RU2628512C2 - Grease lubricant composition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: grease lubricant composition comprises base oil, thickener and poly (meth)acrylate containing hydroxyl groups, wherein said thickener is urea compound obtained by reacting between isocyanate and primary amine, and said poly(meth)acrylate containing hydroxyl groups is copolymer comprising, as composite monomers, alkyl(meth)acrylate containing C_1-20 alkyl group, and vinyl monomer containing a hydroxyl group.

EFFECT: high wear resistance.

13 cl, 1 tbl, 10 ex

Description

FIELD OF THE INVENTION

The present invention relates to a grease composition, and more specifically, to a grease composition characterized by high wear resistance.

State of the art

Sliding parts and rotating parts of machines require a certain type of lubricant, and they mainly use lubricating oils or greases when, in particular, in many machines there are grease lubrication systems, where the seal structure can be simplified and the equipment can be made small and compact. The range of use is extremely wide, including, for example, various types of ball and roller bearings and sliding bearings, which are a support for rotating bodies, as well as sliding parts of articulated and ball joints or chains, gears, cables and arrows of cranes and the like and the quality required for them is increasing from year to year, while extending the life of the machines and their operation without maintenance are problems common to all mechanisms. In addition, in recent years, as progress has been made in machine technology, material technology and machining accuracy, fatigue failure and damage to materials have become very small, so that the performance of a lubricating oil or grease has become a significant influence on the life of a machine. Thus, improving the lubricating properties of grease and resolving the problems associated with this can make a significant contribution to improving the quality and reliability of machines, and thus are extremely important.

Specifically, cases in which the lubricity of the grease in rotating components or sliding parts of the machine fails and the life of the machine expires can broadly be divided into two groups. Firstly, there is a case where the grease undergoes oxidation when used at high temperature, so that the grease hardens due to evaporation of the oil component or thermal polymerization, or the structure of the grease breaks down with the formation of organic acids or aldehydes, which as a result, impaired lubrication. Secondly, there is a case when, due to the presence of significant sliding friction on the sliding surfaces of machines during use with comparatively low speeds under high loads or at high speeds, the state of the boundary lubricant tends to change, and the grease film of the grease becomes extremely thin, so often a metal / metal contact occurs, and wear increases, leading to damage such as metal detachment or jamming and the like.

Measures to eliminate the situation described in the first aforementioned case include methods aimed at extending the life of the machine by effectively incorporating an antioxidant suitable for use in the grease (see Japanese Patent 2085136) or using a thickener or base oil as a grease, which undergo a slight structural or chemical change under the influence of heat, which thereby improves the function of the grease as a whole in order to extend the life of the machine. Urea-based greases are one example of heat-resistant thickeners, and many technical developments have recently been made using such thickeners (see Japanese Patent 4769456). Since they have a higher dropping point compared to a grease that uses lithium soap as a thickener, and because they are outstanding in terms of their heat resistance, as well as their wear resistance and lubricity, urea greases have been used in a wide range of applications. For example, in the automotive industry, the levels required for heat resistance, wear resistance, and friction characteristics are constantly increasing with respect to various types of vehicle components, such as CV joints (constant velocity joints), electric power steering, generator bearings and wheel bearings, and the like, that there are many cases in which outstanding performance and urea grease additives are used.

In addition, since motor vehicles are used worldwide, the grease used in motor vehicle components is designed and manufactured taking into account regular use in extremely cold conditions, corresponding to approximately -40 ° C, as well as at high temperatures of 100 ° C and more (thermal radiation from the engine compartment + heat emitted from the road surface), thus, in the same way as in obtaining low stable characteristics Its moment in a wide temperature range from low to high temperatures requires a grease that does not detect insufficient oil impregnation due to a drop in viscosity at high temperatures, and which itself also has a long service life corresponding to the service life of the vehicle.

To improve the low temperature characteristics, a technique was described whereby in a synthetic hydrocarbon oil (poly-α-olefin), an ester type base oil, or a glycol type base oil, characterized by outstanding low temperature fluidity as a grease base oil, include methacrylate polymer, but further improvements in quality and performance are required (see publication JP-A-2006-77119).

Remedies for the situation described in the second case above include methods that increase the viscosity of the grease base oil and include a polymer or other viscosity improver so that the lubricant film thickens and the metal / metal contact is suppressed (see JP publication -A-2008-69282), and methods in which an anti-wear additive, an anti-seize additive, a solid lubricant or other load-bearing additive is introduced into a grease, so that as a result of chemical and and physical action of the additive between the sliding surfaces of a coating or a solid film, thus, protecting the surface (see Japanese Patent No. 3833756 and JP-A-2-18497 publication). However, depending on the type of additive, the structure of the grease may be changed, and there are also many additives that adversely affect machine components. For example, thiophosphates with a high acid number have the disadvantage of easily reacting with the free alkali of a soap-based grease, and additives related to the olefin sulfide type can cause the urea grease to harden over time. In addition, in the case of additives characterized by strong chemical activity, there are many problems, such as stimulated discoloration or corrosion of metals and the decreasing strength of seal materials like nitrile, acrylic or urethane rubbers.

Therefore, with regard to the lubricity of a grease, the ability to maintain an oil film suitable for use and to produce an adsorbed film on lubricated sliding surfaces without any adverse effect on the structure of the grease is extremely effective in terms of stabilizing the quality of parts of motor vehicles and industrial components , as well as ensuring reliability and extending the life of the machine.

Disclosure of invention

The present invention addresses the problem of proposing a grease composition characterized by high wear resistance. As a result of persistent research against this background, the inventors of the present invention have found that it is possible to increase the wear resistance of a grease by using a poly (meth) acrylate derivative that contains hydroxyl groups, and in this case, it is possible to solve the above problem.

Accordingly, the present invention provides a grease composition which is characterized in that a poly (meth) acrylate derivative containing hydroxyl groups is used as an additive in a grease composition containing a base oil and a thickening agent.

A grease composition related to the present invention exhibits an effect of greater wear resistance compared to conventional grease compositions.

The implementation of the invention

The grease composition of this embodiment contains “base oil”, “thickener” and “additive” as mandatory constituent components. Below, in turn, the individual components contained in the grease composition are explained, the amounts (mixed amounts) of the components in the grease composition, the method for producing the grease composition, the properties of the grease composition and the field of application of the grease composition.

