JP2013028749A - Grease composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grease composition having little state variation even under a high temperature, and excellent in oxidation stability.SOLUTION: The grease composition is obtained by mixing 60-95 pts.wt. of a base oil, 3-25 pts.wt. of a urea-based thickener, and 0.05-5 pts.wt. of a hindered amine-based antioxidant, assuming the whole as 100 pts.wt.

Description

  The present invention relates to a grease composition. More specifically, the present invention relates to a grease composition having thermal stability and oxidation stability.

  As a grease lubricant, generally, mineral oil or various synthetic oils are used as the base oil, and calcium soap, lithium soap, calcium composite soap, calcium sulfonate, lithium composite soap, aluminum composite soap, clay, silica gel, Products using urea compounds, sodium terephthalate, fluororesin, etc. are used.

  In recent years, grease lubricants having excellent thermal stability that can be used at high temperatures for a long time have been demanded as machines become smaller, lighter, or faster, and have become more maintenance-free. In general, the thermal stability of a grease lubricant is influenced by the type and content of a thickener that can be said to be the core of the grease structure, although it is affected by the type and viscosity of the base oil used.

  For example, urea greases using urea-based thickeners are superior in thermal stability and oxidation stability, and bearings filled with urea grease show a longer life at higher temperatures than greases using metal soap-based thickeners. It is known. However, the excellent thermal stability and oxidation stability of these urea greases are mainly attributed to urea-based thickeners, although antioxidants are often included. In order to further improve the thermal stability and oxidation stability of urea grease, studies are made by selecting an antioxidant as in Patent Documents 1 to 3. For example, Patent Document 1 discusses a combination of a phosphite and a hindered amine with respect to urea grease using a diurea compound as a thickener. In Patent Document 2, a combination of α-naphthylamines and diphenylamines is examined for urea grease using a diurea compound as a thickener. In patent document 3, the combination of an aralkyl diphenylamine and a hindered phenol is examined with respect to urea grease.

JP 2007-77244 A JP 2004-359809 A International Publication No. 2007-037322

  Therefore, the present invention is superior in oxidation stability by blending an antioxidant suitable for urea grease in which a urea-based thickener is added to a base oil, so that there is little change in state such as curing or liquefaction even at high temperatures. It is an object to provide a grease composition.

  Under such circumstances, the inventors have intensively studied, and as a result, found that the problem can be solved by adding a hindered amine-based antioxidant and optionally further a hindered phenol-based antioxidant to urea grease. .

In more detail, this invention consists of the following this invention (1)-(6).
(1) A grease composition obtained by mixing 60 to 95 parts by weight of a base oil, 3 to 25 parts by weight of a urea-based thickener, and 0.05 to 5 parts by weight of a hindered amine antioxidant, based on 100 parts by weight as a whole.

(2) The grease composition according to item (1), further comprising 0.05 to 5 parts by weight of a hindered phenol antioxidant.

(3) The hindered amine antioxidant is tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, (2,2,6,6-tetra Methyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6) The preceding item (1) which is at least one selected from the group consisting of -pentamethyl-4-piperidyl) sebacate and bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl ester) The grease composition according to 1) or (2).

(4) The hindered phenolic antioxidant is octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythrityl tetrakis [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 1 , 3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, triethylene glycol-bis [3- (3-tert-butyl-5-methyl) -4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2, -Thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy- The grease composition according to any one of (1) to (3), wherein the grease composition is one or more selected from the group consisting of (hydrocinnamamide).

(5) The grease composition according to any one of (1) to (4), wherein the urea thickener is an alkyldiurea compound.

(6) The grease composition according to any one of items (1) to (5), further comprising 0.5 to 30 parts by weight of tricalcium phosphate.

  Since the grease composition of the present invention has excellent thermal stability and oxidation stability at high temperatures, it can function as a lubricant in a wide range of temperatures including a high temperature range.

  Hereinafter, the present invention will be described in detail. However, the present invention is not limited to such specific applications, and it goes without saying that the present invention can be widely applied to arbitrary applications. The grease composition of the present invention contains “base oil”, “thickener” and “antioxidant”. Hereinafter, each component contained in the grease composition, the amount (mixing amount) of each component in the grease composition, the manufacturing method of the grease composition, the properties of the grease composition, and the use of the grease composition will be described in order.

