JP2019038982A - Grease - Google Patents

Abstract

To provide a biodegradable grease having elevated viscosity of a base oil, improved tackiness (torque restraining force), and excellent heat resistance.SOLUTION: The invention relates to [1] a grease containing a base oil (A) 40 mass% or over and 90 mass% or under, a copolymer (B) satisfying the following requirements (B1)-(B3) 1 mass% or over and 50 mass% or under, and a thickener (C) 5 mass% or over and 20 mass% or under [(A)+(B)+(C)=100 mass%, the mass ratio of the copolymer (B) and the thickener (C) (mass of (B)/mass of (C)) is 1/20-50/5], wherein (B1) the copolymer (B) contains a constitutional unit (a) derived from ricinoleic acid, a constitutional unit (b) derived from an aliphatic dicarboxylic acid, and a constitutional unit (c) derived from a diol having a number of carbon atoms of 2-10; (B2) when the sum total of the constitutional units (a), (b) and (c) is 100 mol%, the content of the constitutional unit (a) is 20-90 mol%, the content of the constitutional unit (b) is 5-40 mol%, and the content of the constitutional unit (c) is 5-40 mol%; and (B3) its intrinsic viscosity [IV] is 0.2-1.0 dl/g.SELECTED DRAWING: None

Description

  The present invention relates to a grease having heat resistance and usable in a wide temperature range.

  Petroleum products generally have a so-called viscosity temperature dependency in which the viscosity changes greatly when the temperature changes. The lubricating oil also has a temperature dependency of the viscosity, and it is preferable that the temperature dependency of the viscosity is small. For the purpose of reducing the temperature dependence of the viscosity, a polymer soluble in a lubricating base oil is used as a viscosity index improver. As a typical viscosity modifier, a mineral oil solution of an olefin copolymer or a methacrylic acid ester polymer (hereinafter referred to as PMA) is known.

  On the other hand, in recent years, with the growing awareness of global environmental problems, development of products that reduce the environmental load is desired in each industry. Such a demand is not an exception for lubricating oil compositions, and lubricating oil compositions having various biodegradability have been proposed.

For example, lubricating oil compositions for grease and hydraulic oil containing vegetable oils such as soybean oil and rapeseed oil as synthetic base oils and synthetic esters such as polyol esters have been proposed (for example, see Non-Patent Document 1).
However, such a lubricating oil composition has a limited range of use because of its lower viscosity than conventional lubricating oil compositions.

  Moreover, the lubricating oil composition containing vegetable oil as the base oil has a problem in storage characteristics and stability at low temperatures. When such a lubricating oil composition contains a viscosity modifier such as an OCP (olefin copolymer) viscosity modifier, the viscosity modifier is poorly soluble in vegetable oil and difficult to apply.

  Furthermore, the solubility of the viscosity modifier in the base oil is improved by selecting a PMA (polymethacrylate) viscosity modifier as the viscosity modifier of the lubricating oil composition based on vegetable oil or synthetic ester. However, since the PMA-based viscosity modifier contains 50% by mass or more of mineral oil having a low biodegradation rate as a diluent oil, the biodegradation rate of the lubricating oil composition was significantly reduced.

  On the other hand, Patent Document 1 discloses an attempt to use a ricinoleic acid polymer as a viscosity modifier to be blended in a lubricating oil composition. The ricinoleic acid polymer used in Patent Document 1 is a polymer obtained by homopolymerizing only a ricinoleic acid ester derivative or copolymerizing a ricinoleic acid ester derivative and a hydroxycarboxylic acid ester derivative. And in patent document 1, by employ | adopting such a ricinoleic acid polymer as a viscosity modifier, compared with the case where a PMA type viscosity modifier is used, the obtained lubricating oil composition is equivalent or more. In addition to exhibiting the above-mentioned viscosity characteristics (viscosity index improving effect) and friction characteristics, the biodegradability is remarkably excellent.

International Publication No. 2009/148110

Lubrication Economy December 22nd (2007)

  The basic composition of a biodegradable grease is that a thickener mainly composed of metal soap is usually blended with a vegetable oil or a synthetic fatty acid ester base oil. Since the thickener mainly composed of metal soap is inferior in heat resistance, the heat resistance of the resulting grease may be lowered when the blending amount of the thickener is increased.

Therefore, in order to improve the heat resistance of biodegradable grease and make it usable in a wide temperature range, it has been desired to introduce a viscosity modifier having physical properties that increase the viscosity of the base oil and at the same time have excellent heat resistance. .
An object of the present invention is to obtain a biodegradable grease that improves the adhesiveness (torque stopping power) and is excellent in heat resistance while increasing the viscosity of the base oil.

That is, the present invention relates to the following [1] to [13].
[1] 40% by mass or more and 90% by mass or less of base oil (A), and 1% by mass or more and 50% by mass or less of copolymer (B) satisfying the following requirements (B1) to (B3) The agent (C) is contained in an amount of 5% by mass to 20% by mass [provided that (A) + (B) + (C) = 100% by mass. 〕,And,
Grease having a mass ratio [the mass of (B) / the mass of (C)] of 1/20 to 50/5 of the copolymer (B) and the thickener (C):
(B1) includes a structural unit (a) derived from ricinoleic acid, a structural unit (b) derived from an aliphatic dicarboxylic acid, and a structural unit (c) derived from a diol having 2 to 10 carbon atoms;
(B2) When the total of the structural units (a), (b) and (c) is 100 mol%, the content of the structural unit (a) is 20 to 90 mol%, and the content of the structural unit (b) Is 5 to 40 mol%, and the content of the structural unit (c) is 5 to 40 mol%;
(B3) Intrinsic viscosity [IV] is in the range of 0.2 to 1.0 dl / g.