On the base oil used in the grease composition of this embodiment of the invention, no specific restrictions are imposed. For example, mineral oils, synthetic oils, animal / vegetable oils, and mixtures thereof used in conventional grease compositions can be suitably used. As specific examples, base oils belonging to group I, group II, group III and group IV and so on in the base oil categories from API (American Petroleum Institute), alone or in the form of mixtures, can be used.

Group I base oils include paraffin mineral oils, obtained, for example, from a lubricating oil fraction obtained from atmospheric distillation of a crude oil suitable for use with a combination of refining agents, such as selective solvent refining, hydrogenation refining and dewaxing and the like. Group II base oils include paraffin mineral oils, obtained, for example, from a lubricating oil fraction obtained by atmospheric distillation of a crude oil suitable for use with a combination of refining agents such as hydrocracking and dewaxing and the like. Group II base oils obtained by a hydrogenation purification method such as that of Gulf Co. are characterized by an aggregate sulfur content of less than 10 ppm and an aromatic content of not more than 5%, and in a favorable case can be used in the present invention. Group III base oils and group II + base oils include, for example, paraffin mineral oils obtained from a lubricating oil fraction obtained from atmospheric distillation of crude oil with a high degree of hydrogenation purification, as well as base oils that have been refined using the Isodewaxing method, in which the wax obtained by the method of dewaxing, is converted to isoparaffins, as well as the base oils obtained by the method of Mobil Wax Isomerization, and they can also be used in a favorable case used in this embodiment of the invention.

Examples of synthetic oils include polyolefins, dibasic acid diesters like dioctyl sebacinate, polyol esters, alkyl benzenes, alkyl naphthalenes, esters, polyoxyalkylene glycols, polyoxyalkylene glycol ethers, polyoxyalkylene glycol ethers, polyphenyl ethers, diethyl ethers, diethyl ethers, ethers polyolefins and the like) and silicones and the like. The aforementioned polyolefins include various types of olefin polymer, as well as their hydrogenated products. Any olefin may be used, and examples are ethylene, propylene, butene and α-olefins containing five or more carbon atoms. In preparing the polyolefin, one type of the aforementioned olefin may be used on its own, or a combination of two or more types may be used. In particular, from the viewpoint of improving low temperature fluidity and low temperature lubricity, polyolefins, referred to as poly-α-olefin (PAO) synthetic oils, are preferred, and they are Group IV base oils. Since the viscosity index of poly-α-olefin synthetic oils is high, there is a slight decrease in viscosity at high temperatures, and their ability to retain an oil film is high, in addition to which the viscosity does not increase excessively at low temperatures, and the flowability suitable for use is maintained. so it has a slight decrease in lubricity. When using this outstanding low-temperature behavior for grease base oil, it acts extremely efficiently. For example, if a lubricating oil is used as a base oil, which has an extremely high viscosity at low temperature and thus loses fluidity, the fluidity of the grease will deteriorate completely and there will be virtually no lubricating oil supply on the sliding surface of the machine components, so that wear will continue to develop, while in the case of grease, which includes a base oil characterized by outstanding low temperature fluid Stu, such as poly-α-olefin synthetic oil, there will be no loss of yield, and the lubricating oil can be properly applied to the sliding surface, so that the lubrication function is maintained, and the wear choke.

Oils obtained by the GTL method (gas to liquid), which are oils synthesized from natural gas by the method of conversion to liquid fuel using the Fischer-Tropsch method, are characterized by an extremely low content of sulfur component and aromatic component in comparison with what has the place for mineral oil base oils obtained from the refining of crude oil and the proportion of paraffin structure is extremely high, as a result of which they exhibit excellent oxidation resistance and extremely low evaporation losses, so that they can advantageously be used as a base oil in the present embodiment.

The thickener used as an essential component in this embodiment of the invention is not specifically limited and may be of the type used in conventional grease formulations. Examples are urea-type thickeners, metal soaps, complex soaps, organized bentonite and silica, and the like. Examples of urea-based thickeners are aliphatic diurea, alicyclic diurea, aromatic diurea, triurea, tetraurea, and urea urea. Examples of metal soaps are lithium 12-hydroxystearate, lithium stearate, calcium 12-hydroxystearate, calcium stearate, lithium complex, calcium complex, barium complex, aluminum complex, lithium-calcium mixed soaps and the like. One example of organized bentonite is montmorillonite, which was processed using a quaternary ammonium salt, and one example of silica is ultrafine powdery silica resulting from a gas phase reaction or this ultrafine powdery silica after surface treatment using a lower alcohol such as methanol. Other examples include sulfonate complex, polytetrafluoroethylene, tricalcium phosphate and the like.

Among them, preferred thickeners are urea compounds resulting from the reaction between an isocyanate and a primary amine. The urea compound may be, for example, diurea, trimurea, tetraurea, pentamourea or hexamourea, and it may be aliphatic urea, alicyclic urea or aromatic urea, and it may also contain other groups (like urethane group) (as in the case of urea urea).

A diurea thickener, for example, is obtained as a result of a reaction between 1 mole of diisocyanate and 2 moles of primary monoamine. In addition, a tetraurea thickener is obtained, for example, by carrying out a reaction between 2 moles of diisocyanate and 1 mole of primary diamine plus 2 moles of primary monoamine. In addition, a urea-monourethane thickener is obtained, for example, by reaction between 2 moles of diisocyanate and 1 mole of primary diamine plus 1 mol of primary monoamine and 1 mol of monoalcohol. The following are examples of various feedstock materials used in the synthesis of these urea compounds.

In the case of a diisocyanate, there are aliphatic diisocyanates, alicyclic diisocyanates and aromatic diisocyanates and the like. More specific examples are 4,4ʹ-diphenylmethanediisocyanate (MDI), tolylenediisocyanate (TDI), naphthalene diisocyanate, p-phenylenediisocyanate, trans-1,4-cyclohexanediisocyanate (CHDI), 1,3-bis (isocyanatomethylbenzene), 4,4-methanediocyanate H12MDI), 1,3-bis (isocyanatomethyl) cyclohexane (H6XDI), hexamethylenediisocyanate (HDI), 3-isocyanatomethyl-3,3,5 три-trimethylcyclohexylisocyanate (IPDI), phenylenediisothiene diethiocyanidethiomethylene diisocyanate (p-TMXDI) and the like, in particular 4,4ʹ-diphenylmethanediisocyanate (MDI), tolyland isocyanate (TDI), trans-1,4-cyclohexanediisocyanate (CHDI) and 4,4ʹ-dicyclohexylmethanediisocyanate (H12MDI).

