Lubricant composition

Abstract

To provide a lubricant composition capable of suppressing oxidation degradation at a high level.SOLUTION: A lubricant composition comprises a lubricant base oil and an antioxidant consisting of a zinc porphyrin complex represented by the following general formula (1). In the formula (1), R1 to R12 each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 7 to 25 carbon atoms which may have a substituent.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a lubricating oil composition.

Background Art

[0002] Conventionally, in various mechanical devices having moving parts, lubricating oil compositions have been used from the viewpoints of reducing friction and wear of the members constituting the moving parts and improving the energy saving performance and lifespan of the devices. In such lubricating oil compositions, since the essential lubricating base oil deteriorates by oxidation when it comes into contact with air, in order to suppress such oxidation deterioration, it is common to use a combination of a lubricating base oil and an antioxidant.

[0003] As such antioxidants, generally, phenolic antioxidants and amine antioxidants are used (for example, in Japanese Patent Application Laid-Open No. 2023-049434 (Patent Document 1), in paragraph

[0042] , amine antioxidants and phenolic antioxidants are exemplified as antioxidants to be blended in a lubricating oil composition, and in the column of Examples, a demonstration example using a phenolic antioxidant is disclosed).

[0004] In the field of such lubricating oil compositions, from the viewpoint of designing an appropriate composition according to the use and the like, the emergence of a new composition having antioxidant performance equivalent to or higher than that of the conventional composition while using a component different from the components conventionally used as antioxidants is desired.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the problems of the prior art, and an object thereof is to provide a lubricating oil composition capable of suppressing oxidative degradation at a high level while using a component different from the components conventionally used as antioxidants. [Means for Solving the Problems]

[0007] As a result of intensive studies to achieve the above object, the present inventors have found that by making the lubricating oil composition contain a lubricating base oil and a zinc porphyrin complex represented by the following general formula (1), it is possible to suppress oxidative degradation of the composition at a high level, and thus have completed the present invention.

[0008] That is, the present invention provides the following aspects.

[0009] [1] A lubricating oil composition containing a lubricating base oil and an antioxidant comprising a zinc porphyrin complex represented by the following general formula (1):

[0010] [Chemical Formula]

[0011] (In formula (1), R 1 ~R 12 each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 7 to 25 carbon atoms which may have a substituent.) and .

[0012] [2] A lubricating oil composition containing a lubricating base oil and a compound represented by the following general formula (2):

[0013] [Chemical Formula]

[0014] (In formula (2), R1 ~R 12 each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 7 to 25 carbon atoms which may have a substituent.) an antioxidant comprising a reaction product of a porphyrin compound represented by the formula: and a zinc salt, A lubricating oil composition containing the same.

[0015] Hereinafter, for the sake of convenience, the lubricating oil composition of the present invention described in [1] may be referred to as "the first lubricating oil composition of the present invention" or "the first lubricating oil composition" as the case may be, and the lubricating oil composition of the present invention described in [2] may be referred to as "the second lubricating oil composition of the present invention" or simply "the second lubricating oil composition" as the case may be.

[0016] Although the reason why the above object is achieved by the first and second lubricating oil compositions of the present invention is not necessarily clear, the present inventors presume as follows.

[0017] In the present invention, in order to prevent oxidative deterioration of the lubricating base oil, the zinc porphyrin complex represented by the general formula (1) or the reaction product of the porphyrin compound represented by the general formula (2) (hereinafter, for the sake of convenience, may be simply referred to as "porphyrin-H2") and a zinc salt is used in combination with the lubricating base oil. Here, the reaction product, which is a component in the second lubricating oil composition of the present invention (the lubricating oil composition of the present invention described in [2]), will be briefly described. The reaction product is obtained by mixing and reacting the porphyrin-H2 and the zinc salt, and as a result, such a reaction product becomes the zinc porphyrin complex represented by the general formula (1). Therefore, the reaction product is, as a result, equivalent to the zinc porphyrin complex represented by the general formula (1). Therefore, hereinafter, the reason why the zinc porphyrin complex provides an effect will be considered.

[0018] Generally, in a lubricating oil composition, the oxidation reaction that causes deterioration of the lubricating base oil is considered to be caused as follows. That is, first, when external stimuli such as light and heat are applied to the lubricating oil composition, radicals of the components constituting the base oil (lubricating base oil) in the lubricating oil composition are generated. When an oxygen molecule contacts the radical thus generated, the oxygen molecule is added to the radical to generate a peroxy radical. Next, when the generated peroxy radical attacks the components of the still unreacted base oil, a hydroperoxide and a radical of the attacked base oil component are generated thereby. In this way, the radical propagation reaction occurs continuously. It should be noted that such a radical propagation reaction stops when oxygen-containing compounds such as alcohol, ketone, and carboxylic acid are generated during the reaction, but in other cases, it is basically caused continuously (in a chain). And due to the radical propagation reaction (negative chain reaction) thus caused, the oxidation deterioration reaction of the lubricating base oil proceeds. In order to suppress such an oxidation reaction (deterioration reaction), that is, in order to exert the action of decomposing one or more oxidation active species by itself or intermolecularly, in the present invention, the zinc porphyrin complex is used as an antioxidant.

