Patent Description:
Global government vehicle regulations demand ever better fuel economy to reduce greenhouse gas emissions and conserve fossil fuels. There is an increasing demand for more fuel-efficient vehicles in order to meet the targets regarding CO<NUM> emissions. Therefore, any incremental improvement in fuel economy (FE) is of great importance in the automotive sector.

Lubricants are playing an important role in reducing a vehicle's fuel consumption and there is a continuing need for improvements in fuel economy performance.

Lubricant properties are typically improved by the addition of additives to lubricating oils. Viscosity index (VI) improvers are generally added to a lubricant to improve its thickening efficiency and to protect the engine as they are applied between the surfaces of moving parts, notably metal surfaces.

The thickening efficiency of a VI improver is specified by its KV100 (kinematic viscosity at <NUM>) at a given treat rate. The thickening effect of a polymer increases as its hydrodynamic volume in the oil increases. Increasing temperature increases the solvency of the oil, which, in turn, promotes the uncoiling of the polymer and results in a larger hydrodynamic volume.

The hydrodynamic volume of a polymer in solution depends on many parameters, such as for example the polymer chain length and composition. The longer a polymer chain, the higher is usually the weight-average molecular weight Mw.

The drawback of using VI improvers with a high molecular weight is that they undergo significant and irreversible degradation under mechanical stress. Such degraded polymers then experience a decline in its thickening properties that goes along with an irreversible drop in the viscosity of the lubricant.

One way to overcome this disadvantage is to prepare polymers of lower molecular weight that can associate under higher temperatures by exchanging chemical bonds in a thermo-reversible way.

Patent applications <CIT>, <CIT> and <CIT> disclose a composition resulting from the mixing of at least one copolymer A1 resulting from the copolymerization of at least one monomer functionalized by diol functional groups and of at least one compound A2 comprising at least two boronic ester functional groups. These compounds can associate and exchange chemical bonds in a thermo-reversible way. The polymers according to the present invention are not described.

<CIT> is directed to a composition resulting from the mixing of at least one comb polymer polydiol A1 and at least one compound A2 comprising at least two boronic ester functions. The polymers according to the present invention are not described.

<CIT> is directed to a composition resulting from the mixing of at least one polydiol compound A1 and at least one comb polymer A2 comprising at least two boronic ester functions. The polymers according to the present invention are not described.

<CIT>, <CIT>, <CIT> and <CIT> are directed to a composition resulting from the mixing of at least one oligomer A1, functionalized with diols and optionally comprising repeat units from at least one styrene monomer, and at least one compound A2 comprising at least two boronic ester functions. The polymers according to the present invention are not described.

It was now an object of the present invention to provide thermo-associative polymers that can be used as viscosity index improvers in lubricating oil compositions and that are stable over a broad temperature range. Such polymers should be usable at low treat rates.

Additionally, the synthesis of such polymers should be simple and easy to upscale, and the starting materials should be commercially available.

The Applicant set itself the objective of preparing lubricant compositions based on novel thermoassociative copolymer mixtures which have improved properties when compared with the copolymer mixtures of the prior art. The Applicant also set itself the objective of preparing lubricant compositions based on novel thermoassociative copolymer mixtures which are easy to prepare and are not too costly.

This objective is achieved by means of novel rheological additives which can associate, optionally to form a gel, and which can be exchanged. The additives of the present invention have the advantage of thickening the medium in which they are dispersed, and they maintain this advantage at high temperatures, for instance up to <NUM>. These additives show resistance to chemical degradation during a temperature increase when compared with the additives of the prior art. Lubricant compositions comprising them show better stability of their cycling performance and better reproducibility of the lubricant properties over time.

This characteristic results from the combined use of two particular compounds, a copolymer bearing diol functions and a copolymer comprising boronic ester functions.

It is possible, by means of the compositions of the invention, to provide lubricant compositions which have good lubricant properties during the start-up phases of an engine (cold phase) and good lubricant properties when the engine is running at its service temperature (hot phase). These lubricant compositions make it possible to reduce the fuel consumption of a vehicle in which they are used. They allow better resistance to mechanical degradation than the compositions of the prior art.

The invention is based on the introduction into a base oil, of a thermoassociative copolymer mixture comprising at least a boronic ester-modified polyalkyl (meth)acrylate copolymer A and a diol functionalized polyalkyl (meth)acrylate copolymer B.

The invention relates to a lubricating oil composition, comprising at least:.

A second object of the invention relates to a lubricating oil composition, comprising at least:.

According to a favorite embodiment, the lubricating oil composition, comprises at least:.

- more than <NUM>% by weight, based on the total weight of the lubricating composition, of a base oil,
- a boronic ester-modified polyalkyl (meth)acrylate copolymer A, comprising:.

<CHM>
Wherein the definition of R1, R2 and n is detailed below
and
- a diol functionalized polyalkyl (meth)acrylate copolymer B comprising.

According to a favorite embodiment, in the aminophenylboronic acid ester of general formula (I):
<CHM>.

According to a favorite embodiment, the lubricating oil composition comprises at least:.

Another object of the invention is an additive composition which can be used for the preparation of the lubricating oil composition, comprising at least:.

Another object of the invention is a method of thickening a lubricating oil composition, comprising the steps of:.

The invention is also directed to the use of the lubricating oil composition or the additive oil composition for reducing the fuel consumption of vehicles.

The invention is further directed to a process for reducing the energy losses by mechanical part friction, comprising at least one step of placing a mechanical part in contact with the lubricating oil composition.

The invention is also directed to a process for reducing the fuel consumption of a vehicle, comprising at least one step of placing a mechanical part of the vehicle engine in contact with the lubricating oil composition.

The expression "consists essentially of" followed by one or more features means that, besides the components or steps explicitly listed, components or steps which do not significantly modify the properties and features of the invention may be included in the process or the material of the invention.

The expression "between X and Y" includes the limits, unless explicitly mentioned otherwise. This expression thus means that the targeted range comprises the values X and Y and all the values ranging from X to Y.

The term "copolymer" means a linear or branched oligomer or macromolecule having a sequence formed from several repeating units (or monomer units), of which at least two units have a different chemical structure.

The term "monomer unit" or "monomer" means a molecule that is capable of being converted into an oligomer or a macromolecule by combination with itself or with other molecules of the same type. A monomer denotes the smallest constituent unit whose repetition leads to an oligomer or a macromolecule.

In the context of this invention, the expression: "a copolymer comprising monomer X" (for example a copolymer comprising maleic acid anhydride) means a copolymer comprising repeating units resulting from the copolymerization of monomers X with other monomers. The same applies to each and every monomer and copolymer cited in this application.

In the context of the invention the expression "a polymer" or "the polymer" can be used to designate a copolymer resulting from the copolymerization of two or more different monomers.

The first copolymer of the thermoassociative copolymer mixture is a boronic ester-modified polyalkyl (meth)acrylate copolymer A, comprising maleic acid anhydride, and an aminophenylboronic acid ester of general formula (I)
<CHM>
wherein.

