EP4663723A1

EP4663723A1 - Lubricant composition, lubricant composition additive, and uses of lubricant composition

Info

Publication number: EP4663723A1
Application number: EP24181974.7A
Authority: EP
Inventors: Sergey Mamykin; Dmitry Privalov
Original assignee: NEOL Copper Technologies Ltd
Current assignee: NEOL Copper Technologies Ltd
Priority date: 2024-06-13
Filing date: 2024-06-13
Publication date: 2025-12-17
Also published as: CN121136754A

Abstract

An oil-soluble additive for a lubricant composition contains a metal salt of an organic acid, an aromatic amine, a succinimide derivative, an oil-soluble organic acid and zinc dialkyl dithiophosphate. The lubricant composition includes a base oil and the oil-soluble additive.

Description

This disclosure relates to an additive for lubricants based on mineral and synthetic oils. The additive confers antifriction, extreme pressure tolerance, antioxidant, and detergent and dispersant properties and may be used in the internal combustion engines (ICE) of trucks and cars, locomotives, river and marine fleet. Lubricant compositions comprising the additive and methods of using the lubricant compositions for wear protection of friction surfaces are also disclosed.
From the "Prior art", a metal-containing oil-soluble composition for lubricants is known, which contains a metal salt of an inorganic acid, an aliphatic alcohol, an epoxy resin and a 2-imino-substituted indoline; in addition, it also contains a metal salt of an organic acid, an aromatic amine and a succinimide polymer, wherein the following ratio of components is used, wt%: metal salt of an organic acid: 10-90; metal salt of an inorganic acid: 1.5-25; aliphatic alcohol: 3-55; aromatic amine: 1-8; epoxy resin: 2-10; succinimide polymer: 2-8; 2-imino-substituted indoline: 0.5-6 (see Russian Federation patent No. 2277579 C1, publ. on 10 June 2006 ).
From the "Prior art", a composition for oils ( PCT application WO2012107649, publ. on 16 August 2012 ) is also known, which contains, wt%:

abrasive particles: 0.005-0.1;
metal salt of an organic acid: 10-90;
metal salt of an inorganic acid: 1-25;
aliphatic alcohol: 3-55;
aromatic amine: 1-20;
epoxy resin: 2-18;
succinimide derivative: 2-50;
2-imino-substituted indoline: 0.5-6.

In addition, a lubricant additive composition, including oil-soluble metal salts of inorganic and oil-soluble metal salts of organic acids, is known from the "Prior art". In this case, the additive composition contains from 0.005 wt% to 0.1 wt%, preferably from 0.01 wt% to 0.05 wt%, most preferably from 0.01 wt% to 0.03 wt% abrasive particles, and it also includes at least one of the following substances: an aliphatic alcohol, a succinimide derivative, an aromatic amine, an epoxy resin, and/or a 2-imino-substituted indoline. The average diameter of the abrasive particles ranges from 0.5 µm to 20 µm; in addition, the abrasive particles contain carbonates, nitrides, carbides, and/or oxides of elements of the boron, carbon and/or alkaline earth metal groups (see Finnish patent No. 124709B, publ. on 15 December 2014 , and corresponding PCT application WO2012107649 ).
From Finnish patent No. 124709B, publ. on 15 December 2014 , a lubricant composition is also known, which includes the 10W40 base oil, containing 2.2% of the additive composition. At the same time, the additive composition includes oil-soluble metal salts of inorganic and organic acids.
In addition, the use of a lubricant composition for wear protection of friction surfaces is known, including the application of a lubricant containing from 1 to 5 wt% of the additive composition to the rubbing surfaces, while the indicated additive composition includes oil-soluble metal salts of inorganic and organic acids and from 0.005 wt% to 0.1 wt%, preferably from 0.01 wt% to 0.05 wt%, most preferably from 0.01 wt% to 0.03 wt% of abrasive particles (Finnish patent No. 124709B, publ. on 15 December 2014 ).
However, a technical problem arises from the use of the aforementioned compositions. Due to the presence of metal salts of inorganic acids, in the process of working on friction surfaces, the metals are reduced, and a "strong" inorganic acid is formed. This strong inorganic acid causes the metal surfaces and seal materials in the engine to oxidize. Furthermore, the presence of epoxy resin makes it difficult to form a metal protective film on the friction surface, and the presence of abrasive materials leads to clogging of the oil channels of the lubrication system of internal combustion engines.
The task of this group of inventions is to eliminate the above disadvantages.
The generalised technical result consists in eliminating damage to the oil channels of the lubrication system of internal combustion engines, as well as in improving anti-wear, extreme pressure and detergent properties and increasing the allowable loads in friction pairs.
The technical result is achieved by the fact that the oil-soluble additive contains a metal salt of an organic acid, an aromatic amine, a succinimide derivative, while it also contains an oil-soluble organic acid and 0.001-1.5 wt% zinc dialkyl dithiophosphate. In one example the following ratio of components is used, wt%:

