JP2021116338A - Organic friction modifier - Google Patents

Abstract

[Problem] To provide an organic friction modifier that can sufficiently reduce friction, has a stable friction coefficient that does not easily change over time, has small wear marks on sliding surfaces, and has excellent load-bearing capacity. provide. SOLUTION: General formula (1): [wherein R1 represents a hydrogen atom or an oxygen radical]. When n is an integer of 2 or more, n R2's are the same or different and represent a hydrocarbon group. R3 and R4 are the same or different and represent a single bond or a carbonyl group. R5 and R6 are the same or different and represent a hydrogen atom or a hydrocarbon group. Note that when R5 is a hydrogen atom, R3 is a single bond, and when R6 is a hydrogen atom, R4 is a single bond. Further, both R5 and R6 are never hydrogen atoms. n represents an integer of 0 to 8. ] An organic friction modifier containing a piperidine compound represented by: [Selection diagram] None

Description

The present invention relates to an organic friction modifier.

In order to realize a society that is in harmony with the environment, there is a strong demand for energy saving and reduction of environmental load in mechanical systems such as automobiles and machine tools, and the establishment of green lubrication technology that can reduce energy loss due to friction to the utmost is worldwide. This is an important issue. In this specification, "green lubrication technology" means science and technology from the viewpoint of tribology (academic related to friction, wear, lubrication, etc.) considering the influence on the environment and living things and harmony with nature. .. Reducing the viscosity of lubricating oil is known as the most effective method for reducing friction loss. It is estimated that the economic effect of improving friction and wear is equivalent to about 2% of GNP. Taking an automobile as an example, the fuel loss due to friction is 388 billion liters per year in the world, and about 1 billion tons of carbon dioxide. Corresponds to emissions. However, when the relative motion speed of the two solid surfaces is low, such as when starting and stopping the engine of an automobile, the low-viscosity lubricating oil cannot sufficiently separate the two solid surfaces, so that friction and wear increase sharply due to direct contact between the solids. However, the durability of the system is impaired. As such a solution, a method of adding a sulfur or phosphorus-based substance or a fatty acid called an organic friction modifier (hereinafter, also referred to as "OFM") to a low-viscosity lubricating oil is used. Has been done. Taking an automobile engine as an example, FIG. 1 shows an image of an OFM additive-containing lubrication system on a surface (sliding surface) that slides while rubbing. Even when sliding at high load and high speed, OFM additive molecules can be firmly adsorbed on the sliding surface to form a film that prevents solid contact, which makes it possible to reduce friction and wear, and further lubrication oil. Holds the key to low viscosity. In other words, the organic friction modifier (OFM) added to the lubricating oil used for the moving parts of automobiles and machine tools is the key to improving fuel efficiency.

Initially, fatty acids such as stearic acid (RCOOH) were put into practical use as OFM, but in order to avoid corrosion of the mechanical system due to the acidity of fatty acids, the carboxyl group was replaced with a functional group such as amide, amine, or glyceryl. Those are common (see, for example, Non-Patent Document 1).

Tribol Lett (2015) 60: 5

A century after stearic acid and its derivatives were used as organic friction modifiers (OFMs), the concept of OFM molecular structure is basically a single terminal functional group that hydrogen bonds to the sliding surface. Since it follows the conventional structure of one alkyl chain, the limit of performance has begun to appear. Therefore, in reality, it is difficult to use OFM alone, and it is indispensable to use it in combination with additives such as molybdenum dithiocarbamate (MoDTC) and dialkyl dithiophosphate (ZnDTP) to supplement the load bearing capacity. However, MoDTC, for example, is very expensive and contains transition metals and sulfur, which has an adverse effect on the environment. In order to contribute to the achievement of the goals of the Paris Agreement and to enhance the market competitiveness, it is essential to further promote the reduction of the viscosity of the lubricating oil. Development is required.

Further, in OFM using a fatty acid derivative which has been conventionally used, the friction cannot be sufficiently reduced, the friction coefficient is liable to change with time, and the friction coefficient is not stable, and the amount of wear is large.

The present invention solves such a problem, the friction can be sufficiently reduced, the friction coefficient does not change easily with time, the friction coefficient is stable, and the wear marks on the sliding surface are small. It is an object of the present invention to provide an organic friction modifier having excellent load bearing capacity.

As a result of repeated studies to achieve the above object, the present inventors can sufficiently reduce the friction of an organic friction modifier containing a piperidine compound having a specific structure, and the friction changes with time. It was found that the coefficient is hard to change and has a stable friction coefficient, the amount of wear is reduced, and the load bearing capacity is also excellent. Based on the above findings, the present inventors have further studied and completed the present invention. That is, the present invention includes the following configurations.

Item 1. General formula (1):

[In the formula, R ¹ represents a hydrogen atom or an oxygen radical. When n is an integer of 2 or more, n R ^2s are the same or different and represent hydrocarbon groups. R ³ and R ⁴ are the same or different and represent a single bond or a carbonyl group. R ⁵ and R ⁶ are the same or different and represent a hydrogen atom or a hydrocarbon group. When R ⁵ is a hydrogen atom, R ³ is a single bond, and when R ⁶ is a hydrogen atom, R ⁴ is a single bond. Moreover, ^{neither R 5} nor R ⁶ becomes a hydrogen atom. n represents an integer from 0 to 8. ]
An organic friction modifier containing a piperidine compound represented by.