[2] The grease according to [1], wherein the base oil (A) is a vegetable oil and / or a synthetic ester.
[3] The grease according to [2], wherein the synthetic ester is a diester or a polyol ester.
[4] The grease according to [2] or [3], wherein the synthetic ester is an aliphatic diester or an aliphatic polyol ester.
[5] In the copolymer (B), the molar ratio [(b) / (c)] of the structural unit (b) to the structural unit (c) is 0.9 to 1 in the requirement (B2). The grease according to any one of [1] to [4], which is .1.
[6] The grease according to any one of [1] to [5], wherein the copolymer (B) is 40 to 90 mol% in the structural unit (a) in the requirement (B2).
[7] The copolymer (B) is any one of [1] to [6], wherein the intrinsic viscosity [IV] is in the range of 0.2 to 0.6 dl / g in the requirement (B3). The grease described.
[8] At least one grease selected from the group consisting of an antioxidant, an extreme pressure agent, a rust inhibitor, a metal deactivator, an antiwear additive, an antifoaming agent, a cleaning dispersant, and a pour point depressant. The grease according to any one of [1] to [7], which contains a seed additive (D).
[9] The grease according to any one of [1] to [8], wherein the structural unit (b) derived from the aliphatic dicarboxylic acid is a structural unit derived from sebacic acid.
[10] The grease according to any one of [1] to [9], wherein the structural unit (c) derived from a diol having 2 to 10 carbon atoms is a structural unit derived from 1,4-butanediol. .
[11] The grease according to any one of [1] to [10], wherein the thickener (C) is a soap-based thickener.
[12] The grease according to [11], wherein the soap-based thickener is at least one of lithium soap and calcium soap.
[13] The grease according to any one of [1] to [12], wherein the thickener (C) includes lithium soap and calcium soap in a mass ratio of 10/90 to 90/10.

  The grease of the present invention contains the base oil (A), the copolymer (B) and the thickener (C) in the above range, and the mass of the copolymer (A) and the thickener (C). Since the ratio satisfies the above range, the base oil has a high viscosity, can be used in a wide temperature range, and has excellent heat resistance.

FIG. 1 is a schematic view of a two-cylinder torque tester used for measuring the torque stopping force of grease according to the present invention.

Hereinafter, the grease according to the present invention will be described in detail for each component.
[Base oil (A)]
The base oil (A) contained in the grease of the present invention is a compound selected from vegetable oils, synthetic esters, low molecular weight poly α-olefins and the like. Of these compounds, vegetable oils and synthetic esters are preferred. In this case, the base oil (A) may be a vegetable oil, a synthetic ester, or a combination thereof.

  In addition, the synthetic ester used as the base oil (A) is different from the copolymer (B) according to the present invention. That is, in the present invention, an ester that can correspond to both the synthetic ester that can be used as the base oil (A) and the copolymer (B) described later is handled as a copolymer that corresponds to the copolymer (B) described later. .

  Here, preferred examples of the vegetable oil include rapeseed oil, soybean oil, castor oil, palm oil, sunflower oil, safflower oil, corn oil, meadow foam oil, rice bran oil, olive oil, jojoba oil, etc. Of these, rapeseed oil, soybean oil, castor oil, and palm oil are more preferable. Moreover, you may use these vegetable oils individually by 1 type or in combination of 2 or more types. These vegetable oils are excellent in biodegradability.

  On the other hand, preferred examples of the synthetic ester include diesters and polyol esters. Adopting these as the base oil (A) is preferable because the resulting lubricating oil composition can be used under a wide range of temperature conditions.

  Among diesters and polyol esters, preferred examples of diesters include aliphatic diesters such as di-2-ethylhexyl sebacate, dioctyl adipate, dioctyl decanedioate, diisodecyl adipate, dioctyl sebacate, and the like. Examples include aliphatic polyol esters such as pentaerythritol tetraoleate, trimethylolpropane tripelargonate, and neopentyl polyol fatty acid ester. When these aliphatic diesters and aliphatic diesters are employed as the base oil (A), the lubricating oil composition can be used under a wide range of temperature conditions from a low temperature range (below room temperature) to a high temperature range (50 ° C. to 100 ° C.). This is preferable because it can be used.

These synthetic esters may be used alone or in combination of two or more.
As the base oil (A), one or more kinds of vegetable oils and one or more kinds of synthetic esters may be mixed and used.

In order to obtain a lubricating oil composition having appropriate lubricity, the base oil (A) should have a kinematic viscosity at 40 ° C. (based on ASTM 445 kinematic viscosity test method) of 10 to 80 mm ² / s. Is preferable, and it is more preferable to set it as 14-60 mm < ² > / s.

  In addition, in order to obtain a lubricating oil composition having proper fluidity in a low temperature range (room temperature or lower), the pour point of the base oil (A) (according to the measurement method of JIS K2269) is set to 0 to −50 ° C. Is preferred.

[Copolymer (B)]
The copolymer (B) contained in the grease of the present invention satisfies the following requirements (B1) to (B3).
Requirement (B1): A structural unit (a) derived from ricinoleic acid, a structural unit (b) derived from an aliphatic dicarboxylic acid, and a structural unit (c) derived from a diol having 2 to 10 carbon atoms are included.

[Structural unit derived from ricinoleic acid (a)]
In the present invention, the structural unit (a) derived from ricinoleic acid (hereinafter sometimes simply referred to as “structural unit (a)”) is ricinoleic acid (12-hydroxy-cis-9-octadecenoic acid) or ricinol. It is a structural unit derived from an acid derivative. In the present invention, when the copolymer (B) contains such a structural unit (a), the obtained grease is excellent in viscosity characteristics and storage stability, and high biodegradability can be expected.

  Examples of derivatives of ricinoleic acid include condensates of ricinoleic acid, esterified products of ricinoleic acid and carboxylic acid, esterified products of ricinoleic acid and alcohols (for example, ricinoleic acid methyl ester), and reaction products of ricinoleic acid and an epoxy compound. 12-hydroxystearic acid hydrogenated from ricinoleic acid and its condensates, esterified products of 12-hydroxystearic acid and carboxylic acids or alcohols (for example, 12-hydroxystearic acid methyl ester), etc. Examples thereof include various compounds that give the derived structural unit (a).

In the present specification, the monomer component corresponding to the structural unit (a), that is, the ricinoleic acid and the derivative of ricinoleic acid may be referred to as “monomer component (a ′)”.
Thus, since the derivative of ricinoleic acid includes 12-hydroxystearic acid and its ester, the structural unit (a) in the present invention is specifically represented by the following formula (1) or It is a structural unit represented by Formula (2).

Here, the ratio of the total of the structural units derived from 12-hydroxystearic acid and its ester derivatives in all the structural units (a), that is, the structure represented by the above formula (2) in all the structural units (a). The proportion of the total of the units is not particularly limited, and the total of the structural units (a) derived from ricinoleic acid (that is, the structural unit represented by the above formula (1) and the structural unit represented by the above formula (2)) ) Is 100 mol%, it is optional in the range of 0 to 100 mol%.

