WO2015060399A1 - Grease composition - Google Patents

Abstract

A grease composition according to the present invention comprises: a lubricant oil base oil having a urea adduct fraction of 4% by mass or less, a %C_P of 70 or more, a %C_A of 2 or less and a viscosity index of 105 or more; and a thickening agent.

Description

Grease composition

The present invention relates to a grease composition.

Grease is a lubricant made by dispersing a solid lipophilic solid thickener in base oil to make it semi-solid. Therefore, it is possible to make the lubrication system simple, and it is mainly used for lubrication of machine elements such as rolling bearings, plain bearings, ball screws, linear motion guides, gears, etc. for industrial machinery and transportation machinery systems. Widely used. Rolling bearings, in particular, include ball bearings and roller bearings, and are widely used in machine tool spindles, railway vehicle vehicles, engine accessories such as automobile alternators, constant velocity joints, wheels, and the like.

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, etc., in order to ensure fuel efficiency, to reduce the viscosity of the lubricant base oil as much as possible, to reduce energy loss due to the viscous resistance of the lubricant, and to reduce the frictional resistance of the sliding part It is considered effective to optimally formulate various additives such as friction reducing agents (Patent Document 1).

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

JP 2012-102281 A

Lubricating grease basics and applications, pp. 49-89, edited by Japan Society of Tribology Grease Study Group, Yokendo, 2007

However, it is not always easy to secure the consistency required for the mechanical system while reducing the viscous resistance. In the case of conventional greases, there has been no choice but to empirically carry out an optimal formulation while balancing the base oil composition and the amount of thickener.

The problem to be solved by the present invention is to provide a grease composition that has a low bearing rotation resistance, in particular, can greatly reduce the torque during rotation of the bearing, and can satisfy an excellent bearing fatigue life. is there.

As a result of diligent research to solve the above problems, the inventor of the present invention uses a base oil having specific properties for grease, thereby significantly reducing the torque during rotation of the bearing while maintaining the bearing fatigue life. Found that you can.

In order to reduce the energy required to rotate the bearing and reduce the torque, it is necessary to reduce the rolling resistance between the bearing rolling elements (balls, rollers) and the race rings (inner ring and outer ring) as much as possible. In general, it is considered useful to reduce the viscosity of a base oil of a lubricant (lubricant or grease). However, in the case of grease, it is necessary to expose the base oil to a high temperature condition of 160 ° C. or higher in the process of producing the thickener, and there is a limit to reducing the viscosity in terms of evaporation of the base oil and safety. That is, the base oil used for the grease needs to have at least a flash point of 160 ° C. or higher.

On the other hand, the present inventor first paid attention to the oil film forming ability of the bearing and the viscosity change of the lubricating base oil accompanying the temperature change, and by forming a sufficient oil film between the bearing rolling element and the bearing ring, the direct contact between them. In order to reduce energy loss, it is effective that the base oil has a specific property, in particular, contains a large amount of paraffin components (ndM ring analysis), which is a component having a high viscosity index. I found out.

However, even if there are many paraffin components in the lubricating base oil, if the paraffin components do not have an appropriate branch, the viscosity increase in the low temperature range will increase, and the torque will increase at the start of the bearing at a low temperature, causing a practical problem. It becomes.

Therefore, as a result of further studies, the present inventor has found that the urea adduct value is effective as an index of the content of paraffin that causes a torque increase at the start of the bearing at a low temperature. Further, by using a lubricant base oil whose urea adduct value,% C _P ,% C _A and viscosity index satisfy specific conditions, the low torque of the bearing from the normal temperature to the high temperature range while suppressing a rapid increase in starting torque at low temperature. It was found that the torque loss of mechanical elements such as bearings can be reduced.

This invention is made | formed based on said knowledge, and provides the grease composition as described in following [1] or [2].
[1] _A grease composition containing a lubricant base oil having a urea adduct value of 4% by mass or less,% _CP of 70 or more,% CA of 2 or less, and a viscosity index of 105 or more, and a thickener. .
[2] The grease composition according to [1], wherein the lubricating base oil has a viscosity index of 120 or more.
[3] The grease composition according to [1] or [2], containing 70 to 95% by mass of the lubricating base oil and 5 to 30% by mass of the thickener based on the total amount of the grease composition.
[4] Use of the grease composition according to any one of [1] to [3] for a machine element.
[5] Use for a machine element according to [5], wherein the machine element is a bearing.
[6] A method for reducing torque of a machine element, wherein the machine element is lubricated with the grease composition according to any one of [1] to [3].

