JP7399468B2 - organic friction modifier - Google Patents

Description

The present invention relates to organic friction modifiers.

In order to realize a society in harmony with the environment, there is a strong need for mechanical systems such as automobiles and machine tools to save energy and reduce environmental impact, and the establishment of green lubrication technology that can minimize energy loss due to friction is a global goal. This is an important issue. In this specification, "green lubrication technology" refers to science and technology from the perspective of tribology (a study related to friction, wear, lubrication, etc.) that considers the impact on the environment and living organisms and harmony with nature. . Lowering the viscosity of lubricating oil is known as the most effective method for reducing friction loss. The economic effect of improving friction and wear is estimated to be equivalent to about 2% of GNP. For example, in automobiles, fuel loss due to friction is 388 billion liters per year worldwide, and approximately 1 billion tons of carbon dioxide is lost. Equivalent to emissions. However, when the relative motion speed of the two solid surfaces is low, such as when starting and stopping an automobile engine, the low viscosity lubricating oil cannot sufficiently separate the two solid surfaces, so friction and wear rapidly increase due to direct contact between the solids. and the durability of the system is compromised. As a solution to this problem, a method is used in which sulfur or phosphorus-based substances and fatty acids called organic friction modifiers (hereinafter sometimes referred to as "OFM") are added to low-viscosity lubricating oils. I've been exposed to it. Using an automobile engine as an example, Figure 1 shows an image of a lubrication system containing OFM additives on surfaces that rub against each other (sliding surfaces). Even during high-load and high-speed sliding, the OFM additive molecules can firmly adsorb to the sliding surface and form a film that prevents solid contact, which reduces friction and wear and further improves the lubricant's performance. Holds the key to lower viscosity. In other words, organic friction modifiers (OFM), which are added to the lubricating oil used in the moving parts of automobiles and machine tools, hold the key to improving the fuel efficiency of automobiles and machine tools.

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

Tribol Lett (2015) 60: 5

A century has passed since stearic acid and its derivatives were used as organic friction modifiers (OFM), but the concept of OFM's molecular structure still remains basically based on one terminal functional group that hydrogen bonds with the sliding surface. Because it follows the conventional structure of a single alkyl chain, the limits of performance are beginning to appear. Therefore, in reality, it is difficult to use OFM alone, and it is essential to use it in combination with additives such as molybdenum dithiocarbamate (MoDTC) and dialkyldithiophosphoric acid (ZnDTP) to supplement the load-bearing capacity. However, MoDTC, for example, is very expensive and contains transition metals and sulfur, which has a negative impact on the environment. In order to contribute to achieving the goals of the Paris Agreement and increase market competitiveness, it is essential to further reduce the viscosity of lubricating oils. development is required.

Furthermore, conventionally used OFMs using fatty acid derivatives were unable to sufficiently reduce friction; the coefficient of friction tended to change over time and was unstable, and the amount of wear was high.

The present invention solves these problems, and is capable of sufficiently reducing friction, has a stable friction coefficient that does not easily change over time, and has small wear marks on sliding surfaces. The purpose of the present invention is to provide an organic friction modifier that also has excellent load-bearing capacity.

As a result of repeated studies to achieve the above object, the present inventors found that an organic friction modifier containing a piperidine compound having a specific structure can sufficiently reduce friction, and that It has been found that the friction coefficient is stable and does not change easily, the amount of wear is reduced, and the load bearing capacity is excellent. The present inventors conducted further studies based on the above knowledge 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 ² 's are the same or different and represent a hydrocarbon group. 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. Note that 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. Furthermore, both R ⁵ and R ⁶ are never hydrogen atoms. 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 above. ]
Item 2. The organic friction modifier according to Item 1, which is a piperidine compound represented by:

Item 3. Item 3. The organic friction modifier according to Item 1 or 2, wherein each of R ² is an alkyl group.