According to a favorite embodiment of the present invention, the boronic ester-modified polyalkyl (meth)acrylate copolymer A comprises maleic acid anhydride, at least an aminophenylboronic acid ester of general formula (I), and C1-<NUM> alkyl (meth)acrylates.

According to a more favorite embodiment of the present invention, the maleic acid anhydride, the aminophenylboronic acid ester(s) of general formula (I), and the C1-<NUM> alkyl (meth)acrylates represent from <NUM>% to <NUM>% by weight of the monomers composing copolymer A, preferably from <NUM>% to <NUM>% by weight, even more preferably they represent <NUM>% by weight of the monomers composing copolymer A.

According to a first embodiment of the invention, the first copolymer of the thermoassociative copolymer mixture is a boronic ester-modified polyalkyl (meth)acrylate copolymer A, comprising <NUM> mol% to <NUM> mol% of maleic acid anhydride, and <NUM> mol% to <NUM> mol% of an aminophenylboronic acid ester of general formula (I)
<CHM>.

Wherein R<NUM>, R<NUM> and n are as defined above and in detail above and here-under. According to a favorite variant of this embodiment of the present invention, the boronic ester-modified polyalkyl (meth)acrylate copolymer A comprises from <NUM> mol% to <NUM> mol% of maleic acid anhydride, from <NUM> mol% to <NUM> mol% of an aminophenylboronic acid ester of general formula (I), and from <NUM>% to <NUM>% molar of C1-<NUM> alkyl (meth)acrylates.

According to another favorite embodiment of the present invention, the boronic ester-modified polyalkyl (meth)acrylate copolymer A, comprises:.

The content of each component (a1), (a2), (a3), (a4) and (a5) is based on the total composition of the boronic ester-modified polyalkyl (meth)acrylates A. In a particular embodiment, the proportions of components (a1), (a2), (a3), (a4) and (a5) add up to <NUM>% by weight.

According to a favorite embodiment of the present invention, in the boronic ester-modified polyalkyl (meth)acrylates A, the C10-<NUM> alkyl (meth)acrylates are a mixture of C12-<NUM> alkyl (meth)acrylates and C16-<NUM> alkyl (meth)acrylates in a weight ratio of <NUM>:<NUM> to <NUM>:<NUM>.

According to a favorite embodiment of the present invention, in the boronic ester-modified polyalkyl (meth)acrylate A as defined further above, in general formula (I), n denotes an integer <NUM> or <NUM> and R<NUM> together with R<NUM> form a ring of general formula (IIa)
<CHM>
wherein R<NUM> and R<NUM> are independently selected from the group consisting of H and C1-<NUM> alkyl, R<NUM> and R<NUM> are independently selected from the group consisting of H and C1-<NUM> alkyl, and the stars "*" represent the bonds to the oxygen atoms.

In the boronic ester-modified polyalkyl (meth)acrylate copolymer A as defined further above, in general formula (I), the amino function can be in the ortho, meta or para position with regards to the bore substituent. According to a favorite embodiment of the present invention the amino function is in the ortho or para position with regards to the bore substituent, even more preferably in the para position.

The weight-average molecular weight of the boronic ester-modified polyalkyl (meth)acrylates A used in the lubricating composition according to the present invention is preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol, more preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol. The number-average molecular weight of the polyalkyl(meth)acrylate polymers according to the present invention is preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol, more preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol.

Preferably, the polyalkyl(meth)acrylate copolymers A used in the lubricating composition according to the present invention have a polydipersity index (PDI) Mw/Mn in the range of <NUM> to <NUM>, more preferably in the range of <NUM> to <NUM>.

Mw and Mn are determined by size exclusion chromatography (SEC) using commercially available polymethylmethacrylate standards. The determination was done by gel permeation chromatography with THF as eluent.

The term "(meth)acrylates" refers to both, esters of acrylic acid and esters of methacrylic acid. Esters of methacrylic acid are preferred.

The C1-<NUM> alkyl (meth)acrylates for use in accordance with the invention are esters of (meth)acrylic acid and straight chain or branched alcohols having <NUM> to <NUM> carbon atoms. The term "C1-<NUM> alkyl (meth)acrylates" encompasses individual (meth)acrylic esters with an alcohol of a particular length, and likewise mixtures of (meth)acrylic esters with alcohols of different lengths.

Suitable C1-<NUM> alkyl (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate), iso-propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate and tert-butyl (meth)acrylate. Particularly preferred C<NUM>-<NUM> alkyl (meth)acrylates are methyl (meth)acrylate and n-butyl (meth)acrylate; methyl methacrylate and n-butyl methacrylate are especially preferred.

Suitable C1-<NUM> alkyl (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate) and iso-propyl (meth)acrylate. Particularly preferred C1-<NUM> alkyl (meth)acrylate is methyl (meth)acrylate.

The C10-<NUM> alkyl (meth)acrylates for use in accordance with the invention are esters of (meth)acrylic acid and straight chain or branched alcohols having <NUM> to <NUM> carbon atoms. The term "C10-<NUM> alkyl (meth)acrylates" encompasses individual (meth)acrylic esters with an alcohol of a particular length, and likewise mixtures of (meth)acrylic esters with alcohols of different lengths. Suitable C10-<NUM> alkyl (meth)acrylates include, for example, <NUM>-butyloctyl (meth)acrylate, <NUM>-hexyloctyl (meth)acrylate, decyl (meth)acrylate, <NUM>-butyldecyl (meth)acrylate, <NUM>-hexyldecyl (meth)acrylate, <NUM>-octyldecyl (meth)acrylate, undecyl (meth)acrylate, <NUM>-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, <NUM>-methyldodecyl (meth)acrylate, <NUM>-hexyldodecyl (meth)acrylate, <NUM>-octyldodecyl (meth)acrylate, tridecyl (meth)acrylate, <NUM>-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate, <NUM>-decyltetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, <NUM>-methylhexadecyl (meth)acrylate, <NUM>-dodecylhexadecyl (meth)acrylate, heptadecyl (meth)acrylate, <NUM>-isopropylheptadecyl (meth)acrylate, <NUM>-tert-butyloctadecyl (meth)acrylate, <NUM>-ethyloctadecyl (meth)acrylate, <NUM>-isopropyloctadecyl (meth)acrylate, octadecyl (meth)acrylate, <NUM>-decyloctadecyl (meth)acrylate, <NUM>-tetradecyloctadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, cetyleicosyl (meth)acrylate, stearyleicosyl (meth)acrylate, docosyl (meth)acrylate and/or eicosyltetratriacontyl (meth)acrylate. <NUM>-decyl-tetradecyl (meth)acrylate, <NUM>-decyloctadecyl (meth)acrylate, <NUM>-dodecyl-<NUM>-hexadecyl (meth)acrylate, <NUM>,<NUM>-octyl-<NUM>-dodecyl (meth)acrylate, <NUM>-tetradecylocadecyl (meth)acrylate, <NUM>,<NUM>-tetradecyl-octadecyl (meth)acrylate and <NUM>-hexadecyl-eicosyl (meth)acrylate.