The grease composition of the present invention exhibits a special effect that the torque required for rotation of the bearing can be reduced while maintaining the bearing fatigue life.

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

Grease compositions according to embodiments of the present invention, the urea adduct value of 4 wt% or less,% C _P is 70 or more,% C _A of 2 or less, and the lubricating oil base oil is a viscosity index of 105 or more, thickening And an agent.

The urea adduct value of the lubricating base oil is 4% by mass or less, preferably 3.5% by mass or less from the viewpoint of suppressing an increase in viscosity at a low temperature range and suppressing an increase in torque at the start of the bearing at a low temperature. More preferably, it is 3 mass% or less, More preferably, it is 2.5 mass% or less. The urea adduct value of the lubricant base oil may be 0% by mass, but a lubricant base oil having a higher viscosity index can be obtained while sufficiently suppressing an increase in torque at the start of the bearing at a low temperature. It is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 0.8% by mass or more from the viewpoint of ease of dewaxing conditions and excellent economic efficiency.

The urea adduct value as used in the present invention is measured by the following method. 100 g of 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 stirred at room temperature for 6 hours. As a result, white granular crystals are produced 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 separatory funnel, and the toluene phase is washed three 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, the normal paraffin in the case where the normal paraffin remains in the lubricating base oil, as well as the components that cause a torque increase at the start of the bearing at a low temperature among isoparaffins. Can be collected accurately and reliably, it is excellent as an index of the content ratio of normal paraffin and the specific isoparaffin. The inventors of the present invention have analyzed by using GC and NMR that the main component of the urea adduct is a normal paraffin and an isoparaffin urea adduct having 6 or more carbon atoms from the end of the main chain to the branch position. Confirm that there is.

Further, the% C _p of the lubricating base oil is 70 or more, preferably 70 to 99, more preferably 72 to 97. If% _Cp is less than 70, the viscosity index is low, and the torque reduction effect is insufficient. From the viewpoint of availability and cost,% C _p is preferably 99 or less.

% C _A of the lubricating base oil, from the viewpoint of high viscosity index of, 2 or less, preferably 0.7 or less, more preferably 0.6 or less.

In the present invention,% C _P and% C _A are the percentages of the number of paraffin carbons to the total number of carbons determined by a method (ndM ring analysis) based on ASTM D 3238-85, respectively. It means the percentage of the total number of aromatic carbons. That is, the preferable ranges of% C _P and% C _A described above are based on values obtained by the above method.

The viscosity index of the lubricating base oil in the present embodiment is 105 or more, preferably 110 to 200, more preferably 120 to 180. When the viscosity index is less than 105, the effect of suppressing the decrease in viscosity due to heat generation is insufficient, and when it exceeds 200, the flow resistance increases due to the small decrease in viscosity at high temperature, and the torque cannot be reduced.

The kinematic viscosity at 100 ° C. of the lubricating base oil in the present embodiment is preferably 2.0 to 22 mm ² / s, more preferably 2.2 to 20 mm ² / s, and further preferably 2.4 to 15 mm ^2. / S, particularly preferably 3.0 to 8.0 mm ² / s. When the kinematic viscosity at 100 ° C. of the lubricating base oil is less than 2.0 mm ² / s, the lubricating base oil may volatilize due to high-temperature heating during grease production. Moreover, when it is intended to obtain a lubricating base oil having a kinematic viscosity at 100 ° C. exceeding 22.0 mm ² / s, the yield is lowered, and the decomposition rate is increased even when heavy wax is used as a raw material. Tend to be difficult.

The kinematic viscosity at 40 ° C. of the lubricating base oil in this embodiment is preferably 5.0 to 200 mm ² / s, more preferably 8.0 to 150 mm ² / s, and even more preferably 10 to 100 mm ² / s. It is.