  However, in the present invention, since the grease having high transparency and high low temperature fluidity tends to be obtained, the structural unit (a) derived from ricinoleic acid is a structural unit represented by the above formula (1). It is preferable to include. In that sense, the above ratio is preferably 0 to 80 mol%, and more preferably 0 to 60 mol%. By being in the preferable range, it is excellent in terms of fluidity at a low temperature and dispersibility in a base oil (particularly vegetable oil). However, when the grease of the present invention is used for an application that does not necessarily require high transparency, the ratio does not necessarily need to be in the preferred range. For example, the structural unit (a) derived from ricinoleic acid However, it does not exclude the fact that it consists only of the structural unit represented by the above formula (2).

[Structural unit derived from aliphatic dicarboxylic acid (b)]
The structural unit (b) derived from an aliphatic dicarboxylic acid (hereinafter sometimes simply referred to as “structural unit (b)”) is derived from an aliphatic dicarboxylic acid or an aliphatic dicarboxylic acid ester. Specifically, the structural unit (b) referred to in the present invention is a structural unit having a structure in which —OH is excluded from two carboxyl groups contained in the aliphatic dicarboxylic acid.

It is preferable that the aliphatic dicarboxylic acid leading to the structural unit (b) is aliphatic in order not to lower the biodegradability and solubility in the base oil of the obtained copolymer.
The aliphatic dicarboxylic acid is not particularly limited as long as it has no other functional group having reactivity in the system in which the ester polymerization reaction is performed, for example, a hydroxyl group, and may be used alone or in combination of two or more. Specifically, malonic acid (3 carbon atoms), dimethyl malonic acid (5 carbon atoms), succinic acid (4 carbon atoms), glutaric acid (5 carbon atoms), adipic acid (6 carbon atoms) 2-methyladipic acid (7 carbon atoms), trimethyladipic acid (9 carbon atoms), pimelic acid (7 carbon atoms), 2,2-dimethylglutaric acid (7 carbon atoms), 3,3- Examples include diethyl succinic acid (8 carbon atoms), suberic acid (8 carbon atoms), azelaic acid (9 carbon atoms), sebacic acid (10 carbon atoms), and the like. On the other hand, examples of the aliphatic dicarboxylic acid ester include various esters of the above aliphatic dicarboxylic acid.

Of these, aliphatic dicarboxylic acids having 6 to 12 carbon atoms are preferred, and sebacic acid is particularly preferred.
In the present specification, the monomer component corresponding to the structural unit (b), that is, the aliphatic dicarboxylic acid and the aliphatic dicarboxylic acid ester may be referred to as “aliphatic dicarboxylic acid component (b ′)”. .

[Structural unit derived from diol having 2 to 10 carbon atoms (c)]
Specifically, the structural unit (c) derived from the diol having 2 to 10 carbon atoms (hereinafter sometimes simply referred to as “structural unit (c)”) has 2 to 10 carbon atoms in terms of form. It is a structural unit having a structure obtained by removing -H from two hydroxyl groups contained in the diol. As the diol having 2 to 10 carbon atoms for leading the structural unit (c), one kind may be used alone, or two or more kinds may be used in combination. Specific examples include the following compounds.

  Examples of the diol having 2 to 10 carbon atoms include aliphatic diols having 2 to 10 carbon atoms. Examples of such aliphatic diols include 1,2-ethanediol (ethylene glycol: 2 carbon atoms), 1,3-propanediol (trimethylene glycol: 3 carbon atoms), 1,2-propanediol ( Propylene glycol: 3 carbon atoms, 1,4-butanediol (tetramethylene glycol: 4 carbon atoms), 2,2-dimethylpropane-1,3-diol (neopentyl glycol: 5 carbon atoms), 1 , 6-hexanediol (hexamethylene glycol: 6 carbon atoms), 1,8-octanediol (octamethylene glycol: 8 carbon atoms), 1,9-nonanediol (nonamethylene glycol: 9 carbon atoms), etc. Is mentioned.

  Among these aliphatic diols, side chain alkyl group-containing glycols include 2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol, 2-hexyl-1,3-propanediol, 2-hexyl-1,6-propanediol, neopentyl glycol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-n -Butyl-1,3-propanediol, 1,3-nonanediol, 2-methyl-1,8-octanediol, and the like.

Among the above diols, 1,4-butanediol is particularly preferable.
In the present specification, the monomer component corresponding to the structural unit (c), that is, the diol having 2 to 10 carbon atoms may be referred to as “diol component (c ′)”.

  As described above, the copolymer (B) used in the present invention includes the structural units (b) and (c) in addition to the structural unit (a). Thus, when copolymer (B) also contains said structural unit (b) and (c), it shows in the following Example mentioned later that the heat resistance and handling property in the grease which are obtained are more strictly mentioned. Thus, it is excellent in heat resistance and adhesiveness. The reason why such an effect is obtained will be described later in “Characteristics of Copolymer (B)”.

[Other structural units]
The copolymer (B) used in the present invention is preferably composed only of the structural units (a) to (c). However, as long as the effects of the present invention are not impaired, the structural unit (a) To (c) may further include a structural unit (hereinafter referred to as “other structural unit”). Other structural units include furandicarboxylic acid such as 2,5-furandicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, alicyclic dicarboxylic acid such as 1,3-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, 2 A structural unit derived from various dicarboxylic acids and carboxylic acid esters not corresponding to the aliphatic dicarboxylic acid component (b ′), such as aromatic dicarboxylic acids such as methyl terephthalic acid and naphthalenedicarboxylic acid, and having 11 or more carbon atoms A structural unit derived from an aliphatic diol, a structural unit derived from an aromatic diol, a trihydric or higher polyhydric alcohol such as trimethylolethane or glycerin, a trivalent or higher polyvalent carboxylic acid such as butanetricarboxylic acid or trimellitic acid Examples include acids and oxydicarboxylic acids such as 4-hydroxyphthalic acid.

  In the present specification, monomer components corresponding to “other structural units”, that is, various dicarboxylic acids and carboxylic acid esters that do not correspond to the above-mentioned aliphatic dicarboxylic acid component (b ′), and those having 11 carbon atoms. The above aliphatic diols, aromatic diols, trivalent or higher polyhydric alcohols, trivalent or higher polyvalent carboxylic acids and oxydicarboxylic acids may be referred to as “other monomer components”.

  Requirement (B2): When the total of the structural units (a), (b) and (c) is 100 mol%, the content of the structural unit (a) is 20 to 90 mol%, and the structural unit (b) Is 5 to 40 mol%, and the content of the structural unit (c) is 5 to 40 mol%.