The C12-<NUM> alkyl (meth)acrylates for use in accordance with the invention are esters of (meth)acrylic acid and alcohols having <NUM> to <NUM> carbon atoms. The term "C12-<NUM> alkyl (meth)acrylates" encompasses individual (meth)acrylic esters with an alcohol of a particular length, and likewise mixtures of (meth)acrylic esters with alcohols of different lengths.

Suitable C12-<NUM> alkyl (meth)acrylates include, for example, decyl (meth)acrylate, undecyl (meth)acrylate, <NUM>-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, <NUM>-methyldodecyl (meth)acrylate, tridecyl (meth)acrylate, <NUM>-methyltridecyl (methacrylate, tetradecyl (meth)acrylate and/or pentadecyl (meth)acrylate.

Particularly preferred C12-<NUM> alkyl (meth)acrylates are methacrylic esters of a linear C12-<NUM> alcohol mixture (C12-<NUM> alkyl methacrylate).

The C16-<NUM> alkyl (meth)acrylates for use in accordance with the invention are esters of (meth)acrylic acid and alcohols having <NUM> to <NUM> carbon atoms. The term "C16-<NUM> alkyl (meth)acrylates" encompasses individual (meth)acrylic esters with an alcohol of a particular length, and likewise mixtures of (meth)acrylic esters with alcohols of different lengths.

Suitable C16-<NUM> alkyl (meth)acrylates include, for example, <NUM>-hexyldecyl (meth)acrylate, <NUM>-octyldecyl (meth)acrylate, undecyl (meth)acrylate, <NUM>-methylundecyl (meth)acrylate and dodecyl (meth)acrylate.

Particularly preferred C16-<NUM> alkyl (meth)acrylates are methacrylic esters of a linear C16-<NUM> alcohol mixture (C16-<NUM> alkyl methacrylate).

The comonomers for use in accordance with the present invention can be selected from the group consisting of styrene monomers having from <NUM> to <NUM> carbon atoms, vinyl esters having from <NUM> to <NUM> carbon atoms in the acyl group, vinyl ethers having from <NUM> to <NUM> carbon atoms in the alcohol group, (di)alkyl fumarates having from <NUM> to <NUM> carbon atoms in the alcohol group, (di)alkyl maleates having from <NUM> to <NUM> carbon atoms in the alcohol group, dispersing nitrogen-functionalized monomers, and mixtures of these monomers.

Examples of styrene monomers having from <NUM> to <NUM> carbon atoms are styrene, substituted styrenes having an alkyl substituent in the side chain, for example alpha-methylstyrene and alphaethylstyrene, substituted styrenes having an alkyl substituent on the ring, such as vinyltoluene and para-methylstyrene, halogenated styrenes, for example monochlorostyrenes, dichlorostyrenes, tribromostyrenes and tetrabromostyrenes; preferred is styrene.

Examples of vinyl esters having from <NUM> to <NUM> carbon atoms in the acyl group include vinyl formiate, vinyl acetate, vinyl propionate, vinyl butyrate. Preferred vinyl esters include from <NUM> to <NUM>, more preferably from <NUM> to <NUM> carbon atoms in the acyl group. The acyl group here may be linear or branched.

Examples of vinyl ethers having from <NUM> to <NUM> carbon atoms in the alcohol group include vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl butyl ether. Preferred vinyl ethers include from <NUM> to <NUM>, more preferably from <NUM> to <NUM> carbon atoms in the alcohol group. The alcohol group here may be linear or branched.

The notation "(di)ester" means that monoesters, diesters and mixtures of esters, especially of fumaric acid and/or of maleic acid, may be used. The (di)alkyl fumarates having from <NUM> to <NUM> carbon atoms in the alcohol group include monomethyl fumarate, dimethyl fumarate, monoethyl fumarate, diethyl fumarate, methyl ethyl fumarate, monobutyl fumarate, dibutyl fumarate, dipentyl fumarate and dihexyl fumarate. Preferred (di)alkyl fumarates comprise from <NUM> to <NUM>, more preferably from <NUM> to <NUM> carbon atoms in the alcohol group. The alcohol group here may be linear or branched. The (di)alkyl maleates having from <NUM> to <NUM> carbon atoms in the alcohol group include monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, methyl ethyl maleate, monobutyl maleate, dibutyl maleate. Preferred (di)alkyl maleates comprise from <NUM> to <NUM>, more preferably from <NUM> to <NUM> carbon atoms in the alcohol group. The alcohol group here may be linear or branched. Examples of dispersing nitrogen-functionalized monomers are aminoalkyl (meth)acrylates, such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-diethylaminopentyl (meth)acrylate, N,N-dibutylaminohexadecyl (meth)acrylate; aminoalkyl(meth)acrylamides, such as N,N-dimethylaminopropyl(meth)acrylamide; heterocyclic (meth)acrylates, such as <NUM>-(<NUM>-imidazolyl)ethyl (meth)acrylate, <NUM>-(<NUM>-morpholinyl)ethyl (meth)acrylate, <NUM>-(<NUM>-methacryloyloxyethyl)-<NUM>-pyrrolidone, N-methacryloylmorpholine, N-methacryloyl-<NUM>-pyrrolidinone, N-(<NUM>-methacryloyloxyethyl)-<NUM>-pyrrolidinone, N-(<NUM>-methacryloyloxypropyl)-<NUM>-pyrrolidinone; heterocyclic vinyl compounds, such as <NUM>-vinylpyridine, <NUM>-vinylpyridine, <NUM>-methyl-<NUM>-vinylpyridine, <NUM>-ethyl-<NUM>-vinylpyridine, <NUM>,<NUM>-dimethyl-<NUM>-vinylpyridine, vinylpyrimidine, vinylpiperidine, <NUM>-vinylcarbazole, <NUM>-vinylcarbazole, <NUM>-vinylcarbazole, <NUM>-vinylimidazole, <NUM>-methyl-<NUM>-vinylimidazole, N-vinylpyrrolidone, N-vinylpyrrolidine, <NUM>-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, vinyloxolane, vinylfuran, vinyloxazoles and hydrogenated vinyloxazoles.

The N-dispersant monomer may specifically be at least one monomer selected from the group consisting of N-vinyl pyrrolidinone, N,N-dimethylaminoethyl methacrylate, and N,N-dimethylaminopropyl methacrylamide.

A further embodiment of the present invention is directed to a lubricating composition comprising the boronic ester-modified polyalkyl (meth)acrylates A as outlined further above, wherein the aminophenylboronic acid ester of general formula (I) is selected from the group consisting of <NUM>-aminophenylboronic acid pinacol ester, <NUM>-aminophenylboronic acid pinacol ester, <NUM>-aminophenylboronic acid <NUM>,<NUM>-dihydroxybenzene ester, <NUM>-aminophenylboronic acid <NUM>,<NUM>-dihydroxybenzene ester, <NUM>-aminophenylboronic acid <NUM>,<NUM>-dihydroxycyclohexyl ester and <NUM>-aminophenylboronic acid <NUM>,<NUM>-dihydroxycyclohexyl ester, preferably <NUM>-aminophenylboronic acid pinacol ester and <NUM>-aminophenylboronic acid pinacol ester, more preferably <NUM>-aminophenylboronic acid pinacol ester:
<CHM>.