In producing the lubricating base oil in the present embodiment, a raw material oil containing normal paraffin can be used. The raw material oil may be either mineral oil or synthetic oil, or may be a mixture of two or more of these. Further, the content of normal paraffin in the raw material oil is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, more preferably 90% by mass, based on the total amount of the raw material oil. Especially preferably, it is 95 mass% or more, Most preferably, it is 97 mass% or more.

Further, the raw material oil used in the present invention is preferably a wax-containing raw material that boils in the lubricating oil range defined in ASTM D86 or ASTM D2887. The wax content of the raw material oil is preferably 50% by mass or more and 100% by mass or less based on the total amount of the raw material oil. The wax content of the raw material can be measured by an analytical technique such as nuclear magnetic resonance spectroscopy (ASTM D5292), correlated ring analysis (ndM) method (ASTM D3238), solvent method (ASTM D3235).

Examples of the wax-containing raw material include oils derived from solvent refining methods such as raffinate, partially solvent dewaxed oil, dewaxed oil, distillate, reduced pressure gas oil, coker gas oil, slack wax, foots oil, and Fisher- Examples include Tropsch wax, and among these, slack wax and Fischer-Tropsch wax are preferable.

Slack wax is typically derived from hydrocarbon raw materials by solvent or propane dewaxing. Slack wax may contain residual oil, which can be removed by deoiling. Foots oil corresponds to deoiled slack wax.

Fischer-Tropsch wax is produced by a so-called Fischer-Tropsch synthesis method.

Furthermore, a commercial product may be used as a raw material oil containing normal paraffin. Specific examples include Paraflint 80 (hydrogenated Fischer-Tropsch wax) and shell MDS waxy raffinate (Shell MDS Waxy Raffinate) (hydrogenated and partially isomerized middle distillate synthetic waxy raffinate). It is done.

Further, the raw material oil derived from solvent extraction is obtained by sending a high-boiling petroleum fraction from atmospheric distillation to a vacuum distillation apparatus and extracting the distillation fraction from this apparatus with solvent. The residue from the vacuum distillation may be denitrified. In the solvent extraction method, aromatic components are dissolved in the extraction phase while leaving more paraffinic components in the raffinate phase. Naphthene is partitioned into the extraction phase and the raffinate phase. As a solvent for solvent extraction, phenol, furfural, N-methylpyrrolidone and the like are preferably used. By controlling the solvent / oil ratio, the extraction temperature, the method of contacting the distillate to be extracted with the solvent, etc., the degree of separation between the extraction phase and the raffinate phase can be controlled. Furthermore, a bottom fraction obtained from a fuel oil hydrocracking apparatus may be used as a raw material by using a fuel oil hydrocracking apparatus having higher hydrogenation resolution.

The raw material oil is subjected to a process of hydrocracking / hydroisomerization so that the urea adduct value of the material to be treated is 4% by mass or less and the viscosity index is 100 or more. A lubricating base oil can be obtained. The hydrocracking / hydroisomerization step is not particularly limited as long as the urea adduct value and the viscosity index of the obtained workpiece satisfy the above conditions. The preferred hydrocracking / hydroisomerization step in the present invention is:
A first step of hydrotreating a raw oil containing normal paraffin using a hydrotreating catalyst;
A second step of hydrodewaxing the object to be treated obtained in the first step using a hydrodewaxing catalyst;
The to-be-processed object obtained by a 2nd process is equipped with the 3rd process of hydrotreating using a hydrotreating catalyst.

In the conventional hydrocracking / hydroisomerization, a hydrotreating step is provided before the hydrodewaxing step for the purpose of desulfurization / denitrogenation for the prevention of poisoning of the hydrodewaxing catalyst. There is a thing. On the other hand, in the first step (hydrotreating step) in the present invention, a part of the normal paraffin in the feedstock (for example, about 10% by weight, preferably 1 to 10% by mass), and desulfurization / denitrogenation is possible in the first step, but the purpose is different from that of the conventional hydrotreatment. Providing such a first step is preferable for ensuring that the urea adduct value of the article to be processed (lubricant base oil) obtained after the third step is 4% by mass or less.