metal salt of an organic acid: 3-10;

aromatic amine: 15-35;

succinimide derivative: 20-65 or 45-65;

organic acid: 5-15;

zinc dialkyl dithiophosphate: 0.001-1.5.
As a metal salt of an organic acid, metal salts of organic acids with a carbon number of C₁₅...C₁₈ may be used. As aromatic amines, diphenylamine or its homologues may be used, and as a succinimide derivative, industrially manufactured additives S-5A, S-1500 or S-1500V (sometimes referred to as C-5A, C-1500 and C-1500B) may be used.
The zinc dialkyl dithiophosphate (ZDDP) is derived from primary alcohols, secondary alcohols or a combination of primary and secondary alcohols. The inventors have found that ZDDP serves as a regulating agent in the composition, regulating the intensity of hydrogen polishing and the speed of copper film formation. It slows down free hydrogen activity in the friction zone. It does not allow this process to be too intense, which would cause surface destruction, thus allowing time for copper film to form with a smaller amount of copper particles at the surface. This is in contrast to its usual use as a primary anti-wear additive, in which it is thought to work by forming a layer consisting primarily of amorphous zinc phosphate under pressure, a mechanism unrelated to copper film formation. Due to the above-mentioned problems arising from the use of metal salts of inorganic acids, zinc dialkyl dithiophosphate is the only metal salt of an inorganic acid present in the additive. Furthermore, it is present in lower concentrations than it is typically present when used as an anti-wear additive.
An example of a commercially available ZDDP which has been found to work in the additive composition is Infineum^® C9417 which is a mixed primary/secondary zinc dialkyl dithiophosphate.
The technical result is also ensured by the fact that the lubricant composition includes a base oil and an oil-soluble additive, optionally comprising 95 to 98 wt% base oil and 2 to 5 wt% oil-soluble additive, for example wherein the following ratio of components is used, wt%:

base oil: 95-99

oil-soluble additive: 1-5; or

base oil: 97-98

oil-soluble additive: 2-3; or

base oil: 97.3-97.8;

oil-soluble additive: 2.2-2.7.
The base oil used in the lubricant composition, according to this invention, may be selected from any of the Group I-V base oils. Good results have been achieved with Grade III base oil.
In addition, the technical result is ensured by the fact that the use of a lubricant composition for wear protection of friction surfaces is provided, including the application of a lubricant composition containing 1 to 5 wt%, 2 to 3 wt% or 2.2 to 2.7 wt% of an oil-soluble additive to the rubbing surfaces.
The essence of this group of inventions is illustrated by the following illustrations:

Fig. 1 is a representation of the graphical dependence of the friction coefficient on the spindle speed for three samples of the lubricant composition (1) of the closest analogue, 2) of a lubricant composition with an additive containing 0.25% ZDDP, 3) of a lubricant composition with an additive containing 0.5% ZDDP);
Fig. 2 is a representation of the graphical dependence of the wear scar size on the spindle speed for three samples of the lubricant composition (1) of the closest analogue, 2) of a lubricant composition with an additive containing 0.25% ZDDP, 3) of a lubricant composition with an additive containing 0.5% ZDDP);
Fig. 3 is a representation of the graphical dependence of thermal heating on the spindle speed for three samples of the lubricant composition (1) of the closest analogue, 2) of a lubricant composition with an additive containing 0.25% ZDDP, 3) of a lubricant composition with an additive containing 0.5% ZDDP).

Base oil

The base oil used in the lubrication oil compositions according to this invention may be selected from any of the Group I-V base oils indicated in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines.