≪Grease composition (component) ≫
[Base oil]
As the base oil used in the grease composition of the present invention, mineral oils, synthetic oils, animal and vegetable oils, and mixed oils used for ordinary lubricating oils can be used as appropriate, and the kinematic viscosity is about 100 ° C. The thing of about 2-40 mm < ² > / s is preferable. In particular, base oils belonging to Group 1, Group 2, Group 3, Group 4, etc. in the API (American Petroleum Institute) base oil category can be used alone or as a mixture.

For Group 1 base oils , for example, paraffin obtained by applying a suitable combination of solvent refining, hydrotreating, dewaxing, etc., to a lubricating oil fraction obtained by atmospheric distillation of crude oil There are mineral oils. For Group 2 base oils , for example, paraffinic mineral oil obtained by appropriately combining refining means such as hydrocracking and dewaxing for lubricating oil fractions obtained by atmospheric distillation of crude oil There is. Group 2 base oils refined by hydrorefining methods such as the Gulf Company method have a total sulfur content of less than 10 ppm and an aroma content of 5% or less, and can be suitably used in the present invention. Group 3 base oil and Group 2 plus base oil include, for example, a paraffinic mineral oil produced by advanced hydrorefining and a dewaxing process for a lubricating oil fraction obtained by atmospheric distillation of crude oil. There are base oils refined by the ISODEWAX process for converting and dewaxing the produced wax to isoparaffins, and base oils refined by the mobile WAX isomerization process, and these can also be suitably used in the present invention.

Synthetic oils include, for example, polyolefins, dibasic acid diesters such as dioctyl sebacate, polyol esters, alkylbenzenes, alkylnaphthalenes, esters, polyoxyalkylene glycols, polyoxyalkylene glycol esters, polyoxyalkylene glycol ethers, polyphenyls. Examples include ether, dialkyldiphenyl ether, fluorine-containing compounds (perfluoropolyether, fluorinated polyolefin, etc.), silicone, and the like. The polyolefin includes polymers of various olefins or hydrides thereof. Any olefin may be used, and examples thereof include ethylene, propylene, butene, and α-olefins having 5 or more carbon atoms. In the production of polyolefin, one of the above olefins may be used alone, or two or more may be used in combination. Particularly preferred are polyolefins called poly α-olefins (PAO), which are Group 4 base oils .

  GTL (Gas Liquid) synthesized by the Fischer-Tropsch method, which is a natural gas liquid fuel technology, has an extremely low sulfur content and aromatic content compared to mineral oil base oil refined from crude oil. Is extremely high, so that it has excellent oxidation stability and very low evaporation loss, and can be suitably used as the base oil of the present invention.

[Thickener]
The thickener used in the present invention is not particularly limited, but contains a urea-based thickener as an essential component from the viewpoint of oxidation stability at high temperatures, bearing life and the effect of preventing damage to machine parts. As components, tricalcium phosphate, soap-based thickener, benton, silica gel and the like may be contained. These thickeners preferably have a dropping point of the grease composition of 200 ° C. or higher, more preferably 250 ° C. or higher. This is because if the dropping point of the grease composition is 250 ° C. or higher, the possibility of lubrication problems, for example, softening at high temperatures, leakage and seizure associated therewith, can be suppressed.

  The urea-based thickener used in the present invention refers to any thickener containing a urea bond, and this urea bond is generally obtained by reacting an isocyanate with an amine. Examples of the urea thickener include monourea compounds such as monourea and monourea monourethane, diurea compounds such as diurea, diurea monourethane and diurea diurethane, triurea, triurea monourethane, triurea diurethane and triurea. Polyurea compounds such as triurethane, tetraurea, tetraurea monourethane, tetraureadiurethane, tetraureatriurethane, tetraureatetraurethane and the like can be mentioned, but are not particularly limited.

  The diurea compound is obtained, for example, by reaction of diisocyanate and monoamine. Examples of the diisocyanate include tolylene diisocyanate, bitolylene diisocyanate, m-xylene diisocyanate, phenylene diisocyanate, diphenyl diisocyanate, phenyl diisocyanate, diphenylmethane diisocyanate, occadecane diisocyanate, decane diisocyanate, hexane diisocyanate, and monoamines include octyl. Examples include amine, dodecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-chloroaniline, benzylamine, m-xylidine, p-toluidine, o-toluidine, cyclohexylamine, and furfurylamine.

