JP6857985B2 - Lithium composite soap-based grease composition - Google Patents

Description

The present invention relates to a lithium composite soap-based grease composition.

Lithium composite soap-based grease is generally known to have excellent heat resistance and oxidative stability. From the viewpoint of high temperature durability, lithium composite soap-based grease is used in all industrial machine parts such as constant velocity joints, various bearings, linear guides, and gears.
In recent years, with the achievement of both miniaturization and high output of machines and devices, grease tends to be used under a higher load and a higher temperature, and the environment in which grease is used has become harsher. Therefore, it is desired to enclose lithium composite soap-based grease having excellent heat resistance in the parts of machines and devices. In particular, in a heavy-load lubrication environment such as a spindle bearing for wind power generation, a speed increaser for wind power generation, and a speed reducer for industrial robots, load bearing performance is strongly required for grease.

Conventionally, it has been known to blend a solid lubricant such as graphite, molybdenum disulfide, or an organic molybdenum compound in order to impart load-bearing performance to grease (see, for example, Non-Patent Document 1).
Further, a grease composition for gear lubrication having excellent wear resistance, which uses lithium soap as a thickener and is added with molybdenum dithiocarbamate and calcium sulfonate, is disclosed (see, for example, Patent Document 1).
Further, it contains a base oil and a thickener as a grease composition having excellent wear resistance and extreme pressure resistance and having a long life even when used in a geared motor or the like, and as an extreme pressure agent, 0 in terms of sulfur content. At least one of 0.01% by mass to 1% by mass (based on the total amount of the composition) and zinc dithiocarbamate, and a phosphorus-based extreme pressure of 150% by mass to 4000% by mass (based on the total amount of the composition) in terms of phosphorus amount. A grease composition containing an agent is disclosed (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2004-269722 Japanese Unexamined Patent Publication No. 2008-143927

Japan Tribology Society Grease Study Group ed .: "Basics and Applications of Lubricating Grease", Yokendo, 2007, p. 77

However, in reality, even if the extreme pressure type grease is used, the sufficient lubrication function is not always exhibited, and the metal parts of the machine and the device may reach the end of their life earlier than expected.
In order to improve the life of metal parts, a technique for preventing seizure under a high load and suppressing metal wear is required.
The grease compositions described in Patent Documents 1 and 2 may not have sufficient wear resistance under a load capacity. Further, the grease composition using lithium soap described in Patent Document 1 does not have sufficient heat resistance. Further, as the heat-resistant grease, urea-based grease is also common, but compared to other metal soap-based greases, urea-based grease can obtain the effect of the additive when the same additive is blended. It can be difficult.
Therefore, there is a demand for grease having heat resistance and excellent load-bearing performance and wear-resistant performance.

The present invention has been made in view of the above, and an object of the present invention is to provide a lithium composite soap-based grease composition having heat resistance and excellent load-bearing performance and abrasion-resistant performance.

As a result of diligent studies to solve the above problems, the present inventors have made a grease composition containing lithium composite soap as a thickener, and a specific amount of sulfur-based extreme pressure agent and a specific amount of phosphorus-based wear. It has been found that the load-bearing performance and the wear-resistant performance of the grease composition are improved by adding at least one of each of the preventive agents. The present invention has been completed based on these findings.
Means for solving the above problems include the following embodiments.

<1> A base oil, a lithium composite soap as a thickener, and at least one sulfur-based extreme pressure agent selected from the group consisting of polysulfide, sulfide olefin, sulfide ester, and sulfide fat and oil are applied to the total mass of the grease composition. A grease composition of at least one phosphorus-based anti-wear agent selected from the group consisting of 0.1% by mass to 2% by mass in terms of sulfur amount and an amine salt of a phosphoric acid ester, an acidic phosphoric acid ester and an acidic phosphoric acid ester. A lithium composite soap-based grease composition containing 0.1% by mass to 1% by mass in terms of phosphorus amount with respect to the total mass of the substance.

<2> The lithium composite soap-based grease composition according to <1>, wherein the phosphorus-based anti-wear agent is an acidic phosphoric acid ester.

According to the present invention, there is provided a lithium composite soap-based grease composition having heat resistance and excellent load bearing performance and abrasion resistance.