Item 2. The piperidine compound has the general formula (1A):

[In the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are the same as described above. ]
Item 2. The organic friction modifier according to Item 1, which is a piperidine compound represented by.

Item 3. Item 2. The organic friction modifier according to Item 1 or 2, wherein R ^{2 is an alkyl group.}

Item 4. ^{Item 3.} The organic according to any one of Items 1 to 3, wherein R 3 is a carbonyl group, R ⁴ is a single bond, R ⁵ is a hydrocarbon group, and R ^{6 is a hydrogen atom.} Friction modifier.

Item 5. General formula:

2,2,6,6-tetramethylpiperidin 1-oxyl compound represented by.

Item 6. Item 5. An organic friction modifier containing the 2,2,6,6-tetramethylpiperidin1-oxyl compound according to Item 5.

Item 7. Item 2. The organic friction modifier according to any one of Items 1 to 4 and 6, which is an organic friction reducing agent.

Item 8. Item 2. The organic friction modifier according to any one of Items 1 to 4 and 6 to 7, which is used for metallic materials.

Item 9. A lubricant containing the organic friction modifier according to any one of Items 1 to 4 and 6 to 8 and a base oil.

According to the present invention, the friction can be sufficiently reduced without using an additive containing a transition metal such as molybdenum dithiocarbamate (MoDTC) or sulfur, and the friction coefficient does not change easily with time, and the friction is stable. It is possible to provide an organic friction modifier having a coefficient, reducing the amount of wear, and having an excellent load-bearing capacity.

The organic friction modifier (OFM) in the moving parts of an automobile engine is shown. The change in the sliding surface due to the change with time when the organic friction modifier is applied to the moving part of the automobile engine is shown. The schematic diagram of the pin-on disk type unidirectional tribotester used for the friction measurement in an Example is shown. In the lubricating oils of Example 7, Comparative Example 1 and Comparative Example 2, changes in the dynamic friction coefficient with increasing sliding speed are shown. In the lubricating oils of Example 7, Comparative Example 2 and Comparative Example 3, changes in frictional force with an increase in vertical load are shown. Friction over time when a friction test was performed using the lubricating oils of Examples 8 and Comparative Examples 4 to 5 with a vertical load of 5 N, a sliding speed of 20.4 mm / s, and a test time of 3600 seconds. The change of the coefficient and the state of the wear mark after the test are shown.

As used herein, "contains" is a concept that includes any of "comprise," "consist essentially of," and "consist of." Further, in the present specification, when the numerical range is indicated by "A to B", it means A or more and B or less.

As used herein, the term "sliding surface" means a surface that slides while rubbing relative to each other. Further, in the present specification, the "sliding speed" means the relative speed of the surfaces that slide while rubbing relative to each other.

In the present specification, the "organic friction modifier", particularly the "organic friction reducing agent", means an additive containing an organic compound for the purpose of reducing friction on a sliding surface. Usually, it is dissolved in a base oil and used, and a film can be formed by physical or chemical adsorption on a sliding surface, whereby friction can be reduced.

As used herein, the "coefficient of friction" means the ratio of the frictional force to the load acting perpendicular to the contact surface (vertical load). It is a coefficient that expresses the difficulty of slipping, and the larger it is, the less slippery it is.

As used herein, the "pin-on disc test" is one of the standard friction tests. A pin-shaped sample is pressed against a rotating disk sample, and the amount of wear, changes in frictional force, and changes in friction coefficient can be measured.

In the present specification, "hard acid", "hard base", "soft acid" and "soft base" are proposed to RG Pearson, and the compatibility of acid and base (bond strength and reaction). Ease of use) is a concept classified using the expressions hardware and software. In general, a hard acid and a hard base easily form a strong bond and easily react with each other. On the other hand, a soft acid and a soft base easily form a strong bond and easily react with each other.

1. 1. Organic Friction Modifiers Currently, fatty acid derivatives and aliphatic amines are mainly used as organic friction modifiers, but their improvement effects are limited. In practice, it is essential to use it in combination with molybdenum dithiocarbamate (MoDTC) or dialkyl dithiophosphate (ZnDTP) to supplement the load-bearing capacity. However, MoDTC, for example, is very expensive and contains transition metals and sulfur, which has an adverse effect on the environment. Therefore, in order to reduce the environmental load, an organic friction modifier capable of reducing the amount of additives such as molybdenum dithiocarbamate (MoDTC) and dialkyl dithiophosphate (ZnDTP) is required.

On the other hand, the organic friction modifier of the present invention has the general formula (1) :.

[In the formula, R ¹ represents a hydrogen atom or an oxygen radical. When n is an integer of 2 or more, n R ^2s are the same or different and represent hydrocarbon groups. R ³ and R ⁴ are the same or different and represent a single bond or a carbonyl group. R ⁵ and R ⁶ are the same or different and represent a hydrogen atom or a hydrocarbon group. When R ⁵ is a hydrogen atom, R ³ is a single bond, and when R ⁶ is a hydrogen atom, R ⁴ is a single bond. Moreover, ^{neither R 5} nor R ⁶ becomes a hydrogen atom. n represents an integer from 0 to 8. ]
Contains a piperidine compound represented by.

In order for the organic friction modifier to continuously exhibit a friction reducing effect, it is preferable that the organic friction modifier is always adsorbed on the sliding surface. By the way, the sliding surface generally changes with the sliding time. Taking the case where an organic friction modifier is applied to a moving part of an automobile engine as an example, as shown in FIG. 2, the sliding surface is generally a metal oxide which is an oxide film formed on the surface of a metal material. , When the surface is worn by contact, a new metal surface appears. The sliding surface during actual operation is in a state where metal oxide and unoxidized metal are mixed. Therefore, an organic friction modifier that adsorbs to both the surface of the metal oxide and the new metal surface is preferable.