  The polyurea compound is obtained, for example, by reacting diisocyanate with diamine and monoamine. Examples of diisocyanate and monoamine include those used for the production of diurea compounds. Examples of diamines include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, phenylenediamine, tolylenediamine, And xylenediamine. Further, a compound containing a urethane bond in addition to a urea bond can be obtained by reacting an isocyanate with an alcohol. Examples of the alcohol include octyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, and eicosin alcohol. In addition, the alkyl diurea obtained by reaction of diisocyanate and an alkyl monoamine is preferable from handling of a raw material and manufacture ease.

(Other thickeners)
In the grease composition of the present invention, other thickeners can be used in combination with the above urea thickener. These other thickeners include tribasic calcium phosphate, alkali metal soaps, alkali metal composite soaps, alkaline earth metal soaps, alkaline earth composite soaps, alkali metal sulfonates, alkaline earth metal sulfonates, other metal soaps, Examples thereof include silica (silicon oxide) such as talamate metal salt, clay and silica airgel, and fluororesin such as polytetrafluoroethylene, and one or more of these can be used in combination. In addition to these, any substance that can impart a viscosity effect to a liquid substance can be used.

As the tricalcium phosphate, Ca ₃ (PO ₄ ) ₂ can be used. Generally, the chemistry of the hydroxyapatite composition represented by [Ca ₃ (PO ₄ ) ₂ ] ₃ · Ca (OH) ₂ is used. What has a structure can be used. As for the particle size, it can be used if the average particle size is about 100 μm or less, preferably 20 μm or less, particularly preferably 10 μm or less. In the present invention, when the content is displayed, it is expressed by a mass based on [Ca ₃ (PO ₄ ) ₂ ] ₃ · Ca (OH) ₂ . Alkali metal soaps or alkaline earth metal soaps generally include those obtained by the reaction of fatty acids with alkali metal hydroxides or alkaline earth metals. These fatty acids include lauric acid, myristic acid, palmitic acid. Examples include acids, stearic acid, 12-hydroxystearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, and eicosanoic acid. Examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkaline earth metal include calcium and magnesium. Examples of these alkali metal soaps include lithium soap, lithium composite soap, sodium soap, sodium composite soap, potassium soap, and potassium composite soap. Alkaline earth metal soaps include calcium soap, calcium composite soap, and magnesium. Examples include soaps, magnesium composite soaps, barium soaps, and barium composite soaps. Furthermore, examples of other metal soap include aluminum soap and aluminum composite soap.

  The composite soap is a composite soap containing a metal salt of a second acid in a metal soap of a fatty acid as described above. For example, the lithium composite soap includes those containing a metal salt of a second acid in addition to a lithium salt of a fatty acid, specifically, a blend of lithium 12-hydroxystearate and lithium azelate. It is done. Specific examples of the aluminum composite soap include aluminum stearate benzoate. Examples of the terephthalamate metal salt include sodium terephthalate and lithium terephthalate, and sodium terephthalate is preferably used.

[Antioxidant]
The grease composition of the present invention contains an antioxidant for the purpose of stabilizing against oxidation. As the antioxidant, a hindered amine antioxidant is used as an essential component, and it is more preferable to use a hindered phenol antioxidant together.

(Hindered amine antioxidant)
Examples of the hindered amine antioxidant in the present invention include tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, (2,2,6, 6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2, 6,6-pentamethyl-4-piperidyl) sebacate, bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl ester), etc.

(Hindered phenolic antioxidant)
Examples of the hindered phenol antioxidant in the present invention include octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythrityl tetrakis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5- Triazine, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, triethylene glycol-bis [3- (3-t-butyl- 5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) pro Onate], 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-t- Butyl-4-hydroxy-hydrocinnamamide) and the like.