<Lithium composite soap-based grease composition>
The lithium composite soap-based grease composition of the present invention (hereinafter, also referred to as “grease composition”) is a group consisting of a base oil, a lithium composite soap as a thickener, polysulfide, an olefin sulfide, a sulfide ester, and a sulfide oil / fat. At least one sulfur-based extreme pressure agent selected from the above is 0.1% by mass to 2% by mass in terms of sulfur amount with respect to the total mass of the grease composition, and phosphoric acid ester, acidic phosphoric acid ester and acidic phosphoric acid ester. At least one phosphorus-based anti-wear agent selected from the group consisting of amine salts of the above is contained in an amount of 0.1% by mass to 1% by mass in terms of phosphorus amount with respect to the total mass of the grease composition.
The grease composition may contain other components in addition to the above components.
Hereinafter, each component of the grease composition will be described.

(1) Base oil The grease composition of the present invention contains a base oil. The base oil is not particularly limited, and may be, for example, a mineral oil, a synthetic oil, or a mixed oil thereof. As the base oil, synthetic oil is preferable from the viewpoint of excellent lubrication long life of grease and heat resistance of the base oil.
Examples of the synthetic oil include ether-based synthetic oils such as alkyldiphenyl ether, ester-based synthetic oils such as diesters, polyol esters and complex-type polyol esters, synthetic hydrocarbon oils such as polyα-olefins, and alkylnaphthalene-based synthetic oils.

(2) Thickener (i) Composition of Lithium Composite Soap Lithium composite soap is a composite soap in which a lithium salt of a higher fatty acid and a lithium salt of a dicarboxylic acid are combined.
From the viewpoint of heat resistance, the lithium composite soap is a complex that combines a lithium salt of a monocarboxylic acid having 12 to 24 carbon atoms and a lithium salt of a dicarboxylic acid having 2 to 12 carbon atoms. Is preferable.
Suitable monocarboxylic acids include stearic acid, 12-hydroxystearic acid and the like. In addition, suitable dicarboxylic acids include succinic acid, malonic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid and the like.

(Ii) Content The content of the thickener can be appropriately adjusted according to the desired mixing consistency, and is preferably 5% by mass to 20% by mass with respect to the total mass of the grease composition, which is more preferable. Is 5% by mass to 15% by mass.

(3) Additives (i) Sulfur-based extreme pressure agent The grease composition of the present invention contains at least one selected from the group consisting of polysulfide, sulfide olefin, sulfide ester and sulfide oil and fat as the sulfur-based extreme pressure agent.
Among them, as the sulfur-based extreme pressure agent, at least one selected from the group consisting of polysulfide and olefin sulfide is preferable from the viewpoint of load-bearing performance and wear-resistant performance.

Examples of polysulfide include diisobutyldisulfide, dioctylpolysulfide, di-tert-butylpolysulfide, di-tert-nonylpolysulfide, dibenzylpolysulfide and the like.

Examples of the sulphide olefin include those obtained by sulphurizing olefins such as polyisobutylene and terpenes with a sulfide such as sulfur.

The content of the sulfur-based extreme pressure agent is 0.1% by mass to 2% by mass, preferably 0.25% by mass to 1.5% by mass, in terms of the amount of sulfur, based on the total mass of the grease composition. , More preferably 0.5% by mass to 1.25% by mass. If the content of the sulfur-based extreme pressure agent is less than 0.1% by mass, the effect of improving the load bearing performance is not sufficient. If the content of the sulfur-based extreme pressure agent exceeds 2% by mass, no effect can be expected for the content, and the thermal stability may be impaired.

(Ii) Phosphorus-based anti-wear agent The grease composition of the present invention contains at least one selected from the group consisting of a phosphoric acid ester, an acidic phosphoric acid ester and an amine salt of an acidic phosphoric acid ester as a phosphorus-based anti-wear agent. .. As the phosphorus-based anti-wear agent, at least one selected from the group consisting of a phosphoric acid ester, an acidic phosphoric acid ester, and an amine salt of an acidic phosphoric acid ester is preferable from the viewpoint of load-bearing performance and wear-resistant performance, and acidic phosphorus is preferable. At least one selected from the group consisting of amine salts of acid esters and acidic phosphoric acid esters is more preferable.