(1-1) Piperidine compound
According to RG Pearson's concept of hard acids and hard bases, as well as soft acids and soft bases, metal oxides are hard acids and metallized surfaces are soft acids. As described above, since the chemical properties of the two are different, it has been difficult to achieve the purpose with the conventional organic friction modifier. On the other hand, according to the organic friction modifier of the present invention, it is possible to adsorb it on both the surface of the metal oxide and the new metal surface, and as a result, the friction can be sufficiently reduced, and the friction can be sufficiently reduced due to aging. The friction coefficient does not change easily and has a stable friction coefficient, and the amount of wear can be reduced. Moreover, since the piperidine compound represented by the general formula (1) in the organic friction modifier of the present invention has a piperidine ring having a cyclic structure, it can withstand a high load. Therefore, the piperidine compound represented by the general formula (1) can reduce the amount of additives such as molybdenum dithiocarbamate (MoDTC) and dialkyl dithiophosphate (ZnDTP), and sulfur, phosphorus, and transition. Since it does not contain any metal, it is environmentally friendly.

Further, the piperidine compound represented by the general formula (1) is difficult to derivatize with an organic friction modifier using stearic acid or a derivative thereof, and is intended for R ¹ , R ⁵ , R ^{6 and the} like. It is possible to freely introduce functional groups according to the performance, and the degree of freedom in design is high. It is also possible to freely adjust the compatibility with other additives contained in the lubricating oil as an actual product.

In the piperidine compound represented by the general formula (1), when R ¹ is a hydrogen atom, it is a hard base and is particularly easily adsorbed on the surface of a metal oxide which is a hard acid. On the other hand, in the piperidine compound represented by the general formula (1), when R ¹ is an oxygen radical, it is a soft base and is particularly easily adsorbed on the metal formation surface which is a soft acid. Therefore, when the ^{piperidine compound represented by the general formula (1) in which R 1} is a hydrogen atom and the piperidine compound represented by the general formula (1) in which R ¹ is an oxygen radical are used in combination, a metal is used. It can be more easily adsorbed on both the surface of the oxide and the regenerated metal surface, the friction can be further reduced, the friction coefficient can be more stable even with aging, and the amount of wear on the sliding surface can be further reduced. Among these, as R ^1, solubility, synthetic ease, friction reduction, stable friction coefficient, wear amount, from the viewpoint of load bearing capacity, of the hydrogen atoms and oxygen radicals, oxygen radicals are preferred. At present, the friction modifier that easily adsorbs to the metal formation surface, which is a soft acid, is a friction modifier containing sulfur, which is regarded as a problem from the viewpoint of environmental harmony.

In the general formula (1), the ^{hydrocarbon group represented by R 2} is not particularly limited as long as it is a monovalent hydrocarbon group, and for example, an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group or an alkynyl group can be used. Can be mentioned. These hydrocarbon groups may contain heteroatoms such as oxygen atoms and nitrogen atoms.

The alkyl group as the hydrocarbon group represented by R ^2, for example, a methyl group, an ethyl group, a propyl group (n- propyl group, an isopropyl group, etc.), butyl (n- butyl group, isobutyl group, sec- butyl Groups, tert-butyl groups, etc.), pentyl groups (n-pentyl groups, neopentyl groups, etc.), hexyl groups (n-hexyl groups, etc.) and other alkyl groups having 1 to 6 carbon atoms can be mentioned.

The alkenyl group as the hydrocarbon group represented by R ^2, for example, vinyl group, 1-propenyl group, isopropenyl group, 2-methyl-1-propenyl, 1-butenyl, 2-butenyl, 3- Butenyl group, 2-ethyl-1-butenyl group, 1-pentenyl group, 2-pentenyl group, 3-pentenyl group, 4-pentenyl group, 4-methyl-3-pentenyl group, 1-hexenyl group, 2-hexenyl group , 3-Hexenyl group, 4-hexenyl group, 5-hexenyl group and other linear or branched alkenyl groups having 2 to 10 carbon atoms can be mentioned. The position and number of double bonds are arbitrary and can be adjusted as appropriate.

The alkynyl group as the hydrocarbon group represented by R ^2, for example, ethynyl group, 1-propynyl, 2-propynyl, 1-butynyl group, 2-butynyl, 3-butynyl, 1-pentynyl group, Linear or branched carbons such as 2-pentynyl group, 3-pentynyl group, 4-pentynyl group, 1-hexynyl group, 2-hexynyl group, 3-hexynyl group, 4-hexynyl group, 5-hexynyl group The number 2 to 10 alkynyl groups can be mentioned. The position and number of triple bonds are arbitrary and can be adjusted as appropriate.

Among these, as R ^2, ease of synthesis, friction reduction, stable friction coefficient, wear amount, from the viewpoint of load bearing capacity, is preferably an alkyl group. If the number of R ² n is 2 or more, it is preferred that all of the alkyl group. Further, when n, which is the number of ^{R 2 , is 2 or more, R 2} may be the same or different.

In the general formula (1), n is the number of the hydrocarbon group represented by R ² is not particularly limited, ease of synthesis, friction reduction, stable friction coefficient, wear amount, from the viewpoint of load bearing capacity, An integer of 0 to 8 is preferable, an integer of 1 to 7 is more preferable, and an integer of 2 to 6 is even more preferable.

