JP6669343B2 - Biodegradable lubricating oil composition - Google Patents

Description

  The present invention relates to a biodegradable lubricating oil composition containing an ester-based synthetic base oil.

  In recent years, biodegradable lubricating oils have been put into practical use in the lubricating oil field from the viewpoint of measures against environmental pollution. Since a high biodegradation rate is required for a biodegradable lubricating oil, it is difficult to use a large amount of mineral oil that is widely used as a base oil in ordinary lubricating oils. Therefore, it is necessary to use a base oil selected from limited ones such as natural vegetable oil, polyalkylene glycol-based synthetic base oil, and ester-based synthetic base oil. Conventionally, among these, ester-based synthetic base oils which are relatively excellent in heat stability, oxidation stability and the like have been often used.

  As ester synthetic base oils used in biodegradable lubricating oils, fatty acid diesters using aliphatic dicarboxylic acids as carboxylic acids, hindered esters using aliphatic hindered polyols as polyols, and the like are known. . Further, for example, Patent Document 1 discloses that a phenolic antioxidant, a low base number calcium sulfonate and a phenolic antioxidant are added to a base oil containing 50% by mass or more of a hindered ester in order to improve lubrication performance, oxidation stability, corrosion prevention performance, and the like. And a biodegradable lubricating oil comprising a triazole compound.

JP 2005-213451 A

By the way, the required performance of the lubricating oil composition is improving year by year, and the biodegradable lubricating oil composition is required to have a longer life and an improved wear resistance. However, as described in Patent Document 1, for example, even if a hindered ester is used as a base oil and a plurality of types of additives are blended, it is difficult to extend the life because oxidation stability is not sufficiently improved. Also, the abrasion resistance is not sufficiently improved, and the required performance may not be satisfied.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a biodegradable lubricating oil composition having improved oxidation resistance while improving abrasion resistance.

The present inventors have conducted intensive studies and found that a specific ester-based synthetic base oil was used as the base oil to increase the transmittance of the lubricating oil composition at 3005 ± 1 cm ⁻¹ , so that a small amount of the specific additive was obtained. It has been found that the agent makes it possible to sufficiently improve oxidation stability and abrasion resistance while maintaining good biodegradability, and completed the present invention described below. That is, the present invention provides the following.
Ester-based synthetic base oil (A) 50% by mass or more, amine-based antioxidant (B1) 0.1 to 3% by mass, phenol-based antioxidant (B2) 0.1 to 3% by mass, sulfur- 0.01 to 2% by mass of a phosphorus-based extreme pressure agent (C),
A biodegradable lubricating oil composition having a transmittance of 50% or more at 3005 ± 1 cm ⁻¹ in infrared absorption analysis of a liquid film of 0.1 mm.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the biodegradable lubricating oil composition which improved the oxidation stability, making the abrasion resistance favorable.

Hereinafter, the present invention will be described using embodiments.
[Biodegradable lubricating oil composition]
The biodegradable lubricating oil composition according to one embodiment of the present invention includes at least 50% by mass or more of an ester-based synthetic base oil (A) and 0.1% of an amine-based antioxidant (B1) as an antioxidant (B). 1 to 3% by mass, 0.1 to 3% by mass of a phenolic antioxidant (B2), and 0.01 to 2% by mass of a sulfur-phosphorus extreme pressure agent (C).

Further, the biodegradable lubricating oil composition of the present embodiment has a transmittance of 50% or more at 3005 ± 1 cm ⁻¹ in infrared absorption analysis of a liquid film of 0.1 mm. The transmittance at 3005 ± 1 cm ⁻¹ in the infrared absorption analysis is an index of the amount of unsaturated bonds in the biodegradable lubricating oil composition. When the transmittance becomes 50% or more, the transmittance in the composition becomes 50% or more. This reduces the number of saturated bonds.
In the lubricating oil composition containing the ester-based synthetic base oil (A) as a main component (50% by mass or more) as in the present embodiment, the unsaturated bond is mostly derived from the ester-based synthetic base oil (A). However, by reducing unsaturated bonds in the ester synthetic base oil (A), the transmittance of the composition can be made 50% or more. In the present embodiment, a small amount of the specific antioxidant (B) and a small amount of the specific antioxidant (B) are used by reducing the amount of the unsaturated bond in the lubricating oil composition by using the ester synthetic base oil (A) having a small unsaturated bond amount. The extreme pressure agent (C) makes it possible to sufficiently improve the oxidation stability and wear resistance of the biodegradable lubricating oil composition.
The above-mentioned transmittance of the lubricating oil composition is preferably 55% or more from the viewpoint of reducing the amount of unsaturated bonds in the lubricating oil composition, and is preferably 60% or more in order to hardly contain unsaturated bonds. Is more preferred. The upper limit of the transmittance is 100%, but due to its characteristics, the transmittance is usually about 80% or less.

Hereinafter, each component contained in the biodegradable lubricating oil composition will be described in detail.
[Ester-based synthetic base oil (A)]
The ester-based synthetic base oil (A) may be appropriately selected from synthetic base oils having an ester bond, and specifically, a polyol ester-based base oil (A1) which is an ester of a polyol and an aliphatic monocarboxylic acid. ), Diester base oils (A2) which are esters of aliphatic dicarboxylic acids and monoalcohols, and ester base oils (A3) comprising a copolymer of an unsaturated dibasic acid ester and an α-olefin. . As the ester-based synthetic base oil (A), one kind of ester may be used alone, or two or more kinds of esters may be used in combination.