[0019] Here, a general porphyrin complex will be described. The porphyrin complex is a compound that has been known for a long time, and various complexes using various metal cations are known as such compounds. Such a porphyrin complex has a stable planar four-coordinate structure (xy plane) in which the central metal is surrounded by the porphyrin moiety, and has sites where bonding and coordination with the central metal can occur in a direction perpendicular to the plane (±z-axis direction). In addition, due to its structure, the site in the plus z-axis direction and the site in the minus z-axis direction in the complex cannot form two or more bonds (including two or more coordination bonds), respectively, and the coordination sites adjacent thereto, that is, the xy plane, are blocked by porphyrin. Therefore, the site in the plus z-axis direction and the site in the minus z-axis direction can only carry out a reaction that forms one bond (including a coordination bond in such a bond), and usually cannot form two or more bonds. Thus, the porphyrin complex is considered to be very stable based on its structural characteristics.

[0020] Next, a general zinc complex will be described. Conventionally, a zinc-bipyridyl complex, which is a type of zinc complex, is known to be capable of efficiently causing a reaction in which superoxide, which is an oxidative active species, disproportionates into oxygen molecules and peroxide, which has lower oxidative activity than superoxide (see, for example, Angew. Chem. Int. Engl., “Superoxide disproportionation driven by zinc complexes with various steric and electrostatic properties”, 2013, vol. 52, P. 12293 - P. 12297 (Reference 1)). However, Reference 1 does not describe zinc-porphyrin complexes at all, and there has been no particular report on the reaction of zinc-porphyrin complexes with oxidative active species. Thus, although it has been conventionally known to use zinc-bipyridyl complexes to cause a disproportionation decomposition reaction of superoxide, which is an oxidative active species, there has been no report on using zinc porphyrin complexes to suppress the oxidative degradation of lubricating oil compositions.

[0021] Under such circumstances, as a result of intensive research, the present inventors have found that by using the zinc porphyrin complex as an antioxidant, it is possible to highly suppress the above-described oxidation reaction (degradation reaction). Thus, although the reason why it becomes possible to highly suppress the oxidation reaction (degradation reaction) by using the zinc porphyrin complex is not necessarily clear, the present inventors speculate that it may be because the structure of the complex itself becomes very stable by using zinc as the central metal of the porphyrin complex, and it becomes possible to efficiently utilize the properties of zinc that decomposes oxidative active species. That is, the present inventors speculate that the zinc porphyrin complex can more efficiently utilize the properties of zinc that decomposes oxidative active species, thereby making it possible to efficiently cause a decomposition reaction of peroxyl radicals and the like, and suppress the oxidative degradation of the lubricating oil composition at a high level.

Advantages of the Invention

[0022] According to the present invention, it is possible to provide a lubricating oil composition capable of suppressing oxidative degradation at a high level while using a component different from the components conventionally used as antioxidants.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, the present invention will be described in detail according to its preferred embodiments. In this specification, unless otherwise specified, the notation "X to Y" for numerical values X and Y means "X or more and Y or less". When a unit is attached only to the numerical value Y in such notation, the unit shall also be applied to the numerical value X.

[0024] 〔First Lubricating Oil Composition〕 The first lubricating oil composition of the present invention is a lubricating base oil, and the following general formula (1):

[0025]

Chemical formula

[0026] (In formula (1), R 1 ~R 12 each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 7 to 25 carbon atoms which may have a substituent.) an antioxidant composed of a zinc porphyrin complex represented by the formula, and It is characterized by containing. Thus, the lubricating oil composition of the present invention contains a lubricating base oil and an antioxidant composed of the formamide compound.

[0027] 〈Antioxidant〉 The antioxidant according to the present invention may be composed of a zinc porphyrin complex represented by the general formula (1). R 1 ~R 12is independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 7 to 25 carbon atoms which may have a substituent, and is one kind thereof.

[0028] Such R 1 ~R 12 The alkyl group that can be selected as such has 1 to 18 carbon atoms. By setting the number of carbon atoms of such an alkyl group to be equal to or less than the above upper limit, it is possible to obtain an excellent balance between solubility in the base oil and antioxidant effect. In addition, by appropriately selecting the number of carbon atoms of such an alkyl group within the range of being equal to or less than the above upper limit, the solubility in the base oil can be easily adjusted according to the type of the base oil, and thereby the solubility in the base oil can be easily maintained at a high level.

[0029] Also, such R 1 ~R 12 The alkyl group having 1 to 18 carbon atoms that can be selected as such is not particularly limited. For example, linear alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, decyl group, dodecyl group, hexadecyl group, octadecyl group; branched-chain alkyl groups such as isopropyl group, isobutyl group, tertiary butyl group, isohexyl group, 2-ethylhexyl group; cyclic alkyl groups having a ring structure as the main structure such as cyclopentyl group, cyclohexyl group; can be mentioned as preferred ones. Among them, from the viewpoint of easy availability of raw materials, linear alkyl groups are preferred.