Examples of the phosphoric acid ester include compounds represented by the following general formula (1).

In the general formula (1), R ^{1 to} R ³ independently represent monovalent hydrocarbon groups having 1 to 30 carbon atoms.

Examples of the monovalent hydrocarbon group of R ^{1 to} R ³ include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group, and any of them may be used. Among these, an aliphatic hydrocarbon group is preferable as the monovalent hydrocarbon group of ^{R 1 to} R ^3.
When ^{the hydrocarbon groups of R 1 to} R ³ are aliphatic hydrocarbon groups, the aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. ..
Further, the aliphatic hydrocarbon group may be a linear aliphatic hydrocarbon group or a branched chain aliphatic hydrocarbon group.

Specific examples of the aliphatic hydrocarbon group include saturated aliphatic hydrocarbon groups such as methyl group, ethyl group, n-propyl group and isopropyl group; alkenyl group such as vinyl group and allyl group, and alkynyl group such as ethynyl group. Examples include unsaturated aliphatic hydrocarbon groups.

Specific examples of the alicyclic hydrocarbon group include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and the like.

Specific examples of the aromatic hydrocarbon group include a phenyl group, a toluyl group, a xsilyl group, a mesityl group, a propylphenyl group and the like.

Specific examples of the phosphoric acid ester include benzyl diphenyl phosphate ester, allyl diphenyl phosphate ester, triphenyl phosphate ester, tricresyl phosphate ester, tributyl phosphate ester, cresyl diphenyl phosphate ester, and dicredyl phenyl phosphate ester. Examples thereof include compounds such as ethylphenyldiphenylphosphate, diethylphenylphenylphosphate, propylphenyldiphenylphosphate, dipropylphenylphenylphosphate, triethylphenylphosphate, and tripropylphenylphosphate.

Examples of the acidic phosphoric acid ester include compounds represented by the following general formula (2).

In the general formula (2), R ^{3 to} R ⁵ independently represent a hydrogen atom and a monovalent hydrocarbon group having 1 to 30 carbon atoms. However, ^{one or two of R 3 to} R ⁵ are hydrogen atoms, the rest are hydrocarbon groups having 1 to 30 carbon atoms, and ^{all of R 3 to} R ⁵ are hydrogen atoms or hydrocarbon groups. There is no.

From the viewpoint of wear resistance, R ^{3 to} R ⁵ preferably have 1 to 20 carbon atoms, and more preferably 3 to 18 carbon atoms.
Examples of the hydrocarbon group of R ^{3 to} R ⁵ include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group, and any of them may be used. Among these, ^{the hydrocarbon group of R 3 to} R ⁵ is preferably an aliphatic hydrocarbon group.
When the ^{hydrocarbon group in R 3 to} R ⁵ is an aliphatic hydrocarbon group, the aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. ..
Further, the aliphatic hydrocarbon group may be a linear aliphatic hydrocarbon group or a branched chain aliphatic hydrocarbon group.
Specific examples of the aliphatic hydrocarbon group are the same as those exemplified by the general formula (1).

From the viewpoint of metal corrosiveness, R ^{3 to} R ⁵ are preferably branched-chain aliphatic hydrocarbon groups, and more preferably branched-chain aliphatic hydrocarbon groups having 3 to 18 carbon atoms.

In addition, examples of the compound represented by the general formula (2) include compounds having a linear aliphatic hydrocarbon group or a branched chain aliphatic hydrocarbon group.

Specific examples of the compound having a branched aliphatic hydrocarbon group include 2-ethylhexyl acid phosphate ester, isostearyl acidic phosphoric acid ester and the like.

Specific examples of the compound having a linear aliphatic hydrocarbon group include n-octyl acidic phosphoric acid ester and oleyl acidic phosphoric acid ester.

Examples of the amine salt of the acidic phosphoric acid ester include those obtained by neutralizing the acidic phosphoric acid ester with an amine compound represented by the following general formula (3).