Item 4. Item 4. The organic compound 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:

A 2,2,6,6-tetramethylpiperidine 1-oxyl compound represented by:

Item 6. Item 5. An organic friction modifier containing the 2,2,6,6-tetramethylpiperidine 1-oxyl compound according to item 5.

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

Section 8. The organic friction modifier according to any one of Items 1 to 4 and 6 to 7, which is used for metal 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, friction can be sufficiently reduced without using additives containing transition metals such as molybdenum dithiocarbamate (MoDTC) or sulfur, and the friction coefficient is less likely to change over time, resulting in stable friction. It is possible to provide an organic friction modifier having a high coefficient of wear, reduced wear amount, and excellent load-bearing ability.

Figure 2 illustrates organic friction modifiers (OFM) in moving parts of automobile engines. This figure shows changes in sliding surfaces over time when an organic friction modifier is applied to the moving parts of an automobile engine. 1 shows a schematic diagram of a pin-on-disk type unidirectional tribo tester used for friction measurement in Examples. 2 shows changes in the dynamic coefficient of friction as the sliding speed increases in the lubricating oils of Example 7, Comparative Example 1, and Comparative Example 2. 2 shows changes in frictional force as the vertical load increases in the lubricating oils of Example 7, Comparative Example 2, and Comparative Example 3. Friction over time when a friction test was conducted using the lubricating oils of Example 8 and Comparative Examples 4 and 5 with a vertical load of 5 N, a sliding speed of 20.4 mm/s, and a test time of 3600 seconds. Changes in the coefficient and appearance of wear marks after the test are shown.

In this specification, "contain" is a concept that includes all of "comprise," "consist essentially of," and "consist of." Furthermore, in this specification, when a numerical range is expressed as "A to B", it means greater than or equal to A and less than or equal to B.

In this specification, "sliding surface" means a surface that slides against each other while rubbing against each other. Furthermore, in this specification, "sliding speed" means the relative speed of surfaces that slide against each other while rubbing against each other.

As used herein, the term "organic friction modifier", particularly "organic friction reducer", refers to an additive containing an organic compound for the purpose of reducing friction on sliding surfaces. Usually, it is used by dissolving it in base oil, and a film can be formed by physical or chemical adsorption on the sliding surface, thereby reducing friction.

As used herein, "coefficient of friction" means the ratio of frictional force to the load acting perpendicularly to the contact surface (vertical load). This is a coefficient that expresses the slip resistance, and the larger the coefficient, the more difficult it is to slip.

As used herein, the "pin-on-disc test" is one of the standard friction tests. By pressing a pin-shaped sample against a rotating disk sample, it is possible to measure the amount of wear, changes in frictional force, and changes in friction coefficient.

In this specification, the terms "hard acid," "hard base," "soft acid," and "soft base" were proposed by R. G. Pearson, and are based on the compatibility (bond strength and reaction) of acids and bases. This is a concept that uses the expressions hardware and software to classify the ease of use. Generally, hard acids and hard bases tend to form strong bonds and react easily. On the other hand, soft acids and soft bases tend to form strong bonds and react easily.

1. Organic Friction ModifiersCurrently , fatty acid derivatives and aliphatic amines are mainly used as organic friction modifiers, but there are limits to their improvement effects. In fact, it is essential to use it in combination with molybdenum dithiocarbamate (MoDTC) and dialkyldithiophosphoric acid (ZnDTP) to supplement the load-bearing capacity. However, MoDTC, for example, is very expensive, contains transition metals and sulfur, and has a negative impact on the environment. Therefore, in order to reduce the environmental impact, there is a need for an organic friction modifier that can reduce the amount of additives such as molybdenum dithiocarbamate (MoDTC) and dialkyldithiophosphoric acid (ZnDTP) used.