In the general formula (1), ^{n, which is the number of hydrocarbon groups represented by R 2} , is 4 from the viewpoints of ease of synthesis, friction reduction, stable friction coefficient, wear amount, load bearing capacity, and the like. Is particularly preferable. That is, the general formula (1A):

[In the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are the same as described above. ]
The piperidine compound represented by is preferable.

In the general formula (1), R ³ and R ⁴ represent a single bond or a carbonyl group. However, when R ⁵ is a hydrogen atom, R ³ is a single bond, and when R ⁶ is a hydrogen atom, R ⁴ is a single bond. When R ⁵ is a hydrogen atom, R ³ is a single bond or a carbonyl group, and when R ⁶ is a hydrogen atom, R ⁴ is a single bond or a carbonyl group. Among them, when ^{both R 5} and R ⁶ are hydrocarbon groups, it is ^{preferable that both R 3} and R ⁴ have a single bond, and when ^{only one of R 5} and R ⁶ is a hydrocarbon group, for example, R. ^{When 5} is a hydrocarbon group and R ^{6 is a hydrogen atom, R 3} is a carbonyl group from the viewpoints of solubility, ease of synthesis, friction reduction, stable friction coefficient, amount of wear, load bearing capacity, etc. Yes, R ⁴ is preferably a single bond.

In the general formula (1), the hydrocarbon group represented by R ⁵ and R ^6, not particularly limited as long as it is a monovalent hydrocarbon radical, e.g., an alkyl group, an alkenyl group, aliphatic and alkynyl groups carbide Hydrogen group: An aromatic hydrocarbon group such as an aryl group (phenyl group, biphenyl group, terphenyl group, etc.) can be mentioned. These hydrocarbon groups may contain heteroatoms such as oxygen atoms and nitrogen atoms. Further, in the case of an alkenyl group or an alkynyl group, the position and number of double bonds or triple bonds are arbitrary and can be appropriately adjusted. Here, from the viewpoints of solubility, ease of synthesis, friction reduction, stable friction coefficient, amount of wear, load-bearing capacity, etc., an aliphatic hydrocarbon group is preferable, a linear hydrocarbon group is more preferable, and the number of carbon atoms is more preferable. Is more preferably moderately large. From this viewpoint, the hydrocarbon group represented by ^{R 5} and ^{R 6,} a linear alkyl group having 5 to 25 carbon atoms (particularly 7-20, more 9-15), alkenyl or alkynyl group preferable. Specifically,-(CH ₂ ) _n1 CH ₃ (n1 is an integer of 4 to 24), -CH = CH- (CH ₂ ) _n2 CH ₃ (n2 is an integer of 2 to 22),- CH ≡ CH − (CH 2) _n3 CH ₃ (n3 is an integer of _{2 to 22) and the like.}

^{Both R 5} and R ⁶ in the general formula (1) do not become hydrogen atoms from the viewpoints of solubility, ease of synthesis, friction reduction, stable friction coefficient, wear amount, load bearing capacity, and the like. That is, at least one is the above-mentioned hydrocarbon group. Further, ^{it is possible to use only one of R 5} and R ⁶ as a hydrocarbon group and the other as a hydrogen atom, but by increasing the number of hydrocarbon chains, the adsorption film density is further improved, and the load bearing capacity is increased. ^{Both R 5} and R ⁶ may be hydrocarbon groups for the purpose of further improving the friction reducing effect and the like.

Among the above-mentioned piperidine compounds, the general formula:

The 2,2,6,6-tetramethylpiperidin1-oxyl compound represented by is a novel compound not described in the literature.

(1-2) Method for Synthesizing Piperidine Compound The piperidine compound represented by the general formula (1) contained in the organic friction modifier of the present invention as described above is, for example, an amino group-containing piperidine compound and a carboxylic acid compound. It can be easily synthesized by introducing the above-mentioned carbonyl hydrocarbon group by a condensation reaction or by introducing the above-mentioned hydrocarbon group by a reaction between an amino group-containing piperidine compound and a halogenated hydrocarbon compound. That is, the piperidine compound represented by the general formula (1) contained in the organic friction modifier of the present invention can be easily derivatized by selecting various groups.

The amino group-containing piperidine compound is not particularly limited, and the general formula (2):

[In the formula, R ¹ , R ² and n are the same as described above. ]
An amino group-containing piperidine compound represented by is used.

The carboxylic acid compound in which the carbonyl hydrocarbon group is introduced is not particularly limited, and the general formula (3):
R ^5a COR ⁷ (3)
[In the formula, R ^5a represents a hydrocarbon group. R ⁷ represents a hydroxy group or a halogen atom. ]
A carboxylic acid compound represented by is used.

In the general formula (3), the hydrocarbon group represented by ^{R 5a} is not particularly limited, and the hydrocarbon group described in ^{R 5} and R ^{6 can be adopted.}

In the general formula (3), the ^{halogen atom represented by R 7} is not particularly limited, and examples thereof include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Of these, a chlorine atom is preferable from the viewpoint of ease of synthesis and the like.

In the amino group-containing piperidine compound represented by the general formula (2), when R ¹ is a hydrogen atom, R ⁷ is preferably a hydroxy group, and when R ¹ is an oxygen radical, R ⁷ is a halogen atom. preferable.