In the general formula (3), R ^{6 to} R ⁸ independently represent a monovalent hydrocarbon group or a hydrogen atom having 1 to 22 carbon atoms, and at least one of ^{R 6 to} R ^{8 is a hydrocarbon.} Indicates a group. R ^{6 to} R ⁸ are preferably monovalent hydrocarbon groups or hydrogen atoms having 4 to 18 carbon atoms.
Specific examples of the amine compound represented by the general formula (3) include dibutylamine, octylamine, dioctylamine, laurylamine, dilaurylamine, oleylamine, coconutamine, and beef tallow amine.

(Ii) Content The content of the phosphorus-based anti-wear agent is 0.1% by mass to 1% by mass, preferably 0.25% by mass to 0% by mass, in terms of phosphorus amount, based on the total mass of the grease composition. It is 5% by mass, more preferably 0.35% by mass to 0.5% by mass. If the content of the phosphorus-based wear inhibitor is less than 0.1% by mass, the effect of improving the wear resistance performance is not sufficient, and if it exceeds 1% by mass, corrosion wear tends to be promoted.

(4) Other Additives In the grease composition of the present invention, additives such as antioxidants, corrosion inhibitors, rust preventives and the like other than the above additives can be appropriately added as needed. Other additives may be used alone or in combination of two or more.

Antioxidants include alkylphenols such as 2,6-di-tert-butyl-p-cresol, bisphenols such as 4,4'-methylenebis- (2,6-di-t-butylphenol), and n-octadecyl. Examples thereof include phenolic compounds such as -3- (4'-hydroxy-3', 5'-di-t-butylphenol) propionates, aromatic amine compounds such as naphthylamines and dialkyldiphenylamines, and zinc thiophosphate compounds.
When the antioxidant is added, the addition ratio is preferably 0.5% by mass to 5% by mass, more preferably 1% by mass to 4% by mass, based on the total mass of the grease composition.

Examples of the corrosion inhibitor include benzotriazole and benzimidazole.

Examples of the rust preventive include a sulfonic acid metal salt compound and a sorbitan compound.

Hereinafter, the present invention will be specifically described with reference to Examples. The present invention is not limited to these examples.

(Examples 1 to 8 and Comparative Examples 1 to 5)
In Examples and Comparative Examples, the following components * 1 to * 10 were contained in the proportions of the blending amounts (mass) shown in Tables 1 and 2 to prepare a grease composition. In addition, "-" in the figure means that the said component is not blended.

* 1: Base oil (hydrorefined mineral oil, kinematic viscosity at 40 ° C: 47 mm ² / s)

* 2: Lithium composite soap <Procedure for manufacturing lithium composite soap>
Base oil, 12-hydroxystearic acid, and dibutyl sebacate were added to a heat-resistant container, heated to about 90 ° C. with stirring, and then an aqueous lithium hydroxide solution was added and reacted for about 120 minutes. Then, the reaction solution was heated to 230 ° C. with stirring and then cooled to 60 ° C. to obtain a lithium composite soap.

* 3: Lithium soap <Lithium soap manufacturing procedure>
Base oil, stearic acid, and 12-hydroxystearic acid were added to a heat-resistant container, heated to about 90 ° C. with stirring, and then an aqueous lithium hydroxide solution was added and reacted for about 120 minutes. Then, the reaction solution was heated to 230 ° C. with stirring and then cooled to 60 ° C. to obtain lithium soap.

* 4: Aliphatic diurea <Procedure for manufacturing aliphatic diurea>
The base oil shown in Table 2 and diphenylmethane-4,4'-diisocyanate are added to a heat-resistant container, heated to about 90 ° C. with stirring, and then a mixed solution of the base oil and octylamine is added. The reaction was carried out for about 60 minutes. Then, the mixture was heated to 160 ° C. with stirring and then cooled to 60 ° C. to obtain an aliphatic diurea.