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 ² 's are the same or different and represent a hydrocarbon group. 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. Note that 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. Furthermore, both R ⁵ and R ⁶ are never hydrogen atoms. 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 constantly adsorbs to the sliding surface. Incidentally, the sliding surface generally changes with sliding time in many cases. Taking the case of applying an organic friction modifier to the moving parts of an automobile engine as an example, as shown in Figure 2, the sliding surface is generally a metal oxide, which is an oxide film formed on the surface of a metal material. As the surface wears down due to contact, a new metal surface appears. The sliding surface during actual operation is a mixture of metal oxide and unoxidized metal. For this reason, 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 the concepts of hard acids and bases and soft acids and soft bases by RG Pearson, metal oxides are hard acids and metal nascent surfaces are soft acids. As described above, since the chemical properties of the two are different, it has been difficult to achieve the objective with conventional organic friction modifiers. In contrast, the organic friction modifier of the present invention can be adsorbed to both the surface of the metal oxide and the new metal surface, and as a result, the friction can be sufficiently reduced and It has a stable friction coefficient that does not easily change, and can also reduce the amount of wear. Moreover, since the piperidine compound represented by the general formula (1) in the organic friction modifier of the present invention has a piperidine ring which is a cyclic structure, it can withstand high loads. Therefore, the piperidine compound represented by general formula (1) can reduce the amount of additives such as molybdenum dithiocarbamate (MoDTC) and dialkyldithiophosphoric acid (ZnDTP), and also It is environmentally friendly as it does not contain any metals.

In addition, the piperidine compound represented by the general formula (1) is difficult to derivatize with organic friction modifiers using stearic acid or its derivatives, but it is difficult to derivatize it with R ¹ , R ⁵ , R ⁶ , etc. It is possible to freely introduce functional groups according to performance, and there is a high degree of freedom in design. Furthermore, it is also possible to freely adjust the compatibility with other additives contained in lubricating oil as an actual product.

In addition, 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 nascent surface, which is a soft acid. Therefore, when using a piperidine compound represented by general formula (1) in which R ¹ is a hydrogen atom and a piperidine compound represented by general formula (1) in which R ¹ is an oxygen radical, metal It can be made to be more easily adsorbed to both the oxide surface and the new metal surface, further reducing friction, having a more stable friction coefficient even with changes over time, and further reducing the amount of wear on the sliding surface. Among these, from the viewpoints of solubility, ease of synthesis, friction reduction, stable friction coefficient, wear amount, load bearing capacity, etc., oxygen radicals are preferable as R ¹ among hydrogen atoms and oxygen radicals. Currently, friction modifiers that are soft acids that tend to be adsorbed to the nascent metal surface are friction modifiers that contain sulfur, which is viewed as a problem from an environmentally friendly perspective.

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 examples include aliphatic hydrocarbon groups such as an alkyl group, an alkenyl group, and an alkynyl group. Can be mentioned. These hydrocarbon groups may contain heteroatoms such as oxygen atoms and nitrogen atoms.

Examples of the alkyl group as a hydrocarbon group represented by ^R2 include methyl group, ethyl group, propyl group (n-propyl group, isopropyl group, etc.), butyl group (n-butyl group, isobutyl group, sec-butyl group, etc.). Examples include alkyl groups having 1 to 6 carbon atoms, such as tert-butyl group, pentyl group (n-pentyl group, neopentyl group, etc.), and hexyl group (n-hexyl group, etc.).

Examples of the alkenyl group as the hydrocarbon group represented by R ² include vinyl group, 1-propenyl group, isopropenyl group, 2-methyl-1-propenyl group, 1-butenyl group, 2-butenyl group, 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 straight-chain or branched alkenyl groups having 2 to 10 carbon atoms. Furthermore, the position and number of double bonds are arbitrary and can be adjusted as appropriate.

Examples of the alkynyl group as a hydrocarbon group represented by R ² include ethynyl group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group, 1-pentynyl group, Straight or branched carbon atoms 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, etc. Examples include 2 to 10 alkynyl groups. Moreover, the position and number of triple bonds are arbitrary and can be adjusted as appropriate.