Examples of the hydrogenation catalyst used in the first step include a catalyst containing a Group 6 metal, a Group 8 to 10 metal, and a mixture thereof. Preferred metals include nickel, tungsten, molybdenum, cobalt, and mixtures thereof. The hydrogenation catalyst can be used in a form in which these metals are supported on a refractory metal oxide support, and the metal is usually present as an oxide or sulfide on the support. When a metal mixture is used, the metal may be present as a bulk metal catalyst in which the amount of metal is 30% by mass or more based on the total amount of the catalyst. Examples of the metal oxide support include oxides such as silica, alumina, silica-alumina, and titania, and among these, alumina is preferable. Preferred alumina is γ-type or β-type porous alumina. The amount of the metal supported is preferably in the range of 0.5 to 35% by mass based on the total amount of the catalyst. Further, when a mixture of Group 9-10 metal and Group 6 metal is used, either Group 9 or Group 10 metal is present in an amount of 0.5-5% by weight, based on the total amount of catalyst, The Group 6 metal is preferably present in an amount of 5 to 30% by mass. Metal loading may be measured by atomic absorption spectroscopy, inductively coupled plasma emission spectroscopy, or other methods specified by ASTM for individual metals.

The acidity of the metal oxide support can be controlled by adding additives, controlling the properties of the metal oxide support (for example, controlling the amount of silica incorporated in the silica-alumina support), and the like. Examples of additives include halogens, especially fluorine, phosphorus, boron, yttria, alkali metals, alkaline earth metals, rare earth oxides, and magnesia. Cocatalysts such as halogen generally increase the acidity of the metal oxide support, but weakly basic additives such as yttria or magnesia tend to weaken the acidity of such support.

Regarding the hydrotreatment conditions, the treatment temperature is preferably 150 to 450 ° C., more preferably 200 to 400 ° C., the hydrogen partial pressure is preferably 1400 to 20000 kPa, more preferably 2800 to 14000 kPa, and the liquid space velocity (LHSV) is preferably 0.1 ~ 10 hr ^-1, more preferably 0.1 ~ ^{5 hr -1,} a hydrogen / oil ratio is preferably 50 ~ 1780m ³ / ^{m 3,} more preferably 89 ~ 890m ³ / M ³ . In addition, said conditions are an example and the hydrotreating conditions in the 1st process for the urea adduct value and viscosity index of the to-be-processed object obtained after a 3rd process satisfy | fill the said conditions respectively are a raw material, a catalyst, an apparatus, etc. It is preferable to select appropriately according to the difference.

The object to be processed after the hydrogenation treatment in the first step may be used as it is in the second step, but the object to be processed is stripped or distilled to generate gas from the object to be processed (liquid product). It is preferable to provide a step of separating and removing the object between the first step and the second step. Thereby, the nitrogen content and sulfur content contained in the workpiece can be reduced to a level that does not affect the long-term use of the hydrodewaxing catalyst in the second step. The object of separation and removal by stripping or the like is mainly gaseous foreign matters such as hydrogen sulfide and ammonia, and stripping can be performed by ordinary means such as a flash drum and a fractionator.

Moreover, when the conditions of the hydrogenation treatment in the first step are mild, there is a possibility that the remaining polycyclic aromatics may pass through depending on the raw materials used. It may be removed by purification.

Further, the hydrodewaxing catalyst used in the second step may contain either crystalline or amorphous material. Examples of the crystalline material include molecular sieves having a 10- or 12-membered ring passage mainly composed of aluminosilicate (zeolite) or silicoaluminophosphate (SAPO). Specific examples of zeolite include ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-57, ferrierite, ITQ-13, MCM-68, MCM-71 and the like. An example of an aluminophosphate is ECR-42. Examples of molecular sieves include zeolite beta and MCM-68. Among these, it is preferable to use one or more selected from ZSM-48, ZSM-22, and ZSM-23, and ZSM-48 is particularly preferable. Although the reduction of the hydrodewaxing catalyst can occur in situ at the time of hydrodewaxing, a hydrodewaxing catalyst that has been subjected to a reduction treatment in advance may be subjected to hydrodewaxing.

Further, examples of the amorphous material for the hydrodewaxing catalyst include alumina doped with a group 3 metal, fluorinated alumina, silica-alumina, fluorinated silica-alumina, silica-alumina and the like.

