JP5283427B2 - Grease composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition having heat resistance equivalent to heat resistance of silicone grease, fluorine grease and grease using a polyphenylether as a base oil, while the grease composition has an inexpensive base oil. <P>SOLUTION: The grease composition contains a poly-&alpha;-olefin and/or ester oil as the base oil and a compound represented by general formula (1) (wherein, R<SP>1</SP>denotes a hydrogen atom or a methyl group, R<SP>2</SP>denotes a 6-20C aliphatic hydrocarbon group, A denotes a hydrocarbon group which may include one or more atoms selected from an oxygen atom, a nitrogen atom and a sulfur atom and m and n each denotes a number of 1 to 5) as an antioxidant. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a grease composition that is less deteriorated even at high temperatures and excellent in sustainability.

  In recent years, along with demands for miniaturization, weight reduction, and quietness improvement of automobiles, downsizing and weight reduction of mechanical devices have been attempted. On the other hand, high output and high efficiency of the apparatus are required, and a method of compensating for the decrease in output caused by the miniaturization by rotating at high speed is adopted. Therefore, mechanical parts such as bearings and gears tend to be hotter than ever. Further, unlike liquid lubricating oil, grease is poor in fluidity, and a part in contact with a high temperature part of a machine part is partially heated, so that higher heat resistance is required than liquid lubricating oil. For this reason, the demand for grease having high heat resistance is increasing.

  Here, it is known that the heat resistance and sustainability of the grease can be improved by selecting the base oil used for the grease. As such greases, silicone grease, fluorine grease, and grease using polyphenyl ether as a base oil are known (for example, see Patent Documents 1 to 3). These greases are silicone oil and fluorine oil, respectively. Polyphenyl ether oil is used as the base oil. However, these base oils are all very expensive, and it has been impossible to economically use greases using these base oils for general purposes.

  In addition, an antioxidant may be added to a relatively inexpensive base oil to improve the heat resistance of the grease. This method is generally used in general-purpose applications, and amine antioxidants and phenolic antioxidants are generally known as antioxidants used (for example, Patent Documents 4 and 5). See). However, if these antioxidants continue to be hot, problems such as decomposition and sublimation will occur, so that they will not be able to exert sufficient antioxidant effects, and grease with good heat resistance in situations where high temperatures continue. Could not get.

  On the other hand, it is known that hindered amine compounds can also be used as antioxidants for lubricating oils (see, for example, Patent Document 6). However, it was considered that the hindered amine compounds had almost no difference in antioxidant performance compared to the amine compounds and phenol compounds described above.

JP 2002-021859 A JP 2005-098505 A JP 2003-27079 A JP-A-11-241087 JP 2001-026794 A JP 60-28496 A

  Therefore, the problem to be solved by the present invention is to provide a grease composition having heat resistance equivalent to that of a grease using silicone grease, fluorine grease and polyphenyl ether as a base oil while being an inexpensive base oil. It is in.

（式中、Ｒ^１は水素原子又はメチル基を表わし、Ｒ^２は炭素数６〜２０の脂肪族炭化水素基を表わし、Ａは酸素原子を含んでもよい炭化水素基を表わし、ｍ及びｎはそれぞれ１〜５の数を表わす。）
で表わされる化合物を含有することを特徴とするグリース組成物である。 Therefore, the present inventors diligently studied to arrive at the present invention. That is, the present invention provides a poly-α-olefin and / or ester oil as a base oil, and the following general formula (1) as an antioxidant.

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an aliphatic hydrocarbon group having 6 to 20 carbon atoms, A represents also be a hydrocarbon group in free I oxygen atom, m and n represents a number of 1 to 5)
The grease composition characterized by containing the compound represented by these.

  The effect of the present invention is to provide a grease composition excellent in heat resistance using an inexpensive base oil.

  The antioxidant that can be used in the present invention is represented by the following general formula (1).