Among these, an alkyl group is preferable as R ² from the viewpoints of ease of synthesis, friction reduction, stable friction coefficient, amount of wear, load-bearing ability, and the like. When n, which is the number of R ² s, is 2 or more, it is preferable that all of them are alkyl groups. Further, when n, which is the number of R ² s, is 2 or more, each R ² may be the same or different.

In general formula (1), n, which is the number of hydrocarbon groups represented by R ² , is not particularly limited, and from the viewpoints of ease of synthesis, friction reduction, stable friction coefficient, amount of wear, load-bearing ability, etc. An integer of 0 to 8 is preferred, an integer of 1 to 7 is more preferred, and an integer of 2 to 6 is even more preferred.

In general formula (1), n, the number of hydrocarbon groups represented by ^R2 , should be 4 from the viewpoint of ease of synthesis, friction reduction, stable friction coefficient, amount of wear, load-bearing capacity, etc. is particularly preferred. That is, general formula (1A):

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

In 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. Further, 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 these, when both R ⁵ and R ⁶ are hydrocarbon groups, R ³ and R ⁴ are preferably both single bonds, 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 viewpoint of solubility, ease of synthesis, friction reduction, stable friction coefficient, amount of wear, load bearing capacity, etc. and R ⁴ is preferably a single bond.

In general formula (1), the hydrocarbon groups represented by R ⁵ and R ⁶ are not particularly limited as long as they are monovalent hydrocarbon groups, such as aliphatic hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups. Hydrogen group; examples include aromatic hydrocarbon groups such as aryl groups (phenyl group, biphenyl group, terphenyl group, etc.). 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 adjusted as appropriate. Here, from the viewpoints of solubility, ease of synthesis, friction reduction, stable friction coefficient, wear amount, load-bearing capacity, etc., aliphatic hydrocarbon groups are preferable, linear ones are more preferable, and the number of carbon atoms is It is further preferable that the value is appropriately large. From this viewpoint, the hydrocarbon group represented by R ⁵ and R ⁶ is a straight-chain alkyl group, alkenyl group, or alkynyl group having 5 to 25 carbon atoms (especially 7 to 20 carbon atoms, and even 9 to 15 carbon atoms). preferable. Specifically, -(CH ₂ ) _n1 CH ₃ (n1 is an integer from 4 to 24), -CH=CH-(CH ₂ ) _n2 CH ₃ (n2 is an integer from 2 to 22), - CH≡CH-(CH ₂ ) _n3 CH ₃ (n3 is an integer from 2 to 22), and the like.

R ⁵ and R ⁶ in general formula (1) cannot both be hydrogen atoms from the viewpoints of solubility, ease of synthesis, friction reduction, stable friction coefficient, amount of wear, load bearing capacity, etc. That is, at least one of them is the above hydrocarbon group. In addition, only one of R ⁵ and R ⁶ can be a hydrocarbon group and the other can be a hydrogen atom, but by increasing the number of hydrocarbon chains, the adsorption film density can be further improved, and the load-bearing capacity and Both R ⁵ and R ⁶ can also be hydrocarbon groups for the purpose of further improving the friction reduction effect and the like.

Among the above-mentioned piperidine compounds, general formula:

The 2,2,6,6-tetramethylpiperidine 1-oxyl compound represented by is a new compound that has not been described in any literature.

(1-2) Synthesis method of 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, a combination of an amino group-containing piperidine compound and a carboxylic acid compound. It can be easily synthesized by introducing the above-mentioned carbonyl hydrocarbon group through a condensation reaction, or by introducing the above-mentioned hydrocarbon group through 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.

There are no particular limitations on the amino group-containing piperidine compound, and general formula (2):

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

The carboxylic acid compound to which a carbonyl hydrocarbon group is introduced is not particularly limited, and can be represented by 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 can be used.

In the general formula (3), the hydrocarbon group represented by R ^5a is not particularly limited, and the hydrocarbon groups described for R ⁵ and R ⁶ above can be employed.

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, an iodine atom, and the like. Among these, a chlorine atom is preferred from the viewpoint of ease of synthesis.

