments was 3 times. The obtained results are shown in Tables 3-5. The bearing power consumption and the power reduction rate (%: sample oil 2-11 standard) in Tables 3 to 5 are average values of three experiments.

[Evaluation test 2-2]
The same test as the evaluation test 1 was performed on each grease composition. The obtained results are shown in Tables 3-5. The bearing power consumption and the power reduction rate (%: sample oil 2-11 standard) in Tables 3 to 5 are average values of three experiments.

[Sample oil 3-1 to 3-8]
Base oils A and B, thickeners, and organic molybdenum compounds as molybdenum dithiocarbamate (molybdenum element content 29 mass%, sulfur element content 28 mass%) and molybdenum dithiophosphate (molybdenum element content 8 mass). %, Phosphorus element content 6% by mass, sulfur element content 12% by mass) were added to the stainless steel container in the blending amounts shown in Tables 6 to 7 (indicated by mass%. Molybdenum element amount conversion value is also shown). . When a metal soap compound (single soap) is used as a thickener, lithium stearate is added to a lubricating base oil, heated to 200 ° C. and then cooled to obtain a semi-solid composition. . When a metal soap compound (complex soap) is used as a thickener, 12-hydroxystearic acid, azelaic acid, and lithium hydroxide are added to a lubricating base oil and heated to 200 ° C to react to form a complex soap. A semi-solid composition was obtained by cooling. When a urea compound is used as a thickener, amine and isocyanate, which are the raw materials of the urea compound, are added to the lubricating base oil in the container, heated to 150 ° C., stirred with a magnetic stirrer to remove the amine and The diisocyanate was reacted. Then, after dehydration, it was cooled to room temperature to obtain a semi-solid composition. Furthermore, other additives (phenolic antioxidants, corrosion inhibitors, etc.) were added to each of the obtained semi-solid compositions, and the mixture was subjected to a dispersion treatment with a three-roll mill, and a grease having the composition shown in Tables 6 to 7 was obtained. A composition was obtained. Further, the obtained grease composition was measured for penetration (blending consistency) according to JIS K2220.

[Evaluation test 3-1 (bearing life)]
A high temperature grease bearing life test was performed for each grease composition. Specifically, according to ASTM-D3336, the bearing (6204ZZ) was filled with 2 g of sample grease, and the bearing was continuously operated at a rotation speed of 10000 rpm and a thrust load of 66 N at an temperature of 150 ° C. to perform abnormal operation due to poor lubrication. The time required to reach was recorded as the bearing life (hr).

[Evaluation test 3-2 (bearing power consumption)]
The same test as the evaluation test 2-1 was performed on each grease composition. The obtained results are shown in Tables 6-7. The bearing power consumption and the power reduction rate (%: sample oil 3-7 standard) in Tables 6 to 7 are average values of three experiments.

  The grease composition of the present invention has a special effect that the amount of electric power consumed for bearing rotation is small. Therefore, the grease of the present invention can be suitably used for lubricating mechanical elements such as rolling bearings, sliding bearings, ball screws, linear motion guides, and gears, and is useful in industrial machines, transportation machine systems, and the like.

Claims (5)

A grease composition comprising a lubricating base oil, a thickener, and an organic molybdenum compound containing at least one selected from molybdenum dithiocarbamate and molybdenum dithiophosphate.
_A first lubricating base oil having a% dA ring analysis value according to ASTM D3238 of 2 to 8% CA and 50 to 75% C _P ;
% C _{A of} n-d-M ring analysis value by ASTM D3238 is 1 or less,% C _P is 70 or more, urea adduct value is 4% by mass or less, and kinematic viscosity at 40 ° C. is 20 mm ² / s or more. A second lubricating base oil,
Consists of
Based on the total amount of the lubricating base oil, the content of the first lubricating base oil is 30 to 60 mass%, the content of the second lubricating base oil is 40 to 70 mass%,
A grease composition having a consistency of 220 to 300. The grease composition according to claim 1, wherein the first lubricating base oil has a kinematic viscosity at 40 ° C. of 10 to 700 mm ² / s and a viscosity index of 90 to 120. The grease composition according to claim 1, wherein the second lubricating base oil has a kinematic viscosity at 40 ° C. of 20 to 5000 mm ² / s and a viscosity index of 110 to 150.   The grease composition according to any one of claims 1 to 3, wherein the second lubricating base oil contains at least one selected from mineral oils and synthetic hydrocarbons.   The grease composition according to any one of claims 1 to 4, wherein the thickener contains at least one selected from metal soap compounds and urea compounds.