[0030] Such R 1 ~R 12The aryl group which may have a substituent and can be selected as such has 6 to 24 carbon atoms. By appropriately selecting the number of carbon atoms of such an aryl group within the range not exceeding the above upper limit, according to the type of base oil, the solubility in the base oil can be easily adjusted, and thereby it becomes possible to easily maintain the solubility in the base oil at a high level. Such an aryl group having 6 to 24 carbon atoms which may have a substituent is not particularly limited, but for example, a phenyl group, a tolyl group, a naphthyl group, a xylyl group, etc. can be mentioned as preferable ones. Further, when such an aryl group has a substituent, such a substituent is preferably an alkyl group having 1 to 18 carbon atoms. Furthermore, among such aryl groups having 6 to 24 carbon atoms which may have a substituent, in particular, a phenyl group or a phenyl group having a substituent is preferable, and a phenyl group, a toluyl group (tolyl group), or a xylyl group is particularly preferable. In addition, when the aryl group is a toluyl group or a xylyl group, the substitution position of the methyl group is arbitrary. Also, in such an aryl group having 6 to 24 carbon atoms which may have a substituent, according to the solubility in the base oil to be used (desired solubility), the type of the substituent of the aryl group, the position where the substituent substitutes, etc. may be appropriately changed.

[0031] Also, such R 1 ~R 12 The aralkyl group which may have a substituent and can be selected as such has 7 to 25 carbon atoms. By appropriately selecting the number of carbon atoms of such an aralkyl group within the range not exceeding the above upper limit, according to the type of base oil, the solubility in the base oil can be adjusted, and thereby it becomes possible to easily maintain the solubility in the base oil at a high level. Also, such an aralkyl group having 7 to 25 carbon atoms which may have a substituent is not particularly limited, but for example, aralkyl groups such as a benzyl group, a phenethyl group, a phenylpropyl group, etc. can be mentioned as preferable ones. When such an aralkyl group has a substituent, such a substituent is preferably an alkyl group having 1 to 18 carbon atoms.

[0032] Incidentally, such R 1 ~R 12 As the group selected, from the viewpoints of the availability of the raw material compound in the production of the porphyrin-based compound described later and the solubility of the finally obtained zinc porphyrin complex in the base oil (the base oil to be combined), etc., it may be appropriately selected from a hydrogen atom, the alkyl group, the aryl group, and the aralkyl group.

[0033] Such a zinc porphyrin complex can be produced, for example, by reacting a porphyrin-based compound (porphyrin-H2) represented by the following general formula (2):

[0034]

Chemical formula

[0035] (In formula (2), R 1 ~R 12 each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 6 to 25 carbon atoms which may have a substituent.) It may also be produced by a method of obtaining a zinc porphyrin complex as a reaction product by reacting a porphyrin-based compound (porphyrin-H2) represented by with a zinc salt.

[0036] In addition, as a method for preparing the porphyrin-H2, it is not particularly limited, and known methods can be appropriately adopted. For example, the following formula:

[0037]

Chemical formula

[0038] A synthesis method using a dehydration condensation reaction (a dehydration condensation reaction of a compound represented by the general formula (A) (for example, pyrrole) and an aldehyde represented by the general formula (B)) as represented may be adopted. Here, R 1 in formula (2), R 2 、R 4 、R5 , R 7 , R 8 , R 10 , and, R 11 is a group derived from the groups R and R' possessed by the compound represented by the general formula (A), and R in formula (2) 3 , R 6 , R 9 , and, R 12 are all groups derived from the group R'' possessed by the aldehyde represented by the general formula (B). Therefore, R, R', and R'' are each independently a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 6 to 25 carbon atoms which may have a substituent, and are each selected from the group consisting of one kind (these groups are synonymous with those described as the groups selected as R 1 to R 12 ).

[0039] Regarding the compound represented by such a general formula (A), from the viewpoint of availability, R and R' in the formula are each independently preferably a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, more preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, or an isopropyl group, still more preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably, both R and R' are hydrogen atoms (when both R and R' are hydrogen atoms, the compound represented by the general formula (A) becomes pyrrole). Such a compound represented by the general formula (A) may be used alone or in combination of two or more kinds.

[0040] Also, regarding the aldehyde represented by the general formula (B), R'' in the formula is preferably an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, or an aralkyl group having 6 to 25 carbon atoms which may have a substituent. For example, it may be a phenyl group, a tolyl group, a naphthyl group, a xylyl group, a benzyl group, a phenethyl group, a phenylpropyl group, etc. From the viewpoint of improving solubility, such R'' is preferably an aryl group having 6 to 18 carbon atoms which may have a substituent, and more preferably a phenyl group or a phenyl group having a substituent. That is, as the aldehyde represented by the general formula (B), benzaldehyde or a substituted benzaldehyde is more preferable. Among them, benzaldehyde and a substituted benzaldehyde in which an alkyl group is substituted at the para position (however, the total number of carbon atoms of the phenyl group and the alkyl group substituted at the para position needs to be 7 to 24) are more preferable, and benzaldehyde and 4-methylbenzaldehyde are particularly preferable. Such a compound represented by the general formula (A) may be used alone or in combination of two or more.