Preferred embodiments of the dewaxing catalyst include those equipped with a metal hydrogenation component that is difunctional, ie, at least one Group 6 metal, at least one Group 8-10 metal, or a mixture thereof. Preferred metals are group 9-10 noble metals such as platinum, palladium or mixtures thereof. The mounting amount of these metals is preferably 0.1 to 30% by mass based on the total amount of the catalyst. Examples of the catalyst preparation and the metal mounting method include an ion exchange method and an impregnation method using a decomposable metal salt.

In addition, when using a molecular sieve, it may be combined with a binder material having heat resistance under hydrodewaxing conditions, or may be without a binder (self-bonding). Binder materials include silica, alumina, silica-alumina, binary combinations of silica and other metal oxides such as titania, magnesia, tria, zirconia, silica-alumina-tria, silica-alumina-magnesia, etc. Inorganic oxides such as a combination of three components of oxides such as The amount of molecular sieve in the hydrodewaxing catalyst is preferably 10 to 100% by mass, more preferably 35 to 100% by mass, based on the total amount of the catalyst. The hydrodewaxing catalyst is formed by a method such as spray drying or extrusion. The hydrodewaxing catalyst can be used in a sulfided or non-sulfided form, and a sulfided form is preferred.

Regarding hydrodewaxing conditions, the temperature is preferably 250 to 400 ° C., more preferably 275 to 350 ° C., the hydrogen partial pressure is preferably 791 to 20786 kPa, more preferably 1480 to 17339 kPa, and the liquid space velocity is preferably is 0.1 ~ 10 hr ^-1, more preferably 0.1 ~ ^{5 hr -1,} a hydrogen / oil ratio is preferably 45 ~ 1780m ³ / ^{m 3,} more preferably 89 ~ 890m ³ / ^{m 3.} In addition, said conditions are an example and the hydrodewaxing conditions in the 2nd process for the urea adduct value and viscosity index of the to-be-processed object obtained after a 3rd process satisfy | fill the said conditions are a raw material, a catalyst, and an apparatus, respectively. It is preferable to select appropriately according to the difference.

The material to be treated that has been hydrodewaxed in the second step is subjected to hydrorefining in the third step. Hydrorefining is a form of mild hydrotreating that aims to saturate olefins and residual aromatic compounds by hydrogenation in addition to removal of residual heteroatoms and hues. The hydrorefining in the third step can be carried out in cascade with the dewaxing step.

The hydrorefining catalyst used in the third step is preferably a metal oxide carrier on which a Group 6 metal, a Group 8-10 metal, or a mixture thereof is supported. Preferred metals include noble metals, especially platinum, palladium and mixtures thereof. If a mixture of metals is used, it may be present as a bulk metal catalyst where the amount of metal is 30% by weight or more based on the catalyst. The metal content of the catalyst is preferably 20% by mass or less for non-noble metals and 1% by mass or less for noble metals. The metal oxide support may be either amorphous or crystalline oxide. Specific examples include low acid oxides such as silica, alumina, silica-alumina or titania, with alumina being preferred. From the viewpoint of saturation of the aromatic compound, it is preferable to use a hydrorefining catalyst in which a metal having a relatively strong hydrogenation function is supported on a porous support.

As a preferred hydrorefining catalyst, a mesoporous material belonging to the M41S class or system catalyst can be exemplified. M41S series catalysts are mesoporous materials with high silica content, and specifically include MCM-41, MCM-48 and MCM-50. Such a hydrorefining catalyst has a pore diameter of 1.5 to 10 nm, and MCM-41 is particularly preferable. MCM-41 is an inorganic porous non-layered phase having a hexagonal arrangement of uniformly sized pores. The physical structure of MCM-41 is like a bundle of straws where the opening of the straw (cell diameter of the pores) is in the range of 1.5 to 10 nm. MCM-48 has cubic symmetry and MCM-50 has a layered structure. MCM-41 can be made with pore openings of different sizes in the mesoporous range. The mesoporous material may have a metal hydrogenation component that is at least one of Group 8, 9 or 10 metal, and the metal hydrogenation component is preferably a noble metal, particularly a Group 10 noble metal, platinum Most preferred is palladium, or a mixture thereof.