[Optional additives]
(Other antioxidants)
Along with the hindered amine antioxidants and hindered phenol antioxidants, other antioxidants (zinc dithiophosphate, dithiocarbamate, ashless dithiocarbamate, benzimidazole, phosphorous acid and organic thioacid) Etc.) can be used together. Examples of the dithiocarbamate salt include nickel dibutyldithiocarbamate, zinc dimethyldithiocarbamate, and zinc diethyldithiocarbamate. Examples of the benzimidazole type include 2-mercaptobenzimidazole. Examples of the phosphorous acid system include tris (nonylphenyl) phosphite and trioctadecyl phosphite. Examples of the organic thioic acid type include dilauryl thiodipropionate, distearyl thiodipropionate, and lauryl stearyl thiodipropionate. Said antioxidant can be used individually or in combination of multiple.

(Other additives)
In addition to the above-described components, the grease composition of the present invention includes an arbitrary rust preventive agent, extreme pressure agent, metal deactivator, metal-based detergent, non-metal detergent, antifoaming agent, thickener, and coloring. You may add additives, such as an agent and a water repellent. Examples of the rust inhibitor include metal sulfonates and succinic acid esters. Examples of metal detergents include metal sulfonates, metal salicylates, and metal finates. Examples of non-metallic detergents include succinimide. Examples of the metal deactivator include benzotriazole and thiadiazole. Examples of the antifoaming agent include methyl silicone, dimethyl silicone, fluorosilicone, and polyacrylate.

≪Grease composition (mixing amount of each component) ≫
Next, the blending amount in the grease composition according to the present invention will be described.
[Base oil]
The blending amount of the base oil is preferably 60 to 95 parts by weight, more preferably 70 to 90 parts by weight, based on 100 parts by weight of the entire grease composition.

[Thickener]
(Urea-based thickener)
The blending amount of the urea-based thickener is preferably 3 to 25 parts by weight, more preferably 5 to 20 parts by weight, and still more preferably 8 to 18 parts by weight, based on 100 parts by weight of the entire grease composition. If the blending amount is too small, the thickening effect is small and it is not in the form of a grease. If the blending amount is too large, the grease becomes too hard to obtain a sufficient lubricating effect.

(Other thickeners)
Various other thickeners (tricalcium phosphate, soap thickener, benton, silica gel, etc.) may be added as necessary. When added, the total amount of the grease composition is preferably 0.1 parts by weight. 05 to 30 parts by weight, more preferably 0.1 to 20 parts by weight, still more preferably 1 to 10 parts by weight.

(Total amount of thickener)
A urea-based thickener can be used alone or in combination with other thickeners, but the total amount of both is preferably 3 to 40 parts by weight, more preferably 100 parts by weight of the entire grease composition, more preferably It is preferable to use so that it may become 5-20 weight part.

[Antioxidant]
(Hindered amine antioxidants and hindered phenol antioxidants)
The amount of the hindered amine-based oxidizing agent is preferably 0.05 to 5.0 parts by weight, more preferably 0.1 to 4.0 parts by weight, and still more preferably 0.2 to 100 parts by weight based on the entire grease composition. It is preferable to use 2.0 parts by weight. The hindered phenol-based antioxidant may be used in addition to the hindered amine-based antioxidant, and is preferably 0.05 to 5.0 parts by weight, more preferably 0. 07 to 2.5 parts by weight, more preferably 0.08 to 2.25 parts by weight are used. When the hindered amine-based antioxidant and the hindered phenol-based antioxidant are used together, the total blending amount is preferably 0.1 to 8.0 parts by weight, more preferably 0.8 parts, based on 100 parts by weight of the entire grease composition. 15 to 6.0 parts by weight, more preferably 0.20 to 4.0 parts by weight are used. When blending both a hindered amine antioxidant and a hindered phenol antioxidant, for example, preferably hindered amine antioxidant: hindered phenol antioxidant = 5: 1 to 1: 5, more preferably Can be used in an arbitrary weight ratio of 3: 1 to 1: 3, more preferably 4: 1 to 1: 1.

(Optional additive)
As long as the said arbitrary additive has the objective and effect of this invention, arbitrary quantity can be used as needed.

≪Grease composition manufacturing method≫
The grease composition of the present invention can be produced by a generally used method for producing urea grease. For example, an isocyanate compound and an amine compound are dissolved in a base oil heated to 50 ° C., and a urea compound that is a thickener is produced in the base oil by further heating and stirring. Then, add a hindered amine antioxidant and optionally a hindered phenol antioxidant, stir and mix, cool to room temperature, finish using a three-roll mill, etc., and add the desired urea grease. Can be obtained.