（式中、Ｒ^１は水素原子又はメチル基を表わし、Ｒ^２は炭素数６〜２０の脂肪族炭化水素基を表わし、Ａは酸素原子、窒素原子及び硫黄原子から選ばれる１つ以上の原子を含んでもよい炭化水素基を表わし、ｍ及びｎはそれぞれ１〜５の数を表わす。）

(Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents an aliphatic hydrocarbon group having 6 to 20 carbon atoms, and A represents one or more atoms selected from an oxygen atom, a nitrogen atom and a sulfur atom) And m and n each represent a number of 1 to 5.)

R ^{1 in the} general formula (1) represents a hydrogen atom or a methyl group, and is preferably a hydrogen atom because of its high antioxidant performance.

R ² in the general formula (1) represents an aliphatic hydrocarbon group having 6 to 20 carbon atoms. Examples of such aliphatic hydrocarbon groups include linear and branched octyl groups, 2-ethylhexyl groups, secondary octyl groups, linear and branched nonyl groups, secondary nonyl groups, linear and branched decyl groups, Secondary decyl group, linear and branched undecyl group, secondary undecyl group, linear and branched dodecyl group, secondary dodecyl group, linear and branched tridecyl group, secondary tridecyl group, linear and branched tetradecyl Group, secondary tetradecyl group, linear and branched hexadecyl group, secondary hexadecyl group, linear and branched stearyl group, linear and branched eicosyl group, 2-butyloctyl group, 2-butyldecyl group, 2-hexyl Octyl group, 2-hexyldecyl group, 2-octyldecyl group, 2-hexyldecyl group, 2-octyldodecyl group, monomethyl-branched isosteric group, etc. Alkenyl group; hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group, eicosenyl group, etc. An alkenyl group is mentioned. These aliphatic hydrocarbon groups may be one kind or a mixture of two or more kinds, and are preferably an alkyl group having 6 to 20 carbon atoms, and more preferably an alkyl group having 7 to 18 carbon atoms because of good antioxidant performance. A 7-18 branched alkyl group is more preferred. When the carbon number is less than 6 or exceeds 20, good antioxidant performance cannot be obtained.

  M and n of General formula (1) are numbers of 1-5, respectively. The sum of m and n is 2 to 10. However, since the dispersibility in grease is good and the antioxidant performance is also good, the sum of m and n is preferably 3 to 6, and the sum of m and n is 3 More preferably, it is -6 and the value of m is 2-5. When the sum of m and n is greater than 10, the dispersibility in grease decreases, and as a result, the performance as an antioxidant may not be exhibited, or the molecular weight may be too large to disperse in the grease. Further, when m is 0, it does not function as an antioxidant, and when n is 0, the antioxidant performance at high temperature is inferior compared with the case where n is 1 or more.

  Next, A in the general formula (1) will be described. A may be a group derived from any compound as long as it is a hydrocarbon group that may contain one or more atoms selected from an oxygen atom, a nitrogen atom and a sulfur atom, but the compound of the general formula (1) can be easily synthesized. Therefore, A is preferably a group derived from an organic polyvalent carboxylic acid represented by the following general formula (2).

（Ａは酸素原子、窒素原子及び硫黄原子から選ばれる１つ以上の原子を含んでもよい炭化水素基を表わし、ｑは２〜１０の数を表わす。）

(A represents a hydrocarbon group which may contain one or more atoms selected from an oxygen atom, a nitrogen atom and a sulfur atom, and q represents a number of 2 to 10.)