  Thus, the lower limit of the content of the structural unit (a) is 20 mol%, more preferably 30 mol%, still more preferably 40 mol%, and particularly preferably 50 mol%. It is preferable that the content of the structural unit (a) is 20 mol% or more in terms of imparting appropriate stickiness. When it is 30 mol% or more, it is more preferable in terms of improving the viscosity characteristics of the resulting composition and the storage stability, that is, the turbidity (haze) of the base oil. Storage stability is particularly preferable when it is 40 mol% or more. Also, shear stability is preferred. On the other hand, the upper limit of the content of the structural unit (a) is 90 mol%, but 85 mol% is more preferable. It is preferable that the content of the structural unit (a) is 90 mol% or less from the viewpoint of heat resistance and tackiness of the resulting composition. Considering these, the content of the structural unit (a) is preferably 40 to 90 mol%, more preferably 45 to 85 mol%.

Moreover, it is preferable that molar ratio ((b) / (c)) of the said structural unit (b) and the said structural unit (c) is 0.9-1.1.
In the production method described later, it can be adjusted to the above range by changing the ratio of introducing ricinoleic acid or ricinoleic acid derivative, aliphatic dicarboxylic acid and diol having 2 to 10 carbon atoms into the polymerization system.

  The copolymer (B) according to the present invention is preferably composed of only the structural units (a) to (c) as described above, but includes other structural units as long as the effects of the invention are not impaired. You may go out. When the copolymer (B) contains other structural units, the content of the other structural units in the copolymer (B) is the sum of the above structural units (a) to (c) and the other structural units. The mol% is preferably 20 mol% or less, more preferably 10 mol% or less, and particularly preferably 5 mol% or less.

The contents of the structural units (a) to (c) and “other structural units” in the copolymer (B) can be determined by an appropriate technique such as NMR.
Requirement (B3): Intrinsic viscosity [IV] is in the range of 0.2 to 1.0 dl / g. Preferably it is 0.2-0.6 dl / g. By being in the above range, the workability of the copolymer is excellent, and the obtained grease is excellent in the shear stability and various physical properties.

  The measurement conditions for the intrinsic viscosity [IV] are as described in the Examples section. By using the copolymer (B) having an intrinsic viscosity [IV] in such a range, it is possible to impart excellent thickening and viscosity index improving effects to the obtained grease. Moreover, when the said base oil (A) is a vegetable oil, favorable low-temperature storage stability can be provided to the grease obtained. Intrinsic viscosity [IV] can be adjusted to the said range by adjusting the molecular weight of a copolymer (B).

  Moreover, the copolymer (B) used by this invention is a copolymer containing the structural unit represented by the said Formula (1) as said structural unit (a) among the copolymers (B) as needed. B0) may be subjected to a treatment such as hydrogenation.

[Features of copolymer (B)]
The copolymer (B) according to the present invention has less ester bonds derived from secondary hydroxyl groups (12-position hydroxyl groups) than the homopolymer of ricinoleic acid derivatives, and the length between adjacent ester groups (of the carbon chain). It is characterized in that it includes a structure having a relatively short length represented by the number of carbon atoms. This means that there are few thermally unstable bonds in the copolymer (B), which is considered to contribute to heat resistance stability. Further, the high ester group density is likely to have a compact structure due to intermolecular interaction, which is considered to contribute to workability (handling properties and solubility).

  Furthermore, the copolymer (B) according to the present invention can proceed the ester polymerization reaction more stably because the monomer component has more primary hydroxyl groups than the homopolymer of the ricinoleic acid derivative, It is thought that the effect which is excellent in heat-resistant stability is acquired by suppressing the spin-drying | dehydration in a polymer and suppressing the double bond amount of the copolymer obtained.

  Furthermore, the copolymer copolymer (B) according to the present invention has a relatively low ratio of a ricinoleic acid derivative having a long side chain, as compared with a homopolymer of a ricinoleic acid derivative. It is considered that excellent shear stability can be obtained.

[Production Method of Copolymer (B)]
The copolymer (B) is a compound that leads to the structural units (a), (b), and (c), that is, the monomer component (a ′) and the aliphatic dicarboxylic acid component (b ′). And obtained by performing an ester polymerization reaction on the diol component (c ′). That is, the ricinoleic acid or ricinoleic acid derivative described above in the section “Structural unit derived from ricinoleic acid (a)” and the aliphatic dicarboxylic acid described above in the “structural unit derived from aliphatic dicarboxylic acid (b)” It is obtained by subjecting the aliphatic dicarboxylic acid ester and the diol having 2 to 10 carbon atoms described above in the section “Structural unit (c) derived from diol having 2 to 10 carbon atoms” to ester polymerization reaction with each other. This ester polymerization reaction is carried out by using various dicarboxylic acids, carboxylic acid esters, aliphatic diols having 11 or more carbon atoms, aromatic diols, trihydric or higher polyhydric alcohols, trivalent or higher. When the reaction is carried out in the presence of a polyvalent carboxylic acid, oxydicarboxylic acid or the like, a copolymer (B) containing "other structural units" can be obtained.

As a production method, a conventionally known direct esterification method, transesterification method, or the like can be applied.
In the direct esterification method, the monomer component (a ′), the aliphatic dicarboxylic acid component (b ′), the diol component (c ′), and the optional “other monomer component” are mixed in a conventional manner. A copolymer can be obtained by direct condensation polymerization. For example,
The monomer component (a ′),
A dicarboxylic acid component (the aliphatic dicarboxylic acid component (b ′) and various dicarboxylic acids described above in the section “Other structural units”);
The diol (the diol component (c ′) and the various diols described in the section “Other structural units” above) is heated under pressure, and the condensed water produced is removed from the reaction system while removing the condensed water from the reaction system. Then, the reaction system is depressurized in the presence of a polycondensation catalyst such as a titanium compound, a germanium compound, or an antimony compound, and the diol is distilled out of the system. Thereby, a high molecular weight polyester resin can be manufactured. In this example, the case where the monomer component (a ′), the dicarboxylic acid component and the diol are reacted is mentioned. However, as the “other monomer component”, a trihydric or higher polyhydric alcohol and / or Or when trivalent or more polyvalent carboxylic acid coexists, it can carry out similarly.