The primary monoamine may be an aliphatic, alicyclic or aromatic monoamine. As an aliphatic amine, a C ₈ -C ₂₄ saturated or unsaturated aliphatic amine may be used, which may be branched or straight chain, but straight chain aliphatic amines are preferred. Specific examples of primary monoamine include octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, oleylamine, aniline, p-toluidine and cyclohexylamine.

The primary diamine may be an aliphatic, alicyclic or aromatic diamine. Examples include C ₂ -C ₁₂ diamines such as aliphatic diamines like ethylenediamine, trimethylenediamine, tetramethylene diamine, hexamethylenediamine and decamethylene diamine, alicyclic diamines such as diaminocyclohexane and aromatic diamine diamines dienamides dienamides.

The monoalcohol may be aliphatic, alicyclic or aromatic alcohol. As an aliphatic monoalcohol in this case, a C ₈ -C ₂₄ saturated or unsaturated aliphatic alcohol can be used, which may be branched or straight chain, but straight chain alcohols are preferred. Specific examples include octyl alcohol, decyl alcohol, dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol and oleyl alcohol, while one example of alicyclic alcohol is cyclohexyl alcohol, benzyl alcohol, phenyl alcohol, cinnamon alcohol, hydrocinnamic alcohol and the like.

Particularly preferred are alkyl diureas, more preferably compounds described by the general formula (I):

(where each of R ¹ and R ³ represents a C _8-12 aliphatic hydrocarbon group, and R ² represents a C _6-15 divalent aromatic group). In this case, it is preferable that R ¹ and R ³ would be a mutually independently octal group containing eight carbon atoms, or a lauryl group containing twelve carbon atoms. In addition, R ² preferably represents a diphenylmethane group. In more preferred embodiments, compounds are used where R ² is a diphenylmethane group and (1) R ¹ and R ³ are octal groups containing eight carbon atoms, or (2-1) a mixture of a compound where each of R ¹ and R ³ represents octal groups containing eight carbon atoms, and compounds where R ¹ and R ³ are lauryl groups containing twelve carbon atoms, (2-2) a compound where either R ¹ or R ³ are octal a group containing eight carbon atoms, while mja as another representative of the number of R ¹ and R ³ is a lauryl group containing twelve carbon atoms, and (2-3) a mixture of one or two compounds (2-1) and compound (2-2). Among them, particularly preferred are options ranging from (2-1) to (2-3).

In a grease composition in this embodiment of the invention, it is possible to share another thickener together with a main thickener {which is, for example, the aforementioned urea compound (such as alkyl diurea)}. Thus, in the case where a urea compound is used as the main thickener, it is possible to use tricalcium phosphate, alkali metal soap, alkali metal soap, alkaline earth metal soap, complex soap as the other thickener. alkaline earth metal, alkali metal sulfonate, alkaline earth metal sulfonate, other metal soaps, terephthalamate metal salt, clay, colloidal powdered silica or as another type of silica (silicon dioxide) or a fluoropolymer such as polytetrafluoroethylene and the like, and is possible to use one member of them by itself, or two or more of them may be used in combination. As well as these materials, it is also possible to use any material that can create the effect of increasing viscosity.

The additive used as an essential component in this embodiment is a poly (meth) acrylate that contains hydroxyl groups. This poly (meth) acrylate containing hydroxyl groups is a copolymer and contains a comonomer based on an alkyl (meth) acrylate containing a C _1-20 alkyl group and a vinyl monomer containing a hydroxyl group, as its obligatory composite monomers.

Specific examples of the aforementioned alkyl (meth) acrylate (a) containing a C _1-20 alkyl group are

(a1) alkyl (meth) acrylates containing a C _1-4 alkyl group:

examples of which are methyl (meth) acrylate, ethyl (meth) acrylate, n- or isopropyl (meth) acrylate and n-, iso- or sec-butyl (meth) acrylate,

(a2) alkyl (meth) acrylates containing a C _8-20 alkyl group:

examples of which are n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-decyl (meth) acrylate, n-isodecyl (meth) acrylate, n-undecyl (meth) acrylate, n-dodecyl (meth) acrylate 2-methylundecyl (meth) acrylate, n-tridecyl (meth) acrylate, 2-methyldodecyl (meth) acrylate, n-tetradecyl (meth) acrylate, 2-methyltridecyl (meth) acrylate, n-pentadecyl (meth) acrylate, 2 -methyltetradecyl (meth) acrylate, n-hexadecyl (meth) acrylate, n-octadecyl (meth) acrylate, n-eicosyl (meth) acrylate, n-docosyl (meth) acrylate, methacrylate Dovanol 23 [C ₁₂ / C ₁₃ oxo- alcohol mixture obtained from Mitsubishi Chemical Corp.] and Dovanol methacrylate 45 [C ₁₃ / C ₁₄ oxo-alcohol mixture obtained from Mitsubishi Chemical Corp.] and the like, (a3) alkyl (meth) acrylates containing a C _5-7 alkyl group: examples of which are n-pentyl (meth) acrylate and n-hexyl (meth) acrylate and the like.

Among the above options, in the range from (a1) to (a3), monomers related to the options (a1) and (a2) are preferred, with those that belong to the option (a2) being particularly preferred. In addition, from the point of view of solubility in the base oil from among the monomers in embodiment (a2), those containing from 10 to 20 carbon atoms in the alkyl group are preferred, and those containing from 12 to 14 carbon atoms are particularly preferred.