Each of the ester-based synthetic base oils (A) used in the lubricating oil composition has a liquid film thickness of 0.1 mm in order to reduce the amount of unsaturated bonds and increase the transmittance in the lubricating oil composition as described above. In the infrared absorption analysis, the transmittance at 3005 ± 1 cm ⁻¹ is preferably 50% or more, more preferably 55% or more, and is preferably 60% or more in order to hardly include an unsaturated bond. More preferred. The upper limit of the transmittance of the ester-based synthetic base oil (A) is 100%, but the transmittance is usually about 80% or less due to the characteristics of the ester-based synthetic base oil (A).
When two or more ester-based synthetic base oils (A) are used in combination, for example, it is preferable to mix two or more of those having a transmittance of 50% or more. Further, a mixture having a transmittance of 50% or more and a mixture having a transmittance of less than 50% may be used as a mixture. It is preferred to include more than less than.

  The ester-based synthetic base oil (A) is contained in an amount of 50% by mass or more as described above, preferably 70% by mass or more, more preferably 80% by mass or more, based on the total amount of the lubricating oil composition. More preferably, the content is more preferably 90% by mass or more. The content of the ester-based synthetic base oil (A) is less than 99.8% by mass relative to the total amount of the lubricating oil composition, but is preferably 99% by mass in order to make the amount of the additives described below an appropriate amount. %, More preferably 98% by mass or less.

  The polyol ester base oil (A1) used in the ester synthetic base oil (A) has one or more quaternary carbons in the molecule, and at least one of the quaternary carbons has one methylol group. A hindered ester which is an ester of a hindered polyol having up to 4 bonds and an aliphatic monocarboxylic acid is exemplified. More specific examples of hindered polyols include those having the following general formula (I):

(In the formula, R ¹ and R ² each independently represent a hydrocarbon group having 1 to 6 carbon atoms or a methylol group, and n represents an integer of 0 to 4.)

In the general formula (I), as the hydrocarbon group having 1 to 6 carbon atoms among R ¹ and R ^2, a linear or branched alkyl group is preferable, and an alkyl group having 1 or 2 carbon atoms is more preferable. preferable. Further, n is preferably an integer of 0 to 2.
The hindered polyol represented by the general formula (I) includes, for example, dialkylpropanediol (the alkyl group has 1 to 6 carbon atoms) and trimethylolalkane (the alkane has 2 to 7 carbon atoms). ), Hindered polyols such as pentaerythritol, and dehydration condensates thereof, specifically, neopentyl glycol, 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,2 3-propanediol, trimethylolethane, trimethylolpropane, trimethylolbutane, trimethylolpentane, trimethylolhexane, trimethylolheptane, pentaerythritol, 2,2,6,6-tetramethyl-4-oxa-1,7 -Heptanediol, 2,2,6,6,10,10-hexamethyl-4,8 Dioxa-1,11-undecadiol, 2,2,6,6,10,10,14,14-octamethyl-4,8,12-trioxa-1,15-pentadecadiol, 2,6-di ( (Hydroxymethyl) -2,6-dimethyl-4-oxa-1,7-heptanediol, 2,6,10-tri (hydroxymethyl) -2,6,10-trimethyl-4,8-dioxa-1,11 -Undecadiol, 2,6,10,14-tetra (hydroxymethyl) -2,6,10,14-tetramethyl-4,8,12-trioxa-1,15-pentadecadiol, di (pentaerythritol ), Tri (pentaerythritol), tetra (pentaerythritol), penta (pentaerythritol) and the like.
Among these hindered polyols, trimethylolpropane, neopentyl glycol, pentaerythritol, and dehydration condensates of these two or three molecules are preferable, among which neopentyl glycol, trimethylolpropane, and pentaerythritol are more preferable. .

Examples of the aliphatic monocarboxylic acid used for the polyol ester base oil (A1) include a saturated aliphatic monocarboxylic acid having 5 to 22 carbon atoms. The acyl group of the saturated aliphatic monocarboxylic acid may be linear or branched. Examples of such saturated aliphatic monocarboxylic acids include valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, Linear saturated monocarboxylic acids such as heptadecanoic acid, stearic acid, nonadecanoic acid, arachinic acid, and behenic acid; isomiristic acid, isopalmitic acid, isostearic acid, 2,2-dimethylpropanoic acid, 2,2-dimethylbutanoic acid 2,2-dimethylpentanoic acid, 2,2-dimethyloctanoic acid, 2-ethyl-2,3,3-trimethylbutanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,5,5- Trimethyl-2-t-butylhexanoic acid, 2,3,3-trimethyl-2-ethylbutanoic acid, 2,3-dimethyl-2-iso Ropirubutan acid, 2-ethylhexanoic acid, 3,5,5-like branched saturated monocarboxylic acids, such as trimethyl hexanoate and the like.
In the case of esterification, these aliphatic monocarboxylic acids may be used alone or in a combination of two or more. Furthermore, the polyol ester is usually a complete ester in which all the hydroxyl groups of the polyol are esterified, but a partial ester in which some of the hydroxyl groups are left unesterified as long as the effects of the present invention are not affected. May be contained in a small amount.