The amount of the carboxylic acid compound represented by the general formula (3) is usually preferably 0.2 to 2 mol with respect to 1 mol of the amino group-containing piperidine compound represented by the general formula (2). More preferably, 5 to 1.5 mol.

The reaction can also be carried out in the presence of a base. The base is not particularly limited, and amine compounds such as trimethylamine, triethylamine and diisopropylamine; pyridine compounds such as pyridine and N, N-dimethyl-4-aminopyridine (DMAP) can be used. These bases can be used alone or in combination of two or more.

The amount of the base used is usually preferably 0.5 to 5 mol, more preferably 1 to 2.5 mol, based on 1 mol of the amino group-containing piperidine compound represented by the general formula (2).

In the amino group-containing piperidine compound represented by the general formula (2), when R ¹ is a hydrogen atom, the reaction can also be carried out in the presence of a condensing agent. Examples of the condensing agent include carbodiimide-based condensing agents (N, N'-dicyclohexylcarbodiimide (DCC), 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDAC), diisopropylcarbodiimide) and imidazole-based condensing agents. Agent (carbonyldiimidazole, 2-chloro-1,3-dimethylimidazolinium chloride), triazine-based condensing agent (4- (4,6-dimethoxy-1,3,5-triazine-2-yl) -4- A condensing agent such as methylmorpholinium chloride) can be used. These condensing agents may be used alone or in combination of two or more.

The amount of the condensing agent used is usually preferably 0.5 to 3 mol, more preferably 1 to 2 mol, based on 1 mol of the amino group-containing piperidine compound represented by the general formula (2).

The reaction can usually be carried out in the presence of a reaction solvent. Examples of the reaction solvent that can be used include ether compounds such as diethyl ether, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, dimethoxyethane and cyclopentylmethyl ether; aromatic hydrocarbon compounds such as benzene, toluene and xylene; dichloromethane and dichloroethane. , Chloroform, aliphatic halogenated hydrocarbon compounds such as carbon tetrachloride; nitrile compounds such as acetonitrile; amide compounds such as dimethylformamide, dimethylsulfoxide and the like, and ether compounds from the viewpoint of ease of synthesis, yield and the like. , An aliphatic halogenated hydrocarbon compound is preferable, tetrahydrofuran, dichloromethane and the like are preferable. These reaction solvents can be used alone or in combination of two or more.

As the reaction atmosphere, an inert gas atmosphere (argon gas atmosphere, nitrogen gas atmosphere, etc.) can be usually adopted. The reaction temperature can be carried out under heating, at room temperature or under cooling, and is usually preferably −50 to 100 ° C., more preferably −20 to 50 ° C. The reaction time is not particularly limited, and can be set to a time during which the reaction proceeds sufficiently.

After completion of the reaction, a piperidine compound represented by the general formula (1) can be obtained by purifying the reaction according to a conventional method, if necessary.

^{When a piperidine compound in which R 1} is a hydrogen atom is synthesized as described above, it is also possible to synthesize a piperidine compound in which ^{R 1} is an oxygen radical by subsequent oxidation by a conventional method. ..

(1-3) Organic Friction Modifier The organic friction modifier of the present invention contains the piperidine compound represented by the above general formula (1).

The organic friction modifier of the present invention may adopt a composition consisting only of the piperidine compound represented by the above general formula (1), but it is not necessarily limited to the piperidine compound represented by the above general formula (1). It is not necessary to configure with.

For example, impurities such as raw material compounds, condensing agents, and bases used in the synthesis process may remain as unavoidable impurities in a small amount. In this case, the content of these unavoidable impurities is not particularly limited, but is preferably 0 to 5% by mass from the viewpoints of solubility, ease of synthesis, friction reduction, stable friction coefficient, wear amount, load bearing capacity, and the like. , 0 to 2% by mass is more preferable.

The organic friction modifier of the present invention having such conditions can sufficiently reduce friction, has a stable friction coefficient whose friction coefficient does not change easily with time, and can also reduce the amount of wear. It also has excellent load-bearing capacity. Therefore, by applying the organic friction modifier of the present invention to the lubricant, the amount of additives such as molybdenum dithiocarbamate (MoDTC) and dialkyl dithiophosphate (ZnDTP) can be reduced, and organic friction can be reduced. It is useful as an agent.

Such an organic friction modifier of the present invention is particularly useful in applications where friction and wear rapidly increase due to direct contact between solids, such as when starting and stopping an automobile engine. That is, it is particularly useful for metal materials that are sliding surfaces when applied to automobile engines. Examples of such a metal material include stainless steel and carbon steel. In this case, when an oxide film is formed on the surface of the metal material, the metal inside is exposed as the friction progresses. In this case, the friction reducing effect is recognized for both the metal oxide and the metal. Be done.

2. Lubricant The lubricant of the present invention (particularly the lubricating oil) contains the organic friction modifier of the present invention and a base oil.

The base oil is not particularly limited, but is preferably selected in consideration of the solubility of the organic friction modifier of the present invention. Examples of such a base oil include mineral oil, poly-α-olefin compound (PAO), alkyldiphenyl ether compound, polypropylene glycol and the like. These base oils can be used alone or in combination of two or more.

In the lubricant of the present invention, the content of the organic friction modifier of the present invention is not particularly limited, but from the viewpoints of solubility, friction reduction, stable friction coefficient, wear amount, load bearing capacity, etc., 100 parts by mass of the base oil is used. On the other hand, 0.1 to 5 parts by mass is preferable, and 0.5 to 3 parts by mass is more preferable.