The aforementioned vinyl monomer containing a hydroxyl group, (b) from which the copolymer is formed together with an alkyl (meth) acrylate containing a C1-20 alkyl group, is a vinyl monomer containing one or more (preferably 1 or 2) hydroxyl groups in the molecule. Specific examples are (b1) hydroxyalkyl (C _2-6 ) (meth) acrylates: such as 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 1-methyl -2-hydroxyethyl (meth) acrylate and the like,

(b2) mono- or dihydroxyalkyl (C _1-4 ) substituted (meth) acrylamides:

such as N, N-dihydroxymethyl (meth) acrylamide, Ν, Ν-dihydroxypropyl (meth) acrylamide, N, N-di-2-hydroxybutyl (meth) acrylamide and the like,

(b3) vinyl alcohol (obtained by hydrolysis of vinyl acetate units),

(b4) C _3-12 alkenols:

such as (meth) allyl alcohol, crotyl alcohol, isocrotyl alcohol, 1-octenol, 1-undecenol and the like,

(b5) C _4-12 alkenediols:

such as 1-buten-3-ol, 2-buten-1-ol, 2-butene-1,4-diol and the like,

(b6) hydroxyalkyl (C _1-6 ) alkenyl (C _3-10 ) ethers:

such as 2-hydroxyethylpropenyl ether and the like,

(b7) aromatic monomers containing a hydroxyl group:

such as o-, m- or p-hydroxystyrene and the like,

(b8) polyhydric alcohols (from tri- to eight-atomic):

such as alkanopoliols, as well as their intramolecular or intermolecular dehydrocondensates and alkenyl (C3-C10) ethers or (meth) acrylates Sugars (e.g. glycerol, pentaerythritol, sorbitol, sorbitan, diglycerol or sucrose) (e.g. sucrose (meth) simple allyl ether) and the like,

(b9) vinyl monomers containing a polyoxyalkylene chain and a hydroxyl group (s):

such as mono (meth) acrylate or mono (meth) allyl ether of polyoxyalkylene glycol (C _2-4 alkylene group; degree of polymerization in the range of 2 to 50) or polyoxyalkylene polyol {polyoxyalkylene ether of the aforementioned tri-eight-atomic alcohol (C _2-4 alkyl group; polymerization degree in the range from 2 to 100)} {examples of which are polyethylene glycol- (polymerization degree 2-9) -mono (meth) acrylate, polypropylene glycol- (polymerization degree 2-12) -mono (meth) acrylate, polyethylene glycol- (degree of polymerization 2-30) -mono (meth) llilovy} ether, and the like.

It is also possible to copolymerize with the aforementioned monomers (a) and (b) in the aforementioned poly (meth) acrylate copolymer containing hydroxyl groups and other monomers, and for example, a monomer (c) which contains a nitrogen atom can be used. Its specific examples are

(c1) monomers containing a nitro group: such as 4-nitrostyrene, and the like,

(c2) vinyl monomers containing primary, secondary or tertiary amino groups: examples of which are

(c2-1) vinyl monomers containing a primary amino group; such as C _3-6 alkenylamines [(meth) allylamine, crotylamine and the like], aminoalkyl (C _2-6 ) (meth) acrylates [aminoethyl (meth) acrylate and the like],

(c2-2) vinyl monomers containing a secondary amino group; such as alkyl (C _1-6 ) aminoalkyl (C _2-6 ) (meth) acrylates [tert-butylaminoethyl methacrylate, methylaminoethyl (meth) acrylate and the like], diphenylamine (meth) acrylamides [4-diphenylamine (meth) acrylamide, 2 diphenylamine (meth) acrylamide and the like], C _6-12 dialkenylamines [di (meth) allylamine and the like],

(c2-3) vinyl monomers containing a tertiary amino group; such as dialkyl (C _1-4 ) aminoalkyl (C _2-6 ) (meth) acrylates [dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate and the like], dialkyl (C _1-4 ) aminoalkyl (C _2-6 ) (meth) acrylamides [dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide and the like], aromatic vinyl monomers containing a tertiary amino group, [Ν, Ν-dimethylaminamines and the like],

(c2-4) vinyl monomers containing a nitrogen-containing heterocycle, [morpholinoethyl (meth) acrylate, 4-vinylpyridine, 2-vinylpyridine, N-vinylpyrrole, N-vinylpyrrolidone, N-vinylthiopyrrolidone and the like],

(c3) amphoteric vinyl monomers: examples of which are

N-alkyl (C _1-5 ) carboxylates (or sulfates) N- (meth) acryloyloxy (or amino) alkyl (C _1-10 ) Ν, Ν-dialkyl (C _1-5 ) ammonium, similar to N- methyl carboxylate (meth) acryloyloxyethyl-N, N-dimethylammonium, N- (meth) acryloylaminopropyl-N, N-dimethylammonium N-methylcarboxylate and N- (meth) acryloyloxyethyl-N, N-dimethylammonium propyl sulfate and the like; and

(c4) monomers containing a nitrile group, such as (meth) acrylonitrile and the like.

In addition, other examples of such copolymerized monomers are vinyl monomers of the type of aliphatic hydrocarbon (d). Examples thereof are C _2-20 alkenes [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene and the like] and C _4-12 alkadienes [butadiene, isoprene, 1,4-pentadiene, 1 , 6-heptadiene, 1,7-octadiene and the like].

Again, there are vinyl monomers of the type of alicyclic hydrocarbon, (e): examples of which are cyclohexene, (di) cyclopentadiene, pinene, limonene, indene, vinylcyclohexene and ethylidene bicycloheptene and the like.

In addition, there are vinyl monomers of the aromatic hydrocarbon type (f): examples of which are styrene, α-methyl styrene, vinyl toluene, 2,4-dimethyl styrene, 4-ethyl styrene, 4-isopropyl styrene, 4-butyl styrene, 4- phenylstyrene, 4-cyclohexylstyrene, 4-benzylstyrene, 4-crotylbenzene and 2-vinylnaphthalene and the like.

Again, in addition, there are vinyl esters, vinyl ethers and vinyl ketones (g): examples of which are vinyl esters of saturated C _2-12 fatty acids [vinyl acetate, vinyl propionate, vinyl butyrate, vinyl octanoate and the like], C _{1- 12} alkyl, aryl or alkoxyalkyl vinyl ethers [methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, phenyl vinyl ether, vinyl-2-methoxyethyl ether, vinyl-2 butoxyethyl ether and the like] and C _1-8 alkyl or aryl vinyl ketones [methyl vinyl ketone, ethyl vinyl ketone, phenyl vinyl ketone and the like].

In addition, there are esters of unsaturated polycarboxylic acids (h): examples of which are alkyl, cycloalkyl and aralkyl esters of unsaturated polycarboxylic acids, in particular C _1-8 alkyl esters of unsaturated dicarboxylic acids [such as maleic acid, fumaric acid and itaconic acid] [like dimethyl maleate, dimethyl fumarate, diethyl maleate and dioctyl maleate and the like].

It is also possible to use vinyl monomers that contain a polyoxyalkylene chain (but not containing hydroxyl groups), (i): their examples are mono (meth) acrylates of a monoalkyl (C _1-18 ) polyoxyalkylene glycol ether (C _2-4 alkylene group) ; polymerization degree 2-50) or polyoxyalkylene polyol [polyoxyalkylene ether of the aforementioned tri-eight-atomic alcohol (C _2-4 alkyl group; polymerization degree 2-100)] [such as methoxypolyethylene glycol (Mw 110-310) (meth) acrylate or (meth ) acrylate adduct lauryl alcohol and ethylene oxide (2-30 moles) and the like].