A further embodiment of the present invention is directed to a lubricating oil composition comprising the boronic ester-modified polyalkyl (meth)acrylate copolymers A as outlined further above, wherein the maleic acid anhydride is grafted.

A further embodiment of the present invention is directed to a lubricating oil composition comprising grafted boronic ester-modified polyalkyl (meth)acrylate copolymers A consisting of a base copolymer A1 and units A2 that are grafted thereon, wherein the base copolymer A1 comprises:.

The content of each component (a1), (a2), (a3), (a4) and (a5) is based on the total composition of the boronic ester-modified polyalkyl (meth)acrylate A. In a particular embodiment, the proportions of components (a1), (a2), (a3), (a4) and (a5) add up to <NUM>% by weight.

The copolymers used in the lubricating oil composition according to the present invention are characterized by their ability to form association-related thickeners.

The diol functionalized polyalkyl (meth)acrylate copolymer B comprises at least one diol selected from C2-<NUM>α,β-di-hydroxyalkyl (meth)acrylate, preferably from C2-<NUM>α,β-dihydroxyalkyl (meth)acrylates, preferably selected from the group consisting of <NUM>,<NUM>-dihydroxypropyl methacrylate and <NUM>,<NUM>-dihydroxyhexyl methacrylate, preferably <NUM>,<NUM>-dihydroxypropyl methacrylate.

According to a first favorite embodiment, the diol functionalized polyalkyl (meth)acrylate copolymer B comprises from <NUM>% to <NUM>% molar of C1-<NUM> alkyl (meth)acrylates, and from <NUM>% to <NUM>% molar of a C2-<NUM>α,β-di-hydroxyalkyl (meth)acrylate.

According to a second favorite embodiment, the diol functionalized polyalkyl (meth)acrylate copolymer B comprises from <NUM>% to <NUM>% by weight of a diol selected from C2-<NUM>α,β-dihydroxyalkyl (meth)acrylates and from <NUM> to <NUM>% by weight of C1-<NUM> alkyl (meth)acrylates.

According to a favorite embodiment, the diol selected from C2-<NUM>α,β-dihydroxyalkyl (meth)acrylates and the C1-<NUM> alkyl (meth)acrylates represent from <NUM> to <NUM> % by weight of monomers composing copolymer B, preferably from <NUM>% to <NUM>% by weight, even more preferably they represent <NUM>% by weight of the monomers composing copolymer B.

Advantageously, the polyalkyl (meth)acrylate copolymer B comprises the following monomers:.

The content of each component (b1), (b2), (b3) and (b4) is based on the total composition of the polyalkyl (meth)acrylate copolymer B. In a particular embodiment, the proportions of components (b1), (b2), (b3) and (b4) add up to <NUM>% by weight.

The weight-average molecular weight of the diol functionalized polyalkyl (meth)acrylate copolymer B used in the present invention is preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol, more preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol. The number-average molecular weight of the polyalkyl(meth)acrylate copolymers B used in the present invention is preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol, more preferably in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol.

Preferably, the diol functionalized polyalkyl(meth)acrylate copolymers B used in the present invention have a polydipersity index (PDI) Mw/Mn in the range of <NUM> to <NUM>, more preferably in the range of <NUM> to <NUM>, more preferably in the range of <NUM> to <NUM>.

The proportions of copolymer A and copolymer B in the compositions comprising them.

The favorite proportions of copolymer A and copolymer B apply to the lubricant compositions and also to the stock solutions (or concentrated solutions) comprising them.

According to a favorite embodiment, the lubricant composition of the present invention comprises.

According to a favorite embodiment, the component aminophenylboronic acid ester of general formula (I) of the boronic ester-modified polyalkyl (meth)acrylate copolymer A and the component C2-<NUM>α,β-di-hydroxyalkyl (meth)acrylate of the diol functionalized polyalkyl (meth)acrylate copolymer B are present in a molar ratio of <NUM> :<NUM> to <NUM> :<NUM>, preferably from <NUM> :<NUM>,<NUM> to <NUM>,<NUM> :<NUM>, even more preferably of <NUM>:<NUM>.

According to a favorite embodiment, the component aminophenylboronic acid ester of general formula (I) of the boronic ester-modified polyalkyl (meth)acrylate copolymer A and the component C2-<NUM>α,β-di-hydroxyalkyl (meth)acrylate of the diol functionalized polyalkyl (meth)acrylate copolymer B are present in amounts of <NUM> mol% to <NUM> mol% of the respective copolymers. According to a favorite embodiment, the lubricant composition of the present invention comprises a mixture of:.

(A) a boronic ester-modified polyalkyl (meth)acrylate copolymer A, comprising:.

<CHM>
wherein n denotes an integer <NUM> to <NUM>, R<NUM> and R<NUM> are as defined above; and
(B) a polyalkyl (meth)acrylate copolymer B comprising the following monomers:.

in amounts such that the weight ratio (A) :(B) is <NUM> :<NUM> to <NUM> :<NUM>, preferably <NUM> :<NUM>,<NUM> to <NUM>,<NUM> :<NUM>, even more preferably <NUM>:<NUM>.

According to a favorite embodiment, the component (a5) aminophenylboronic acid ester of general formula (I) of the boronic ester-modified polyalkyl (meth)acrylate copolymer A and the component (b4) C2-<NUM>α,β-di-hydroxyalkyl (meth)acrylate of the diol functionalized polyalkyl (meth)acrylate copolymer B are present in a molar ratio (a5) : (b4) of <NUM> :<NUM> to <NUM> :<NUM>, preferably from <NUM> :<NUM>,<NUM> to <NUM>,<NUM> :<NUM>, even more preferably of <NUM>:<NUM>.

The content of each component (a1), (a2), (a3), (a4) and (a5) is based on the total composition of the boronic ester-modified polyalkyl (meth)acrylate copolymer A. In a particular embodiment, the proportions of components (a1), (a2), (a3), (a4) and (a5) add up to <NUM>% by weight.

Advantageously, in the lubricating composition of the present invention, in the mixture as defined further above, component (a5) of the boronic ester-modified polyalkyl (meth)acrylate copolymer A and component (b4) of the polyalkyl (meth)acrylate copolymer B are present in amounts of <NUM> mol% to <NUM> mol% of the respective copolymers.