Group	Sulphur content, wt%	Saturated hydrocarbon content	Viscosity (VI)
I	>0.03 and/or	<90	80-119
II	≤0.03 and	≥90	80-119
III	≤0.03 and	≥90	≥120
IV	PAO (polyalphaolefins)
V	All others not included in Groups I-IV (naphthenic base oils and non-PAO synthetic oils)

Group IV base oils contain true synthetic chemical compounds obtained by the polymerisation of olefinically unsaturated hydrocarbons. Many Group V base oils are also truly synthetic and may include diesters, esters of polyhydric alcohols, polyalkylene glycols, alkylated aromatic compounds, phosphate esters, polyvinyl ethers and/or polyphenyl ethers, and the like, but may also be natural oils such as vegetable oils. It should be noted that, even though Group III base oils are derived from mineral oil, the careful processing that these fluids undergo results in their physical properties becoming very similar to some true synthetic compounds such as PAO. Therefore, oils derived from the Group III base oils may be referred to as synthetic fluids in this industry. The base oil used in the lubrication oil composition, according to this invention, may be a mineral oil, an animal oil, a vegetable oil, a synthetic oil, or mixtures thereof. Suitable oils may be obtained by hydrocracking, hydrogenation, hydrotreating from crude, refined and re-refined oils and mixtures thereof. Crude oils are oils obtained from a natural, mineral or synthetic source, with little or no further refining treatment. Refined oils are similar to crude oils and differ in that they undergo one or more refining steps that may lead to an improvement in one or more properties. Examples of suitable refining methods include solvent extraction, re-distillation, acid or base extraction, filtration, percolation, and the like. Oils refined to the characteristics of edible oils may or may not be useful. Edible oils may also be referred to as white oils. According to some embodiments, the lubrication oil compositions do not contain edible or white oils. Re-refined oils are also known as regenerated or recycled oils. These oils are obtained in a similar manner to refined oils, using the same or similar processes. Often, these oils are additionally processed by means of using methods aimed at removing the additives already used and oil degradation products. Mineral oils may include oils derived from boreholes or from plants or animals, or any mixtures thereof. For example, such oils may include, but are not limited to, castor oil, lard oil, olive oil, peanut oil, corn oil, soybean oil, and linseed oil, as well as mineral lubrication oils such as liquid petroleum oils and solvent or acid treated mineral lubrication oils of the paraffinic, naphthenic, or mixed paraffinic/naphthenic types. If necessary, such oils may be partially or fully hydrogenated. Oils derived from coal or shale may also be useful. Useful synthetic lubrication oils may include hydrocarbon oils such as polymerised, oligomerised, or interpolymerised olefins (for example, polybutylenes, polypropylenes, polypropylene/isobutylene copolymers); poly(1-hexanes), poly(1-octenes), trimers or oligomers of 1-decene, for example, poly(1-decene), such materials are often referred to as α-olefins, and mixtures thereof; alkyl benzenes (for example, dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)-benzenes); polyphenyls (for example, biphenyls, terphenyls, alkylated polyphenyls); diphenylalkanes, alkylated diphenylalkanes, alkylated diphenyl ethers and alkylated diphenyl sulfides and their derivatives, analogues or homologues, or mixtures thereof. Polyalphaolefins are usually hydrogenated substances. Other synthetic lubrication oils include esters of polyhydric alcohols, diesters, liquid esters of phosphorus-containing acids (for example, tricresyl phosphate, trioctyl phosphate, and decane phosphonic acid diethyl ester), or polymeric tetrahydrofurans. Synthetic oils may be obtained from the Fischer-Tropsch process, and they may usually be hydroisomerised hydrocarbons or Fischer-Tropsch waxes. According to one embodiment, oils may be obtained from the Fischer-Tropsch synthesis with regard to converting natural gas to liquids, as well as other oils derived from natural gas. More than 50 wt% of the base oil included in the lubricant composition may be selected from the group consisting of Group I, Group II, Group III, Group IV, Group V and a combination of two or more of the above, and where more than 50 wt% of the base oil differs from base oils resulting from the inclusion of additive components or viscosity index enhancers in the composition. According to another embodiment, more than 50 wt% of the base oil included in the lubricant composition may be selected from the group consisting of Group II, Group III, Group IV and Group V and a combination of two or more of the above, and where more than 50 wt% of the base oil differs from diluent oils resulting from the inclusion of additive components or viscosity index enhancers in the composition. According to some embodiments, the lubrication oil composition contains less than 10 wt% Group IV oils and Group V oils, alone or in combination. According to some embodiments, the lubrication oil compositions contain less than 5 wt% Group V oil. According to other embodiments, the lubrication oil composition does not contain any Group VI oils, while according to other embodiments, the lubrication oil composition does not contain any Group V oils. According to some embodiments, more than 50% of the base oil is a Group III base oil alone.
The lubrication oil composition includes an additive containing a metal salt of an organic acid, an aromatic amine, a succinimide derivative, an oil-soluble organic acid, and zinc dialkyl dithiophosphate (ZDDP).