In the transesterification method, a corresponding dialkyl ester of dicarboxylic acid may be used as a starting material. In this case, a corresponding dialkyl ester is employed as the aliphatic dicarboxylic acid component (b ′), the monomer component (a ′), the diol component (c ′), and the optional “other unit”. A copolymer can be obtained by carrying out direct polycondensation with a monomer component "by a conventional method. At this time, various dicarboxylic acids described in the above-mentioned monomer component (a ′) and / or the above-mentioned “other structural unit” may also be used in the form of the corresponding alkyl ester. For example,
The monomer component (a ′),
A dialkyl ester of a dicarboxylic acid (the aliphatic dicarboxylic acid component (b ′) and various dicarboxylic acids described above in the section “Other structural units”);
The diol (the diol component (c ′) and the various diols described above in the section “Other structural units”) is heated at normal pressure, and the low molecular weight condensation is performed while removing the generated alkyl alcohol from the reaction system. Then, the reaction system is depressurized in the presence of a polycondensation catalyst such as a titanium compound, a germanium compound, or an antimony compound, and the diol is distilled out of the system. Thereby, a high molecular weight polyester resin can be manufactured. In this example, the case where the monomer component (a ′) is reacted with a dialkyl ester of a dicarboxylic acid and a diol is described. However, as the “other monomer component”, a trihydric or higher polyhydric alcohol is used. It can also be carried out in the same manner when a trivalent or higher polyvalent carboxylic acid coexists.

The esterification reaction in the direct esterification method and transesterification method proceeds even without a catalyst, but it is preferable to use a polycondensation catalyst as exemplified above.
In both the direct esterification method and the transesterification production method, while maintaining the reaction system in a uniform liquid state, while raising the reaction system so that the reaction temperature does not fall below the melting point of the oligomer and polyester produced It is preferable to proceed the reaction. If it is necessary to further increase the molecular weight (weight average molecular weight), the copolymerized polyester resin obtained by melt polymerization can be subjected to solid phase polymerization to increase the molecular weight.

  The copolymer (B) according to the present invention can also be produced by an ester polymerization reaction with lipase. In this method, the monomer component (a ′), the aliphatic dicarboxylic acid component (b ′), the diol component (c ′) and the optional “other monomer component” are added in the presence of lipase. A copolymer can be obtained by condensation polymerization. As the lipase, an immobilized lipase derived from Burkholderia cepacia (for example, Lipase PS-C Amano II (trade name), PS-D Amano I (trade name), etc., manufactured by Wako Chemical Co., Ltd.)) is preferable. However, since the lipase is not easily deactivated, the reaction temperature can be increased to 90 ° C. The reaction conditions are preferably a batch method using a reactor equipped with a stirrer under bulk conditions. The reaction time is usually 4 to 7 days, although it varies depending on conditions such as catalyst concentration and polymerization temperature.

  Further, the ester polymerization reaction is a reversible reaction, and it is preferable to sequentially remove the generated alcohol and water in order to advance an efficient polymerization reaction. Specifically, maintaining the pressure state in the reaction system in a reduced pressure state, or performing a synthesis reaction after placing a hygroscopic agent such as synthetic zeolite (for example, molecular sieve 4A) in the reaction system in a non-contact manner. Is mentioned. By carrying out the polymerization reaction under such conditions, the polymerization reaction can be advanced simply and easily, and the copolymer (B) can be synthesized efficiently.

  In the present invention, the monomer component (a ′), the aliphatic dicarboxylic acid component (b ′), the diol component (c ′), and the optional “other monomer component” in each ester polymerization reaction. The ratio of the amount of "" can be adjusted as appropriate according to the contents of the structural units (a), (b), (c) and "other structural units" to be achieved in the copolymer (B). .

  The copolymer obtained by such ester polymerization reaction may be used as it is as the copolymer (B), but further, a hydrogenation reaction is carried out using a conventionally known appropriate method. Thus, hydrogenation may be carried out on some or all of the double bonds contained in the structural unit (a). For example, first, a copolymer (B0) containing the structural unit represented by the above formula (1) as the structural unit (a) in the copolymer (B) is prepared by an ester polymerization reaction. The copolymer (B0) may be partially or completely hydrogenated, and a product obtained by such hydrogenation may be employed as the copolymer (B).

[Thickener (C)]
As the thickener (C) contained in the grease composition of the present invention, various known thickeners can be used. Specifically, for example, a soap-based thickener represented by lithium soap and composite lithium soap, a urea-based thickener represented by diurea, an inorganic thickener represented by organic clay and silica, polytetra Examples thereof include organic thickeners such as fluoroethylene and melamine cyanurate.

  Examples of the soap-based thickener include sodium soap, lithium soap, calcium soap, aluminum soap, composite sodium soap, composite lithium soap, composite calcium soap, composite aluminum soap, composite barium soap and the like. Of these soaps, lithium soaps having high versatility and excellent balance in heat stability and water resistance are preferable, and lithium 12-hydroxystearate and / or calcium 12-hydroxystearate are particularly preferable.

  The urea-based thickener can be obtained, for example, by reacting a predetermined diisocyanate with a predetermined monoamine in a base oil. A preferred specific example of the diisocyanate is diphenylmethane-4,4′-diisocyanate. Monoamines include aliphatic amines, aromatic amines, alicyclic amines or mixtures thereof. Specific examples of the aliphatic amine include octylamine, dodecylamine, hexadecylamine, octadecylamine and oleylamine. Specific examples of the aromatic amine include aniline and p-toluidine. Specific examples of alicyclic amines include cyclohexylamine.

[Grease]
The grease of the present invention comprises the base oil (A) in an amount of 40% by mass to 90% by mass, the copolymer (B) in an amount of 1% by mass to 50% by mass, and the thickener (C). 5 mass% or more and 20 mass% or less [However, (A) + (B) + (C) = 100 mass%. And the mass ratio [the mass of (B) / the mass of (C)] of the copolymer (A) and the thickener (C) is in the range of 1/20 to 50/5. .

  The grease of the present invention contains the base oil (A), the copolymer (B), and the thickener (C) in the above range, and the copolymer (A) and the thickener (C). When the mass ratio of the base oil satisfies the above range, a grease having high base oil viscosity, usable in a wide temperature range, and excellent in heat resistance can be obtained.

  The grease of the present invention is preferably 50 to 85% by mass of the base oil (A), 3 to 40% by mass of the copolymer (B), and 5 to 20% by mass of the thickener (C). More preferably, the base oil (A) is contained in an amount of 55 to 85% by mass, the copolymer (B) is contained in an amount of 5 to 30% by mass, and the thickener (C) is contained in an amount of 5 to 15% by mass. .

The grease of the present invention preferably has a mass ratio of 3/20 to 40/5, more preferably 5/15 to 30/5, of the copolymer (A) and the thickener (C). Is in range.
In addition to the base oil (A), the copolymer (B), and the thickener (C), the grease of the present invention is usually an extreme pressure agent, an antiwear agent, and a friction modifier that are usually blended in the grease. In addition, at least one additive (D) selected from the group consisting of a detergent dispersant, a viscosity index improver, an antioxidant, a corrosion inhibitor, a solid lubricant, and a rust inhibitor may be blended.