As the diester base oil (A2), for example, an ester of a saturated dicarboxylic acid having 6 to 12 carbon atoms and an alkyl monoalcohol having 6 to 12 carbon atoms is used. Here, examples of the saturated dicarboxylic acid include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid and the like. Examples of the alkyl monoalcohol include branched alkyl monoalcohols such as isooctanol, isononanol, isodecanol and 2-ethylhexanol; linear chains such as n-octanol, n-nonanol, n-decanol, n-undecanol and n-dodecanol. Alkyl monoalcohol and the like. Preferred specific compounds include dioctyl adipate, diisononyl adipate, diisodecyl adipate, di-2-ethylhexyl azelate, diisooctyl azelate, diisononyl azelate, di-2-ethylhexyl sebacate, diisooctyl sebacate, And diisononyl sebacate and di-2-ethylhexyl dodecane diacid.
The ester used as the diester base oil (A2) may be an ester of one type of alkyl monoalcohol and a saturated dicarboxylic acid, or an ester of two types of alkyl monoalcohol and a saturated dicarboxylic acid. You may.

The ester base oil (A3) is specifically one obtained by copolymerizing an ester of an unsaturated dibasic acid and a monoalcohol with an α-olefin. Examples of the unsaturated dibasic acid used here include maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Examples of the monoalcohol include alkyl monoalcohols having 1 to 20 carbon atoms, and among these, alkyl monoalcohols having 3 to 8 carbon atoms are more preferably used. The alkyl group of the alkyl monoalcohol may be linear or branched. Specific examples of the alkyl monoalcohol include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol and undecanol.
The α-olefin preferably has 3 to 20 carbon atoms, and more preferably 6 to 18 carbon atoms. Examples of such α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene.
This ester base oil (A3) preferably has a kinematic viscosity at 100 ° C. of ²⁰ to 55 mm ² / s, more preferably 25 to 45 mm ² / s.

  The above-mentioned various esters used for the component (A) are generally produced by reacting a carboxylic acid with an alcohol, and as a result, an ester comprising the carboxylic acid residue and the alcohol residue described above. What is necessary is just to have a structure. Therefore, it is not necessary to synthesize the component (A) by a dehydration reaction using the above-mentioned carboxylic acid and alcohol as raw materials, and may be synthesized from other raw materials by another method. For example, it may be produced by a transesterification method.

  The ester-based synthetic base oil (A) preferably contains a polyol ester-based base oil (A1) as a main component among the above-mentioned ester-based synthetic base oils. That is, the ester-based synthetic base oil (A) preferably contains the polyol ester-based base oil (A1) in an amount of more than 50% by mass, more preferably 70% by mass, based on the total amount of the ester-based synthetic base oil (A). To 100% by mass, more preferably 85 to 100% by mass.

  Further, the ester synthetic base oil (A) is a polyol ester base oil having a total carbon number in one molecule of 23 to 50 among the above polyol ester base oils (A1) for reasons of kinematic viscosity and the like. A1-1) is preferably contained as a main component, that is, 50% by mass of a polyol ester base oil (A1-1) having a total of 23 to 50 carbon atoms based on the total amount of the ester synthetic base oil (A). It is preferable to contain more, more preferably 70 to 100% by mass, and still more preferably 75 to 100% by mass.

  In addition, when the ester-based synthetic base oil (A) contains the polyol ester-based base oil (A1-1) having a total number of carbon atoms of 23 to 50 as the main component as described above, the polyol-based base oil (A) is further used. Among A1), an ester base oil (A1-2) having a total number of carbon atoms in one molecule larger than that of the component (A1-1) or an ester base oil (A3) composed of the above-mentioned copolymer is a subcomponent. May be further included. Here, as the ester base oil (A1-2) having a total carbon number in one molecule larger than the component (A1-1), specifically, a polyol having a total carbon number in a molecule of 51 to 80 is used. Ester base oils (A1-2) are mentioned.

The ester-based synthetic base oil (A) is selected from a polyol ester-based base oil (A1-2) having 51 to 80 carbon atoms in one molecule, and an ester-based base oil (A3) composed of the above-described copolymer. It is preferable that at least one type of ester is contained in a proportion of less than 50% by mass, more preferably 1 to 30% by mass, and still more preferably 3 to 25% by mass based on the total amount of the ester base oil (A). contains.
Since the biodegradable lubricating oil composition contains these components (A1-2) and (A3) as subcomponents, the viscosity can be easily adjusted to an appropriate value without impairing oxidation stability and wear resistance. .

  As the polyol ester base oil (A1-1) having a total of 23 to 50 carbon atoms, one or more kinds are appropriately selected from the ester base oils (A1) exemplified above. Is neopentyl glycol (carbon number 6), pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, araquinic acid, behenic acid , Isomyristic acid, isopalmitic acid, isostearic acid, 2,2-dimethyloctanoic acid, 2-ethyl-2,3,3-trimethylbutanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,5 2,5-Trimethyl-2-t-butylhexanoic acid, 2,3,3-trimethyl-2-ethylbutanoic acid, 2,3-dimethyl-2-isopropyl Esters with saturated aliphatic monocarboxylic acids having 9 to 22 carbon atoms such as rubutanoic acid and 3,5,5-trimethylhexanoic acid; pentaerythritol (carbon number 5) with valeric acid, caproic acid, enanthic acid, caprylic acid (Octanoic acid), pelargonic acid, capric acid (decanoic acid), undecanoic acid, 2,2-dimethylpropanoic acid, 2,2-dimethylbutanoic acid, 2,2-dimethylpentanoic acid, 2,2-dimethyloctanoic acid, 2-ethyl-2,3,3-trimethylbutanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,3,3-trimethyl-2-ethylbutanoic acid, 2,3-dimethyl-2-isopropylbutane Esters with saturated aliphatic monocarboxylic acids having 5 to 11 carbon atoms such as acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid; trimethylolpropane ( A prime number 6), caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, 2,2-dimethylbutanoic acid, 2,2-dimethylpentanoic acid, 2,2 2-dimethyloctanoic acid, 2-ethyl-2,3,3-trimethylbutanoic acid, 2,2,3,4-tetramethylpentanoic acid, 2,5,5-trimethyl-2-t-butylhexanoic acid, Saturated aliphatic having 6 to 14 carbon atoms such as 2,3,3-trimethyl-2-ethylbutanoic acid, 2,3-dimethyl-2-isopropylbutanoic acid, 2-ethylhexanoic acid, and 3,5,5-trimethylhexanoic acid Esters with monocarboxylic acids are mentioned.