  When other thickeners are blended, other thickeners can be added to the base oil mixed with a urea-based thickener and an antioxidant. A grease composition can be obtained by adding a urea-based thickener and an antioxidant to a thickener mixed with the above thickener. In this case, a grease composition containing a urea-based thickener and an antioxidant in the base oil and a lubricant composition mainly containing another thickener in the base oil are mixed in an appropriate ratio to mix the grease composition of the present invention. It can also be a grease composition. And by any of the above methods, a grease composition having high thermal stability can be obtained at the high temperature of the present invention.

<Properties of grease composition>
The grease composition of the present invention is considered to have high thermal stability and oxidation stability because the grease state is stable even at high temperatures and the change in hue is extremely small. For example, the grease composition of the present invention preferably satisfies at least one of the following (1), (2) and (3), more preferably all.
(1) In a high-temperature heating test (at 165 ° C. for 24 hours), the immiscibility penetration and the rate of change in the penetration are 50% or less.
(2) In a thin film heating test (100 hours at 150 ° C.), the evaporation amount is 25% or less, and the CO (carbonyl group) absorbance increase rate is 35% or less.
(3) The change in the state of the grease after the thin film heating test (hue change, etc.) is small and good.

≪Use of grease composition≫
The grease composition of the present invention can be used for machines, bearings, gears and the like that are generally used as applications, and can exhibit excellent performance under more severe load conditions. For example, in automobiles, the engine periphery of starters, alternators and various actuators, propeller shafts, constant velocity joints (CVJ), power trains such as wheel bearings and clutches, electric power steering (EPS), braking devices, ball joints, door hinges It can be suitably used for lubricating various parts such as a handle part, a cooling fan motor, and a brake expander. In addition, construction machines such as excavators, bulldozers, cranes, steel industry, paper industry, forestry machinery, agricultural machinery, chemical plants, power generation equipment, drying furnaces, copying machines, railway vehicles, seamless pipe screw joints, etc. -It is also preferable to use for a high load site. Other applications include hard disk bearings, plastic lubrication, cartridge grease, etc., which are also suitable for these applications.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. Various performance test methods in Examples and Comparative Examples were measured according to the following methods.

(Performance test method)
1. Consistency : According to the method described in JIS K 2220, the immiscibility and miscibility were measured.

2. Dropping point (° C.) : Performed according to the method described in JIS K 2220.

3. High temperature heating test : (Change rate of immiscible consistency before and after heating)%
The rate of change in the immiscible penetration before and after heating was measured with a ½ consistency meter (165 ° C., 24 hours). High-temperature heating test: After measuring the immiscible consistency with a JIS K 2220 1/2 consistency meter, put the cup containing the grease used for the measurement into a 165 ° C constant temperature bath and remove it 24 hours later, up to 25 ° C The immiscible penetration was measured after cooling. As a test result, the change rate of the immiscible consistency before and after heating was obtained by the following formula.
Rate of change in immiscibility penetration = (immiscibility penetration before heating test−immiscibility penetration after heating test) / (immiscibility penetration before heating test) × 100

4). Thin film heating test : SPCC steel sheet specified in the wet test method of JIS K 2246 Thickness (1.0 mm to 2.0 mm) x length 60 mm x width 80 mm Specimens on one side of the center area (50 mm x 70 mm) Was applied at a temperature of 150 ° C. for 100 hours, and the following items were measured.

4.1 Evaporation amount: The weight of the SPCC steel plate coated with grease was measured before and after the heating test, and the evaporation amount was determined by the following equation.
Evaporation (%) = (Weight before heating test (g) −Weight after heating test (g)) / (Weight before heating test) (g) × 100

4.2 Absorbance by infrared absorption analysis : Grease before and after the heating test was analyzed by infrared absorption analysis, and 1710 cm ^-1 (CO: absorption of carbonyl group) and 720 cm ^-1
The absorbance at (absorption position serving as a standard peculiar to urea grease) was measured. The following formula was used for calculation of absorbance.
Absorbance at 1710 cm ⁻¹ = log I ₀ / I
_{(I o:} 1800~2000 cm maximum transmittance of ^-1, I: transmittance of 1710 cm ^-1)
Absorbance at 720 cm ⁻¹ = log I ₀ / I
_{(I o:} maximum transmittance of 750~850cm ^-1, I: transmittance of 720 cm ^-1)