[Additive (D)]
The following can be illustrated as an additive used for the grease of this invention, These can be used individually by 1 type or in combination of 2 or more types.

<Extreme pressure agent>
Extreme pressure agent is a generic term for those having the effect of preventing seizure under high loads, and is not particularly limited, but includes sulfides, sulfoxides, sulfones, thiophosphinates, thiocarbonates, sulfurized fats and oils, sulfurized olefins, etc. Examples thereof include sulfur extreme pressure agents; phosphoric acids such as phosphate esters, phosphites, phosphate ester amine salts, and phosphite amines; halogen compounds such as chlorinated hydrocarbons. Two or more of these compounds may be used in combination.

  In addition, by the time the extreme pressure lubrication conditions are reached, hydrocarbons or other organic components constituting the grease composition are carbonized before the extreme pressure lubrication conditions by heating and shearing to form a carbide film on the metal surface. there is a possibility. For this reason, when the extreme pressure agent is used alone, the carbide coating inhibits contact between the extreme pressure agent and the metal surface, and there is a possibility that a sufficient effect of the extreme pressure agent cannot be expected.

  Although the extreme pressure agent may be added alone, the grease composition according to the present invention is mainly composed of a saturated hydrocarbon such as a copolymer, and therefore, together with other additives used in advance, a mineral oil or a synthetic hydrocarbon oil. From the viewpoint of dispersibility, it is preferable to add it in a state dissolved in a lubricating base oil such as the above. Specifically, a grease composition is prepared by selecting a so-called extreme pressure agent package in which various components such as an extreme pressure agent component are blended in advance and further dissolved in a lubricating base oil such as mineral oil or synthetic hydrocarbon oil. The method of adding is more preferable.

Preferable extreme pressure agents (packages) include LUBRIZOL's Angolamol-98A, LUBRIZOL's Angolamol-6043, Angramol-6085U, AFTON CHEMICAL's HITEC1532, AFTON CHEMICAL's HITEC307, AFTON CHEMICAL's HITECCHE33 Additin RC 9410 and the like.
The extreme pressure agent is used in the range of 0 to 10% by mass with respect to 100% by mass of grease as necessary.

<Antiwear agent>
Examples of the antiwear agent include inorganic or organic molybdenum compounds such as molybdenum disulfide, graphite, antimony sulfide, polytetrafluoroethylene, and the like. The antiwear agent is used in the range of 0 to 3% by mass with respect to 100% by mass of grease as necessary.

<Friction modifier>
As the friction modifier, an amine compound, an imide compound or a fatty acid having at least one alkyl group or alkenyl group having 6 to 30 carbon atoms, particularly a linear alkyl group or linear alkenyl group having 6 to 30 carbon atoms in the molecule. Examples include esters, fatty acid amides, fatty acid metal salts, and the like.

Examples of the amine compound include linear or branched, preferably linear aliphatic monoamines having 6 to 30 carbon atoms, linear or branched, preferably linear aliphatic polyamines, or fatty acids thereof. An alkylene oxide adduct of a group amine can be exemplified. Examples of the imide compound include a succinimide having a linear or branched alkyl group or alkenyl group having 6 to 30 carbon atoms and / or a modified compound thereof using carboxylic acid, boric acid, phosphoric acid, sulfuric acid, or the like. . Examples of fatty acid esters include esters of linear or branched, preferably linear, fatty acids having 7 to 31 carbon atoms with aliphatic monohydric alcohols or aliphatic polyhydric alcohols. Examples of fatty acid amides include amides of linear or branched, preferably linear fatty acids having 7 to 31 carbon atoms, and aliphatic monoamines or aliphatic polyamines. Examples of the fatty acid metal salt include an alkaline earth metal salt (magnesium salt, calcium salt, etc.) or zinc salt of a linear or branched, preferably linear fatty acid having 7 to 31 carbon atoms.
A friction modifier is used in the range of 0 to 5.0 mass% with respect to 100 mass% of grease as needed.

<Cleaning dispersant>
Examples of the cleaning dispersant include metal sulfonates, metal phenates, metal phosphonates, and succinimides. The cleaning dispersant is used in the range of 0 to 15% by mass with respect to 100% by mass of grease as necessary.

<Viscosity index improver>
Viscosity index improvers include ethylene-α-olefin copolymers (excluding ethylene-α-olefin copolymers (B)), olefin copolymers and methacrylate copolymers having a molecular weight exceeding 50,000. Known viscosity index improvers such as polymers, polyalphaolefins such as decene oligomers, and liquid polybutene can be used in combination. The viscosity index improver is used in the range of 0 to 80% by mass with respect to 100% by mass of grease as necessary.

<Antioxidant>
As the antioxidant, known antioxidants can be used. Specifically, di (alkylphenyl) amine (alkyl group has 4 to 20 carbon atoms), phenyl-α-naphthylamine, alkyldiphenylamine (alkyl group is 4-20 carbon atoms), N-nitrosodiphenylamine, phenothiazine, N, N′-dinaphthyl-p-phenylenediamine, acridine, N-methylphenothiazine, N-ethylphenothiazine, dipyridylamine, diphenylamine, phenolamine, 2,6- Amine-based antioxidants such as di-t-butyl-α-dimethylaminoparacresol, 2,6-di-t-butylparacresol, 4,4′-methylenebis (2,6-di-t-butylphenol) ), 2,6-di-t-butyl-4-N, N-dimethylaminomethylphenol, 2, -Phenolic antioxidants such as di-t-butylphenol and dioctyldiphenylamine; organic iron salts such as iron octoate, ferrocene and iron naphthoate; organic cerium salts such as cerium naphthoate and cerium toluene; zirconium octoate And organic metal compound-based antioxidants such as organic zirconium salts such as ate. Moreover, although antioxidant may be used independently, it can also be used in combination of 2 or more types.
The antioxidant is used in the range of 0 to 3% by mass with respect to 100% by mass of grease as necessary.

<Corrosion inhibitor>
Examples of the corrosion inhibitor include compounds such as benzotriazole, benzimidazole and thiadiazole. The corrosion inhibitor is used in the range of 0 to 3% by mass with respect to 100% by mass of grease as necessary.

<Solid lubricant>
Examples of the solid lubricant include compounds such as molybdenum disulfide, graphite, and melamine cyanurate, and PTFE. The solid lubricant is used in the range of 0 to 3% by mass with respect to 100% by mass of grease as necessary.