As the component (A1-1), among these, esters of pentaerythritol are preferable from the viewpoint of enhancing the oxidation stability.
On the other hand, from the viewpoint that the viscosity can be appropriately adjusted without using the component (A1-2) or the component (A3), an ester of neopentyl glycol is preferable as the component (A1-1). As the carboxylic acid in the ester of neopentyl glycol, a branched carboxylic acid is preferable, and a saturated aliphatic monocarboxylic acid having 16 to 20 carbon atoms is preferable.
Furthermore, among the above-mentioned polyol ester base oils (A1-1), polyol ester base oils having a total carbon number of 37 to 45 in one molecule are preferable.

The polyol ester base oil (A1-2) having a total carbon number of 51 to 80 is appropriately selected from the polyol ester base oil (A1) which is an ester of a polyol and an aliphatic monocarboxylic acid described above. Species or two or more species may be selected, but preferred specific examples are pentaerythritol, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, isomyristic acid, and isopalmitin. Esters with saturated higher aliphatic monocarboxylic acids having 12 to 18 carbon atoms such as acid, isostearic acid, and 2,5,5-trimethyl-2-t-butylhexanoic acid; trimethylolpropane, pentadecanoic acid, palmitic acid, Heptadecanoic acid, stearic acid, nonadecanoic acid, arachiic acid, behenic acid, isopalmitic acid, Esters with saturated higher aliphatic monocarboxylic acids having 15 to 22 carbon atoms, such as sostearic acid, and the like.
Among these, it is preferable to use an ester of trimethylolpropane as the component (A1-2). Further, it is preferable to use an ester of pentaerythritol for the component (A1-1) and an ester of trimethylolpropane for the component (A1-2). By using such a mixed ester, the viscosity characteristics can be appropriately adjusted without impairing the various characteristics of the lubricating oil composition.
The total number of carbon atoms in one molecule of the polyol ester base oil (A1-2) is preferably 51 to 70.

Further, in order to make the transmittance of the polyester synthetic base oil (A) 50% or more, it is sufficient that the ester contains almost no unsaturated bond. For example, as the component (A1), And an ester of a saturated aliphatic monocarboxylic acid. Here, a saturated aliphatic monocarboxylic acid, or an ester obtained from the carboxylic acid, may be appropriately selected from such carboxylic acids or esters, since many are commercially available as products. Some saturated aliphatic monocarboxylic acids or esters contain an unsaturated bond depending on the product, and some of the esters do not have a transmittance of 50% or more. This is because saturated aliphatic monocarboxylic acids are usually produced from animal oils and vegetable oils containing a large amount of unsaturated bonds.
On the other hand, unsaturated bonds contained in animal oils and vegetable oils are generally hydrogenated and saturated during the production process, or are generally separated by purification. Therefore, in the component (A1) of the present embodiment, it is preferable that the saturated aliphatic monocarboxylic acid used as a raw material has a high hydrogenation rate or a high degree of purification and a small number of unsaturated bonds.
Similarly, also in the component (A2) or (A3), it is preferable that the alkyl monoalcohol or the like as a raw material has a high hydrogenation rate or a high degree of purification.

  The base oil of the biodegradable lubricating oil composition may be composed of the above-mentioned ester-based synthetic base oil (A) alone, but as long as the effects of the present invention are not affected. A base oil component other than the base oil (A) may be included. Specifically, polyether base oils such as polyalkylene glycol and polyvinyl ether; mineral oils exemplified by paraffinic mineral oils, naphthenic mineral oils, intermediate mineral oils, etc .; polybutenes, polypropylenes, olefin copolymers and the like At least one selected from synthetic hydrocarbon oils and the like may be included. However, the content of the base oil component other than the ester-based synthetic base oil (A) is more preferably less than 20% by mass based on the total amount of the lubricating oil composition so that the biodegradability can be increased as described later. More preferably, it is less than mass%.

[Antioxidant (B)]
The biodegradable lubricating oil composition of the present embodiment contains both an amine antioxidant (B1) and a phenolic antioxidant (B2) as the antioxidant (B). In the present embodiment, by including these two antioxidants in the above-mentioned specific ester-based synthetic base oil (A), high oxidative stability can be exhibited even if the respective amounts are suppressed to small amounts. It is possible.

Examples of the amine antioxidant (B1) include monoalkyldiphenylamine having an alkyl group having 4 to 12 carbon atoms, such as mono-t-butyldiphenylamine, monooctyldiphenylamine and monononyldiphenylamine; 4,4′-dibutyldiphenylamine; 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine, 4-butyl-4'-octyl Dialkyldiphenylamines having 4 to 12 carbon atoms in each alkyl group such as diphenylamine; tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine, di (2,4-diethylamine) Phenyl) amine, di (2-ethyl-4-nonylphenyl) amine, etc., a polyalkyldiphenylamine having three or more alkyl groups and each alkyl group having 1 to 10 carbon atoms; methylphenyl-α-naphthylamine, ethyl Phenyl-α-naphthylamine, butylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, nonylphenyl-α-naphthylamine, t-dodecylphenyl-α-naphthylamine, etc. And phenyl-α-naphthylamines exemplified by alkylphenyl-α-naphthylamine having at least one alkyl group having 1 to 12 carbon atoms, or phenyl-α-naphthylamine.
Among these, as the amine-based antioxidant (B1), it is preferable to use dialkyldiphenylamine or alkylphenyl-α-naphthylamine, and it is more preferable to use dialkyldiphenylamine.