Metal salt of an organic acid

As a metal salt of an organic acid (anti-wear agent), the additive may include a salt of copper and carboxylic acid (C₁₅-C₁₈), such as a copper salt of oleic acid. The metal salt of an organic acid may be a copper, silver, gold or platinum salt of an organic acid. Copper salts are particularly useful as they allow the formation of protective copper films on the metal surfaces under pressure. The more reducing metals from the reactivity series such as silver, gold or platinum should react in the same way, although they are less abundant and more expensive than copper. The metal salt of an organic acid may be present in the additive in an amount of from 1 to 10 wt%, or 1 to 9.5 wt% or 3 to 9.5 wt% or 3 to 10 wt%. The range 3 to 10 wt% is preferred. Preferably, the copper salt of an organic acid may be present in the additive in an amount of from 1 to 10 wt%, or 1 to 9.5 wt% or 3 to 9.5 wt% or 3 to 10 wt%. The range 3 to 10 wt% is preferred. Preferably, the copper salt of an organic acid is copper oleate and may be present in the additive in an amount of from 1 to 10 wt%, or 1 to 9.5 wt% or 3 to 9.5 wt% or 3 to 10 wt%. The range 3 to 10 wt% is preferred.

Aromatic amine

The antiknock component is an aromatic amine. Any aromatic amine suitable for use as an antiknock additive in a lubricant composition, or in a fuel composition for a spark ignition internal combustion engine, may be used in this invention.
Aromatic amine compounds suitable for use in this invention include aniline and alkyl-substituted aniline compounds, 1,2,3,4-tetrahydroquinoline, diphenylamine and alkyl-substituted diphenylamine compounds such as butyldiphenylamine, octyldiphenylamine and di-octyl-diphenylamine, 2-ethylhexyl-4-(dimethylamino)benzoate, indoline, N,N-dimethyl-1,4-phenylenediamine, o-toluidine, p-toluidine, p-anisidine, p-phenethidine, and the like, and mixtures thereof. Diphenylamine has been found to work very well for this purpose. Equally effective is butylated octylated diphenylamine, also known as BODPA or butyl octyl diphenylamine and sold under the name TL57 Butyl Octyl Diphenylamine.
The aromatic amine may be present in an amount of from 15 to 35 wt%, optionally 19 to 34 wt% or 19 to 32 wt%. Good results have been achieved with 19 to 32 wt% diphenylamine. BODPA is equally effective.

Succinimide derivative

The detergent component is a succinimide derivative, and the industrially manufactured additives, S-1500V or preferably S-5A and S-1500 (sometimes referred to as C-1500B, C-5A, C-1500) may be used. The succinimide derivative acts as a dispersant in the additive composition. The succinimide derivative may be selected from any succinimide-based dispersant, optionally selected from polyisobutylene succinimides, often referred to as PIBSI, a polyalkenyl succinimide or an alkenyl succinimide. The succinimide derivative may optionally be a bisuccinimide. The succinimide derivative may optionally be boronated. The use of succinimide derivatives in additives for lubricants is known from the prior art. The inventors have found that a higher amount of succinimide derivative than is used in prior art additive compositions is beneficial. The quantity used in the additive is within the conventional range, from 2 to 65 wt%, optionally 10 to 65 wt%, optionally 20 to 65 wt% or 45 to 65 wt%.
Commercially available succinimides are often provided in an oil-soluble solvent such as polyisobutylene or mineral oil. The solvent may be a mixture of oil-soluble solvents such as polyisobutylene and mineral oil. It has been found that the presence of these solvents does not hinder the efficacy of the additive. Additive S-5A is an ashless dispersant comprising a 40 to 52 wt% solution of alkenyl succinimide in mineral oil and polyisobutene. Additive S-1500 is an ashless dispersant comprising succinimide in polyisobutylene with an average molecular weight of 1300. S-1500V is an ashless dispersant comprising succinimide in polyisobutylene with an average molecular weight of 1300, modified with boron. Equally effective is the preferred commercially available boron containing T145B Polyisobutylene Bis-succinimide. This polyisobutylene bis-succinimide contains 1.1-1.3 wt% nitrogen and at least 0.3 wt% boron.

Organic acid

The additive contains an oil-soluble organic acid as an antioxidant. Examples of suitable fatty acids include oleic acid, linolenic acid, palmitoleic acid, or mixtures thereof. Often, fatty acids are obtained from lard oil, tallow oil, peanut oil, soybean oil, cottonseed oil, sunflower oil, or mixtures thereof. Oleic acid is preferred and has been used in the additive with good results. The organic acid may be present in an amount of from 5 to 20 wt%, preferably 5 to 15 wt%, for example 10 to 15 wt% or approximately 15 wt% in the additive.
An example of an oleic acid which has been found to work in the invention is oleic acid provided by Far Ocean Trade Co Limited, which comprises 1.144 wt% C14, 6.829 wt% C16, 1.167 wt% C18, 73.61 wt% C18:1, 7.57 wt% C18:2 and 1.033 wt% C18:3.