In addition, the lubricant of the present invention includes antioxidants (hindered phenol compounds, aromatic secondary amine compounds, etc.), viscosity index improvers (polybutene, polyisobutene, polyisobutylene, polyisoprene, polymethacrylate, etc.), and the like. Oiliness improver (long-chain fatty acid compound such as oleic acid or its ester, long-chain amine compound such as oleylamine or its ester, etc.), extreme pressure agent (sulfur-containing compound such as monosulfide, disulfide, sulfoxide, sulfur phosphide; chlorination Chlorine-containing compounds such as paraffin), solid lubricants (molybdenum disulfide, graphite, boron nitride, melamine cyanurate, polytetrafluoroethylene, etc.), rust preventives (paraffin oxide, metal carboxylate, metal sulfonic acid salt, etc.) Additives such as a carboxylic acid ester, a sulfonic acid ester, etc.) and a flow lowering agent (polyalkyl methacrylate, polyalkyl acrylate, polyalkyl styrene, polyvinyl acetate, etc.) can also be contained. In this case, the content of each additive can be an amount normally used conventionally.

The spillover effect of the organic friction modifier of the present invention as described above is enormous both socially and economically. This is because organic friction modifiers are used with lubricants everywhere in the generation and transmission of power. Its fields of use are manufacturing (chemical industry, petrochemical industry, steel industry, etc.), transportation (automobiles, aircraft, railroads, ships, etc.), power generation (power plants, cogeneration power plants, etc.), and residences (indoor heating, cooling equipment, etc.). , Ventilation equipment, etc.).

Hereinafter, the present invention will be described in detail in the form of examples. The following examples do not limit the use of the present invention in any way.

Examples 1-3: C with carboxylic acid chloride _n Synthesis of TEMPO

In the formula, THF represents tetrahydrofuran.

[Example 1: C ₉ TEMPO]
It was synthesized according to the previous report (Magnetic Resonance Imaging 1992, 10, 445-455). 0 in a mixture of 4-amino-2,2,6,6-tetramethylpiperidin 1-oxyl free radical (Compound 1; 1.28 g, 7.5 mmol), tetrahydrofuran (80 mL) and triethylamine (2.0 mL, 14 mmol). A mixture of nonanoyl chloride (Compound 2; 1.2 mL, 6.5 mmol) and tetrahydrofuran (20 mL) was slowly added dropwise at ° C. After stirring at 0 ° C. for 14 hours, solid matter was removed by filtration through Celite. After removing the solvent, the resulting oil was dissolved in dichloromethane (70 mL). After washing this with 0.5 M hydrochloric acid (50 mL × 2), the organic layer was dried over sodium sulfate. After removing the solvent, the obtained crude product was purified by a medium-pressure preparative purification device [hexane: ethyl acetate = 50: 50, flow velocity 20 mL / min, silica gel column (Purif-Pack®-EX). SI 50 μm, SIZE 60, SHOKO SCIENCE, Yokohama, Japan)] and C ₉ TEMPO (1.50 g, yield 74%) were obtained as an oily substance of wine red. Mass spectrometry (FAB-MS) [calcd for C ₁₈ H ₃₅ N ₂ O ₂ [M] ^{+ ·} 311, found 311] supported the structure of _{C 9 TEMPO.}

[Example 2: C ₁₂ TEMPO]
As in Example 1, 4-amino-2,2,6,6-tetramethylpiperidine1-oxyl free radical (Compound 1; 1.21 g, 7.1 mmol), tetrahydrofuran (150 mL) and triethylamine (0.90 mL, 6.5). A mixture of lauroyl chloride (Compound 3; 1.5 mL, 6.4 mmol) and tetrahydrofuran (100 mL) was slowly added dropwise to the mixture of mmol) at 0 ° C., and C ₁₂ TEMPO (compound 3; 1.5 mL, 6.4 mmol) was stirred at 0 ° C. for about 4 hours. 1.82 g (80% yield) was obtained as a solid wine red. Mass spectrometry (FAB-MS) [calcd for C ₂₁ H ₄₁ N ₂ O ₂ [M] ^{+ ·} 353, found 353; calcd for C ₂₁ H ₄₃ N ₂ O ₂ [M + 2H] ⁺ 355, found 355] and elemental analysis (Anal. Calcd for C ₂₁ H ₄₁ N ₂ O ₂ : C, 71.34; H, 11.69; N, 7.92. Found: C, 71.16; H, 11.88; N, 7.86) supported the structure of _{C 12 TEMPO.} ..

[Example 3: C ₁₈ TEMPO]
4-Amino-2,2,6,6-tetramethylpiperidin 1-oxyl free radical (Compound 1; 1.21 g, 7.0 mmol), tetrahydrofuran (100 mL) and triethylamine (2.0 mL, 14), as in Example 1. _{C 18} by slowly adding a mixture of stearoyl chloride (Compound 4; 2.2 mL, 6.5 mmol) and tetrahydrofuran (24 mL) to the mixture of mmol) at 0 ° C. and stirring at 0 ° C. for about 5 hours and 30 minutes. TEMPO (1.75 g, 62% yield) was obtained as a wine red solid. Mass spectrometry (FAB-MS) [calcd for C ₂₇ H ₅₃ N ₂ O ₂ [M] ^{+ ·} 437, found 437; calcd for C ₂₇ H ₅₅ N ₂ O ₂ [M + 2H] ⁺ 439, found 439] is C ₁₈ Supported the structure of TEMPO.