<Phenolic antioxidant (B2)>
Examples of the phenol-based antioxidant (B2) include a monophenol-based antioxidant and a bisphenol-based antioxidant.
Monophenolic antioxidants include n-octyl-3- (3,5-di-t-butyl4-hydroxyphenyl) propionate and 6-methylheptyl-3- (3,5-di-t-butyl-). Alkyl-3- (3,5-di-tert-butyl-4-hydroxy) such as 4-hydroxyphenyl) propionate and n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate Phenyl) propionate (alkyl groups include those having 4 to 20 carbon atoms, and preferably 8 to 18 carbon atoms); 2,6-di-t-butyl-4-methylphenol, 2,6 2,6-di-t-butyl-4-alkylphenol such as -di-t-butyl-4-ethylphenol (1 to 4 carbon atoms in the alkyl group); 2,4-dimethyl-6-t- Butylphenol, 2,6-di -t- amyl -p- cresol.

Examples of bisphenol antioxidants include 4,4'-methylenebis (2,6-di-t-butylphenol), 4,4'-bis (2,6-di-t-butylphenol), and 4,4'- Bis (2-methyl-6-t-butylphenol), 2,2′-methylenebis (4-ethyl-6-t-butylphenol), 2,2′-methylenebis (4-methyl-6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 4,4'-isopropylidenebis (2,6-di-t-butylphenol), 2,2'-methylenebis (4-methyl-6- Nonylphenol), 2,2'-isobutylidenebis (4,6-dimethylphenol), 2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 4,4'-thiobis (2 Methyl-6-t-butylphenol), 4,4′-thiobis (3-methyl-6-t-butylphenol), 2,2′-thiobis (4-methyl-6-t-butylphenol), bis (3-methyl -4-hydroxy-5-t-butylbenzyl) sulfide, bis (3,5-di-t-butyl-4-hydroxybenzyl) sulfide, thiodiethylenebis [3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate].
As the phenolic antioxidant, among the above, a monophenolic antioxidant is preferable, and among them, alkyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate is more preferable.

Further, as described above, the biodegradable lubricating oil composition contains 0.1 to 3% by mass of the amine-based antioxidant (B1) and 0.1 to 3% by mass of the phenol-based antioxidant (B2) based on the total amount of the composition. -3% by mass. By setting the content of each of these antioxidants (B1) and (B2) to 0.1% by mass or more, it becomes possible to impart high oxidation stability to the biodegradable lubricating oil composition. In addition, by making each content 3% by mass or less, an effect commensurate with the content is exhibited, and the biodegradability of the biodegradable lubricating oil composition is reduced due to the antioxidant (B). To prevent In particular, the amine-based antioxidant (B1) tends to decrease the biodegradability of the lubricating oil composition, but in the present embodiment, the amine-based antioxidant (B1) is used in combination with the specific ester-based synthetic base oil (A) described above. This makes it possible to sufficiently improve the oxidation stability even with a small amount of the amine-based antioxidant (B1). Therefore, in the present embodiment, it is possible to minimize the decrease in the biodegradation rate.
Further, in order to further increase the oxidation stability while preventing the biodegradation rate from decreasing, the content of the amine-based antioxidant (B1) is preferably 0.2 to 2.5% by mass, and 0.1 to 2.5% by mass. 3 to 1.8% by mass is more preferable. From the same viewpoint, the content of the phenolic antioxidant (B2) is preferably from 0.2 to 2.5% by mass, more preferably from 0.3 to 1.5% by mass.

[Sulfur-phosphorus extreme pressure agent (C)]
The biodegradable lubricating oil composition of the present embodiment further contains a sulfur-phosphorus extreme pressure agent (C). When the above-mentioned ester-based synthetic base oil (A) is used, even if an extreme pressure agent is added to the composition, the extreme pressure performance may not be exhibited. By using the sulfur-phosphorus extreme pressure agent (C), the extreme pressure performance can be sufficiently exhibited and the wear resistance of the lubricating oil composition can be improved.
Examples of the sulfur-phosphorus extreme pressure agent (C) include: monothiophosphate, dithiophosphate, trithiophosphate, amine base of monothiophosphate, amine salt of dithiophosphate, monothiophosphite, dithiophosphite. Phosphoric acid esters, trithiophosphorous acid esters and the like are mentioned, and among these, dithiophosphoric acid esters are preferable.
In addition, from the viewpoint of improving abrasion resistance, among the dithiophosphates, a dithiophosphate having a carboxyl group at a terminal is preferable. Since the sulfur-phosphorus extreme pressure agent (C) has a carboxyl group at the terminal and thus has a high polarity, even in the present embodiment using the above specific ester synthetic base oil (A) as a base oil, It becomes easy to exhibit the function as an extreme pressure agent.

Specific examples of the dithiophosphate having a carboxyl group at the terminal include a compound represented by the following general formula (II).
In the formula (II), R ³ represents a linear or branched alkylene group having 1 to 8 carbon atoms, and R ⁴ and R ⁵ each independently represent a hydrocarbon group having 3 to 20 carbon atoms.