Zinc dialkyl dithiophosphate

ZDDP compounds may include the ZDDP derived from primary alcohols, secondary alcohols or a combination of primary and secondary alcohols. The lubrication oil compositions contain at least one ZDDP in which at least part of the ZDDP is derived from a secondary alcohol and more than 20% of the total alkyl groups of the ZDDP compounds are derived from a secondary alcohol. The molar ratio of secondary alcohol to primary alcohol used to obtain the ZDDP in the lubrication oil composition is from approximately 20:100 to 100:0, or from approximately 25:100 to 100:0, or from approximately 35:100 to 100:0, or from approximately 40:100 to 100:0, or from approximately 50:50 to 100:0, or from approximately 25:100 to 75:25, or from approximately 35:100 to 60:40. As a result, more than 20% to 100% of all alkyl groups in the ZDDP compounds are secondary alkyl groups, or 25-100% of the alkyl groups in the ZDDP compounds are secondary alkyl groups, or 35-100% are secondary alkyl groups, or 40-100% are secondary alkyl groups, or 50-100% are secondary alkyl groups, or 25-75% are secondary alkyl groups, or 35-60% are secondary alkyl groups.
The ZDDP may have a P:Zn ratio of approximately 1:0.8 to approximately 1:1.7. According to some embodiments, the additive contains at least two different zinc dialkyldithiophosphate salts. The two alkyl groups in a zinc dialkyldithiophosphate salt may be the same or different. According to some embodiments, 100 mol. percent of the alkyl groups of at least one zinc dialkyldithiophosphate salt may be derived from secondary alcohol groups. According to some embodiments, mixtures of zinc dialkyldithiophosphate salts, which are entirely derived from primary alcohols, and zinc dialkyldithiophosphate salts, which are entirely derived from secondary alcohols, are provided. Alcohols suitable for deriving zinc dialkyldithiophosphate salts may be primary alcohols, secondary alcohols, or a mixture of primary and secondary alcohols. The alcohols may contain any branched, cyclic or straight chains. According to some embodiments, the alkyl groups of at least one zinc dialkyldithiophosphate salt may be derived from a mixture of primary and secondary alcohol groups. The alcohol mixture may have a molar ratio of secondary alcohol to primary alcohol from 20:100 to 100:0, or from approximately 25:100 to approximately 100:0, or from approximately 35:100 to approximately 90:10, or from approximately 40:100 to approximately 80:20, or from approximately 40:60 to approximately 60:40, or approximately 50:50.
At least one zinc dialkyldithiophosphate salt may be oil-soluble salts of dihydrocarbyl dithiophosphoric acids, or the DF-11 additive, or the RF 2202A additive. Infineum^® C9417 which is a mixed primary/secondary zinc dialkyl dithiophosphate, has been found to be particularly effective.
The additive may comprise 0.001 to 1.5 wt%, or 0.01 to 1.0 wt%, or 0.1 to 1.0 wt%, or 0.1 to 0.7 wt%, or 0.1 to 0.5 wt%, or 0.25 to 0.5 wt% zinc dialkyl dithiophosphate. An amount of approximately 0.25 to 0.5 wt% was found to work well. The concentration of additive added to the lubricant can be adjusted such that the final concentration of ZDDP in the lubricant is from 0.001 to 0.1 wt%, where good results have been found in the range 0.005 to 0.015 wt% and 0.007 to 0.011 wt% ZDDP in the lubricant.

Other features

The additive is free of inorganic acids. The additive is preferably free of copper, cobalt, lead, tin and nickel salts of inorganic acids. Many previous applications use these salts for the formation of a protective metal film under pressure. However, the present inventors have found that these salts of inorganic acids lead to the formation of damaging strong inorganic acids in situ over time. ZDDP is the only metal salt of an inorganic acid present in the additive.
The additive is free of resins such as epoxy resin. This aids the formation of a protective copper film on friction surfaces under pressure.
The additive is homogenous and all components of the additive are oil-soluble. The additive is free of particles including abrasive particles. This prevents the clogging of the oil channels of the lubrication system of internal combustion engines.