* 5: Sulfur-based extreme pressure agent; polysulfide (compound name: di-tert-dodecyltrisulfide, trade name: TPS20, manufactured by Atofina Japan Co., Ltd.)
* 6: Sulfur-based extreme pressure agent; olefin sulfide (compound name: isobutylene sulfide, trade name: ELCO217, manufactured by The Elco Corporation)
* 7: Phosphorus-based anti-wear agent; acidic phosphoric acid ester (having 8 carbon atoms and having a branched chain. Compound name: 2-ethylhexylic phosphate ester, trade name: Phoslex A-8, SC Organic Chemistry Co., Ltd.) Made)
* 8: Phosphorus-based anti-wear agent; amine salt A of acidic phosphoric acid ester (* 7 amine salt. Compound name: oleylamine salt of 2-ethylhexylic phosphate ester, trade name: Phospair-16, SC Organic Chemistry Co., Ltd. ) Made)
* 9: Phosphorus-based anti-wear agent; amine salt B of acidic phosphoric acid ester (trade name: VANLUBE672, manufactured by Vanderbilt Chemicals)
* 10: Phosphorus-based anti-wear agent; Phosphate ester (Compound name: tricresylphosphate, trade name: TCP, manufactured by Daihachi Chemical Industry Co., Ltd.)

The obtained grease composition was evaluated for its mixing consistency, load-bearing performance, seizure-preventing performance, and heat resistance.

(Measuring method)
(1) Mixing consistency Measured based on the consistency test method of JIS K 2220: 2013.

(2) Load-bearing performance and seizure-proof performance As an evaluation of load-bearing performance and wear-resistant performance, a four-ball extreme pressure test was carried out based on ASTM D 2596. As the test conditions, the rotation speed was 1770 ± 60 rpm, the time was 10 seconds, and the temperature was room temperature. In the four-ball extreme pressure test, the fusion load (WP; Weld Point, unit: kgf) and the maximum non-seizure load (LNSL; Last Non-Seizure Load, unit: kgf) were determined.

(3) Drip point As an evaluation of heat resistance, measurement was performed based on the drip point test method of JIS K 2220: 2013. As a test condition, the expected dropping point was set to 190 ° C. If the sample did not drip even when the test temperature reached 230 ° C, the result was described as "230 ° C or higher".

As for the fusion load (WF), the larger the value of the fusion load, the more excellent the load bearing capacity. In this test, the fusion load (WF) preferably exceeds 315 kgf, and more preferably 400 kgf or more, from the viewpoint of load bearing performance.

As for the maximum non-seizure load (LNSL), the larger the value of the maximum non-seizure load, the better the wear resistance. In this test, the maximum non-seizure load (LNSL) is preferably 126 kgf or more, and more preferably 160 kgf or more, from the viewpoint of wear resistance performance.

As shown in Table 1, the grease composition of Examples 1 to 8 containing a lithium composite soap as a thickener, and at least one specific amount of a sulfur-based extreme pressure agent and a specific amount of a phosphorus-based anti-wear agent. Compared with Comparative Examples 1 to 5, the products had higher values of fusion load and maximum non-seizure load, were excellent in load bearing performance and wear resistance, and also had heat resistance.
On the other hand, the grease compositions of Comparative Examples 1 to 3 which do not contain at least one each of a specific amount of a sulfur-based extreme pressure agent and a phosphorus-based anti-wear agent, and Comparative Example 5 which does not contain lithium composite soap as a thickener. All of the grease compositions of No. 1 had low values of fusion load and maximum non-seizure load, and were inferior in load bearing performance and wear resistance performance. Further, the grease composition of Comparative Example 4 containing no lithium composite soap as a thickener had a low fusion load value and a low drip point temperature, and was inferior in load bearing performance and heat resistance.

The lithium composite soap-based grease composition of the present invention can be suitably used for various industrial machines, automobiles, etc., and is particularly suitable as grease for gear mechanisms such as speed reducers for wind power generation and speed reducers for robot machines. ..

Claims (1)

Base oil and
Lithium composite soap as a thickener,
At least one sulfur-based extreme pressure agent selected from the group consisting of polysulfide, olefin sulfide, sulfide ester, and sulfide oil and fat was added in an amount of 0.1% by mass to 2% by mass in terms of sulfur amount with respect to the total mass of the grease composition.
At least one phosphorus-based anti-wear agent selected from the group consisting of phosphoric acid ester, acidic phosphoric acid ester and amine salt of acidic phosphoric acid ester is 0.1% by mass in terms of phosphorus amount with respect to the total mass of the grease composition. ~ 1% by mass,
Contains ,
The phosphorus-based anti-wear agent is a 2-ethylhexylyl phosphate ester.
Lithium composite soap-based grease composition.