Advantageously, in the lubricating composition of the present invention, in the mixture as defined further above, component (a5) of the boronic ester-modified polyalkyl (meth)acrylate copolymer A and component (b4) of the polyalkyl (meth)acrylate copolymer B are present in molar ratio (a5) : (b4) from <NUM> :<NUM> to <NUM> :<NUM>, more advantageously from <NUM> :<NUM>,<NUM> to <NUM>,<NUM> :<NUM>, even more preferably equal to <NUM>. The mixture comprising the above recited amounts of a boronic ester-modified polyalkyl (meth)acrylate copolymer A and a polyalkyl (meth)acrylate copolymer B can be used to thicken a lubricating oil composition.

The term "oil" means a fatty substance that is liquid at room temperature (<NUM>) and atmospheric pressure (<NUM> mmHg i.e. <NUM><NUM> Pa).

The term "base oil" or "lubricant oil" means an oil which attenuates the friction between two moving parts in order to facilitate the functioning of these parts. The lubricant oils may be of natural, mineral or synthetic origin.

The lubricant oils of natural origin may be oils of plant or animal origin, preferably oils of plant origin such as rapeseed oil, sunflower oil, palm oil, coconut kernel oil, etc..

The lubricant oils of mineral origin are of petroleum origin and are extracted from petroleum fractions originating from the atmospheric and vacuum distillation of crude oil. The distillation may be followed by refining operations such as solvent extraction, deasphalting, deparaffinning with solvent, hydrotreatment, hydrocracking, hydroisomerization, hydrofinishing, etc. By way of illustration, mention may be made of paraffinic mineral base oils such as the oil Bright Stock Solvent (BSS), naphthenic mineral base oils, aromatic mineral oils, hydrorefined mineral bases whose viscosity index is about <NUM>, hydrocracked mineral bases whose viscosity index is between <NUM> and <NUM>, or hydroisomerized mineral bases whose viscosity index is between <NUM> and <NUM>. The lubricant oils of synthetic origin (or synthetic bases) originate, as their name indicates, from chemical synthesis, such as the addition of a product to itself or polymerization, or the addition of one product to another product such as esterification, alkylation, fluorination, etc., of components originating from petrochemistry, carbon chemistry and mineral chemistry such as: olefins, aromatics, alcohols, acids, halogen-based, phosphorus-based, silicon-based compounds, etc. By way of illustration, mention may be made of:.

The base oil may also be defined as specified by the American Petroleum Institute (API) (see April <NUM> version of "Appendix E-API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils", section <NUM> Sub-heading <NUM>. "Base Stock Categories").

The API currently defines five groups of lubricant base stocks (API <NUM>, Annex E - API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils, September <NUM>). Groups I, II and III are mineral oils which are classified by the amount of saturates and sulphur they contain and by their viscosity indices; Group IV are polyalphaolefins; and Group V are all others, including e.g. ester oils. The table below illustrates these API classifications.

The kinematic viscosity at <NUM> (KV100) of appropriate apolar base oils used to prepare a lubricating composition in accordance with the present invention is preferably in the range of <NUM>,<NUM><NUM>/s to <NUM><NUM>/s, more preferably in the range of <NUM>,<NUM><NUM>/s to <NUM><NUM>/s, according to ASTM D445.

Further base oils which can be used in accordance with the present invention are Group II-III Fischer-Tropsch derived base oils.

Fischer-Tropsch derived base oils are known in the art. By the term "Fischer-Tropsch derived" is meant that a base oil is, or is derived from, a synthesis product of a Fischer-Tropsch process. A Fischer-Tropsch derived base oil may also be referred to as a GTL (Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oils that may be conveniently used as the base oil in the lubricating composition of the present invention are those as for example disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Especially for engine oil formulations are used base oils of API Group II to V.

A further embodiment of the present invention is directed to a method of thickening a lubricating oil composition, comprising the steps of:.

The favorite embodiments recited for the copolymers A and B and their proportions apply to the method of thickening a lubricating oil composition.

Another embodiment of the present invention is directed to a lubricating oil composition, comprising:.

The favorite embodiments recited above for the copolymers A and B, their combination and their proportions apply to the lubricating oil composition.

The content of each component (A), (B), (C) and (D) is based on the total composition of the lubricating oil composition. In a particular embodiment, the proportions of components (A), (B), (C) and (D) add up to <NUM>% by weight.

The lubricating oil composition according to the invention may also contain, as component (D), further additives selected from the group consisting of conventional VI improvers, dispersants, defoamers, detergents, antioxidants, pour point depressants, antiwear additives, extreme pressure additives, friction modifiers, anticorrosion additives, dyes and mixtures thereof.

Conventional VI improvers include hydrogenated styrene-diene copolymers (HSDs, <CIT>, <CIT> and <CIT>), especially based on butadiene and isoprene, and also olefin copolymers (OCPs, <NPL>), especially of the poly(ethylene-co-propylene) type, which may often also be present in N/O-functional form with dispersing action, or PAMAs, which are usually present in N-functional form with advantageous additive properties (boosters) as dispersants, wear protection additives and/or friction modifiers (<CIT> to Röhm and Haas, <CIT> to RohMax Additives).

Compilations of VI improvers and pour point improvers for lubricant oils, especially motor oils, are detailed, for example, in <NPL>: <NPL>; or<NPL>.

Appropriate dispersants include poly(isobutylene) derivatives, for example poly(isobutylene)succinimides (PIBSIs), including borated PIBSIs; and ethylene-propylene oligomers having N/O functionalities.

Dispersants (including borated dispersants) are preferably used in an amount of <NUM> to <NUM>% by weight, based on the total amount of the lubricating oil composition.

Suitable defoamers are silicone oils, fluorosilicone oils, fluoroalkyl ethers, etc..

The defoaming agent is preferably used in an amount of <NUM> to <NUM>% by weight, based on the total amount of the lubricating oil composition.

The preferred detergents include metal-containing compounds, for example phenoxides; salicylates; thiophosphonates, especially thiopyrophosphonates, thiophosphonates and phosphonates; sulfonates and carbonates. As metal, these compounds may contain especially calcium, magnesium and barium. These compounds may preferably be used in neutral or overbased form.

Detergents are preferably used in an amount of <NUM> to <NUM>% by weight, based on the total amount of the lubricating oil composition.

The suitable antioxidants include, for example, phenol-based antioxidants and amine-based antioxidants.