General method

The additive for lubricant compositions is obtained as follows. In an unsaturated carboxylic acid, selected from the number of fractions C₁₅-C₁₈, for example, the technical oleic one of grade B-115, which is a mixture of unsaturated carboxylic acids C₁₅-C₁₈, monovalent copper oxide is introduced, mixing is carried out, for example, passing the mixture through a hydrodynamic apparatus, with mixing criteria Re=10,000-60,000 and the temperature range from 30 °C to 180 °C. Dispersion and dissolution is carried out for 30-60 min., while salts of unsaturated carboxylic acids are formed. After dissolving the oxides in the acid, the unreacted oxides are separated by filtration.
As a result of auto-oxidation and auto-reduction (disproportionation) reaction, monovalent and divalent salts of unsaturated carboxylic acids are formed, the ratio between which is regulated by the process duration and the value of the Reynolds number. Then, an aromatic amine (diphenylamine), an unsaturated carboxylic acid (selected from the number of fractions C₆-C₂₂), a succinimide derivative (C-5A or C-1500) at room temperature, and ZDDP are introduced into the purified solution with stirring.
The quality control of the finished product is carried out by the percentage of copper, which is determined by dissolving a sample of the product in glacial acetic acid, followed by iodometry titration. The content of copper, Cu⁺¹ and Cu^+II, in the additive may be determined by X-ray photoelectron spectroscopy (XPS).
The use of unsaturated carboxylic acids makes it possible to obtain the necessary molecular structure of an additive to lubricant compositions, which ensures the achievement of the required physical and chemical properties.
The use of the additive in lubricant compositions may significantly reduce the friction coefficient for various friction pairs, including those with a high degree of loading and high frequencies of mutual displacement, as well as eliminate damage to the oil channels of the lubrication system of internal combustion engines and improve anti-wear and detergent properties.

Examples

The invention is illustrated by the following examples of additive implementation.

Additive Example 1

The oil-soluble additive contains a metal salt of an organic acid, an aromatic amine, a succinimide derivative; it also contains ZDDP and an oil-soluble organic acid, wherein the following ratio of components is used, wt%:

salt of copper and carboxylic acid (C₁₅-C₁₈): 3.25;

diphenylamine: 19.5;

commercial succinimide derivative (C-5A): 62;

oleic acid: 15;

ZDDP: 0.25.

Additive Example 2

The oil-soluble additive contains a metal salt of an organic acid, an aromatic amine, a succinimide derivative, it contains ZDDP and an oil-soluble organic acid, wherein the following ratio of components is used, wt%:

salt of copper and carboxylic acid (C₁₅-C₁₈): 9.3;

diphenylamine: 30.2;

commercial succinimide derivative (C-1500): 45;

oleic acid: 15;

ZDDP: 0.5.
In Additive Example 1 and Additive Example 2 the salt of copper and carboxylic acid (C₁₅-C₁₈) is copper oleate and ZDDP is a mixed primary/secondary zinc dialkyl dithiophosphate.
The base oil and the oil-soluble additive are heated during mixing, for example, for 5-48 hours at a temperature of approximately 30 °C to approximately 70 °C, for example, for approximately 24 hours at a temperature of approximately 60 °C. Mixing is carried out at speeds from approximately 2,000 rpm to approximately 5,000 rpm. Prior to the examination and use, mixtures are usually cooled for 10-24 hours to a temperature of approximately 25 °C.
The invention, in the form of a lubricant composition, is illustrated by the following examples of its implementation.

Lubricant comprising the additive of Example 1

The lubricant composition contains a polyalkylene glycol base oil and an additive, including a metal salt of an organic acid, an aromatic amine, a succinimide derivative, ZDDP (0.25 wt% in the additive) and an oil-soluble organic acid, wherein the following ratio of components is used, wt%:

polyalkylene glycol base oil: 97.3;

additive: 2.7.

Lubricant comprising the additive of Example 2

The lubricant composition contains a synthetic base oil in the form of polyalphaolefins and an additive, including a metal salt of an organic acid, an aromatic amine, a succinimide derivative, ZDDP (0.5 wt%), an oil-soluble organic acid, wherein the following ratio of components is used, wt%:

synthetic base oil in the form of polyalphaolefins: 97.8;

additive: 2.2.
The application of an additive in concentrations from 2.2-2.7 % to lubricant compositions when applied to the rubbing surfaces may significantly reduce the friction coefficient for various friction pairs, including at a high degree of loading and high frequencies of mutual displacement.
Tribological tests of lubricants are carried out using a friction machine that simulates the operation of a heavy-loaded friction unit under slippage conditions.
For comparative tests, the following was used:

Sample 1: Group III base oil modified with an additive according to Finnish patent No. 124709B including inorganic copper salt, succinimide derivative, aromatic amine, copper chloride, tin chloride, high molecular weight alcohol, epoxy resin and abrasive particles, (Comparative Example);
Sample 2: Group III base oil modified with an additive (2.7 wt%) according to Example 1;
Sample 3: Group III base oil modified with an additive (2.2 wt%) according to Example 2.