Regarding the hydrorefining conditions, the temperature is preferably 150 to 350 ° C., more preferably 180 to 250 ° C., the total pressure is preferably 2859 to 20786 kPa, and the liquid space velocity is preferably 0.1 to 5 hr ^−1. More preferably, it is 0.5 to 3 hr ⁻¹ and the hydrogen / oil ratio is preferably 44.5 to 1780 m ³ / m ³ . In addition, said conditions are an example and the hydrogenation production | generation conditions in the 3rd process for the urea adduct value and viscosity index of the to-be-processed object obtained after a 3rd process satisfy | fill the said conditions respectively are the difference of a raw material or a processing apparatus. It is preferable to select appropriately according to.

Moreover, about the to-be-processed object obtained after a 3rd process, you may separate and remove a predetermined component by distillation etc. as needed.

Lubricating oil base oil is preferably 70 to 95% by mass, particularly preferably 75 to 90% by mass, based on the total amount of the grease composition. If the content of the lubricating base oil is outside the range of 70 to 95% by mass, it becomes difficult to easily prepare a grease composition having a desired consistency.

Thickeners include soap-type thickeners such as metal soaps and composite metal soaps, benton, silica gel, urea-type compounds (diurea compounds, urea / urethane compounds, urethane compounds, etc.) Any thickener can be used. From the viewpoint of heat resistance, it is desirable to contain at least one selected from urea compounds and urea / urethane compounds.

Examples of the soap-based thickener include sodium soap, calcium soap, aluminum soap, lithium soap, calcium composite soap, aluminum composite soap, lithium composite soap and the like.

Examples of the urea thickener include urea compounds such as diurea compounds, triurea compounds, tetraurea compounds, and polyurea compounds; urea / urethane compounds; urethane compounds such as diurethane compounds, or a mixture of two or more of these. Of these, diurea compounds are preferred.

Examples of the diurea thickener include diurea compounds obtained by reaction of diisocyanate and amine.

Examples of diisocyanates include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of these diisocyanates include diisocyanates having a hydrocarbon group. The hydrocarbon group may be saturated or unsaturated, and may be linear or branched. As an example, the aliphatic diisocyanate includes octadecane diisocyanate, decane diisocyanate, hexane diisocyanate, the alicyclic diisocyanate includes cyclohexyl diisocyanate, dicyclohexylmethane diisocyanate, and the aromatic diisocyanate includes phenylene diisocyanate, tolylene diisocyanate, diphenyl diisocyanate. , Diphenylmethane diisocyanate and the like are preferable. Examples of monoamines include aliphatic monoamines, alicyclic monoamines, and aromatic monoamines. Examples of these monoamines include amines having a hydrocarbon group. The hydrocarbon group may be saturated or unsaturated, and may be linear or branched. For example, alicyclic monoamines include octylamine, dodecylamine, hexadecylamine, stearylamine, oleylamine, alicyclic monoamines include cyclohexylamine, dicyclohexylamine, and aromatic monoamines such as aniline and p-toluidine. preferable.

Thickeners may be used alone or in combination of two or more. The content of the thickener is only required to obtain a desired consistency. For example, it is preferably 2 to 30% by mass or 5 to 30% by mass, more preferably 5 to 20% by mass, based on the total amount of the grease composition. % Or 10 to 20% by mass.

In addition to the above components, the grease composition according to the present embodiment is generally used in lubricating oils and greases as necessary. For example, detergents, dispersants, antiwear agents, viscosity index improvers, and antioxidants An agent, extreme pressure agent, rust inhibitor, corrosion inhibitor and the like can be added as appropriate. Components other than the above components are preferably 10% by mass or less, more preferably 5% by mass or less, based on the total amount of the grease composition.

The method for producing a grease composition according to this embodiment includes a step of obtaining a grease composition by mixing a lubricating base oil and a thickener.

In this embodiment, a thickener prepared in advance may be mixed with a lubricating base oil, or a raw material for the thickener is blended with the lubricating base oil and reacted in the lubricating base oil. You may obtain a thickener. For example, when a urea-based thickener is used, it may be blended with the lubricating base oil in the form of a urea compound, but diisocyanate and amines are blended with the lubricating base oil and reacted during the preparation of the grease. A system thickener may be used.