In the formula (II), R ³ is preferably a linear or branched alkylene group having 1 to 8 carbon atoms from the viewpoint of improving the solubility in the base oil, and is preferably a linear or branched alkylene group having 2 carbon atoms. It is more preferably an alkylene group of from 4 to 4, more preferably a branched alkylene group. _{Specifically, -CH 2 CH 2 -, -} CH 2 CH (CH 3) -, - CH 2 CH (CH 2 CH 3) -, CH 2 CH (CH 3) CH 2 -, and -CH ₂ CH _{(CH 2 CH 2 CH 3)} - , and the like _{preferably, -CH 2 CH (CH 3)} -, - CH 2 CH (CH 3) CH 2 - , more _{preferably, -CH 2 CH (CH 3)} - is More preferred.

Further, each of R ⁴ and R ⁵ is preferably a straight-chain or branched alkyl group having 3 to 8 carbon atoms from the viewpoint of improving solubility in base oil while improving the extreme pressure performance. Alternatively, a branched alkyl group having 4 to 6 carbon atoms is more preferable. Specifically, it is selected from the group consisting of propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, isopentyl, hexyl, 2-ethylbutyl, 1-methylpentyl, 1,3-dimethylbutyl and 2-ethylhexyl. Preferably, isobutyl and t-butyl are more preferred.

The biodegradable lubricating oil composition contains 0.01 to 2% by mass of the sulfur-phosphorus extreme pressure agent (C) as described above, based on the total amount of the composition. When the content of the sulfur-phosphorus extreme pressure agent (C) is 0.01% by mass or more, extreme lubricity can be imparted to the lubricating oil composition and the wear resistance can be improved. Further, when the content is 2% by mass or less, an effect commensurate with the content is exhibited, and the biodegradability and oxidation stability of the biodegradable lubricating oil composition are caused by the sulfur-phosphorus extreme pressure agent (C). To prevent the deterioration of performance.
Further, in order to further increase the abrasion resistance while preventing the biodegradation rate and the oxidation stability from lowering, the content of the sulfur-phosphorus extreme pressure agent (C) is 0.02 to 1% by mass. Is preferable, and 0.03 to 0.5% by mass is more preferable.

[Viscosity index improver]
The biodegradable lubricating oil composition in this embodiment may contain a viscosity index improver.
Examples of the viscosity index improver include polymethacrylate, dispersion-type polymethacrylate, olefin-based copolymer (for example, ethylene-propylene copolymer, etc.), dispersion-type olefin-based copolymer, and styrene-based copolymer (for example, styrene- Diene copolymer, styrene-isoprene copolymer, etc.), among which polymethacrylate is preferred. The polymethacrylate used as a viscosity index improver generally has a weight average molecular weight of 10,000 to 70,000, preferably 20,000 to 55,000. The weight average molecular weight is a value measured by gel permeation chromatography and determined from a calibration curve prepared using polystyrene.
The content of the viscosity index improver is preferably from 0.1 to 10% by mass, more preferably from 0.5 to 5% by mass, based on the total amount of the lubricating oil composition.

[Triazole compound]
The biodegradable lubricating oil composition of the present embodiment may further contain a triazole compound. The triazole-based compound acts as a metal deactivator and imparts an anticorrosive effect to non-ferrous metals and the like to the biodegradable lubricating oil composition. Specific examples of the triazole compound include benzotriazole, carboxybenzotriazole, 3-aminotriazole, 4-aminotriazole, 2,5-diaminotriazole, 3-mercaptotriazole, N-diethylaminomethyl-1,2,3-benzo. Examples thereof include N-dialkyl (C3 to C12) aminomethyl-1,2,3-benzotriazole such as triazole, and a compound having a benzotriazole skeleton (benzotriazole-based compound) is preferable.
The content of the triazole compound is preferably from 0.01 to 1% by mass, more preferably from 0.02 to 0.5% by mass, based on the total amount of the lubricating oil composition.

[anti-rust]
The biodegradable lubricating oil composition may contain at least one selected from alkaline earth metal sulfonates and succinates as a rust inhibitor. When the biodegradable lubricating oil composition contains a rust inhibitor, it becomes possible to enhance the anticorrosion effect on metals such as iron.
The alkaline earth metal sulfonate is obtained by sulfonating an alkyl aromatic compound and converting it into an alkaline earth metal salt, and includes calcium sulfonate, magnesium sulfonate, and barium sulfonate. Of these, calcium sulfonate is preferable. In addition, the alkaline earth metal sulfonate is desirably low basic, and specifically, the total base number (TBN) is preferably from 0 to 100 mgKOH / g, more preferably from 0 to 50 mgKOH / g. In addition, the total base number is measured by JIS K-2501: perchloric acid method. In addition, by using the alkaline earth metal sulfonate, it is also possible to exert a cleaning and dispersing action.
In addition, examples of the alkenyl succinate include half esters of alkenyl succinic acid and an alcohol such as a polyhydric alcohol.
As the rust inhibitor, one kind may be used alone, or two or more kinds may be used in combination. The content of the rust inhibitor is preferably in the range of 0.01 to 1.0% by mass, more preferably 0.03 to 0.5% by mass, based on the total amount of the lubricating oil composition.

(Other additives)
The biodegradable lubricating oil composition may contain an extreme pressure agent other than the sulfur-phosphorus extreme pressure agent (C). Specific examples include phosphoric acid esters such as tricresyl phosphate (TCP), amine salts of acidic phosphoric acid esters, and phosphorus-based extreme pressure agents such as phosphites. The content of the phosphorus-based extreme pressure agent is preferably from 0.1 to 2% by mass, more preferably from 0.2 to 1.5% by mass, based on the total amount of the lubricating oil composition.