  The polyvalent carboxylic acid represented by the general formula (2) is a polyvalent carboxylic acid containing 2 to 10 carboxyl groups. Examples of the polyvalent carboxylic acid include oxalic acid, malonic acid, and succinic acid. Acid, glutaric acid, adipic acid, suberic acid, sebacic acid, decamethylene dicarboxylic acid, maleic acid, itaconic acid, acetylenedicarboxylic acid, bis (3,5-di-tert-butyl-4-hydroxybenzyl) malonic acid, thio Dipropionic acid, thioglycolic acid, methylenebisthioglycolic acid, iminodiacetic acid, tartaric acid, malic acid, thiomalic acid, dihydrotartaric acid, epoxysuccinic acid, 3,4-dioxythiophenedicarboxylic acid, 1,4-biscarboxyethylpiperazine , Phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalate Divalent carboxylic acids such as acid, 5-bicyclo (2,2,1) heptene-2,3-dicarboxylic acid, 5-bicyclo (2,2,2) heptene-2,3-dicarboxylic acid; propanetricarboxylic acid, Trivalent carboxylic acids such as butanetricarboxylic acid, butenetricarboxylic acid, nitrotriacetic acid, citric acid, triscarboxyethyl isocyanurate, trimellitic acid; butanetetracarboxylic acid, ethylenetetracarboxylic acid, ethylenediaminetetraacetic acid, pyromellitic acid, 1, Tetravalent carboxylic acids such as 3-bis (aminomethyl) cyclohexane-N, N, N ′, N′-tetraacetic acid; hexavalent carboxylic acids such as 1,6,7,8,9,14-tetradecanehexacarboxylic acid Polymer of carboxylic acid-containing monomers such as acrylic acid and methacrylic acid (oligomer having 2 to 10 carboxyl groups) Etc. Among these polyvalent carboxylic acids, those that do not contain an oxygen atom, a nitrogen atom, and a sulfur atom are preferable because they have excellent antioxidant properties, do not contain an oxygen atom, a nitrogen atom, and a sulfur atom, and do not contain a carboxyl group. What contains 3-6 pieces is more preferable. Moreover, as carbon number of A of General formula (2), 2-20 are preferable and 3-10 are more preferable. Examples of such preferable polyvalent carboxylic acid include propanetricarboxylic acid, butanetricarboxylic acid, trimellitic acid, butanetetracarboxylic acid, and ethylenetetracarboxylic acid.

The production method of the antioxidant for grease of the present invention is not particularly specified, and any method may be used as long as it is a known method. As a preferred synthesis method, for example, the general formula (2) An esterification reaction of an organic polyvalent carboxylic acid represented with 2,2,6,6-tetramethyl-4-hydroxypiperidine and an alcohol represented by R ² OH, or an organic polyvalent polyvalent represented by general formula (2) Examples include transesterification of a carboxylic acid methyl ester with an alcohol represented by 2,2,6,6-tetramethyl-4-hydroxypiperidine and R ² OH. Any method can be used for these reactions as long as it is a known method, and the ratio of m and n can be adjusted by the mixing ratio of alcohol.

  Base oils that can be used in the present invention are poly-α-olefins and / or ester oils. In use, one or a mixture of these may be used.

The specific structure of the poly-α-olefin may be one obtained by homopolymerizing or copolymerizing one or more monomers selected from α-olefins having 2 to 18 carbon atoms. Among these, those using a monomer having 4 to 14 carbon atoms are preferable, and a polymer having a number average molecular weight of 500 to 20000 and a kinematic viscosity at 100 ° C. of 1 to 20 mm ² / s is more preferable.

  As ester oil, diester oil, triester oil, tetraester oil, or a mixture thereof can be used. The diester oil is a reaction product of a dibasic acid and a monoalcohol or a reaction product of a divalent alcohol and a monofatty acid. Examples of the dibasic acid include 2 exemplified in the above polyvalent carboxylic acid. Can be mentioned monovalent carboxylic acids.