In addition, in the amino group-containing piperidine compound represented by 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 general formula (3) to be used is usually preferably 0.2 to 2 mol, and 0.2 to 2 mol, per 1 mol of the amino group-containing piperidine compound represented by general formula (2). More preferably 5 to 1.5 mol.

Moreover, 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, diisopropylamine, etc.; pyridine compounds such as pyridine, N,N-dimethyl-4-aminopyridine (DMAP), etc. 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, per 1 mol of the amino group-containing piperidine compound represented by general formula (2).

In the amino group-containing piperidine compound represented by 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 condensing agents (N,N'-dicyclohexylcarbodiimide (DCC), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC), diisopropylcarbodiimide), and imidazole condensing agents. agent (carbonyldiimidazole, 2-chloro-1,3-dimethylimidazolinium chloride), triazine condensing agent (4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4- Condensing agents such as methylmorpholinium chloride) can be used. These condensing agents can 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, per 1 mol of the amino group-containing piperidine compound represented by general formula (2).

The reaction can usually be carried out in the presence of a reaction solvent. Examples of reaction solvents that can be used include ether compounds such as diethyl ether, diisopropyl ether, tetrahydrofuran, 1,4-dioxane, dimethoxyethane, and cyclopentyl methyl ether; aromatic hydrocarbon compounds such as benzene, toluene, and xylene; dichloromethane, dichloroethane, etc. , chloroform, aliphatic halogenated hydrocarbon compounds such as carbon tetrachloride; nitrile compounds such as acetonitrile; amide compounds such as dimethylformamide, dimethyl sulfoxide, etc. From the viewpoint of ease of synthesis, yield, etc., ether compounds , aliphatic halogenated hydrocarbon compounds are preferred, and tetrahydrofuran, dichloromethane and the like are preferred. 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 usually be employed. 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 that allows the reaction to proceed sufficiently.

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

In addition, 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 using a conventional method. .

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

The organic friction modifier of the present invention can adopt a structure consisting only of the piperidine compound represented by the above general formula (1), but does not necessarily contain only the piperidine compound represented by the above general formula (1). There is no need to configure it.

For example, there is no problem even if a small amount of impurities such as raw material compounds, condensing agents, bases, etc. used in the synthesis process remain as unavoidable impurities. 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, amount of wear, load-bearing capacity, etc. , more preferably 0 to 2% by mass.

The organic friction modifier of the present invention that meets these conditions can sufficiently reduce friction, have a stable friction coefficient that is difficult to change due to changes over 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 a lubricant, it is possible to reduce the amount of additives such as molybdenum dithiocarbamate (MoDTC) and dialkyldithiophosphoric acid (ZnDTP), thereby reducing organic friction. It is useful as a drug.

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 solid objects, such as when starting and stopping an automobile engine. In other words, it is particularly useful for metal materials that are sliding surfaces when applied to automobile engines. Examples of such metal materials include stainless steel and carbon steel. In this case, if an oxide film is formed on the surface of the metal material, the internal metal will be exposed as friction progresses, but in this case, a friction reduction effect is recognized for both the metal oxide and the metal. It will be done.

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

The base oil is not particularly limited, but it is preferably selected in consideration of the solubility of the organic friction modifier of the present invention. Examples of such 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 viewpoint of solubility, friction reduction, stable friction coefficient, wear amount, load carrying capacity, etc. On the other hand, it is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight.

The lubricant of the present invention also includes antioxidants (hindered phenol compounds, aromatic secondary amine compounds, etc.), viscosity index improvers (polybutene, polyisobutene, polyisobutylene, polyisoprene, polymethacrylate, etc.), Oiliness improvers (long-chain fatty acid compounds such as oleic acid or their esters, long-chain amine compounds such as oleylamine or their esters, etc.), extreme pressure agents (sulfur-containing compounds such as monosulfides, disulfides, sulfoxides, sulfur phosphides; chlorination) chlorine-containing compounds such as paraffin), solid lubricants (molybdenum disulfide, graphite, boron nitride, melamine cyanurate, polytetrafluoroethylene, etc.), rust inhibitors (paraffin oxides, metal carboxylates, metal sulfonates, It may also contain additives such as carboxylic acid esters, sulfonic acid esters, etc.), flow-reducing agents (polyalkyl methacrylates, polyalkyl acrylates, polyalkylstyrenes, polyvinyl acetates, etc.). In this case, the content of each additive can be the amount conventionally ordinarily used.