In addition, the biodegradable lubricating oil composition may contain additives other than those described above, such as an ashless dispersant, a pour point depressant, an antifoaming agent, a surfactant, and a demulsifier.
Examples of the ashless dispersant include succinimide, boron-containing succinimide, benzylamines, and boron-containing benzylamines.
Examples of the pour point depressant include ethylene-vinyl acetate copolymer, condensate of chlorinated paraffin and naphthalene, condensate of chlorinated paraffin and phenol, polymethacrylate, polyalkylstyrene and the like. The defoaming agent may be a silicone-based defoaming agent or a non-silicone-based defoaming agent.

[Properties of biodegradable lubricating oil composition]
The biodegradable lubricating oil composition of the present embodiment preferably has a biodegradation rate of 60% or more, and more preferably 70% or more, in a test for degrading a chemical substance by a microorganism according to the OECD Test Guideline 301B. preferable. In the present embodiment, a specific ester-based synthetic base oil (A) is used as a main component, and various additives such as an antioxidant (B1) (B2) and a sulfur-phosphorus-based extreme pressure agent (C) are used. The biodegradation rate can be increased by reducing the amount used to a certain amount or less.

Moreover, kinematic viscosity at 40 ° C. biodegradable lubricating oil composition is preferably 10 to 150 mm ² / s, more preferably 15~100mm ² / s. Further, the viscosity index is preferably 130 or more, and more preferably 135 or more. Since the biodegradable lubricating oil composition has the above kinematic viscosity and viscosity index, it can be appropriately used as a lubricating oil in various uses described below.

  The biodegradable lubricating oil composition according to the present embodiment is, for example, a hydraulic fluid that is a power transmission fluid used for power transmission, force control, buffering, and the like in a hydraulic system; an agricultural tractor, or a construction or civil engineering machine tool. Lubricating oil or universal oil for transmissions; oil for chainsaws; two-stroke engine oil; and industrial gear oil for wind power generation and the like. Among these, it is more preferable to use as hydraulic oil.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.
The various properties and the evaluation of the lubricating oil composition were determined according to the following procedures.

(1) Kinematic viscosity (40 ° C, 100 ° C)
It measured according to JISK2283.
(2) Viscosity index Measured according to JISK2283.
(3) Acid value Measured by the indicator method according to JISK2501.
(4) Infrared absorption analysis Using an infrared spectrometer (manufactured by JASCO Corporation, trade name: FT-IR6200), the lubricating oil composition was placed between potassium bromide cells through a spacer having a thickness of 0.1 mm. the liquid film 0.1mm by placing the transmittance degradation ^{4 cm -1} in 4000 to 400 ^-1, was measured in cumulative frequency 16 times, read the transmittance at 3005 ± ^{1 cm -1,} the transmission of the lubricating oil composition The rate was measured.
Further, instead of the lubricating oil composition, an ester-based synthetic base oil was inserted between cells, and the transmittance of each ester-based synthetic base oil was measured by the same measurement method.
(5) Shell abrasion test Using a shell abrasion tester, the test conditions were set to a load of 294 N, a rotation speed of 1200 rpm, a temperature of 50 ° C. and a test time of 30 minutes in accordance with ASTM D2783, and a lubricating oil composition was used. Was evaluated for load-bearing performance. The results were expressed as wear marks (mm) on the test hard balls.
In this test, if the wear mark is 0.5 mm or less, it is evaluated as "A" as having good wear resistance, and if it exceeds 0.5 mm, it is considered as "B" because the wear resistance is insufficient. evaluated.
(6) RBOT test Based on the rotating cylinder type oxidation stability test of JIS K 2514-3, the test was performed at a test temperature of 150 ° C and a pressure of 620 kPa, and the time until the pressure decreased from the maximum pressure to 175 kPa was measured.
In this test, if the RBOT value is 250 minutes or more, for example, the oxidation stability is evaluated as “A” even if used as a compressed hydraulic oil, and the oxidation stability is evaluated as less than 250 minutes. It was evaluated as “B” as sufficient.
(7) ISOT test According to JIS K 2514-1, a copper / iron catalyst is present in a sample oil to degrade the sample oil at a test temperature of 130 ° C. and a test time of 168 hours, and the kinematic viscosity of the degraded oil at 40 ° C. Divided by the kinematic viscosity of the undegraded oil at 40 ° C. was calculated as a viscosity ratio. Further, a value obtained by subtracting the acid value of the degraded oil from the acid value of the undegraded oil was calculated as an acid value increase.

Examples 1-4, Comparative Examples 1-6
The biodegradable lubricating oil compositions were adjusted according to the formulations shown in Table 1, and various properties of each composition were measured, and an evaluation test was performed. Table 1 shows the results.
* Each numerical value in the column of base oil and additives indicates mass% based on the total amount of the lubricating oil composition.