Again, as a monomer in the aforementioned copolymerization, it is also possible to use vinyl monomers containing a carboxyl group, (j): examples of which are vinyl monomers containing one carboxyl group, like unsaturated monocarboxylic acids [(meth) acrylic acid, α-methyl (meth) acrylic acid, crotonic acid, cinnamic acid and the like], and monoalkyl (C _1-8) esters of unsaturated dicarboxylic acids [monoalkyl ester of maleic acid, monoalkyl layer ny ester of fumaric acid monoalkyl ester, itaconic acid and the like]; and vinyl monomers containing two or more carboxyl groups like maleic acid, fumaric acid, itaconic acid and citraconic acid and the like.

Among the additional monomers described above (c), (d), (e), (f), (g), (h), (i) and (j), monomers (c) and two or more of these monomers are preferred (c) may be used in combination. Among the monomers (c), monomers (c2) are preferred, with dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate being particularly preferred.

The hydroxyl number of a poly (meth) acrylate containing hydroxyl groups used as an additive is in the range from 10 to 100, preferably from 20 to 50, and more preferably from 25 to 35. The hydroxyl number is a numerical value obtained by measurements based on JIS K3342 (1961), and it expresses the number of hydroxyl groups in the additive.

If a poly (meth) acrylate containing hydroxyl groups is included in the grease, there will be no adverse effect on the structure of the grease, a suitable film of oil will be provided on the lubricated sliding surfaces and, in addition, a chemical structure containing hydroxyl groups acts efficiently and an adsorbed film forms on lubricated sliding surfaces. Therefore, when using a grease containing this poly (meth) acrylate containing hydroxyl groups, it is possible to obtain ideal lubricity on the sliding surfaces and suppress wear for lubricated parts of motor vehicle components and industrial components, and it is extremely effective in achieving stability and reliability in relation to the quality of machine parts and the extension of their service life. The main difference between lubricating oil and grease is that in the case of grease, the thickener and the additive forming the skeleton of the grease structure interact with each other, and thus, to the extent that the effect can be maintained in the case of grease oils, when using grease, there may be no effect at all, or alternatively, wear may actually be promoted. Therefore, an additive that is stable and gives an effective lubricity to grease, as in the case of this present procedure, is extremely favorable.

The grease composition of this embodiment may also optionally contain additional additives, such as antioxidants, anti-corrosion inhibitors, oil improvers, anti-seize additives, anti-wear additives, solid lubricants, metal deactivators, polymers, metal-based cleaners, non-metallic based cleaners , dyes and the like. Examples of antioxidants include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-p-cresol, p, pʹ-dioctyl diphenylamine, N-phenyl-α-naphthylamine and phenothiazine. Examples of corrosion inhibitors include oxidized paraffin, metal and carboxylic acid salts, metal and sulfonic acid esters, carboxylic acid esters, sulfonic acid esters, salicylic acid esters, succinic acid esters, sorbitan esters and various types of amine salts. Examples of additives that enhance lubricity, extreme pressure additives and antiwear additives include dialkilditiofosfatsulfid zinc diallilditiofosfatsulfid zinc dialkilditiokarbamatsulfid zinc diallilditiokarbamatsulfid zinc dialkilditiofosfatsulfid molybdenum diallilditiofosfatsulfid molybdenum dialkilditiokarbamatsulfid molybdenum diallilditiokarbamatsulfid molybdenum organomolybdenum complexes olefinsulfid, triphenyl phosphate, trifenilfosforotionat, tricresyl phosphate and other esters phosphorne hydrochloric acid and sulfonated oil / fats and the like. Examples of solid lubricants include molybdenum disulfide, graphite, boron nitride, melamine cyanurate, PTFE (polytetrafluoroethylene), tungsten disulfide, fluorinated graphite and calcium phosphate. Examples of metal deactivators include N, Nʹ-disalicylidene-1,2-diaminopropane, benzotriazole, benzimidazole, benzothiazole and thiadiazole and the like. Examples of polymers include polybutene, polyisobutene, polyisobutylene, polyisoprene, polymethacrylate and the like. Examples of metal-based cleaners are metal sulfonates, metal salicylates and metal phenolates. Examples of non-metallic based purifiers include succinimide and the like. However, these examples are not intended to limit the invention.

The following is an explanation of the amounts of the respective components used in the grease composition in relation to this embodiment of the invention. Unless otherwise approved,% will denote the mass percentage level of content.

The mixed amount of the base oil is preferably 60-95% (mass.), More preferably 70-90% (mass.), And even more preferably 75-90% (mass.), When taking the total grease composition as 100% (mass. .).

The amount of thickener incorporated {such as a urea compound (eg, an alkyl urea compound)} is preferably 1-20% (mass), more preferably 2-17% (mass), and even more preferably 3-15% (mass), when taking the total composition of the grease for 100% (mass.).

The amount of included poly (meth) acrylate containing hydroxyl groups is preferably 2-20% (mass.), And more preferably 4-10% (mass.), When the total grease composition is taken as 100% (mass.).

The number of other additives is in the range, for example, from 0.03 to 20% (mass.) For the combination of these optional components, when taking the total composition of the grease for 100% (mass.).

One particularly preferred embodiment of the mixing (in particular with respect to the thickener and the PMA polymer containing hydroxyl groups) is as follows, in the case in which the type of thickener is selected from the above options (2-1) to (2-3) , the level of content of the thickener = 7.5-15% (mass.) (more preferably 10-15% (mass.)), and the level of the polymer PMA containing hydroxy groups = 7.5-15% (mass.) in that if the type of a given PMA polymer containing hydroxyl groups is where (g Idroxyl number = 20-50, number average molecular weight = 1.0 × 104-2.0 × 104).