[0041] In addition, when porphyrin-H2 is synthesized by adopting the above synthesis method, R in the formula (2) 3 , R 6 , R 9 , and R 12 are all groups derived from the group R'' possessed by the aldehyde represented by the general formula (B). Therefore, similar to the group R'' possessed by the aldehyde represented by the general formula (B), R in the formulas (1) and (2) 3 , R 6 , R 9 , and R 12 are each independently preferably an aryl group having 6 to 24 (more preferably 6 to 18) carbon atoms which may have a substituent, more preferably a phenyl group or a substituted phenyl group, and even more preferably a phenyl group, a tolyl group, or a xylyl group.

[0042] In addition, when synthesizing porphyrin-H2 by adopting the said synthesis method, R in the said formula (2) 1 , R 2 , R 4 , R 5 , R 7 , R 8 , R 10 , and R 11 are groups derived from the groups R and R' possessed by the compound represented by the said general formula (A). Therefore, similar to R and R' in formula (A), R 1 , R 2 , R 4 , R 5 , R 7 , R 8 , R 10 , and R 11 are each independently preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tertiary butyl group, a pentyl group, an isopentyl group, a neopentyl group, a hexyl group, an isohexyl group, an octyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, or an octadecyl group, more preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, or an isopropyl group, still more preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably all of them being hydrogen atoms.

[0043] In addition, when synthesizing porphyrin-H2, from the viewpoint of efficiently advancing the said dehydration condensation reaction, it is preferable to use an acid catalyst such as a carboxylic acid or a sulfonic acid.

[0044] In addition, the zinc salt to be reacted with porphyrin-H2 to produce the zinc porphyrin complex is not particularly limited. For example, zinc fluoride, zinc chloride, zinc bromide, zinc iodide, zinc nitrate, zinc sulfate, zinc oxide, zinc sulfide, zinc phosphate, zinc acetate, zinc propionate, zinc butyrate, zinc hexanoate, zinc adipate, zinc octanoate, zinc 2-ethylhexanoate, zinc benzoate, zinc cyclohexanoate, zinc naphthenate, etc. can be mentioned. From the viewpoint of easy availability, zinc chloride, zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate are preferable as such zinc salts. Among them, zinc acetate, zinc 2-ethylhexanoate, and zinc naphthenate are more preferable from the viewpoint that they have higher solubility in lubricating base oils.

[0045] In addition, the reaction conditions (various conditions such as reaction temperature) adopted when reacting porphyrin-H2 with a zinc salt to synthesize a porphyrin complex are not particularly limited. They may be appropriately set according to the types of porphyrin-H2 and zinc salt used so that they react, and conditions similar to the known conditions used when producing conventional porphyrin complexes (complexes with metal cations) may be appropriately adopted. Further, when reacting porphyrin-H2 with a zinc salt to synthesize a porphyrin complex as the reaction product, it is preferable to contact porphyrin-H2 with the zinc salt under basic conditions. Such basic conditions are not particularly limited either, and conditions similar to those used when producing conventional porphyrin complexes (complexes with metal cations) can be appropriately adopted.

[0046] In addition, as the zinc porphyrin complex according to the present invention, in addition to those produced as described above, commercially available products may also be used.

[0047] In addition, the antioxidant according to the present invention only needs to contain the above porphyrin complex, and within the range not impairing the effects of the present invention, together with the porphyrin complex, known antioxidants (for example, antioxidants described in JP-A-2022-158124 (aromatic amine-based antioxidants, hindered amine-based antioxidants, phenolic antioxidants, etc.)) etc.) may be used in combination. Note that it is more preferable that the antioxidant according to the present invention consists only of the above porphyrin complex.

[0048] 〈Lubricating oil base oil〉 The lubricating oil base oil is not particularly limited, and base oils known in the field of lubricating oil compositions can be appropriately used. For example, mineral oil-based base oils, synthetic base oils, or their mixed base oils can be used.

[0049] Examples of the mineral oil-based base oil include paraffinic mineral oils, normal paraffin-based base oils, isoparaffin-based base oils, and naphthenic base oils obtained by purifying a lubricating oil fraction obtained by subjecting crude oil to atmospheric distillation and / or vacuum distillation by one or a combination of two or more selected from purification treatments such as solvent deasphalting, solvent extraction, hydrocracking, hydroisomerization, solvent dewaxing, catalytic dewaxing, solvent refining, hydrorefining, chemical washing, and clay treatment; and mixtures of two or more of these; and the like.