Next, the absorbance ratio (A) before the heating test and the absorbance ratio (B) after the heating test were determined by the following equations.
A (absorbance ratio of grease before heating test) = (absorbance at 1710 cm ⁻¹ ) / (absorbance at 720 cm ⁻¹ )
B (absorbance ratio of grease after heating test) = (absorbance at 1710 cm ⁻¹ ) / (absorbance at 720 cm ⁻¹ )

  Further, the absorbance increase rate indicating the degree of oxidative degradation of the grease was determined from the formula “absorbance increase rate: (BA) / A × 100”.

4.3 Visual observation of grease: The state of the grease after the heating test was visually observed with a focus on hue change. In the table, ◎ indicates very good (there is almost no change in hue), ○ indicates good (a slight change in hue is observed), and x indicates inappropriate (a large change in hue is observed).

(Raw materials used in this composition)
The raw materials used in the examples and comparative examples are as follows.
○ Thickener raw material Thickener A: Diurea thickener (MDI, C8 / C12 = 30/70, alkyldiurea)
MDI (4,4'-diphenylmethane-diisocyanate): Mitsui Chemicals Cosmonate PH
C8 (Caprylylamine): Kao Co., Ltd. Farmin 08D
C12 (laurylamine): Farmin 20D, Kao Corporation
Thickener B: Taihei Chemical Industry Co., Ltd. Tricalcium phosphate

Base oil Base oil A: A paraffinic mineral oil obtained by solvent dewaxing refining, belonging to Group 1, having a kinematic viscosity at 100 ° C. of 11.25 mm ² / s and a viscosity index of 97.
Base oil B: Poly α-olefin belonging to group 4, having a kinematic viscosity at 100 ° C. of 6.34 mm ² / s and a viscosity index of 136.
Base oil C: A paraffinic mineral oil produced by advanced hydrorefining, belonging to Group 3, having a kinematic viscosity at 100 ° C. of 7.603 mm ² / s and a viscosity index of 128.
Base oil D: GTL (Gas Liquid) synthesized by Fischer-Tropsch method, belonging to Group 3, 100 ° C kinematic viscosity 7.77mm ² / s, 40 ° C kinematic viscosity 43.88mm ² / s @, The viscosity index is 148.

Antioxidant Antioxidant A: Tetrakis (2,2,6,6-tetramethyl-4-piperidyl-1,2,3,4-butanetetracarboxylate (trade name: ADEKA AIN-570, hindered amine oxidation) Inhibitor)
Antioxidant B: Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (trade name: ADEKA AIN-100, hindered phenol-based antioxidant)
Antioxidant C: Pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (trade name: IRGANOX L101, hindered phenol antioxidant)
Antioxidant D: 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine (trade name: Irganox 565, hinder) Dophenol antioxidants)
Antioxidant E: 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (trade name: Irganox 1330, hindered phenol antioxidant) )
Antioxidant F: p, p′-dioctyldiphenylamine (trade name: Vanlube 81, aromatic amine antioxidant)
Antioxidant G: Styrenated diphenylamine (trade name: Stearer-LAS, aromatic amine antioxidant)

Example and Comparative Example Composition Production Method
(1) Examples 1 to 3, 8 to 10 and Comparative Examples 1 to 4 (amount of urea thickener: 14%)
After reacting 4,4′-diphenylmethane-diisocyanate (MDI) (16.52 g, 0.066 mol) and caprylylamine (17.08 g, 0.132 mol) at about 50 ° C. in 688 g of base oil A, then MDI (31.60 g, 0.126 mol) was reacted with laurylamine (46.80 g, 0.253 mol), heated to about 165 ° C. and held for 1 hour with stirring. Thereafter, antioxidants were added and mixed according to the formulations of Examples and Comparative Examples shown in Table 1, and allowed to cool to room temperature, and then subjected to finishing treatment with a three-roll mill to obtain the title grease.