The grease composition of this embodiment of the invention can be obtained using generally used methods for the production of grease, and there are no particular restrictions on them, but as one example of a method for producing a urea grease composition, in order to produce a grease used together with a base oil, a diurea thickener is synthesized, obtained as a result of the reaction between 1 mole of diisocyanate and 2 moles of primary monoamine as a starting material for a urea thickener, or a tetraurea thickener of a grease obtained by the reaction between 2 moles of diisocyanate and 1 mole of primary diamine plus 2 moles of primary monamine as starting materials for a urea thickener, or trimourea monourethane reactions for 2 moles of diisocyanate, 1 mole of primary diamine, 1 mole of primary monoamine plus 1 mole of monoalcohol as starting materials for urea th thickening agent, in each case in the boiler for the production of grease. As for a more specific production method, after the synthesis of a specific thickener in the base oil is carried out, the temperature is increased to a temperature of approximately 180 ° C, after which cooling is carried out and an additive (derivative of poly (meth) acrylate is introduced at a temperature of 100-80 ° C, containing hydroxyl groups) and thoroughly mixed, after which the mixture is cooled to room temperature. After that, when using a kneading machine (such as a three-roll mill and the like), a homogeneous grease composition can be obtained.

The dropping point of the grease composition in this embodiment of the invention is preferably at least 180 ° C, more preferably at least 210 ° C, even more preferably at least 250 ° C, and especially higher or more 260 ° C. In the case of a dropping point of a grease composition of at least 180 ° C., it is believed that the possibility of lubrication problems, such as, for example, loss of viscosity at high temperature and associated leakage or jamming and the like, is suppressed. Drop point refers to the temperature at which the structure of the thickener breaks down in the case of a grease exhibiting a viscosity with increasing temperature. The dropping point can be measured in accordance with JIS K2220 8.

In a consistency test, the consistency of the grease in this embodiment is preferably in the range from grade 000 to grade 6 (85-475), more preferably grade 0 to grade 4 (175-385), and even more preferably grade 1 to Grade 3 (220-340). Consistency refers to the physical hardness of a grease. When measuring consistency, a working penetration measurement can be carried out in accordance with JIS K2220 7.

The friction test was carried out on the basis of a high-speed test on a four-ball friction machine to determine the properties of wear protection in accordance with ASTM D2596 when using steel ball bearings in conditions including rotation speed of 1200 rpm, load of 40 kG and ambient temperature (without regulation temperature), for 30 minutes, and then assessed the diameter of the wear spot on the fixed balls.

The grease composition of this embodiment of the invention can not only be used in commonly used mechanisms, bearings and gears and the like, but it also exhibits excellent performance under more severe conditions, such as in the case of high temperature conditions. For example, in the case of motor vehicles, it can be used in a favorable case when lubricating the starter, alternator, various types of actuator block and other peripheral devices of the engine, drive shaft, constant velocity joints (CV joints), wheel bearings, clutch and others areas of transmission, electric power steering (EUR), brake equipment, hinges, door hinges, handles, cooling fan motor, brake wedges and spills other types of components and the like. In addition, it is suitable for use in various lubricated areas of single-bucket excavators, bulldozers, cranes and other types of construction machinery and in the railway industry or the pulp and paper industry or for forestry equipment, agricultural equipment, a chemical plant, wind power plants, electric generators, drying ovens, copying equipment, railway rolling stock and threaded joints for sshovnyh pipes and the like at specific positions exposed to high temperature / high loads. Other intended applications include hard disk bearings, grease lubrication, cartridge grease, and the like, and satisfactory adaptation to such applications is also possible.

Examples

Now the present invention will be explained in even more detail when using working examples and comparative examples, but the invention is not limited to the examples presented.

The feedstock materials used in the working examples and comparative examples are as follows.

Feedstock materials for thickener

As regards thickeners A and B, diurea components having the following chemical structures were used as thickeners.

Thickener A: urea type I

Thickener B: Urea Type II

Thickener C: Urea Type III

(In these formulas, R ₂ represents a diphenylmethane group, a R ₁ represents an octal group containing eight carbon atoms, R ₃ represents a lauryl group containing twelve carbon atoms, and R ₄ represents a phenyl group containing six carbon atoms).

Thickener D: It was commercially available lithium 12-hydroxystearate for industrial use.

Base oils from A to C

Base oil A: it is a paraffin mineral oil obtained by dewaxing / purification with selective solvents, and it belongs to group I; its kinematic viscosity is 14.28 mm ² / s at 100 ° C and 144.9 mm ² / s at 40 ° C; its viscosity index is 96.

Base oil B: this is a poly-α-olefin (PAO) synthetic oil belonging to group IV and it contains a mixture of a low viscosity PAO polymer and a high viscosity PAO polymer in order to bring the kinematic viscosity at 100 ° C to 15.4 mm ² / s . The kinematic viscosity of the mixture of PAO polymers at 40 ° C is 118.9 mm ² / s, and its viscosity index is 136.

Base oil C: This is the oil obtained by the GTL method (gas to liquid), synthesized by the Fischer-Tropsch method, and it belongs to group III; its kinematic viscosity is 8.2 mm ² / s at 100 ° C and 47.9 mm ² / s at 40 ° C; and its viscosity index is 144.

Additives

Additive A: PMA polymer containing hydroxyl groups (commercial name: Aclube A-1070, manufactured by Sanyo Chemical Industries Ltd .; Mw = 1.7 × 10 ⁴ , hydroxyl number 30)

Additive B: PMA polymer free of hydroxyl groups (commercial name: Aclube V-815, manufactured by Sanyo Chemical Industries Ltd .; Mw = 2.1 × 10 ⁴ )

Additive C: PMA polymer free of hydroxyl groups (commercial name: Aclube 812, manufactured by Sanyo Chemical Industries Ltd .; Mw = 3.3 × 10 ⁴ )

Additive D: PMA polymer free of hydroxyl groups (commercial name: Aclube C728, manufactured by Sanyo Chemical Industries Ltd .; Mw = 4.5 × 10 ⁴ )

Additive Ε: ethylene-α-olefin copolymer (commercial name: Lucant HC100, manufactured by Mitsui Chemicals Inc.)

Additive F: Polybutene (commercial name: Nisseki Polybutene HV-100, manufactured by JX Nippon Oil & Energy Corp.)

Working example 1

Starting materials, a base oil and an additive were prepared and measured with the proportions shown in Table 1, and a grease corresponding to working example 1 was obtained by the conventional method for the production of urea grease. The molar ratio between diisocyanate and primary amine, which constituted the starting materials for the diurea thickener the grease used in this case corresponded to a ratio of 1: 2. As for the detailed description of the production method, 60% (mass) of the total amount of the previously obtained group I base oil, i.e. base oil A, was introduced into a sealed boiler for pilot production of grease, i.e. diphenylmethane-4,4ʹ-diisocyanate was immediately added the starting material for the urea thickener and with stirring, the temperature was increased to 50 ° C. After that, the remaining 40% (mass.) Of the base oil of group I was dissolved, respectively, octylamine and laurylamine, which, in turn, was then introduced into the boiler for pilot production, causing the reaction to pass and obtaining a thickener related to type II urea. After this, heating was continued and the temperature was increased to approximately 180 ° C, causing the stabilization of the structure of the thickener. Then, cooling was started and, at a temperature of 80 ° C., additive A was added during the cooling process, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, a homogeneous grease was obtained from working example 1.