Phenol-based antioxidants include, for example, octadecyl-<NUM>-(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyphenyl)propionate; <NUM>,<NUM>' -methylenebis(<NUM>,<NUM>-di-tert-butylphenol); <NUM>,<NUM>' -bis(<NUM>,<NUM>-di-t-butylphenol); <NUM>,<NUM>' -b is(<NUM>-methyl-<NUM>-t-butylphenol); <NUM>,<NUM>' -methylenebis(<NUM>-ethyl-<NUM>-t-butylphenol); <NUM>,<NUM>' - methylenebis( <NUM>-methyl-<NUM>-t-butyl phenol); <NUM>,<NUM>' -butyl idenebis(<NUM>-methyl-<NUM>-t-butylphenol); <NUM>,<NUM>'-isopropylidenebis(<NUM>,<NUM>-di-t-butylphenol); <NUM>,<NUM>'-methylenebis(<NUM>-methyl-<NUM>-nonylphenol); <NUM>,<NUM>'-isobutylidenebis(<NUM>,<NUM>-dimethylphenol); <NUM>,<NUM>'-methylenebis(<NUM>-methyl-<NUM>-cyclohexylphenol); <NUM>,<NUM>-di-t-butyl-<NUM>-methylphenol; <NUM>,<NUM>-di-t-butyl-<NUM>-ethyl-phenol; <NUM>,<NUM>-dimethyl-<NUM>-t-butylphenol; <NUM>,<NUM>-di-t-amyl-p-cresol; <NUM>,<NUM>-di-t-butyi-<NUM>-(N,N'-dimethylaminomethylphenol); <NUM>,<NUM>'thiobis(<NUM>-methyl-<NUM>-t-butylphenol); <NUM>,<NUM>'-thiobis(<NUM>-methyl-<NUM>-t-butylphenol); <NUM>,<NUM>'-thiobis(<NUM>-methyl-<NUM>-t-butylphenol); bis(<NUM>-methyl-<NUM>-hydroxy-<NUM>-t-butylbenzyl) sulfide; bis(<NUM>,<NUM>-di-t-butyl-<NUM>-hydroxybenzyl) sulfide; n-octyl-<NUM>-(<NUM>-hydroxy-<NUM>,<NUM>-di-t-butylphenyl)propionate; n-octadecyl-<NUM>-(<NUM>-hydroxy-<NUM>,<NUM>-di-t-butylphenyl)propionate; <NUM>,<NUM>'-thio[diethyl-bis-<NUM>-(<NUM>,<NUM>-di-t-butyl-<NUM>-hydroxyphenyl)propionate], etc. Of those, especially preferred are bis-phenol-based antioxidants and ester group containing phenol-based antioxidants.

The amine-based antioxidants include, for example, monoalkyldiphenylamines such as monooctyldiphenylamine, monononyldiphenylamine, etc.; dialkyldiphenylamines such as <NUM>,<NUM>' - dibutyldiphenylamine, <NUM>,<NUM>'-dipentyldiphe nylamine, <NUM>,<NUM>'- dihexyldiphenylamine, <NUM>,<NUM>'-diheptyldiphenylamine, <NUM>,<NUM>'-dioctyldiphenylamine, <NUM>,<NUM>'-dinonyldiphenylamine, etc.; polyalkyldiphenylamines such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine, etc.; naphthylamines, concretely alpha-naphthylamine, phenyl-alpha-naphthylamine and further alkyl-substituted phenyl-alpha-naphthylamines such as butylphenyl-alpha-naphthylamine, pentylphenyl-alpha-naphthylamine, hexylphenyl-alpha-naphthylamine, heptylphenyl-alpha-naphthylamine, octylphenyl-alpha-naphthylamine, nonylphenyl-alpha-naphthylamine, etc. Of those, diphenylamines are preferred to naphthylamines, from the viewpoint of the antioxidation effect thereof.

Suitable antioxidants may further be selected from the group consisting of compounds containing sulfur and phosphorus, for example metal dithiophosphates, for example zinc dithiophosphates (ZnDTPs), "OOS triesters" = reaction products of dithiophosphoric acid with activated double bonds from olefins, cyclopentadiene, norbornadiene, α-pinene, polybutene, acrylic esters, maleic esters (ashless on combustion); organosulfur compounds, for example dialkyl sulfides, diaryl sulfides, polysulfides, modified thiols, thiophene derivatives, xanthates, thioglycols, thioaldehydes, sulfur-containing carboxylic acids; heterocyclic sulfur/nitrogen compounds, especially dialkyldimercaptothiadiazoles, <NUM>-mercaptobenzimidazoles; zinc bis(dialkyldithiocarbamate) and methylene bis(dialkyldithiocarbamate); organophosphorus compounds, for example triaryl and trialkyl phosphites; organocopper compounds and overbased calcium- and magnesium-based phenoxides and salicylates.

Antioxidants are used in an amount of <NUM> to <NUM>% by weight, preferably <NUM> to <NUM>% by weight, more preferably <NUM> to <NUM>% by weight, based on the total amount of the lubricating oil composition.

The pour-point depressants include ethylene-vinyl acetate copolymers, chlorinated paraffinnaphthalene condensates, chlorinated paraffin-phenol condensates, polymethacrylates, polyalkylstyrenes, etc. Preferred are polymethacrylates having a mass-average molecular weight of from <NUM> to <NUM>/mol.

The amount of the pour point depressant is preferably from <NUM> to <NUM>% by weight, based on the total amount of the lubricating oil composition.

The preferred antiwear and extreme pressure additives include sulfur-containing compounds such as zinc dithiophosphate, zinc di-C<NUM>-<NUM>-alkyldithiophosphates (ZnDTPs), zinc phosphate, zinc dithiocarbamate, molybdenum dithiocarbamate, molybdenum dithiophosphate, disulfides, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, polysulfides, etc.; phosphorus-containing compounds such as phosphites, phosphates, for example trialkyl phosphates, triaryl phosphates, e.g. tricresyl phosphate, amine-neutralized mono- and dialkyl phosphates, ethoxylated mono- and dialkyl phosphates,phosphonates, phosphines, amine salts or metal salts of those compounds, etc.; sulfur and phosphorus-containing anti-wear agents such as thiophosphites, thiophosphates, thiophosphonates, amine salts or metal salts of those compounds, etc..

The antiwear agent may be present in an amount of <NUM> to <NUM>% by weight, preferably <NUM> to <NUM>% by weight, more preferably <NUM> to <NUM>% by weight, based on the total amount of the lubricating oil composition.

Friction modifiers used may include mechanically active compounds, for example molybdenum disulfide, graphite (including fluorinated graphite), poly(trifluoroethylene), polyamide, polyimide; compounds that form adsorption layers, for example long-chain carboxylic acids, fatty acid esters, ethers, alcohols, amines, amides, imides; compounds which form layers through tribochemical reactions, for example saturated fatty acids, phosphoric acid and thiophosphoric esters, xanthogenates, sulfurized fatty acids; compounds that form polymer-like layers, for example ethoxylated dicarboxylic partial esters, dialkyl phthalates, methacrylates, unsaturated fatty acids, sulfurized olefins or organometallic compounds, for example molybdenum compounds (molybdenum dithiophosphates and molybdenum dithiocarbamates MoDTCs) and combinations thereof with ZnDTPs, copper-containing organic compounds.

Friction modifiers may be used in an amount of <NUM> to <NUM>% by weight, preferably <NUM> to <NUM>% by weight, more preferably <NUM> to <NUM>% by weight, based on the total amount of the lubricating oil composition. Some of the compounds listed above may fulfil multiple functions. ZnDTP, for example, is primarily an antiwear additive and extreme pressure additive, but also has the character of an antioxidant and corrosion inhibitor (here: metal passivator/deactivator).

The above-detailed additives are described in detail, inter alia, in <NPL>; <NPL>".