Example 4: C with carboxylic acid ₁₅ Synthesis of TEMPO

In the formula, EDAC / HCl represents 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride. DMAP represents 4-dimethylaminopyridine.

4-Amino-2,2,6,6-tetramethylpiperidin 1-oxyl free radical (Compound 1; 586 mg, 3.4 mmol), 4-dimethylaminopyridine (556 mg, 4.6 mmol), pentadecanoic acid (Compound 5; To a mixture of 700 mg, 2.9 mmol) and dichloromethane (20 mL) was added 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (879 mg, 4.6 mmol) at 0 ° C. The reaction mixture was stirred at room temperature for 27 hours and then washed with 0.5 M hydrochloric acid (30 mL x 2). The organic layer was dried over sodium sulfate to remove the solvent. The obtained crude product was purified by a medium-pressure preparative purification device [Hexane: Ethyl acetate = 71:29 → 50:50, flow velocity 20 mL / min, silica gel column (Purif-Pack®-EX SI 25 μm). , SIZE 120, SHOKO SCIENCE, Yokohama, Japan)], C ₁₅ TEMPO (1.07 g, yield 94%) was obtained as a solid wine red. Mass Spectrometry (EI-MS) [calcd for C ₂₄ H ₄₇ N ₂ O ₂ [M] ^{+ ·} 395.33375, found 395.36360] and Elemental Analysis (Anal. Calcd for C ₂₄ H ₄₇ N ₂ O ₂ : C, 72.86; H , 11.97; N, 7.08. Found: C, 72.52; H, 12.38; N, 7.11) supported the structure of _{C 15 TEMPO.}

Examples 5-6: C with carboxylic acid _n Synthesis of TEMPI

In the formula, EDAC / HCl represents 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride. DMAP represents 4-dimethylaminopyridine.

[Example 5: C ₁₂ TEMPI]
4-Amino-2,2,6,6-tetramethylpiperidine (Compound 6; 0.60 mL, 3.5 mmol), 4-dimethylaminopyridine (547 mg, 4.5 mmol), lauric acid (Compound 7; 690 mg, 3.4 mmol) ) And dichloromethane (20 mL) was added 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (861 mg, 4.5 mmol) at 0 ° C. The reaction mixture was stirred at room temperature for about 52 hours and then washed with 0.5 M hydrochloric acid (20 mL x 2). The organic layer was dried over sodium sulfate to remove the solvent. The obtained crude product was recrystallized from methanol and diethyl ether to _{obtain C 12} TEMPI (927 mg, yield 80%) as a white powder. Mass spectrometry (FAB-MS) [calcd for C ₂₁ H ₄₃ N ₂ O [M + H] ⁺ 339, found 339] supported the structure of _{C 12 TEMPI.}

To further confirm the generation of C _{12 TEMPI, the obtained C 12} TEMPI was converted to _{C 12} TEMPO according to the conditions previously reported (J. Am. Chem. Soc. 2018, 140, 3798-3808). A _{mixture of C 12} TEMPI (91.2 mg, 0.27 mmol), 30% hydrogen peroxide solution (0.12 mL), sodium tungstate dihydrate (10.3 mg, 0.031 mmol) and methanol (1.3 mL) at 65 ° C. for 24 hours. It was heated and stirred. The crude product obtained by extracting the reaction mixture with ethyl acetate (2 mL × 2) was purified by a medium-pressure preparative purification device [hexane: ethyl acetate = 69:31 → 48:52, flow velocity 10 mL / min, a silica gel column (Purif-Pack (registered trademark) -EX SI 25 μm, SIZE 20, SHOKO SCIENCE, Yokohama, Japan)] and C ₁₂ TEMPO (5.7 mg, yield 6%) were obtained. Mass spectrometry (EI-MS) [calcd for C ₂₁ H ₄₁ N ₂ O ₂ [M] ^{+ ·} 353.32, found 353.32] supported the structure of _{C 12 TEMPO.}

[Example 6: C ₁₈ TEMPI]
4-Amino-2,2,6,6-tetramethylpiperidine (Compound 6; 0.60 mL, 3.5 mmol), 4-dimethylaminopyridine (550 mg, 4.5 mmol), stearic acid (Compound 8; 882 mg, 3.1 mmol) ) And dichloromethane (20 mL) was added 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (857 mg, 4.5 mmol) at 0 ° C. The reaction mixture was stirred at room temperature for about 25 hours and then washed with 0.5 M hydrochloric acid (50 mL x 3). After drying the organic layer with sodium sulfate, the solvent was removed to _{obtain C 18} TEMPI (1.30 g, 99% yield) as a white powder. Mass spectrometry (FAB-MS) [calcd for C ₂₇ H ₅₅ N ₂ O [M + H] ⁺ 423, found 423] supported the structure of _{C 18 TEMPI.}

An organic friction modifier using a synthesized piperidine compound was evaluated by making full use of a pin-on-disc test. The coefficient of friction was measured by these methods. Control experiments were always performed under the same conditions using the stearic acid or stearylamine to be compared.

Lubricating oil (Example 7 and Comparative Examples 1 to 3)
_{The C 12} TEMPO synthesized in Example 2 and the purchased stearic acid and stearonitrile were used as organic friction modifiers.