[0050] In addition, examples of the mineral oil-based base oil include base oils obtained by using any one of the following (1) to (8) as a raw material oil, purifying the raw material oil and / or the lubricating oil fraction recovered from the raw material oil by a predetermined purification method, and recovering the lubricating oil fraction. (1) Distillate oil by atmospheric distillation of paraffin-based crude oil and / or mixed-base crude oil (2) Distillate oil (WVGO) by vacuum distillation of atmospheric distillation residue oil of paraffin-based crude oil and / or mixed-base crude oil (3) Wax (such as slack wax) obtained by the lubricating oil dewaxing process and / or synthetic wax (such as FT wax, GTL wax) obtained by the Fischer-Tropsch (FT) process, Gas-to-Liquid (GTL) process, etc. (4) One kind of mild hydrocracking treated oil selected from the raw oils (1) to (3) and / or mild hydrocracking treated oil of a mixture of two or more kinds selected from the raw oils (1) to (3) (5) Mixed oil of two or more kinds selected from the raw oils (1) to (4) (6) Decanted oil (DAO) of the raw oil (1), (2), (3), (4) or (5) (7) Mild hydrocracking treated oil (MHC) of the raw oil (6) (8) Mixed oil of two or more kinds selected from the raw oils (1) to (7).

[0051] Note that as the above-mentioned predetermined purification method, hydrocracking purification such as hydrocracking and hydrofinishing; solvent purification such as furfural solvent extraction; dewaxing such as solvent dewaxing and catalytic dewaxing; clay purification with acid clay or activated clay; chemical (acid or alkali) washing such as sulfuric acid washing and caustic soda washing are preferable. One of these purification methods may be carried out alone, or two or more kinds may be combined. Also, when combining two or more purification methods, the order is not particularly limited and can be appropriately selected.

[0052] Particularly preferred examples of mineral oil-based base oils include the following base oils (9) or (10) obtained by performing predetermined treatment on the raw oil selected from the above (1) to (8) or the lubricating oil fraction recovered from the raw oil. (9) Hydrocracking the raw oil selected from the above (1) to (8) or the lubricating oil fraction recovered from the raw oil, performing dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the product or the lubricating oil fraction recovered from the product by distillation or the like, or distilling after the dewaxing treatment to obtain a hydrocracked base oil (10) Hydrogenate the base oil selected from the above (1) to (8) or the lubricating oil fraction recovered from the base oil, and perform dewaxing treatment such as solvent dewaxing or catalytic dewaxing on the product or the lubricating oil fraction recovered from the product by distillation or the like, or distill after the dewaxing treatment to obtain a hydroisomerized base oil (note that a base oil produced through a catalytic dewaxing process as the dewaxing step is more preferred).

[0053] In addition, when obtaining the mineral oil-based base oil of the above (9) or (10), a solvent refining treatment and / or a hydrofinishing treatment step may be further performed at an appropriate stage as necessary.

[0054] Moreover, as the mineral oil-based base oil, Group I base oil of the API base oil classification (hereinafter, sometimes referred to as "API Group I base oil"), Group II base oil (hereinafter, sometimes referred to as "API Group II base oil"), or Group III base oil (hereinafter, sometimes referred to as "API Group III base oil"), or a mixed base oil obtained by combining them can be used. Here, the API Group I base oil is a mineral oil-based base oil with a sulfur content exceeding 0.03% by mass and / or a saturate content less than 90% by mass, and a viscosity index of 80 or more and less than 120. The API Group II base oil is a mineral oil-based base oil with a sulfur content of 0.03% by mass or less, a saturate content of 90% by mass or more, and a viscosity index of 80 or more and less than 120. Furthermore, the API Group III base oil is a mineral oil-based base oil with a sulfur content of 0.03% by mass or less, a saturate content of 90% by mass or more, and a viscosity index of 120 or more. The API Group I base oil is usually produced through a solvent refining process, and the API Group II base oil and Group III base oil are usually produced through a hydrocracking process. In this specification, the viscosity index means the viscosity index measured in accordance with JIS K 2283-2000. Also, in this specification, "the sulfur content in the lubricating oil base oil" is measured in accordance with JIS K 2541-2003. Also, in this specification, "the saturate content in the lubricating oil base oil" means the value measured in accordance with ASTM D 2007-93.

[0055] Also, as the synthetic base oil, an API base oil classification Group IV base oil (polyalphaolefin base oil, hereinafter sometimes referred to as "API Group IV base oil"), or an API base oil classification Group V base oil (hereinafter sometimes referred to as "API Group V base oil"), or a mixed base oil obtained by combining them can be used.

[0056] Examples of API Group IV base oils include oligomers and co-oligomers of α-olefins having 2 to 32 carbon atoms (preferably 6 to 16 carbon atoms) such as ethylene-propylene copolymers, polybutenes, 1-octene oligomers, and 1-decene oligomers, and hydrogenated products thereof, such as hydrogenated products of these.

[0057] Also, preferred examples of the API Group V base oil include ester-based base oils such as monoesters (e.g., butyl stearate, octyl laurate, 2-ethylhexyl oleate, etc.); diesters (e.g., ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.); polyesters (e.g., trimellitic acid esters, etc.); polyol esters (e.g., trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargonate, etc.). Other examples of conventional API Group V base oils include aromatic synthetic base oils such as alkylbenzenes, alkylnaphthalenes, dialkyldiphenyl ethers, polyphenyl ethers, etc.