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

[Base oil A]
The bottom fraction obtained from the fuel oil hydrocracking apparatus was used as a raw material for the lubricant base oil, and hydrotreating was performed using a hydrotreating catalyst. At this time, the reaction temperature and the liquid space velocity were adjusted so that the decomposition rate of normal paraffin in the raw material oil was 10% by mass or less. Further, the hydrotreated dewaxing is carried out at a temperature range of 315 to 325 ° C. using a zeolite hydrodewaxing catalyst adjusted to a noble metal content of 0.1 to 5 mass%. And dewaxed oil was obtained. Further, this dewaxed oil was hydrorefined using a hydrorefining catalyst. Thereafter, a lubricating base oil having the following properties obtained by distillation was used as the base oil A.
Urea adduct value: 2% by mass
% C _P : 76
% C _A : 0
Kinematic viscosity at 40 ° C .: 37.8 mm ² / s
Kinematic viscosity at 100 ° C .: 6.7 mm ² / s
Viscosity index: 133

[Base oil B]
The fraction separated by distillation under reduced pressure in the step of refining the solvent refined base oil was subjected to hydrogenation after solvent extraction with furfural and then dewaxed with a mixed solvent of methyl ethyl ketone and toluene. The wax that was removed during solvent dewaxing and obtained as slack wax was used as a raw material for lubricating base oil, and hydrotreated using a hydrotreating catalyst. At this time, the reaction temperature and the liquid space velocity were adjusted so that the decomposition rate of normal paraffin in the raw material oil was 10% by mass or less. Further, the hydrotreated dewaxing is carried out at a temperature range of 315 to 325 ° C. using a zeolite hydrodewaxing catalyst adjusted to a noble metal content of 0.1 to 5 mass%. And dewaxed oil was obtained. Further, this dewaxed oil was hydrorefined using a hydrorefining catalyst. Thereafter, a lubricating base oil having the following properties obtained by distillation was used as the base oil B.
Urea adduct value: 2% by mass
% C _P : 95
% C _A : 0
Kinematic viscosity at 40 ° C .: 33.0 mm ² / s
Kinematic viscosity at 100 ° C .: 6.8 mm ² / s
Viscosity index: 167

[Base oil C]
The base oil C was a lubricating base oil having the following properties, obtained by subjecting a distillate obtained by distilling an atmospheric distillation residue under reduced pressure to a solvent.
Urea adduct value: 5% by mass
% C _P : 66
% C _A : 5
Kinematic viscosity at 40 ° C .: 32.0 mm ² / s
Kinematic viscosity at 100 ° C .: 5.5 mm ² / s
Viscosity index: 100

[Base oil D]
The fraction separated by vacuum distillation of the solvent-purified base oil was subjected to a hydrogenation treatment after solvent extraction with furfural, and then dewaxed with a methyl ethyl ketone-toluene mixed solvent. The wax that was removed during solvent dewaxing and obtained as slack wax was used as a raw material for lubricating base oil, and hydrogenated. At this time, the reaction temperature and the liquid space velocity were adjusted, the temperature condition of the hydrodewaxing of the object to be treated obtained by the hydrotreatment was adjusted to be as low as about 300 ° C., and the resulting raffinate was hydrorefined. Thereafter, a lubricating base oil having the following properties obtained by distillation was used as the base oil D.
Urea adduct value: 5% by mass
% C _P : 75
% C _A : 0
Kinematic viscosity at 40 ° C .: 32.0 mm ² / s
Kinematic viscosity at 100 ° C .: 6.0 mm ² / s
Viscosity index: 130

[Thickener A]
As the thickener A, a lithium stearate compound obtained by reacting stearic acid (1 molar equivalent) with lithium hydroxide (1 molar equivalent) was used.

[Thickener B]
As the thickener B, a diurea compound obtained by reacting diphenylmethane diisocyanate (1 molar equivalent) with cyclohexylamine (2 molar equivalent) was used.

[Antioxidant]
Phenyl-α-naphthylamine was used as an amine antioxidant.