Preferably, the total concentration of the one or more additives (D) is <NUM>% to <NUM>% by weight, more preferably <NUM>% to <NUM>% by weight, based on the total weight of the lubricating oil composition.

Another embodiment of the present invention is directed to an additive composition, comprising:.

The additive composition, also known as stock solution, or concentrated solution, or mother solution, is used to prepare a lubricating composition, by dilution with a base oil which can be identical to or different from the base oil of the additive composition.

The favorite embodiments recited above for the copolymers A and B and their proportions apply to the additive composition.

The content of each component (A), (B), (C) and (D) is based on the total composition of additive. In a particular embodiment, the proportions of components (A), (B), (C) and (D) add up to <NUM>% by weight.

The lubricant compositions and the additive compositions of the invention are prepared by means that are well known to those skilled in the art. For example, it notably suffices for a person skilled in the art:.

The order of addition of the compounds has no influence in the implementation of the process for preparing the lubricant composition.

Alternately, the lubricating oil composition can be prepared by dilution of a concentrated solution of additives.

A further embodiment of the present invention is directed to a process for improving the thickening efficiency of a lubricating oil composition by adding a boronic ester-modified polyalkyl (meth)acrylate copolymer A and a diol functionalized polyalkyl (meth)acrylate copolymer B, comprising the monomers as outlined further above.

The lubricant compositions of the invention result from the mixing of associative copolymers which have the property of increasing the viscosity of the lubricant oil via associations. The lubricant compositions according to the invention have the advantage in that these associations or crosslinking are reversible.

The boronic ester functionalized copolymers A and the diol functionalized copolymers B as defined above have the advantage of being associative and of exchanging chemical bonds, notably in a hydrophobic medium, notably an apolar hydrophobic medium.

Under certain conditions, the boronic ester functionalized copolymers A and the diol functionalized copolymers B as defined above may be crosslinked.

The boronic ester functionalized copolymers A and the diol functionalized copolymers B also have the advantage of being exchangeable.

The term "associative" means that covalent chemical bonds of boronic ester type are established between the boronic ester functionalized copolymers A and the diol functionalized copolymers B. Depending on the functionality of the boronic ester functionalized copolymers A and the diol functionalized copolymers B and depending on the composition of the mixtures, the formation of covalent bonds between boronic ester functionalized copolymers A and the diol functionalized copolymers B will optionally be able to lead to the formation of a three-dimensional polymer network.

The term "chemical bond" means a covalent chemical bond of boronic ester type.

The term "exchangeable" means that the compounds are capable of exchanging chemical bonds between themselves by transesterification without the total number or nature of the chemical functions being modified.

The lubricant compositions according to the invention have improved thermal stability, an improved viscosity index, improved stability to oxidation, better cycling performance, and better reproducibility of the performance qualities over time, and also better resistance to mechanical degradation.

A person skilled in the art knows how to adjust the various parameters of the various constituents of the composition to obtain a lubricant composition whose viscosity is suitable for use.

The amount of boronic ester bonds that can be established between the diol functionalized copolymers B and the boronic ester functionalized copolymers A is adjusted by a person skilled in the art by means of an appropriate selection of the diol functionalized copolymers B, of the boronic ester functionalized copolymers A, and of their amounts.

The boronic ester-modified polyalkyl (meth)acrylate copolymers A and the diol functionalized polyalkyl (meth)acrylate copolymers B as disclosed above can be prepared by free-radical polymerization and by related methods of controlled free-radical polymerization, for example ATRP (= atom transfer radical polymerization) or RAFT (= reversible addition fragmentation chain transfer).

Standard free-radical polymerization is detailed, inter alia, in <NPL>on. In general, a polymerization initiator and optionally a chain transfer agent are used for this purpose.

The usable initiators include azo initiators widely known in the technical field, such as AIBN and <NUM>,<NUM>-azobiscyclohexanecarbonitrile, and also peroxy compounds such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, tert-butyl per-<NUM>-ethylhexanoate, ketone peroxide, tert-butyl peroctoate, methyl isobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide, tert-butyl perbenzoate, <NUM>,<NUM>-bis(tert-butylperoxy)butane, tert-butyl peroxyisopropylcarbonate, <NUM>,<NUM>-bis(<NUM>-ethylhexanoylperoxy)-<NUM>,<NUM>-dimethylhexane, tert-butyl peroxy-<NUM>-ethylhexanoate, tert-butyl peroxy-<NUM>,<NUM>,<NUM>-trimethylhexanoate, dicumyl peroxide, <NUM>,<NUM>-bis(tert-butylperoxy)cyclohexane, <NUM>,<NUM>-bis(tert-butylperoxy)-<NUM>,<NUM>,<NUM>-trimethylcyclohexane, cumyl hydroperoxide, tert-butyl hydroperoxide, bis(<NUM>-tert-butylcyclohexyl) peroxydicarbonate, mixtures of two or more of the aforementioned compounds with one another, and mixtures of the aforementioned compounds with unspecified compounds which can likewise form free radicals. Preferably used in accordance with the present invention are tert-butyl perbenzoate and <NUM>,<NUM>-bis(tert-butylperoxy)butane. Suitable chain transfer agents are especially oil-soluble mercaptans, for example n-dodecyl mercaptan or <NUM>-mercaptoethanol, or else chain transfer agents from the class of the terpenes, for example terpinolene.

The ATRP method is known per se. It is assumed that this is a "living" free-radical polymerization, but no restriction is intended by the description of the mechanism. In these processes, a transition metal compound is reacted with a compound having a transferable atom group. This involves transfer of the transferable atom group to the transition metal compound, as a result of which the metal is oxidized. This reaction forms a free radical which adds onto ethylenic groups. However, the transfer of the atom group to the transition metal compound is reversible, and so the atom group is transferred back to the growing polymer chain, which results in formation of a controlled polymerization system. It is accordingly possible to control the formation of the polymer, the molecular weight and the molecular weight distribution.

This reaction regime is described, for example, by <NPL>), by <NPL>). In <CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose variants of the above-elucidated ATRP. In addition, the polymers of the invention can also be obtained via RAFT methods, for example. This method is described in detail, for example, in <CIT> and <CIT>.

The polymerization can be conducted under standard pressure, reduced pressure or elevated pressure. The polymerization temperature is also uncritical. In general, however, it is in the range from -<NUM> to <NUM>, preferably <NUM> to <NUM> and more preferably <NUM> to <NUM>.

The polymerization can be conducted with or without solvent. The term "solvent" should be understood here in a broad sense. The solvent is selected according to the polarity of the monomers used, it being possible with preference to use 100N oil, comparatively light gas oil and/or aromatic hydrocarbons, for example toluene or xylene.

As outlined further above, the boronic ester-modified polyalkyl (meth)acrylate copolymers A comprise either copolymerized or grafted units of maleic acid anhydride.