[0058] 〈Regarding Additives〉 The lubricating oil composition of the present invention only needs to contain the lubricating base oil and the antioxidant composed of the porphyrin complex. Depending on its use and the like, known additives used in the field of lubricating oil compositions can be appropriately used within the range that does not impair the effects of the present invention. Such additives are not particularly limited, and examples thereof include ashless dispersants, metal detergents, friction modifiers, antiwear agents, extreme pressure agents, viscosity index improvers, pour point depressants, corrosion inhibitors, rust preventives, metal deactivators, demulsifiers, antifoaming agents, and colorants. Further, as such additives, for example, various additives described in WO2017 / 073748, JP-A-2020-76004, WO2020 / 095970, JP-A-2022-158124, JP-A-2022-090378, etc. can be appropriately used.

[0059] Further, such additives are not particularly limited, and examples thereof include known ashless dispersants such as succinimide-based ashless dispersants; known metal detergents such as alkali or alkaline earth metal alkyl salicylates, alkali or alkaline earth metal alkyl benzene sulfonates, and alkali or alkaline earth metal alkyl phenates; oil-based friction modifiers, organic molybdenum compounds, organic boron compounds such as alkyl mercaptyl borate, graphite, molybdenum disulfide, antimony sulfide, boron compounds, and polytetrafluoroethylene; known sulfur-based additives such as metal thiocarbamates (e.g., salts of various metals such as Pb and Sb) and disulfides; known phosphorus-based and phosphorus-sulfur-based additives such as metal dithiophosphates (e.g., salts of various metals such as Pb, Sb, and Mo), phosphate esters, phosphite esters, and amine salts of partial phosphate esters; known viscosity index improvers such as dispersed or non-dispersed polyalkyl (meth) acrylates, non-dispersed or dispersed ethylene-α-olefin copolymers and their hydrogenated products, polyisobutylene and its hydrogenated products, hydrogenated products of styrene-diene copolymers, styrene-maleic anhydride ester copolymers, and polyalkylstyrenes; known pour point depressants such as polymethacrylate-based polymers and ethylene vinyl acetate; and the like.

[0060] <Regarding the composition> In the lubricating oil composition of the present invention, the content of the lubricating base oil is not particularly limited, but it is preferably 70% by mass or more (more preferably 80% by mass or more, still more preferably 95% by mass or more, particularly preferably 99% by mass or more) based on the total amount of the composition. When the content of such a lubricating base oil is not less than the above lower limit, compared with the case where it is less than the lower limit, when using the additive, a more excellent effect can be obtained in terms of the dissolution stability of the additive.

[0061] Further, the content of the zinc porphyrin complex (the compound represented by the general formula (1)) used as the antioxidant is preferably 0.1 micromol to 10 mmol (more preferably 0.3 micromol to 9 mmol, still more preferably 0.5 micromol to 8 mmol) with respect to 1 g of the lubricating base oil. By setting the content of such a zinc porphyrin complex to be not less than the above lower limit, a higher antioxidant performance can be obtained. On the other hand, by setting it to be not more than the above upper limit, a higher effect can be obtained in terms of obtaining high antioxidant performance economically. Note that conventionally known antioxidants basically achieve antioxidant effects by equivalent reactions, and in order to maintain the antioxidant function over a long period, it was necessary to add a large amount depending on the type of the antioxidant. However, when using the antioxidant composed of the zinc porphyrin complex according to the present invention, it is possible to suppress oxidation degradation over a long period even with a relatively small amount of use.

[0062] Further, the content of the zinc porphyrin complex used as the antioxidant is preferably 1 mass ppm to 10 mass% (more preferably 1.5 mass ppm to 9 mass%, still more preferably 2 mass ppm to 8 mass%) based on the total amount of the composition. By setting the content of the zinc porphyrin complex with respect to the total amount of the composition to be not less than the above lower limit, a higher antioxidant performance can be obtained. On the other hand, by setting it to be not more than the above upper limit, a higher effect can be obtained in terms of obtaining high antioxidant performance economically.

[0063] Further, when the lubricating oil composition of the present invention contains the above other additives (ashless dispersants, metal detergents, friction modifiers, anti-wear agents, extreme pressure agents, viscosity index improvers, pour point depressants, corrosion inhibitors, rust preventives, metal deactivators, demulsifiers, defoamers, and colorants, etc.), the amount of use thereof may be appropriately set according to the application of the composition as long as the effects of the present invention are not impaired. As the above additives, for example, when any one or two or more of an ashless dispersant, a viscosity index improver, and a pour point depressant are used, their contents may each be 0.01 to 20% by mass based on the total amount of the composition. Further, as the above additives, for example, when a metal detergent is used, its content may be 0.001 to 5.0% by mass in terms of the amount of metal element based on the total amount of the composition. Furthermore, as the above additives, for example, when any one or two or more of a friction modifier, an anti-wear agent, and an extreme pressure agent are used, their contents may each be 0.05 to 5.0% by mass based on the total amount of the composition. Also, as the above additives, for example, when any one or two or more of a corrosion inhibitor, a rust preventive, and a demulsifier are used, their contents may each be, for example, 0.005 to 5% by mass based on the total amount of the composition. Further, as the above additives, for example, when a metal deactivator is used, its content may be 0.005 to 1% by mass based on the total amount of the composition. Furthermore, as the above additives, for example, when a defoamer is used, its content may be 0.0001 to 0.1% by mass based on the total amount of the composition.