[Examples 1 to 4, Comparative Examples 1 to 4]
In Examples 1 to 4 and Comparative Examples 1 to 4, grease compositions having the compositions shown in Table 1 were prepared.
In Examples 1 and 3 and Comparative Examples 1 and 3, base oil A, B, C or D was used as the lubricating base oil, and stearic acid was added to this lubricating base oil and dissolved by heating. Next, a solution obtained by dissolving lithium hydroxide in water by heating was added, and water was evaporated while heating and stirring. Furthermore, after heating and raising the temperature until the reaction product dissolves, a gel-like substance is produced when the base oil is added, so cool it with stirring, add the antioxidant, and then pass them through a roll mill. The grease compositions of Examples 1 and 3 and Comparative Examples 1 and 3 were obtained.
In Examples 2 and 4 and Comparative Examples 2 and 4, base oil A, B, C or D was used as the lubricating base oil, and diphenylmethane diisocyanate was added to this lubricating base oil and dissolved by heating. Subsequently, when a substance obtained by dissolving cyclohexylamine in the same base oil is added, a gel-like substance is formed. Therefore, after adding an antioxidant, these are passed through a roll mill, and the greases of Examples 2, 4 and Comparative Examples 2, 4 A composition was obtained.

[Evaluation test: Consistency]
Regarding the grease compositions of Examples 1 to 4 and Comparative Examples 1 to 4, the hardness of the grease compositions was compared by the consistency test of JIS K2220. In this test, the consistency was measured after mixing 60 times at a temperature of 25 ° C.

[Evaluation test: Torque evaluation]
Using the grease compositions of Examples 1 to 4 and Examples 1 to 4, torque during bearing rotation was measured by the following method.
A single-row deep groove ball bearing 6204VV was used as the bearing. Before the test, the inside of the bearing was thoroughly washed with an organic solvent, and then 2 g of each grease composition was injected into the gap between the bearing balls, the race rings and the cage with a syringe. As a tester, a Kamata type grease life tester manufactured by Shinko Engineering Co., Ltd. was used. The bearing rotation speed was 8000 rpm, the temperature was room temperature, and the torque at the start of the test (starting torque) was compared with the torque after 20 hours of the test (rotational torque). The number of repeated experiments was two. The obtained results are shown in Table 1. In addition, the starting torque and rotational torque in Table 1 are average values of two experiments.

[Evaluation test: Bearing fatigue life evaluation]
Using the grease compositions of Examples 1 to 4 and Comparative Examples 1 to 4, the bearing fatigue life was measured by the following method.
A single type thrust ball bearing 51110 was used as the bearing. Before the test, 21 of the 24 bearing balls were removed and removed so that the remaining 3 were evenly arranged. After thoroughly washing the inside of the bearing with an organic solvent, each grease composition was applied to the bearing. A Unisteel testing machine manufactured by Shinko Engineering Co., Ltd. was used as the testing machine. In accordance with British Petroleum Institute IP305, L50 (50% life) was calculated from the time until the fatigue life was reached with the bearing rotation speed set at 1500 rpm and the temperature at room temperature. The number of repeated experiments was 10 times. The obtained results are shown in Table 1.

[Evaluation test: Low temperature torque test]
Using the grease compositions of Examples 1 to 4 and Comparative Examples 1 to 4, low temperature torque at −20 ° C. was measured according to JIS K2220.

The grease composition of the present invention has an exceptional effect that the torque required for rotation of the bearing can be reduced while maintaining the bearing fatigue life. Therefore, the grease composition of the present invention can be suitably used for lubrication of machine elements such as rolling bearings, plain bearings, ball screws, linear motion guides, and gears, and is useful in industrial machines and transportation machine systems. .

Claims (6)

_A lubricant base oil having a urea adduct value of 4% by mass or less,% _CP of 70 or more,% CA of 2 or less, and a viscosity index of 105 or more;
A thickener,
Containing a grease composition. The grease composition according to claim 1, wherein the lubricating base oil has a viscosity index of 120 or more. The grease composition according to claim 1 or 2, comprising 70 to 95% by mass of the lubricating base oil and 5 to 30% by mass of the thickener based on the total amount of the grease composition. Use of the grease composition according to any one of claims 1 to 3 for a machine element. The use for a machine element according to claim 4, wherein the machine element is a bearing. A method for reducing torque of a machine element, wherein the machine element is lubricated with the grease composition according to any one of claims 1 to 3.