  The monoalcohol is preferably a monohydric alcohol having 6 to 18 carbon atoms, such as hexanol, isohexanol, secondary hexanol, heptanol, isoheptanol, secondary heptanol, octanol, 2-ethylhexanol, secondary octanol, Nonanol, isononanol, secondary nonanol, decanol, isodecanol, secondary decanol, undecanol, isoundecanol, secondary undecanol, dodecanol, isododecanol, secondary dodecanol, tridecanol, isotridecanol, secondary tridecanol, tetradecane Nord, isotetradecanol, secondary tetradecanol, hexadecanol, isohexadecanol, secondary hexadecanol, stearyl alcohol, isostearyl alcohol, oleyl alcohol Lumpur, and the like.

  The divalent alcohol is preferably a divalent alcohol having 2 to 8 carbon atoms, such as ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, , 5-pentanediol, neopentyl glycol, isoprene glycol (3-methyl-1,3-butanediol), 1,2-hexanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol and the like can be mentioned.

  The mono fatty acid is preferably a monovalent fatty acid having 6 to 18 carbon atoms, such as hexanoic acid (caproic acid), heptanoic acid, isoheptanoic acid, octanoic acid (caprylic acid), 2-ethylhexanoic acid (octylic acid), Isooctanoic acid, nonanoic acid (pelargonic acid), isononanoic acid, decanoic acid (capric acid), isodecanoic acid, undecanoic acid, isoundecanoic acid, dodecanoic acid (lauric acid), isododecanoic acid, tridecanoic acid, isotridecanoic acid, tetradecanoic acid (myristic acid) Acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), isostearic acid and the like.

  The triester oil is a reaction product of a tribasic acid and a monoalcohol or a reaction product of a trivalent alcohol and a monofatty acid. Examples of the tribasic acid include those exemplified in the above polyvalent carboxylic acids. Mention may be made of trivalent carboxylic acids. Moreover, as monoalcohol and monofatty acid, the monoalcohol and monofatty acid illustrated in said diester oil can be mentioned, for example.

  Examples of the trivalent alcohol include glycerin, 1,2,3-butanetriol, 1,2,4-butanetriol, 2-methyl-1,2,3-propanetriol, 1,2,3-pentanetriol. 1,2,4-pentanetriol, 1,3,5-pentanetriol, 2,3,4-pentanetriol, 2-methyl-2,3,4-butanetriol, trimethylolethane, 2,3,4 -Hexanetriol, 2-ethyl-1,2,3-butanetriol, trimethylolpropane, 4-propyl-3,4,5-heptanetriol, pentamethylglycerin (2,4-dimethyl-2,3,4- Pentanetriol) and the like.

  The tetraester oil is a reaction product of a tetrabasic acid and a monoalcohol or a reaction product of a tetravalent alcohol and a monofatty acid. Examples of the tetrabasic acid include those exemplified in the above polyvalent carboxylic acids. Mention may be made of tetravalent carboxylic acids. Moreover, as monoalcohol and monofatty acid, the monoalcohol and monofatty acid illustrated in said diester oil can be mentioned, for example.

  Examples of the tetravalent alcohol include pentaerythritol, 1,2,3,4-pentanetetrol, 2,3,4,5-hexanetetrol, 1,2,4,5-pentanetetrol, 1, Examples include 3,4,5-hexanetetrol, diglycerin, ditrimethylolpropane, sorbitan and the like.

  Among these ester oils, triester oils and tetraester oils are preferable because of good heat resistance, and tetraester oils are more preferable.

  Furthermore, a thickener is mentioned as an essential component of grease. A base grease with a thickener added is called a base grease, but any thickener may be used as long as it is known, such as aluminum, barium, calcium, lithium, sodium, etc. Complex soap thickeners such as soap thickeners, complex lithium, complex calcium, complex aluminum, organic non-soap thickeners such as urea, diurea, triurea, tetraurea, arylurea, terephthalate, bentonite, silica airgel, etc. An inorganic non-soap thickener can be used. These thickeners may be used alone or in combination of two or more. The amount of the thickener is not particularly limited, but the amount of the thickener relative to the base grease is usually 3 to 40% by mass, preferably 5 to 20% by mass.