The tests were carried out using a friction machine with the maximum load G_max,start = 2,600 MPa for 1 hour at a washer rotation speed of 50-4,500 rpm.
The main criteria for comparing the performance of the lubricants were:

the ball contact patch diameter;
the ball temperature increment during testing;
the change in friction coefficients during testing.

The values of the contact patch diameter, the friction coefficients and the temperature characteristics of friction pairs are given in Table 1.

Table 1

Names of lubricants, speed/linear velocity	Contact patch diameter, µm	Maximum amplitude	Heating temperature for 1 hour, °C
50 rpm
Sample 1	399.94	15	2.0330925
Sample 2	252.35	13	-0.0212421
Sample 3	283.77	11.5	0.665535

500 rpm
Sample 1	397.19	14	2.3054847
Sample 2	333.8	14	1.564003
Sample 3	300.79	14	2.3555584

1,000 rpm
Sample 1	271.9	13	3.7125817
Sample 2	270.8	13	3.0330887
Sample 3	400.66	14.5	6.4773979

1,500 rpm
Sample 1	392.5	14	8.9102287
Sample 2	367.65	13	6.9548035
Sample 3	567.5	15	8.9441719

2,000 rpm
Sample 1	460.1	13	12.2219124
Sample 2	466.32	13	11.5877132
Sample 3	462.44	16	10.8514366

2,500 rpm
Sample 1	343.68	12	10.0798836
Sample 2	473.16	15	11.4910316
Sample 3	387.93	16	12.3755798

3,000 rpm
Sample 1	destroyed	destroyed	destroyed
Sample 2	673.77	15	15.459526
Sample 3	501.12	14	14.398037

3,500 rpm
Sample 1	destroyed	destroyed	destroyed
Sample 2	449.44	15	20.2086487
Sample 3	543.11	15	15.7992859

4,000 rpm
Sample 1	destroyed	destroyed	destroyed
Sample 2	512.33	14	14.8537521
Sample 3	516.36	15	24.8939552

4,500 rpm
Sample 1	destroyed	destroyed	destroyed
Sample 2	509.49	14	24.5760518
Sample 3	613.37	15	19.3347664

In the above table, "destroyed" means that there was extreme wear of a particular friction pair, which lead to its destruction.
The analysis of the test results obtained using a friction machine for three samples of a lubricant composition made on the basis of one mixture of base oils and having the following differences in the additive package:

1. basic additive package, in accordance with the closest analogue;
2. basic additive package with the addition of 0.25% of ZDDP;
3. basic additive package with the addition of 0.5% of ZDDP;

1. in the area of low revolutions of the friction machine spindle (50-500 rpm), the friction coefficient is reduced by 13-15%;
2. in the area of low revolutions of the friction machine spindle (50-500 rpm), the ball wear scar decreased by 29-37%;
3. the friction pair remained operational within the spindle speed range from 2,500 to 4,500 rpm.

Therefore, the addition, to the previously developed additive packages, of ZDDP (0.001-1.5% for different base oils) made it possible to significantly improve the performance characteristics of a friction pair in the region of low linear interaction velocities, as well as to increase the maximum linear interaction velocity by 80% while maintaining the normal functioning of the friction pair.
An alternative additive composition comprises, wt%:

salt of copper and oleic acid: 3-10;

butylated octylated diphenylamine: 15-35;

T145B Polyisobutylene Bis-succinimide: 20-65 or 45-65;

oleic acid: 5-15;

ZDDP: 0.25-0.5.
The ZDDP in the alternative additive composition is a mixed primary/secondary zinc dialkyl dithiophosphate. This alternative additive composition has been tested and found to give the same contact patch diameter results as Sample 3.