[0064] The first lubricating oil composition of the present invention has been described above. Hereinafter, the second lubricating oil composition of the present invention will be described.

[0065] 〔Second Lubricating Oil Composition〕 The second lubricating oil composition of the present invention is a lubricating base oil and a reaction product of the porphyrin-based compound represented by the general formula (2) and a zinc salt, and is characterized by containing the same.

[0066] Incidentally, as described above, the reaction product of the porphyrin compound represented by the general formula (2) (abbreviation: porphyrin-H2) and the zinc salt is obtained by reacting the porphyrin-H2 and the zinc salt, and such a reaction product is, as a result, the same as the zinc porphyrin complex represented by the general formula (1). Therefore, the conditions such as the type of lubricating base oil and other components that can be used in the second lubricating oil composition of the present invention and the amounts thereof used are the same as those of the first lubricating oil composition of the present invention. Incidentally, the reaction product of porphyrin-H2 and the zinc salt is the same as the reaction product described in the "zinc porphyrin complex" in the first lubricating oil composition of the present invention.

Examples

[0067] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0068] <Regarding the lubricating base oil> In all of the following Examples and the like, an ester-based base oil (tetraester of pentaerythritol and 2-ethylhexanoic acid (manufactured by Fujifilm Wako Pure Chemical Corporation)) was used as the lubricating base oil. In the following Examples and the like, such a lubricating base oil is simply referred to as "ester-based base oil" for convenience.

[0069] <Regarding the evaluation test of the characteristics of the compositions obtained in each Example and the like> Using each of the lubricating oil compositions obtained in each Example and the like, a test was conducted by adopting the following measurement procedure (conditions) using an "Oxidation Stability Tester RapidOxy (manufactured by Anton Paar)" as the measuring device to evaluate the antioxidant performance of the lubricating oil composition.

[0070] 〔Measurement procedure in the evaluation test〕 First, approximately 5 g of the lubricating oil composition was placed in a glass dish for the measuring device and precisely weighed, and used as a sample (note that the mass of the precisely weighed lubricating oil composition (sample mass) is described in Table 1 for each example). Next, after placing the glass dish containing the sample (lubricating oil composition for testing) in the measuring device and sealing it, pure oxygen (G2 grade) was filled into the device at a pressure of 700 kPa at room temperature (25°C). After pressurizing the inside of the device by introducing pure oxygen (G2 grade) in this way, the test was started after the pressure inside the device stabilized, the temperature inside the device was raised to 150°C, held at 150°C, and from the start of the test, the time until the pressure inside the device dropped to a pressure that is 10% lower than the maximum reached pressure was measured (the time was measured with the point when the pressure became 10% lower than the maximum reached pressure as the end point). Through such measurement, it can be evaluated that the longer the measured time, the higher the antioxidant performance. For the samples of the lubricating oil compositions obtained in Examples 1 to 2 and Comparative Example 3, since the pressure did not reach the end point pressure even after a long time compared with other comparative examples, etc., the time described in Table 1 (19866 seconds (5.52 hours) in Example 1, 29570 seconds (8.21 hours) in Example 2, 29047 seconds (8.07 hours) in Comparative Example 3) was used as the end point to end the test. Here, in Example 1, the ratio of the pressure drop from the maximum reached pressure was 1.6% even at the time when 19866 seconds (5.52 hours) had passed, and in Example 2, the ratio of the pressure drop from the maximum reached pressure was 2.2% even at the time when 19872 seconds (5.52 hours) had passed. Further, in Comparative Example 3, the ratio of the pressure drop from the maximum reached pressure was 3.0% at the time when 19860 seconds (5.52 hours) had passed. In Example 2, the ratio of the pressure drop from the maximum reached pressure at the time when 8.21 hours had passed was 3.9%, and in Comparative Example 3, the ratio of the pressure drop from the maximum reached pressure at the time when 8.07 hours had passed was 5.0%. Considering such pressure drop ratios, etc., the test was ended at the above time. The measurement results are shown in Table 1.

[0071] (Example 1) A solution was prepared by dissolving zinc tetraphenylporphyrin complex (21.8 mg, manufactured by Tokyo Chemical Industry Co., Ltd., compound name: zinc(II) tetraphenylporphyrin [alias: 5,10,15,20-tetraphenyl-21H,23H-porphine zinc(II)]) in acetone (5 ml). The ester-based base oil (10.3905 g, manufactured by Fujifilm Wako Pure Chemical Corporation) was added to such a solution to obtain a mixture. Next, acetone was distilled off using a rotary evaporator until the mixture reached a constant weight, and a lubricating oil composition composed of an ester-based base oil and a zinc tetraphenylporphyrin complex was obtained. The content of the zinc tetraphenylporphyrin complex per 1 g of the lubricating oil base oil was 3.1 μmol / g.