  The amount of the antioxidant blended in the grease composition of the present invention is not particularly limited, but it is preferably 0.1 to 5% by mass, and 0.5 to 3% by mass based on the total amount of the grease composition. Is more preferable. When the blending amount is less than 0.1% by mass, it may not function as an antioxidant, and when it exceeds 5% by mass, an effect corresponding to the addition amount may not be obtained or sludge may be generated.

  Here, the base oil and the antioxidant will be described in more detail. In general, mineral oils, animal and vegetable oils, and synthetic oils that can be used as base oils include poly-α-olefins, alkylbenzenes, alkylnaphthalenes, polyalkylene glycols, polyphenyl ethers, alkyls. There are various types such as substituted diphenyl ether, polyether, polyol ester, dibasic acid ester, polyester, carbonate ester, silicone oil, fluorine-based oil, GTL and the like. Among these oils, those having particularly excellent heat resistance are polyphenyl ether, silicone oil, and fluorine oil. However, these three types of oils excellent in heat resistance cannot be said to be economically superior, and are currently being traded at prices several times to ten times higher than other oils. Therefore, greases using these three types of oils with excellent heat resistance can be used only for limited applications such as precision equipment and electronic equipment, which are used in small quantities. Grease for machine tools, automobiles, etc. Can not be used practically for applications that use a large amount of or for applications that require low cost.

  On the other hand, as a method for improving heat resistance using other base oils, various antioxidants such as amine-based antioxidants, phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants are used. A method of adding hindered amine, dithiocarbamate, dithiophosphate and the like is known. Various studies have been made by adding these antioxidants singly or in combination of two or more. However, in a situation where a high temperature state continues for a long time, satisfactory heat resistance can be obtained with any antioxidant added system. It ’s difficult. Further, in the present invention, a specific hindered amine is used, but even when added to a base oil other than the base oil that can be used in the present invention, the grease does not have excellent heat resistance, and a specific base oil is used. Heat resistance improves only when added to grease.

  In order to improve the performance of the grease composition of the present invention, an oil agent, a solid lubricant, an antiwear agent, an extreme pressure agent, a metal deactivator, a rust inhibitor, a detergent, a dispersant, an antifoaming agent, etc. One or two or more of these additives may be appropriately blended.

  Examples of oily agents include aliphatic saturated and unsaturated monocarboxylic acids such as stearic acid and oleic acid, polymerized fatty acids such as dimer acid and hydrogenated dimer acid, hydroxy fatty acids such as ricinoleic acid and 12-hydroxystearic acid, lauryl alcohol, Examples include aliphatic saturated and unsaturated monoalcohols such as oleyl alcohol, aliphatic saturated and unsaturated monoamines such as stearylamine and oleylamine, and aliphatic saturated and unsaturated monocarboxylic amides such as lauric acid amide and oleic acid amide. . These oil-based agents are usually added in an amount of 0.01 to 5% by weight, preferably 0.1 to 3% by weight, based on the grease composition.

  Examples of the solid lubricant include molybdenum disulfide, polytetrafluoroethylene, graphite, melamine cyanurate, and boron nitride. These solid lubricants are usually added in an amount of 0.1 to 30% by mass, preferably 1 to 20% by mass, based on the grease composition.

  Antiwear or extreme pressure agents include tricresyl phosphate, cresyl diphenyl phosphate, alkylphenyl phosphates, phosphate esters such as tributyl phosphate, dibutyl phosphate, tributyl phosphate, dibutyl phosphate, triisopropyl phosphate, etc. Phosphorous esters of these and their amine salts such as phosphorus, sulfurized fats and oils, sulfurized fatty acids such as sulfurized oleic acid, sulfur such as dibenzyl disulfide, sulfurized olefin, dialkyl disulfide, Zn-dialkyldithiophosphate, Zn- And organometallic compounds such as dialkyldithiocarbamate, Mo-dialkyldithiophosphate, and Mo-dialkyldithiocarbamate. These antiwear or extreme pressure agents are usually added in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the grease composition.