The ripple effects of the organic friction modifier of the present invention as described above are enormous both socially and economically. This is because organic friction modifiers are used along with lubricants wherever power is generated and transmitted. The fields of use are manufacturing (chemical industry, petrochemical industry, steel industry, etc.), transportation (automobiles, aircraft, railways, 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 explained in detail in the form of examples. The following examples do not limit the application of the present invention in any way.

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

In the formula, THF represents tetrahydrofuran.

[Example 1: C ₉ TEMPO]
It was synthesized according to a previous report (Magnetic Resonance Imaging 1992, 10, 445-455). 4-Amino-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (compound 1; 1.28 g, 7.5 mmol), tetrahydrofuran (80 mL) and triethylamine (2.0 mL, 14 mmol) in a mixture of 0 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 x 2), the organic layer was dried with sodium sulfate. After removing the solvent, the obtained crude product was purified using a medium-pressure preparative purification device [hexane:ethyl acetate = 50:50, flow rate 20 mL/min, silica gel column (Purif-Pack (registered trademark)-EX]). C ₉ TEMPO (1.50 g, yield 74%) was obtained as a wine red oil. 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-tetramethylpiperidine 1-oxyl free radical (Compound 1; 1.21 g, 7.1 mmol), tetrahydrofuran (150 mL) and triethylamine (0.90 mL, 6.5 C ₁₂ TEMPO ( 1.82 g (80% yield) was obtained as a wine red solid. 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]
Similar to Example 1, 4-amino-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (Compound 1; 1.21 g, 7.0 mmol), tetrahydrofuran (100 mL) and triethylamine (2.0 mL, 14 C 18 by slowly dropping a mixture of stearoyl chloride (compound 4; 2.2 mL, 6.5 mmol) and tetrahydrofuran (24 mL) into a mixture of C 18 mmol) 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 using carboxylic acid ₁₅ Synthesis of TEMPO

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

4-Amino-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (Compound 1; 586 mg, 3.4 mmol), 4-dimethylaminopyridine (556 mg, 4.6 mmol), Pentadecanoic acid (Compound 5; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (879 mg, 4.6 mmol) was added to a mixture of 700 mg, 2.9 mmol) and dichloromethane (20 mL) at 0°C. After stirring the reaction mixture at room temperature for 27 hours, it was washed with 0.5 M hydrochloric acid (30 mL x 2). The organic layer was dried over sodium sulfate and the solvent was removed. The obtained crude product was purified using a medium pressure preparative purification device [hexane:ethyl acetate = 71:29 → 50:50, flow rate 20 mL/min, silica gel column (Purif-Pack (registered trademark)-EX SI 25 μm , SIZE 120, SHOKO SCIENCE, Yokohama, Japan)], C ₁₅ TEMPO (1.07 g, yield 94%) was obtained as a wine red solid. Mass spectrometry (EI-MS) [calcd for C ₂₄ H ₄₇ N ₂ O ₂ [M] ^+・395.36375, 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 using carboxylic acid _n Synthesis of TEMPI

In the formula, EDAC·HCl represents 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. DMAP stands for 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. After stirring the reaction mixture at room temperature for about 52 hours, it was washed with 0.5 M hydrochloric acid (20 mL x 2). The organic layer was dried over sodium sulfate and the solvent was removed. 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 _C21H43N2O [M+H] ⁺ 339, _found 339] supported the structure _{of C12TEMPI} .