In addition, each component in Table 1 is as follows.
(Base oil)
PE saturated fatty acid ester: Complete ester of pentaerythritol and a mixture of octanoic acid and decanoic acid (transmittance at 3005 ± 1 cm ⁻¹ : 65%)
NPG saturated fatty acid ester: complete ester of neopentyl glycol and isostearic acid (transmittance at 3005 ± 1 cm ⁻¹ : 70%)
TMP saturated higher fatty acid ester: complete ester of trimethylolpropane and isostearic acid (transmittance at 3005 ± 1 cm ⁻¹ : 65%)
Copolymer of unsaturated dibasic acid ester and α-olefin: copolymer of butanol ester of maleic acid and α-olefin having 6 to 18 carbon atoms (100 ° C. kinematic viscosity: 35 mm ² / s, 3005 ± 1 cm ⁻ (Transmissivity at ¹ : 65%)
TMP unsaturated fatty acid ester: complete ester of trimethylolpropane and oleic acid (transmittance at 3005 ± 1 cm ⁻¹ : 38%)
TMP saturated / unsaturated fatty acid ester: complete ester of a mixture of trimethylolpropane, isostearic acid and oleic acid (transmittance at 3005 ± 1 cm ⁻¹ : 45%)
TMP saturated lower fatty acid ester: Complete ester of a mixture of trimethylolpropane, caprylic acid and capric acid (transmittance at 3005 ± 1 cm ⁻¹ : 65%)

(Additive)
Amine antioxidant (B1): 4-butyl-4′-octyldiphenylaminephenol antioxidant (B2): n-octyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate Sulfur-phosphorus extreme pressure agent (C): a compound represented by the following chemical formula
PMA (1): polymethacrylate (weight average molecular weight: 180,000)
PMA (2): polymethacrylate (weight average molecular weight: 45000)
Benzotriazole compound: 1,2,3-benzotriazole rust inhibitor (1): low basic calcium sulfonate (total base number 28 mgKOH / g)
Rust inhibitor (2): alkenyl succinic acid polyhydric alcohol half ester
Phosphorus extreme pressure agent (1): tricresyl phosphate (TCP)
Phosphorus extreme pressure agent (2): Oleyl acid phosphate defoamer: Silicone defoamer

As described above, in Examples 1 to 4, the ester synthetic base oil (A) having a high transmittance was used so that the transmittance of the lubricating oil composition at 3005 ± 1 cm ⁻¹ was 50% or more. , An amine-based antioxidant (B1), a phenol-based antioxidant (B2), and a sulfur-phosphorus-based extreme pressure agent (C) are contained in predetermined amounts. Increase in viscosity and increase in acid value were suppressed, and oxidation stability could be improved under various environments. Furthermore, the amount of wear in the shell wear test was small, and the wear resistance was also good.
In contrast, in Comparative Examples 1 to 3, since the transmittance of the lubricating oil composition was less than 50%, an increase in the viscosity and an increase in the acid value in the ISOT test were observed, and the oxidation stability was not sufficiently improved. This tendency was the same when both the amine-based antioxidant (B1) and the phenol-based antioxidant (B2) were contained as in Comparative Examples 4 and 5. Further, in Comparative Example 6, although the oxidation stability was improved, the abrasion resistance could not be improved because the sulfur-phosphorus extreme pressure agent (C) was not contained.

Claims (9)

Ester-based synthetic base oil (A) 50% by mass or more, amine-based antioxidant (B1) 0.1 to 3% by mass, phenol-based antioxidant (B2) 0.1 to 3% by mass, sulfur- A phosphorus-based extreme pressure agent (C) in an amount of 0.03 to 0.5 % by mass,
In an infrared absorption analysis of a liquid film of 0.1 mm, the transmittance at 3005 ± 1 cm ⁻¹ is 50% or more;
The ester synthetic base oil (A) is a polyol ester base oil (A1), which is an ester of a polyol and an aliphatic monocarboxylic acid, based on the total amount of the ester synthetic base oil (A), A polyol ester base oil (A1) containing more than 50% by mass of a polyol ester base oil (A1-1) having a total carbon number in the molecule of 23 to 50 and being an ester of a polyol and an aliphatic monocarboxylic acid. Wherein the total number of carbon atoms in one molecule is from 51 to 80, selected from polyol ester base oils (A1-2), and copolymers of unsaturated dibasic acid esters and α-olefins (A3). Less than 50% by weight of at least one base oil,
It said sulfur - Ri dithiophosphates der phosphorus extreme pressure agent (C) has a carboxyl group at the end,
A biodegradable lubricating oil composition for hydraulic fluids, which does not contain an amine salt of an acidic phosphate ester .   A hindered polyol in which the polyol ester base oil (A1) has one or more quaternary carbons in the molecule, and has at least one methylol group bonded to at least one of the quaternary carbons; The biodegradable lubricating oil composition according to claim 1, which is an ester with an aliphatic monocarboxylic acid.   The polyol ester base oil (A1-1) is an ester of neopentyl glycol and a saturated aliphatic monocarboxylic acid having 9 to 22 carbon atoms, and pentaerythritol and a saturated aliphatic monocarboxylic acid having 5 to 11 carbon atoms. The biodegradable lubricating oil composition according to claim 1, which is at least one base oil selected from the group consisting of:   The biodegradable according to any one of claims 1 to 3, wherein the polyol ester base oil (A1-2) is an ester of trimethylolpropane and a saturated higher aliphatic monocarboxylic acid having 15 to 22 carbon atoms. Lubricating oil composition.   The biodegradable lubricating oil composition according to any one of claims 1 to 4, wherein the amine antioxidant (B1) is a dialkyldiphenylamine.   The biodegradable product according to any one of claims 1 to 5, wherein the phenolic antioxidant (B2) is an alkyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate. Lubricating oil composition.   The biodegradable lubricating oil composition according to any one of claims 1 to 6, further comprising 0.1 to 10% by mass of a viscosity index improver.   The biodegradable lubricating oil composition according to any one of claims 1 to 7, further comprising 0.01 to 1% by mass of a triazole compound.   The biodegradable lubricating oil composition according to any one of claims 1 to 8, wherein a biodegradation rate is 60% or more in a test for degrading a chemical substance by a microorganism according to the OECD Test Guideline 301B.