  Examples of the metal deactivator include benzotriazole-based, thiadiazole-based, and gallic acid ester-based compounds. These metal deactivators are usually added in an amount of 0.005 to 0.4% by weight, preferably 0.01 to 0.2% by weight, based on the grease composition.

  Antirust agents include alkyl or alkenyl succinic acid derivatives such as dodecenyl succinic acid half ester, octadecenyl succinic anhydride, dodecenyl succinic acid amide, sorbitan monooleate, glycerin monooleate, pentaerythritol monooleate Partial alcohol ester, Ca-petroleum sulfonate, Ca-alkyl benzene sulfonate, Ba-alkyl benzene sulfonate, Mg-alkyl benzene sulfonate, Na-alkyl benzene sulfonate, Zn-alkyl benzene sulfonate, Ca-alkyl naphthalene sulphate Examples thereof include metal sulfonates such as phonates, amines such as rosin amine and N-oleyl sarcosine, and dialkyl phosphite amine salts. These rust inhibitors are usually added in an amount of 0.01 to 5% by weight, preferably 0.05 to 2% by weight, based on the grease composition.

  Examples of the detergent include sulfonates such as calcium, magnesium, and barium, phenates, salicylates, phosphates, and overbased salts thereof. Among these, overbased salts are preferable, and among the overbased salts, those having a TBN (total basic number) of 30 to 500 mgKOH / g are more preferable. Furthermore, salicylate-based detergents having no phosphorus and sulfur atoms are preferred. These detergents are usually added in an amount of 0.5 to 10% by mass, preferably 1 to 8% by mass, based on the grease composition.

  Examples of the dispersant include succinimide, succinate ester, benzylamine, and boron-modified products thereof to which an alkyl group or alkenyl group having a weight average molecular weight of about 500 to 3000 is added. These dispersants are added in an amount of 0.5 to 10% by mass, preferably 1 to 8% by mass, based on the grease composition.

  A liquid silicone is mentioned as an antifoamer, Usually, 0.0005 to 0.01 weight% is good to add with respect to a grease composition.

The grease composition of the present invention can be used in various lubrication locations where grease can be applied, including lubrication locations such as rolling bearings, sliding bearings, sliding surfaces, and gears. In particular, the grease composition of the present invention is effective for use in rolling bearings, sliding bearings, gears and the like of automobiles that require heat resistance.

  Hereinafter, the present invention will be specifically described by way of examples. In the following examples and the like,% is based on mass unless otherwise specified. The compounds used in the test and the test grease are listed below.

(A-1)
In a 4-liter flask having a capacity of 1 liter equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, 34.2 g (0.2 mol) of 2,2,6,6-tetramethyl-4-hydroxypiperidine, 31.6 g (0.2 mol) of tridecanol and 3.35 g (0.0118 mol) of tetraisopropoxytitanium are dissolved in 125 g of an aromatic solvent (Idemitsu Petrochemical Co., Ltd .: Ipsol). , 3,4-Butanetetracarboxylic acid in methanol (23.4 g, 0.1 mol) was added dropwise at 175 ° C. over 3 hours, followed by further reaction for 1 hour, followed by dehydration under reduced pressure for 4 hours. After completion of the reaction, the reaction mixture was cooled to 130 ° C., 1.27 g of water was added to deactivate the catalyst, further cooled to 80 ° C., and washed with 20 g of water three times. After separating the oil and water, the organic layer was heated to 175 ° C. under reduced pressure to dehydrate and remove the solvent, and bis (2,2,6,6-tetramethyl-4-piperidyl) di (isotridecyl) -1,2,3,4 -Butanetetracarboxylate (a-1) was obtained. The following compounds (a-2) to (b-3) were also synthesized by carrying out an esterification reaction in the same manner as (a-1), and (b-4) and (b-5) were commercially available. The product is used.