[0072] (Example 2) A solution was prepared by dissolving zinc tetraphenylporphyrin complex (9.5 mg, manufactured by Tokyo Chemical Industry Co., Ltd., compound name: zinc(II) tetraphenylporphyrin) in acetone (5 ml). The ester-based base oil (10.4956 g, manufactured by Fujifilm Wako Pure Chemical Corporation) was added to such a solution to obtain a mixture. Next, acetone was distilled off using a rotary evaporator until the mixture reached a constant weight, and a lubricating oil composition composed of an ester-based base oil and a zinc tetraphenylporphyrin complex was obtained. The content of the zinc tetraphenylporphyrin complex per 1 g of the lubricating oil base oil was 1.3 μmol / g.

[0073] (Comparative Example 1) Without using the zinc tetraphenylporphyrin complex, only the ester-based base oil was regarded as a lubricating oil composition for comparison and used.

[0074] (Comparative Example 2) Instead of the zinc tetraphenylporphyrin complex, an iron(III) chloride tetraphenylporphyrin complex (Fe 3+ ) was used to obtain a lubricating oil composition for comparison as follows. That is, first, an iron(III) chloride tetraphenylporphyrin complex (Fe 3+, 20.7 mg, manufactured by Tokyo Chemical Industry Co., Ltd., compound name: iron(III) tetraphenylporphyrin chloride) was dissolved in acetone (10 ml) to prepare a solution. To such a solution, the ester-based base oil (11.1417 g, manufactured by Fujifilm Wako Pure Chemical Corporation) was added to obtain a mixture. Then, until the mixture became a constant weight, acetone was distilled off using a rotary evaporator to obtain a lubricating oil composition for comparison composed of an ester-based base oil and an iron tetraphenylporphyrin chloride complex. Regarding the lubricating oil composition obtained in Comparative Example 2, a filtrate was obtained by suction filtration using filter paper (5A: corresponding to Type 5A specified in JIS P 3801), and such a filtrate was used as the lubricating oil composition for the evaluation test of the above-mentioned properties. The content of the iron tetraphenylporphyrin chloride complex with respect to 1 g of the lubricating oil base oil was 2.6 μmol / g.

[0075] (Comparative Example 3) 2,6-Tert-butylparacresol (0.1700 g, manufactured by Tokyo Chemical Industry Co., Ltd.), a phenolic antioxidant, was mixed with the ester-based base oil (20.0000 g, manufactured by Fujifilm Wako Pure Chemical Corporation) to obtain a lubricating oil composition for comparison. The content of the iron tetraphenylporphyrin chloride complex with respect to 1 g of the lubricating oil base oil was 39 μmol / g.

[0076] [Table 1]

[0077] As is clear from the results shown in Table 1, when the zinc porphyrin complex represented by the general formula (1) was used (Examples 1 to 2), it was found that higher antioxidant performance was obtained. That is, at the 5.5-hour point, the rate of pressure drop in Example 1 was lower than that in Example 2, indicating high antioxidant performance. Also, considering that Example 2, where the end point was longer than that in Comparative Example 3, had a lower rate of pressure drop at the end point than Comparative Example 3 and showed high antioxidant performance, it is clear that when the zinc porphyrin complex represented by the general formula (1) was used (Examples 1 to 2), excellent antioxidant performance was obtained compared to the case where a conventional antioxidant was used (Comparative Example 3). According to the present invention, it was found that a composition showing antioxidant performance equal to or higher than that in the case where a conventional antioxidant was used (Comparative Example 3) can be obtained. Further, at the point when about 5.5 hours had elapsed in the test for evaluating antioxidant performance, the ratio of the pressure dropped from the maximum pressure reached was 2.2% or less in Examples 1 to 2 (Example 1: 1.6%, Example 2: 2.2%), while it was 3.0% in Comparative Example 3. Also, considering that the amount of the compound used (contained molar amount) per 1 g of the base oil was smaller in Examples 1 to 2 than in Comparative Example 3, it was found that when the zinc porphyrin complex represented by the general formula (1) was used (Examples 1 to 2), higher antioxidant performance can be obtained even with a smaller contained molar amount per 1 g of the base oil compared to the case where a conventional antioxidant such as 2,6-tert-butylparacresol was used (Comparative Example 3).

Industrial Applicability

[0078] As described above, according to the present invention, it is possible to provide a lubricating oil composition capable of suppressing oxidative degradation at a high level while using a component different from the components conventionally used as antioxidants. Therefore, the lubricating oil composition of the present invention is useful as a composition for lubricating the moving parts of various mechanical devices having moving parts (for example, internal combustion engines, etc.).

Claims

1. a lubricating base oil, the following general formula (1): 【Chemical 1】 (In formula (1), R １ ~R １２ each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 7 to 25 carbon atoms which may have a substituent.) an antioxidant comprising a zinc porphyrin complex represented by and a lubricating oil composition characterized by containing

2. a lubricating base oil, the following general formula (2): 【Chemical 2】 (In formula (2), R １ ~R １２ each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 24 carbon atoms which may have a substituent, and an aralkyl group having 7 to 25 carbon atoms which may have a substituent.) an antioxidant comprising a reaction product of a porphyrin-based compound represented by and a zinc salt, and a lubricating oil composition characterized by containing

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