Claims

An oil-soluble additive for a lubricant composition for an internal combustion engine, the additive containing a metal salt of an organic acid, an aromatic amine, a succinimide derivative, characterised in that it also contains an oil-soluble organic acid and 0.001-1.5 wt% zinc dialkyl dithiophosphate.
The oil-soluble additive according to claim 1 comprising 0.001 to 1.5 wt%, or 0.01 to 1.0 wt%, or 0.1 to 1.0 wt%, or 0.1 to 0.7 wt%, or 0.1 to 0.5 wt%, or 0.25 to 0.5 wt% zinc dialkyl dithiophosphate.
The oil-soluble additive according to any one of claims 1 or 2 comprising 0.25 to 0.5 wt% zinc dialkyl dithiophosphate.
The oil-soluble additive according to any one of claims 1 to 3 wherein zinc dialkyl dithiophosphate is the only metal salt of an inorganic acid present.
The oil-soluble additive according to any one of claims 1 to 4 wherein the zinc dialkyl dithiophosphate is derived from primary alcohols, secondary alcohols, or a combination of primary and secondary alcohols.
The oil-soluble additive according to any one of claims 1 to 5 wherein the metal salt of an organic acid is a copper salt of a C₁₅ to C₁₈ carboxylic acid, or wherein the metal salt of an organic acid is a copper salt of oleic acid; and optionally wherein the metal salt of an organic acid is present in an amount of from 1 to 10 wt%, or 1 to 9.5 wt% or 3 to 9.5 wt% or 3 to 10 wt%.
The oil-soluble additive according to any one of claims 1 to 6 wherein the aromatic amine is selected from aniline and alkyl-substituted aniline compounds, 1,2,3,4-tetrahydroquinoline, diphenylamine and alkyl-substituted diphenylamine compounds such as butyldiphenylamine, octyldiphenylamine and di-octyl-diphenylamine, 2-ethylhexyl-4-(dimethylamino)benzoate, indoline, N,N-dimethyl-1,4-phenylenediamine, o-toluidine, p-toluidine, p-anisidine, p-phenethidine, and the like, and mixtures thereof, or wherein the aromatic amine is diphenylamine or butylated octylated diphenylamine, optionally wherein the aromatic amine is present in an amount of from 15 to 35 wt%, optionally 19 to 34 wt% or 19 to 32 wt%.
The oil-soluble additive according to any one of claims 1 to 7 wherein the organic acid is selected from C₁₅-C₁₈ carboxylic acids, oleic acid, linolenic acid, palmitoleic acid, or mixtures thereof, or fatty acids derived from lard oil, tallow oil, peanut oil, soybean oil, cottonseed oil, sunflower oil, or mixtures thereof, or wherein the organic acid is an unsaturated carboxylic acid, optionally wherein the organic acid is oleic acid; optionally wherein the organic acid is present in an amount of from 5 to 20 wt%, optionally 5 to 15 wt%, optionally 10 to 15 wt% or approximately 15 wt%.
The oil-soluble additive according to any one of claims 1 to 8, wherein the succinimide derivative is present in amount of from 2 to 65 wt%, optionally 10 to 65 wt%, optionally 20 to 65 wt% or 45 to 65 wt%.
The oil-soluble additive according to any one of claims 1 to 9 which is free from copper, cobalt, lead, tin and nickel salts of inorganic acids.
The oil-soluble additive according to any one of claim 1 to 10 containing a metal salt of an organic acid, an aromatic amine, a succinimide derivative, characterised in that it also contains an oil-soluble organic acid and zinc dialkyl dithiophosphate, wherein the following ratio of components is used, wt%: metal salt of an organic acid: 3-10; aromatic amine: 15-35; succinimide derivative: 20-65 or 45-65; organic acid: 5-15; zinc dialkyl dithiophosphate: 0.001-1.5.
The oil-soluble additive according to any one of claims 1 to 11, characterised in that metal salts of organic acids, with the number of carbon atoms being C₁₅...C₁₈, are used as a metal salt of an organic acid, diphenylamine or its homologues are used as aromatic amines, and the industrially manufactured additives, C-5A or C-1500, are used as a succinimide derivative; zinc dialkyl dithiophosphate is derived from primary alcohols, secondary alcohols, or a combination of primary and secondary alcohols.
A lubricant composition for an internal combustion engine, which includes a base oil and an oil-soluble additive in accordance with any one of claims 1 to 12, wherein the following ratio of components is used, wt%: base oil: 95-99 oil-soluble additive: 1-5; or base oil: 97-98 oil-soluble additive: 2-3; or base oil: 97.3-97.8 oil-soluble additive: 2.2-2.7.
A lubricant composition according to claim 13, characterised in that the base oil is selected from any of the Group I-V base oils, optionally a Group III base oil.
The use of a lubricant composition for wear protection of friction surfaces, the use comprising the application of the lubricant composition of any one of claims 11 to 14 to the friction surfaces.