(A-2): Bis (1,2,2,6,6-pentamethyl-4-piperidyl) · di (isotridecyl) -1,2,3,4-butanetetracarboxylate (a-3): Bis ( 2,2,6,6-tetramethyl-4-piperidyl) mono (isotridecyl) trimellitate (a-4): mono (2,2,6,6-tetramethyl-4-piperidyl) monoisotridecyl- Sebacate (a-5): bis (2,2,6,6-tetramethyl-4-piperidyl) di (linear tridecyl) -1,2,3,4-butanetetracarboxylate

(B-1): Tris (2,2,6,6-tetramethyl-4-piperidyl) -trimellitate (b-2): Tetra (2,2,6,6-tetramethyl-4-piperidyl) -1 , 2,3,4-Butanetetracarboxylate (b-3): mono (2,2,6,6-tetramethyl-4-piperidyl) monoisotridecylate (b-4): p, p ′ -Dioctyldiphenylamine (b-5): Octadecyl-3- (3,5-ditertiarybutyl-4-hydroxyphenol) propionate

<Grease 1>
Diphenylmethane-4,4′-diisocyanate (295.2 g) and octylamine (304.8 g) were reacted in a poly-α-olefin (5400 g) obtained by polymerizing an α-olefin having 6 carbon atoms to a number average molecular weight of 8000. The resulting diurea compound was uniformly dispersed to obtain grease 1. The urea compound content is 10% by weight.
<Grease 2>
Lithium-12-hydroxystearate (6370 g) in an ester oil (6370 g) obtained by esterifying 2-ethylhexanoic acid (octyl acid) (a linear fatty acid having 8 carbon atoms) with respect to 1 mol of pentaerythritol 630 g) was dissolved and dispersed uniformly to obtain grease 2. The lithium soap content is 9% by weight.
<Grease 3>
Diurethane produced by reacting diphenylmethane-4,4′-diisocyanate (295.2 g) and octylamine (304.8 g) in refined paraffinic mineral oil (5400 g) having a kinematic viscosity at 100 ° C. of about 15 mm ² / s The compound was uniformly dispersed to obtain a grease. The urea compound content is 10% by weight.

<Test method>
To the above three types of grease, the compounds of (a-1) to (a-5) and (b-1) to (b-4) were respectively added to 1% by mass and mixed until uniform. . 50 g of this grease composition is thinly applied to an aluminum plate having a size of 30 cm × 30 cm so as to be uniform, and this is left in a thermostatic bath and heated to 180 ° C. After 500 hours, the oil is evaporated. The reduced weight was measured. It can be said that grease with good heat resistance can suppress oil deterioration and reduce evaporation. Note that the blank is the result of only the grease with no additive added. The results are shown in the table below.

  When Table 1 and Table 2 are compared, the compound similar to the structure of the general formula (1) and the existing antioxidants may not have much improved heat resistance even when added to the base oil that can be used in the present invention. Recognize. In addition, as shown in Table 3, in the case of a base oil that cannot be used in the present invention, no improvement in heat resistance was observed with any additive.

Claims (4)

Poly-α-olefin and / or ester oil as the base oil, and the following general formula (1) as the antioxidant

(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an aliphatic hydrocarbon group having 6 to 20 carbon atoms, A represents a hydrocarbon group which may contain an oxygen atom, m and n Each represents a number from 1 to 5.)
A grease composition comprising a compound represented by the formula: The grease composition according to claim 1, wherein R ^{1 in the} general formula (1) is a hydrogen atom.   The grease composition according to claim 1 or 2, wherein the total number of m and n in the general formula (1) is 3 to 6.   The grease composition according to any one of claims 1 to 3, wherein the antioxidant is contained in an amount of 0.1 to 5% by mass based on the total amount of the grease composition.