Working example 2

Starting materials, a base oil and an additive were prepared and measured with the proportions shown in Table 1, and a grease corresponding to working example 2 was obtained by the conventional method for the production of urea grease. The molar ratio between diisocyanate and primary amine, which constituted the starting materials for the diurea thickener the grease used in this case corresponded to a ratio of 1: 2. As for the detailed description of the production method, the sealant A boiler for pilot production of grease was injected with 60% (mass) of the total amount of previously obtained synthetic oil, i.e. base oil B, immediately after which diphenylmethane-4,4ʹ-diisocyanate starting material for urea thickener was added and the temperature was increased while stirring up to 50 ° C. After that, octylamine was dissolved in the remaining 40% (mass.) Of synthetic oil, which was introduced into the boiler for pilot production, causing a reaction to pass and a thickener belonging to the diurea type I was obtained. After that, heating was continued and the temperature was increased to approximately 180 ° C, causing stabilization of the structure of the thickener. Then, cooling was started and, at a temperature of 80 ° C., additive A was added during the cooling process, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, a homogeneous grease was obtained from working example 2.

Working example 3

Starting materials, a base oil and an additive were prepared and measured with the proportions shown in Table 1, and a grease corresponding to working example 3 was obtained by the conventional method for the production of urea grease. The molar ratio between diisocyanate and primary amine, which constituted the starting materials for the diurea thickener the grease used in this case corresponded to a ratio of 1: 2. As for the detailed description of the production method, the sealant A boiler for pilot production of grease was injected with 60% (mass) of the total amount of Group III base oil obtained previously, i.e. base oil C, immediately after which diphenylmethane-4,4ʹ-diisocyanate starting material for the urea thickener was added while stirring the temperature was increased to 50 ° C. After that, in the remaining 40% (mass.) Of the base oil of the group. III, octylamine was dissolved, which was introduced into the boiler for pilot production, causing the reaction to proceed and a thickener of the urea type I type was obtained. After that, heating was continued and the temperature was increased to about 180 ° C, causing the structure of the thickener to stabilize. Then, cooling was started and, at a temperature of 80 ° C., additive A was added during the cooling process, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, a homogeneous grease was obtained from working example 3.

Working examples 4-6

Starting materials, a base oil and an additive were prepared and measured with the proportions shown in Table 1, and greases corresponding to working examples 4 to 6 were obtained according to the usual urea grease production method. The molar ratio between diisocyanate and primary amine that comprised the starting materials for each of the urea thickeners of the grease used in this case corresponded to a ratio of 1: 2. As for the detailed description of the production method, 60% (mass) of the total amount of the previously obtained group I base oil, i.e. base oil A, was introduced into a sealed boiler for pilot production of grease, i.e. diphenylmethane-4,4ʹ-diisocyanate was immediately added the starting material for the urea thickener and with stirring, the temperature was increased to 50 ° C. After that, in the remaining 40% (mass.) Of the base oil of group I, octylamine and laurylamine were dissolved, respectively, which, in turn, was introduced into the boiler for pilot production, causing the reaction to pass and obtaining a thickener related to type II urea. After this, heating was continued and the temperature was increased to approximately 180 ° C, causing the stabilization of the structure of the thickener. Then, cooling was started and, at a temperature of 80 ° C., additive A was added during the cooling process, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, each of the homogeneous greases was obtained from working examples from 4 to 6. In working examples from 4 to 6, the balance in the amount of base oil was made in accordance with the varying amounts of the additive used and again the amounts of thickener were also slightly adjusted.

Working example 7

Starting materials, a base oil and an additive were prepared and measured with the proportions shown in Table 1, and a grease corresponding to working example 7 was obtained in the usual urea grease production method. The molar ratio between diisocyanate and primary amine, which constituted the starting materials for the diurea thickener the grease used in this case corresponded to a ratio of 1: 2. As for the detailed description of the production method, 60% (mass) of the total amount of the previously obtained group I base oil, i.e. base oil A, was introduced into a sealed boiler for pilot production of grease, i.e. diphenylmethane-4,4ʹ-diisocyanate was immediately added the starting material for the urea thickener and with stirring, the temperature was increased to 50 ° C. After that, octylamine was dissolved in the remaining 40% (mass.) Of the base oil of group I, which was introduced into the boiler for pilot production, causing the reaction to pass and a thickener belonging to the diurea type I was obtained. After that, heating was continued and the temperature was increased to approximately 180 ° C. causing stabilization of the structure of the thickener. Then, cooling was started and, at a temperature of 80 ° C., additive A was added during the cooling process, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, a homogeneous grease was obtained from working example 7.

Working example 8

Starting materials, a base oil and an additive were prepared and measured with the proportions shown in Table 1, and a grease corresponding to working example 8 was obtained in the usual urea grease production method. The molar ratio between diisocyanate and primary amine, which constituted the starting materials for the diurea thickener the grease used in this case corresponded to a ratio of 1: 2. As for the detailed description of the production method, the cumulative amount of the previously obtained group I base oil, i.e. base oil A, was introduced into a sealed boiler for pilot production of grease, then diphenylmethane-4,4ʹ-diisocyanate starting material for urea thickener was added and while stirring, the temperature was increased to 50 ° C. After that, octylamine was mixed with synthetic oil, that is, base oil B, and laurylamine was mixed and dissolved in a base oil C, belonging to group III, which, in turn, was introduced into the boiler for pilot production, causing the reaction to pass and a thickener related to urea type II. After this, heating was continued and the temperature was increased to approximately 180 ° C, causing the stabilization of the structure of the thickener. Then, cooling was started and, at a temperature of 80 ° C., additive A was added during the cooling process, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, a homogeneous grease was obtained from working example 8.