<Rust inhibitor>
Examples of the rust preventive agent include various amine compounds, carboxylic acid metal salts, polyhydric alcohol esters, phosphorus compounds, sulfonates, and the like. A rust preventive is used in the range of 0 to 3% by mass with respect to 100% by mass of grease as necessary.
In addition to the above additives, a demulsifier, a colorant, an oily agent (oiliness improver), and the like can be used as necessary.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.
[Production of copolymer (B)]
Production of copolymer (B) used in Examples

[Production Example 1]
Copolymer (B-1)
A 500 ml four-necked round bottom glass container is charged with 40.0 grams of ricinoleic acid, 13.6 grams of sebacic acid, 9.7 grams of 1,4-butanediol, and 0.003 grams of a 20 wt% aqueous solution of tetraethylammonium hydroxide. two to N2 supply line into a four-neck, connecting the distillate condensed lines were performed with N ₂ purge. Stirring was performed from one of the remaining ports using a stirring blade, and the other port was sealed and heated from room temperature to 200 ° C. over 30 minutes. After reaching 200 ° C., 0.20 g of titanium tetrabutoxide was added from the sealed portion using a syringe, and the mixture was held at 200 ° C. for 5 hours for esterification reaction.

  After completion of the esterification, 1.36 g of titanium tetrabutoxide was added from the sealed portion, and a vacuum pump was connected to the outlet of the distillate condensation line to reduce the pressure to 0.133 kPa, and a polymerization reaction was carried out for 2 hours. Stirring was terminated when a predetermined stirring torque was reached, and the bottom of the round bottom flask was cut with a glass cutter, and the polyester was extracted into the atmosphere.

[Production Example 2]
Copolymer (B-2)
In the same manner as in Production Example 1, 39.2 grams of 12-hydroxystearic acid, 13.6 grams of sebacic acid, and 9.7 grams of 1,4-butanediol were heated from room temperature to 210 ° C. over 30 minutes. Thereafter, the same esterification reaction and polycondensation reaction as in Production Example 1 were carried out to obtain a polyester copolymer having an IV value of 0.29.
Table 1 shows the physical properties of the copolymer (B-1) and the copolymer (B-2) obtained in Production Example 1 and Production Example 2.

[Evaluation method]
In the following examples and comparative examples, the properties of the copolymer (B), the mixture of the lubricating base oil and the copolymer (B), and the grease were measured by the following methods.

<Physical properties of copolymer (B)>
[Measurement of intrinsic viscosity (IV)]
For intrinsic viscosity (IV: Intrinsic Viscosity), 0.5 g of sample [copolymer (B)] is used in a mixed solution of 1,1,2,2-tetrachloroethane / phenol (50% by mass / 50% by mass). In the mixed solution, the solution is heated and dissolved at 135 ° C. for 40 minutes, then cooled with water at 25 ° C., and the solution viscosity at 25 ° C. is measured and calculated using an Ubbelohde viscometer.

The intrinsic viscosity is a value calculated by the following formula.
[η] = η _SP / [C (1 + kη _SP )]
[η]: Intrinsic viscosity (dl / g)
η _SP : Specific viscosity C: Sample concentration (g / dl)
k: Constant (slope obtained by measuring the specific viscosity of samples with different solution concentrations (3 or more), plotting the solution concentration on the horizontal axis, and η _SP / C on the vertical axis)
Here, the specific viscosity η _SP was determined according to the following formula.
η _SP = (t−t0) / t0
t: Number of seconds that the sample solution flows (seconds)
t0: The number of seconds that the solvent flows (seconds)

[Melting point (Tm), glass transition temperature (Tg)]
The melting point (Tm) of the copolymer (B) was measured using a differential scanning calorimeter (DSC220C type, manufactured by Seiko Instruments Inc.) as a measuring device. Specifically, about 5 mg of copolymer (B) was sealed in an aluminum pan for measurement and heated from room temperature to 150 ° C. at 10 ° C./min. It was kept at 150 ° C. for 5 minutes and then cooled to −100 ° C. at 10 ° C./min. After 5 minutes at −100 ° C., the second heating was performed to 150 ° C. at 10 ° C./min. The peak temperature (° C.) at the second heating was defined as the melting point (Tm) of the copolymer, and the displacement point corresponding to the glass transition was defined as the glass transition temperature (Tg).

[Biodegradability]
The biodegradation rate was measured in accordance with the modified MITI test method “OECD301C”. The Eco Mark certification standard revised in July 1998 requires the biodegradation rate to be 60% or more.

[Preparation of grease]
Components other than the copolymer (B) used in the preparation of the following grease are as follows.
(1) Base oil (A): Croda PRIOLUBE-2089 (polyol ester)
(2) Thickener (C): in base oil (A), fatty acid (commercially available 12-hydroxystearic acid) and metal base [lithium hydroxide / calcium hydroxide = 1/1 (mass ratio) The ratio]) was blended so as to have the amount shown in the table and reacted by heating to obtain a thickener.
(3) Antioxidant (D-1): Sumitomo Chemical's Sumilizer GA80 (Phenol) / Sumitomo Chemical TP-D (Sulfur) = 1: 1 (mass ratio) mixed system (D-2): BASF 2,6-di-t-butyl-p-phenylphenol made by the company As an alternative polymer of the copolymer (B) used in the comparative example, an ester polymer (E) [PRIOLUBE (trademark) -3986 (Croda Made)].

  The grease used in Examples and Comparative Examples is prepared as a first step by first mixing a fatty acid and a metal base in the base oil (A) and mixing them while heating at around 220 ° C. to prepare a base grease. As a second step, the consistency is adjusted while blending the copolymer (B) or alternative polymer and a part of the base oil (A) as a base grease base oil thickener after cooling. As a third step, after treatment with a mill roll, defoaming treatment is finally performed to obtain a homogeneous grease.

<Physical properties of grease>
(1) Immiscible consistency / Admixture consistency
In accordance with ASTM D217, the cone attached to the penetrometer was dropped at 25 ° C., and the depth entered after 5 seconds was measured.

(2) Dropping point
In accordance with ASTM D2265, a cup filled with the sample is placed in a test tube and a thermometer is inserted. This is heated in a heating bath under specified conditions, and the temperature at which the sample is dropped from the opening at the bottom of the cup is defined as the dropping point.