As the base oil, a polyalphaolefin oil having a viscosity of 6 cSt at 100 ° C. (manufactured by Chevron Phillips; hereinafter, sometimes simply referred to as "PAO6") was used. In the friction measurement, three kinds of organic friction modifiers were sonicated and stirred in the base oil PAO6 at a concentration of 1% by mass for about 45 minutes, and then heated in an oil bath at 65 ° C. for about 15 minutes to dissolve them separately. The viscosity of each lubricating oil was measured with a viscometer (TPE-100, manufactured by Toki Sangyo Co., Ltd.) at the same temperature of 40 ° C. as the friction measurement. The results are shown in Table 1.

Lubricating oil (Example 8 and Comparative Examples 4 to 5)
Similar to Example 7 and Comparative Examples 2 and 3 above, except that the contents of _{C 12} TEMPO synthesized in Example 2 and the purchased stearic acid and stearylamine were adjusted to 0.5% by mass, respectively. Lubricants of Example 8 (C ₁₂ TEMPO 0.5% by mass), Comparative Example 4 (stearic acid 0.5% by mass) and Comparative Example 5 (stearylamine 0.5% by mass) were obtained.

Friction measurement Friction measurement was performed with a pin-on-disk rotary tribotester as shown in FIG. The device includes a rotating oil container and fixing pins. A spherical ball having a diameter of 8 mm was used as the pin. The disc was fixed in a rotating vessel and dipped in the sample lubricant. Both the pins and the discs were made of SUS304 stainless steel.

In the measurement, the vertical load applied to the pin was increased from 1.1N to 38.8N. This corresponds to applying a Hertz contact pressure of 0.36 to 1.18 GPa between the pin and the disc. By increasing the rotational speed ω of the oil container, the sliding speed increased from 8.4 to 89.0 mm / s. A heater was embedded under the oil container to fix the temperature at 40 ° C. After running-in for 2 minutes under each load and sliding speed condition, the frictional force was measured for 1 minute at a sampling rate of 1.0 kHz, and the average value was calculated.

Results Figure 4 shows the dynamics of the lubricating oil using pure PAO6 (Comparative Example 1) and the lubricating oil using two types of organic friction modifiers (Example 7 and Comparative Example 2) as the sliding speed increases. It shows the change in the coefficient of friction. The vertical load was fixed at a relatively low value of 1.5 N and the corresponding Hertz contact pressure was 0.40 GPa. Both organic friction modifiers exhibited much smaller friction coefficients than pure base oils, especially at low sliding speeds. With stearic acid, the coefficient of friction remains almost constant at about 0.15 even when the sliding speed changes, whereas with the organic friction modifier of the present invention, it converges to about 0.13 as the sliding speed increases. did. From the above, it is shown that the organic friction modifier of the present invention is effective at any sliding speed.

FIG. 5 shows the change in frictional force with increasing vertical load of the lubricating oil (Example 7, Comparative Example 2 and Comparative Example 3) using three kinds of organic friction modifiers. At a sliding speed of 68.0 mm / s, the frictional forces of all three organic friction modifiers increased linearly with approximately the same gradient (ie, the same friction coefficient) of 0.12. The vertical load increases to a critical value, beyond which the frictional force increases sharply. As a result, the critical load of the organic friction modifier of the present invention was clearly the maximum, which was almost three times the load of stearic acid and stearonitrile. This indicates that the organic friction modifier of the present invention has a high load-bearing capacity.

Next, using the lubricating oils of Examples 8 and Comparative Examples 4 to 5, the vertical load was 5N, the sliding speed was 20.4 mm / s, the test time was 3600 seconds, and the change in friction coefficient with the passage of time was changed. The measurement was performed, and the wear marks were observed under a microscope after the test. The results are shown in FIG. As a result, in Example 8 using the organic friction modifier of the present invention, wear marks could be reduced and the friction coefficient during measurement was small and stable as compared with Comparative Examples 4 to 5. Therefore, it can be understood that the amount of wear can be reduced by the organic friction modifier of the present invention. It is also suggested that the organic friction modifier of the present invention is easily adsorbed on the metal formation surface.

Claims (9)

General formula (1):

[In the formula, R ¹ represents a hydrogen atom or an oxygen radical. When n is an integer of 2 or more, n R ^2s are the same or different and represent hydrocarbon groups. R ³ and R ⁴ are the same or different and represent a single bond or a carbonyl group. R ⁵ and R ⁶ are the same or different and represent a hydrogen atom or a hydrocarbon group. When R ⁵ is a hydrogen atom, R ³ is a single bond, and when R ⁶ is a hydrogen atom, R ⁴ is a single bond. Moreover, ^{neither R 5} nor R ⁶ becomes a hydrogen atom. n represents an integer from 0 to 8. ]
An organic friction modifier containing a piperidine compound represented by. The piperidine compound has the general formula (1A):

[In the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ are the same as described above. ]
The organic friction modifier according to claim 1, which is a piperidine compound represented by. The organic friction modifier according to claim 1 or 2, wherein R ^{2 is an alkyl group.} The one according to any one of claims 1 to 3, wherein R ³ is a carbonyl group, R ⁴ is a single bond, R ⁵ is a hydrocarbon group, and R ^{6 is a hydrogen atom.} Organic friction modifier. General formula:

2,2,6,6-tetramethylpiperidin 1-oxyl compound represented by. An organic friction modifier containing the 2,2,6,6-tetramethylpiperidin1-oxyl compound according to claim 5. The organic friction modifier according to any one of claims 1 to 4 and 6, which is an organic friction reducing agent. The organic friction modifier according to any one of claims 1 to 4 and 6 to 7, which is for a metallic material. A lubricant containing the organic friction modifier according to any one of claims 1 to 4 and 6 to 8 and a base oil.

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