In order to further confirm the production 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 (0.12 mL), sodium tungstate dihydrate (10.3 mg, 0.031 mmol) and methanol (1.3 mL) was incubated at 65°C for 24 hours. The mixture was heated and stirred. The crude product obtained by extracting the reaction mixture with ethyl acetate (2 mL x 2) was purified using a medium pressure preparative purification device [hexane: ethyl acetate = 69:31 → 48:52, flow rate 10 mL/ min, silica gel column (Purif-Pack (registered trademark)-EX SI 25 μm, SIZE 20, SHOKO SCIENCE, Yokohama, Japan)], C ₁₂ TEMPO (5.7 mg, yield 6%) was 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. After stirring the reaction mixture at room temperature for about 25 hours, it was 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, yield 99%) as a white powder. Mass spectrometry (FAB-MS) [calcd for _C27H55N2O [ _M +H] ⁺ 423, found 423] supported the _structure of _C18TEMPI .

An organic friction modifier using a synthesized piperidine compound was evaluated using a pin-on-disk test. The friction coefficient was measured using these methods. Control experiments were always performed under the same conditions using stearic acid or stearylamine for comparison.

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

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

Lubricating oil (Example 8 and Comparative Examples 4-5)
Same as Example 7 and Comparative Examples 2 to 3 above, except that the content of C ₁₂ TEMPO synthesized in Example 2 and the purchased stearic acid and stearylamine were each adjusted to 0.5% by mass. Then, lubricating oils of Example 8 (0.5% by mass of C ₁₂ TEMPO), Comparative Example 4 (0.5% by mass of stearic acid), and Comparative Example 5 (0.5% by mass of stearylamine) were obtained.

Friction Measurement Friction measurement was performed using a pin-on-disk rotating tribo tester as shown in FIG. The device includes a rotating oil container and a fixing pin. A spherical ball with a diameter of 8 mm was used as a pin. The disk was fixed in a rotating container and immersed in sample lubricating oil. Both the pin and the disk were made of SUS304 stainless steel.

In the measurements, the vertical load applied to the pin was increased from 1.1N to 38.8N. This corresponds to applying a Hertzian contact pressure of 0.36 to 1.18 GPa between the pin and the disc. By increasing the rotation 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 a 2-minute break-in operation 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 determined.

Results Figure 4 shows the dynamic behavior 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 friction coefficient. The vertical load was fixed at a relatively low value of 1.5 N, and the corresponding Hertzian contact pressure was 0.40 GPa. Both organic friction modifiers exhibited much lower coefficients of friction than the pure base oils, especially at low sliding speeds. In stearic acid, the coefficient of friction remains approximately constant at approximately 0.15 even if the sliding speed changes, whereas in the organic friction modifier of the present invention, it converges to approximately 0.13 as the sliding speed increases. did. From the above, it has been shown that the organic friction modifier of the present invention is effective at any sliding speed.

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

Next, using the lubricating oils of Example 8 and Comparative Examples 4 and 5, the vertical load was 5 N, the sliding speed was 20.4 mm/s, and the test time was 3600 seconds, and the change in the friction coefficient over time was measured. 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, as compared to Comparative Examples 4 and 5, wear marks could be reduced, and the friction coefficient during measurement was small and stable. Therefore, it can be understood that the amount of wear can be reduced by the organic friction modifier of the present invention. Furthermore, it has been suggested that the organic friction modifier of the present invention is likely to be adsorbed onto nascent metal surfaces.

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 ² 's are the same or different and represent a hydrocarbon group. 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. Note that 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. Furthermore, both R ⁵ and R ⁶ are never hydrogen atoms. 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 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 each of the R ² is an alkyl group. 4. The method according to claim 1, 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:

A 2,2,6,6-tetramethylpiperidine 1-oxyl compound represented by: An organic friction modifier containing the 2,2,6,6-tetramethylpiperidine 1-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 modifier. The organic friction modifier according to any one of claims 1 to 4 and 6 to 7, which is used for metal materials. A lubricant comprising 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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