(3) Evaporation amount
In accordance with ASTM D1742, a sample is weighed into a test vessel and placed in a thermostatic chamber attached to an evaporator and maintained at 99 ° C. The amount of loss of the sample after flowing clean air with a specified flow rate over the sample surface for 22 hours is calculated as the evaporation amount.

(4) Oil separation
In accordance with ASTM D972, the sample is weighed on a wire mesh conical filter, held in a constant temperature air bath at 100 ° C. for 24 hours, the mass of oil separated from the sample is measured, and the degree of oil separation is calculated.

(5) Viscosity-Temperature Dependence Using a Brookfield viscometer (BH type), apparent viscosities at 100 ° C., 0 ° C., and −20 ° C. at a shear rate (10 sec ⁻¹ ) were measured.

(6) Torque stopping force Using the two-cylinder torque tester shown in Fig. 1, apply grease to the thin film on the inner cylinder, set the outer cylinder, and rotate the inner cylinder at 10rpm for 4 minutes at 25 ° C. Measure the force to stop the rotation of the outer cylinder when

(7) Roll stability (mixing consistency)
Using a shell roll tester stipulated in ASTM D1831, the mixing penetration after 80 ° C.-165 rpm-24 hours was measured.

(8) Heat resistance: Steel sheet thin film heating test Apply to steel sheet at 40mm x 60mm x 1mm (thickness), leave it in a constant temperature bath at 100 ° C, and measure the appearance and spread consistency after a certain time (up to 388 hours). did.

[Example 1]
Test greases were prepared by the reaction method with the formulation shown in Table 2. First, a fatty acid and a metal base (ratio of lithium hydroxide / calcium hydroxide = 1/1) were added to the base oil (A) and heated to 220 ° C. to prepare a base grease. Next, after adding an antioxidant to the cooled base grease, the copolymer (B-1) and the base oil (A) of Production Example 1 are partially blended, and the consistency is equivalent to JIS-2 (265- 295) and the physical properties of the obtained grease were evaluated. The results are shown in Table 2.

[Example 2]
A grease was prepared in the same manner as in Example 1 except that the antioxidant (D-1) was changed to the antioxidant (D-2) with the formulation shown in Table 2, and the physical properties of the obtained grease were evaluated. The results are shown in Table 2.

Example 3
A grease was prepared in the same manner as in Example 1 except that the blending ratio of the base oil (A) and the copolymer (B-1) as a thickener was changed according to the formulation shown in Table 2. Physical properties were evaluated. The results are shown in Table 2.

Example 4
A grease was prepared in the same manner as in Example 1 except that the copolymer (B-1) as a thickener was changed to the copolymer (B-2) with the formulation shown in Table 2, and the grease obtained Physical properties were evaluated. The results are shown in Table 2.

Example 5
A grease was prepared in the same manner as in Example 3 except that the antioxidant (D-1) was changed to the antioxidant (D-2) with the formulation shown in Table 2, and the physical properties of the obtained grease were evaluated. The results are shown in Table 2.

Example 6
A grease was prepared in the same manner as in Example 4 except that the blending ratio of the base oil (A) and the copolymer (B-2) as a thickener was changed according to the formulation shown in Table 2. Physical properties were evaluated. The results are shown in Table 2.

[Comparative Example 1]
A grease was prepared in the same manner as in Example 1 except that the copolymer (B-1) as a thickener described in Example 1 was replaced with an ester polymer (E) with the formulation shown in Table 2. The physical properties of the obtained grease were evaluated. The results are shown in Table 2.

[Comparative Example 2]
Grease was prepared using a system described in Table 2 with no thickener added, and the physical properties of the obtained grease were evaluated. The results are shown in Table 2.

[Comparative Example 3]
Physical properties were evaluated using Bio Grease EP (trademark) (manufactured by JX Energy Co., Ltd.) as a commercially available biodegradable grease. The results are shown in Table 2.

Claims (13)

40% by mass or more and 90% by mass or less of the base oil (A), 1% by mass or more and 50% by mass or less of the copolymer (B) satisfying the following requirements (B1) to (B3), and a thickener (C ) Including 5% by mass or more and 20% by mass or less [provided that (A) + (B) + (C) = 100% by mass. 〕,And,
Grease having a mass ratio [the mass of (B) / the mass of (C)] of 1/20 to 50/5 of the copolymer (B) and the thickener (C):
(B1) includes a structural unit (a) derived from ricinoleic acid, a structural unit (b) derived from an aliphatic dicarboxylic acid, and a structural unit (c) derived from a diol having 2 to 10 carbon atoms;
(B2) When the total of the structural units (a), (b) and (c) is 100 mol%, the content of the structural unit (a) is 20 to 90 mol%, and the content of the structural unit (b) Is 5 to 40 mol%, and the content of the structural unit (c) is 5 to 40 mol%;
(B3) Intrinsic viscosity [IV] is in the range of 0.2 to 1.0 dl / g.   The grease according to claim 1, wherein the base oil (A) is a vegetable oil and / or a synthetic ester.   The grease according to claim 2, wherein the synthetic ester is a diester or a polyol ester.   The grease according to claim 2 or 3, wherein the synthetic ester is an aliphatic diester or an aliphatic polyol ester.   In the copolymer (B), in the requirement (B2), the molar ratio [(b) / (c)] of the structural unit (b) and the structural unit (c) is 0.9 to 1.1. The grease according to any one of claims 1 to 4.   The grease according to any one of claims 1 to 5, wherein in the copolymer (B), the structural unit (a) is 40 to 90 mol% in the requirement (B2).   The grease according to any one of claims 1 to 6, wherein the copolymer (B) has an intrinsic viscosity [IV] in the range of 0.2 to 0.6 dl / g in the requirement (B3).   The grease is further added with at least one selected from the group consisting of an antioxidant, an extreme pressure agent, a rust inhibitor, a metal deactivator, an antiwear additive, an antifoaming agent, a cleaning dispersant and a pour point depressant. Grease of any one of Claims 1-7 containing an agent (D).   The grease according to any one of claims 1 to 8, wherein the structural unit (b) derived from an aliphatic dicarboxylic acid is a structural unit derived from sebacic acid.   The grease according to any one of claims 1 to 9, wherein the structural unit (c) derived from a diol having 2 to 10 carbon atoms is a structural unit derived from 1,4-butanediol.   The grease according to any one of claims 1 to 10, wherein the thickener (C) is a soap-based thickener.   The grease according to claim 11, wherein the soap-based thickener is at least one of lithium soap and calcium soap.   The grease according to any one of claims 1 to 12, wherein the thickener (C) contains lithium soap and calcium soap in a mass ratio of 10/90 to 90/10.