Working example 9

Starting materials, a base oil and an additive were prepared and measured with the proportions shown in Table 1, and a grease corresponding to working example 9 was obtained in the usual urea grease production method. The molar ratio between diisocyanate and primary amine, which constituted the starting materials for the diurea thickener the grease used in this case corresponded to a ratio of 1: 2. As for the detailed description of the production method, 60% (mass) of the total amount of the previously obtained group I base oil, i.e. base oil A, was introduced into a sealed boiler for pilot production of grease, i.e. diphenylmethane-4,4ʹ-diisocyanate was immediately added the starting material for the urea thickener and with stirring, the temperature was increased to 50 ° C. After that, in the remaining 40% (mass.) Of the base oil of group I, aniline was mixed and dissolved, which was introduced into the boiler for pilot production, causing the reaction to pass and a thickener of the urea type III type to be obtained. After this, heating was continued and the temperature was increased to approximately 180 ° C, causing the stabilization of the structure of the thickener. Then, cooling was started and, at a temperature of 80 ° C., additive A was added during the cooling process, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, a homogeneous grease was obtained from working example 9.

Working example 10

Commercially available lithium 12-hydroxystearate for industrial use and group I base oil, i.e. base oil A, were prepared with the proportions shown in table 1, and the combined amount of this base oil and lithium 12-hydroxystearate was introduced into a sealed boiler for pilot production of grease and while stirring, the temperature was increased to 230 ° C. After confirmation of the complete dissolution of lithium 12-hydroxystearate, the temperature was gradually reduced to 80 ° C. Then, additive A was added at a given temperature of 80 ° C, in other words, a poly (meth) acrylate derivative containing hydroxyl groups, and after thorough mixing and stirring, cooling was continued up to room temperature. After that, using a three-roll mill, a homogeneous grease was obtained from working example 10.

Comparative Examples 1-3

Using the production method described in working example 6, thickener thickening reactions were carried out and, accordingly, comparative greases were prepared, where comparative example 1 was a basic grease into which no additives were added. In comparative example 2, additive B was administered. In comparative example 3, additive C. was administered.

Comparative Examples 4-6

When using the production method described in working example 1, the thickening reaction was carried out and, accordingly, comparative greases were obtained, in which example, additive D was introduced. In comparative example 5, additive F. was introduced. In comparative example 6, additive F. was introduced.

The results obtained are shown in table 1. As can be seen from table 1, in each case, using greases related to working examples in the range from 1 to 10, get excellent characteristics of wear resistance (wear spot diameter 0.39-0.52 )

Claims (15)

1. A grease composition containing a base oil, a thickening agent and a poly (meth) acrylate containing hydroxyl groups, said thickening agent being a urea compound resulting from a reaction between an isocyanate and a primary amine, and said poly (meth) acrylate containing hydroxyl groups, is a copolymer comprising, as composite monomers, an alkyl (meth) acrylate containing a C _1-20 alkyl group, and a vinyl monomer containing a hydroxyl group. 2. The grease composition according to claim 1, wherein the urea compound is a diurea compound obtained by the reaction between a diisocyanate and a primary monoamine; a tetraurea compound obtained by reaction between a diisocyanate, a primary diamine plus a primary monoamine; or a urea-monourethane compound resulting from a reaction between a diisocyanate, a primary diamine, a primary monoamine and a monoalcohol. 3. The grease composition according to claim 1, in which the urea compound is a compound described by General formula (I):

where each of R ¹ and R ³ represents a C _8-12 aliphatic hydrocarbon group, and R ² represents a C _6-15 divalent aromatic group. 4. The grease composition of claim 1, wherein the alkyl (meth) acrylate containing a C _1-20 alkyl group is an alkyl (meth) acrylate containing a C _8-20 alkyl group. 5. The grease composition according to claim 1, wherein the vinyl monomer containing a hydroxyl group is selected from hydroxyalkyl (C _2-6 ) (meth) acrylates, mono- or dihydroxyalkyl (C _1-4 ) substituted (meth) acrylamides, vinyl alcohol (obtained by hydrolysis of vinyl acetate units), C _3-12 alkenols, C _4-12 alkenediols, hydroxyalkyl (C _1-6 ) alkenyl (C _3-10 ) ethers, aromatic monomers containing a hydroxyl group, polyhydric alcohols and vinyl monomers containing a polyoxyalkylene chain and a hydroxyl group (g ppy). 6. The grease composition according to claim 4, in which the vinyl monomer containing a hydroxyl group is selected from hydroxyalkyl (C_2-6) (meth) acrylates, mono- or dihydroxyalkyl (C_1-4) substituted (meth) acrylamides, vinyl alcohol (obtained by hydrolysis of vinyl acetate units), C_3-12 alkenols, C_4-12 alkenediols, hydroxyalkyl (C_1-6) alkenyl (C_3-10) ethers, aromatic monomers containing a hydroxyl group, polyhydric alcohols and vinyl monomers containing a polyoxyalkylene chain and a hydroxyl group (s). 7. The grease composition according to claim 1, in which the copolymer comprises additional composite monomers selected from monomers containing a nitro group, vinyl monomers containing primary, secondary or tertiary amino groups, amphoteric vinyl monomers and monomers containing a nitrile group. 8. The grease composition according to any one of paragraphs. 4-6, in which the copolymer includes additional composite monomers selected from monomers containing a nitro group, vinyl monomers containing primary, secondary or tertiary amino groups, amphoteric vinyl monomers and monomers containing a nitrile group. 9. The grease composition according to any one of paragraphs. 1-7, in which the hydroxyl number of the poly (meth) acrylate containing hydroxyl groups is in the range from 20 to 50. 10. The grease composition according to claim 8, in which the hydroxyl number of the poly (meth) acrylate containing hydroxyl groups is in the range from 20 to 50. 11. The grease composition according to any one of paragraphs. 1-7 and 10, containing from 60 to 95% (mass.) Base oil, from 1 to 20% (mass.) Thickener and from 2 to 20% (mass.) Poly (meth) acrylate containing hydroxyl groups, with taking the total composition of the grease for 100% (mass.). 12. The grease composition according to claim 8, containing from 60 to 95% (mass.) Base oil, from 1 to 20% (mass.) Thickener and from 2 to 20% (mass.) Poly (meth) acrylate containing hydroxyl groups, when taking the total composition of the grease for 100% (mass.). 13. The grease composition according to claim 9, containing from 60 to 95% (mass.) Base oil, from 1 to 20% (mass.) Thickener and from 2 to 20% (mass.) Poly (meth) acrylate containing hydroxyl groups, when taking the total composition of the grease for 100% (mass.).