(2) Examples 4 to 7 (Urea thickener amount: 16%)
MDI (18.88 g, 0.075 mol) and caprylylamine (19.52 g, 0.151 mol) at about 50 ° C. in 672 g of base oil (the base oil of each example is listed in Tables 1 and 2) After the reaction, MDI (36.12 g, 0.144 mol) was then reacted with laurylamine (53.48 g, 0.289 mol), heated to about 165 ° C. and held for 1 hour with stirring. Thereafter, antioxidants were added and mixed according to the formulations of Examples and Comparative Examples shown in Table 1, and allowed to cool to room temperature, and then subjected to finishing treatment with a three-roll mill to obtain the title grease.

(3) Example 11 and Comparative Example 5 (Urea thickener amount: 10%, CAP: 5.0%)
In Example 1, 400 g of base grease before addition of antioxidant (amount of urea thickener 14.0%) was diluted with 160 g of base oil heated to about 120 ° C., and the amount of urea thickener was 10%. did. Thereafter, tricalcium phosphate (CAP) was stirred and dispersed so as to have a blending amount of 5 parts by weight out of 100 parts by weight of the whole grease to obtain a grease. Thereafter, antioxidants were added and mixed according to the formulations of Examples and Comparative Examples shown in Table 1, and allowed to cool to room temperature, and then subjected to finishing treatment with a three-roll mill to obtain the title grease.

(4) Comparative Example 6
A commercially available mineral oil-based urea grease (trade name: Shell Stamina Grease RL2) was used.

(Consideration of Examples)
1. Consistency The change in the consistency before and after mixing was small as a whole for both the grease composition of the present invention and the grease composition of the comparative example.

2. Dropping point Both the grease composition of the example and the grease composition of the comparative example showed a dropping point of more than 250, and thus it was found that the standards satisfied by the urea grease were satisfied.

3. High-temperature heating test Since the rate of change in consistency before and after heating in the examples was 50% or less, it is preferable that thermosetting is difficult. Although the grease compositions of Comparative Examples 1 and 6 were 50% or less, the grease compositions of Comparative Examples 2 to 5 had a consistency change rate exceeding 50%. Not always enough.

4). Thin film heating test 4.1 Evaporation amount The grease composition of the example had a good evaporation rate of 25% or less, but the grease compositions of the comparative examples all exceeded 25% and were not necessarily good.

4.2 Absorbance Although the grease compositions of the examples all had an absorbance ratio of less than 0.300, the grease compositions of the comparative examples all showed an absorbance ratio of more than 0.300, indicating superiority or inferiority in oxidation stability after heating. It was. When the absorbance increase rate was compared before and after heating, the grease composition of the example was less than 35%, whereas the grease composition of the comparative example exceeded 60%, and the change before and after heating was It was also acknowledged to be large.

4.3 Visual observation of grease Each of the grease compositions of the examples was very good or good in appearance, but the grease composition of the comparative example was used as a grease because the hue change was too large. Some were not suitable.

  Thus, the grease composition of the present invention comprising a base oil, a urea-based thickener and a hindered amine antioxidant as essential components, and more preferably a hindered phenol antioxidant, has a low thermosetting and an evaporation amount. It has a small absorbance specific to the carbonyl group, and further, since the color change of the grease after heating is small, it can be said to be excellent in thermal stability and oxidation stability.

Claims (6)

  A grease composition comprising 60 to 95 parts by weight of a base oil, 3 to 25 parts by weight of a urea thickener, and 0.05 to 5 parts by weight of a hindered amine antioxidant, based on 100 parts by weight as a whole.   Furthermore, the grease composition of Claim 1 formed by mixing 0.05-5 weight part of hindered phenolic antioxidants.   The hindered amine antioxidant is tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylate, (2,2,6,6-tetramethyl-4 -Piperidyl) -1,2,3,4-butanetetracarboxylate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl- 3. One or more selected from the group consisting of 4-piperidyl) sebacate and bis (2,2,6,6-tetramethyl-1 (octyloxy) -4-piperidinyl ester) decanedioic acid The grease composition according to any one of the above.   The hindered phenol antioxidant is octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, pentaerythrityl tetrakis [3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 1,3, 5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4- Hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2-thio Diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamate The grease composition according to any one of claims 1 to 3, which is at least one selected from the group consisting of (mid).   The grease composition according to any one of claims 1 to 4, wherein the urea-based thickener is an alkyldiurea compound.   Furthermore, the grease composition as described in any one of Claims 1-5 formed by mixing 0.5-30 weight part of tribasic calcium phosphates.