In cases where the boronic ester-modified polyalkyl (meth)acrylate copolymers A are subsequently grafted with maleic acid anhydride, this is preferably done by a polymer-analogous reaction after the above-described preparation of boronic ester-modified polyalkyl (meth)acrylate copolymers A. Accordingly, it is possible with preference first to prepare a polymer by the use of reactive polar unsaturated monomers like maleic acid anhydride. The reactive units are subsequently further reacted with an aminophenylboronic acid ester of general formula (I) as described further above. The reaction of the reactive polar unsaturated monomer present in the polymer, preferably of the maleic acid anhydride, with the mentioned aminophenylboronic acid esters can be effected typically between <NUM> and <NUM>, preferably between <NUM> and <NUM> and more preferably between <NUM> and <NUM>. The aminophenylboronic acid ester can preferably be added in an equimolar amount to the reactive polar groups, preferably to the anhydride. If excessive amounts of aminophenylboronic acid ester are added, it can subsequently be removed from the mixture. In the case of excessively small proportions, reactive groups remain, which can optionally be converted to less reactive groups by addition of small amounts of water.

The aminophenylboronic acid ester can be added in pure form to the reaction mixture or in a suitable solvent. Preference is given to polar solvents, especially esters, e.g. butyl acetate, diisononyl adipate or dioctylsebacate.

According to the nature of the reactive reactant group converted, water may be formed. For example, in the case of use of anhydride groups, water is released, which, in a particular aspect of the present invention, can be removed substantially completely from the reaction mixture, it being possible to drive out water, for example, by means of dry nitrogen. In addition, it is possible to use desiccants. Volatile solvents such as butyl acetate, if used, can be distilled off after the reaction, preferably under reduced pressure.

The following figures illustrate the results retrieved for the viscosity indices when using the polymers in the compositions of the present invention:.

The invention is illustrated by the following non-limiting examples.

The boronic ester-modified polyalkyl (meth)acrylate copolymers A and the diol functionalized polyalkyl (meth)acrylate copolymers B were characterized with respect to their molecular weight and PDI.

The weight-average molecular weights (Mw) of the boronic ester-modified polyalkyl (meth)acrylates A and the diol functionalized polyalkyl (meth)acrylates B were determined by gel permeation chromatography (GPC) using polymethyl methacrylate calibration standards according to DIN <NUM>-<NUM> using the following measurement conditions:.

The additive compositions including the boronic ester-modified polyalkyl (meth)acrylate copolymers A and the diol functionalized polyalkyl (meth)acrylate copolymers B were characterized with respect to their viscosity index (VI) to ASTM D <NUM>, kinematic viscosity at <NUM> (KV40) and <NUM> (KV100) to ASTM D445.

In the experimental, the % are expressed by weight of monomers with regards to the total weight of the copolymers unless expressed otherwise.

Base polymers without maleic acid anhydride: Examples 1a, 2a and 5a.

Base polymers with maleic acid anhydride: Examples 3a, 4a and 6a.

A solution of <NUM>% of initiator <NUM>,<NUM>-bis(tert-butylperoxy)butane in the monomer mixture is prepared at room temperature (compositional details of the monomer mixtures are shown in Tables <NUM> and <NUM>). An apparatus with <NUM>-neck flask and precision glass saber stirrer was initially charged with <NUM> NB3043. After heating to <NUM> under nitrogen, <NUM> of a monomer-initiator-mixture was added within <NUM> hours. Then the reaction mixture was cooled down to <NUM> and <NUM>% (based to the total amount of monomers) of <NUM>,<NUM>-bis(tert-butylperoxy)butane was added and the resulting mixture stirred at <NUM> overnight. <NUM> of a <NUM>% solution of polymer in NB3043 was obtained.

The conversion of the used monomers was around <NUM>%; i.e. the net compositions of the resulting polymers correspond to the mixtures used in the copolymerizations.

Maleic acid anhydride was heated up at <NUM>. An apparatus with a <NUM>-neck flask and precision glass saber stirrer was charged with <NUM> of the base polymer mixture as prepared under (<NUM>) and heated up to <NUM> under nitrogen. Subsequently, <NUM> of molten maleic anhydride was added followed by an addition of <NUM> of tert-butyl perbenzoate. Subsequently, the reaction temperature was increased to <NUM>. After <NUM> hour and <NUM> hours, another <NUM> of tert-butyl perbenzoate was each added to the reaction mixture. The mixture was then cooled down to <NUM> to add after <NUM> hours <NUM> of <NUM>,<NUM>-bis(tert-butylperoxy)butane and after <NUM> hours <NUM> of <NUM>,<NUM>-bis(tert-butylperoxy)butane and the mixture is stirred overnight. <NUM> of a <NUM>% solution of polymer in NB3043 was obtained.

Maleic acid anhydride was heated up at <NUM>. An apparatus with a <NUM>-neck flask and precision glass saber stirrer was charged with <NUM> of the base polymer mixture as prepared under (<NUM>) and heated up to <NUM> under nitrogen. Then <NUM> of molten maleic anhydride was added followed by an addition of <NUM> of tert-butyl perbenzoate. Subsequently, the reaction temperature was increased to <NUM>. After <NUM> hour and <NUM> hours, another <NUM> of tert-butyl perbenzoate was each added to the reaction mixture. The mixture was then cooled down to <NUM> to add after <NUM> hours <NUM> of <NUM>,<NUM>-bis(tert-butylperoxy)butane and after <NUM> hours <NUM> of <NUM>,<NUM>-bis(tert-butylperoxy)butane and the mixture is stirred overnight. <NUM> of a <NUM>% solution of polymer in NB3043 was obtained.

Maleic anhydride was heated up at <NUM>. An apparatus with a <NUM>-neck flask and precision glass saber stirrer was charged with <NUM> of the base polymer mixture as prepared under (<NUM>) and heated up to <NUM> under nitrogen. Then <NUM> of molten maleic anhydride was added followed by an addition of <NUM> of tert-butyl perbenzoate. Subsequently, the reaction temperature was increased to <NUM>. After <NUM> hour and <NUM> hours, another <NUM> of tert-butyl perbenzoate was each added to the reaction mixture. The mixture was then cooled down to <NUM> to add after <NUM> hours <NUM> of <NUM>,<NUM>-bis(tert-butylperoxy)butane and after <NUM> hours <NUM> of <NUM>,<NUM>-bis(tert-butylperoxy)butane and the mixture is stirred overnight. <NUM> of a <NUM>% solution of polymer in NB3043 was obtained.

The net compositions of the grafted polymers are shown in the following Table <NUM>.

A solution of <NUM> wt. % of <NUM>-aminophenylboronic acid pinacol ester in dioctylsebacate was prepared. Then an apparatus with a <NUM>-neck flask, precision glass saber stirrer and condenser was charged with <NUM> of the polymer mixture prepared as described under steps (<NUM>) or (<NUM>). After heating to <NUM> under nitrogen, <NUM> of the <NUM>-aminophenylboronic acid pinacol ester solution was added within <NUM> hour. The post-grafting reaction was finished <NUM> hours after the addition of the <NUM>-aminophenylboronic acid pinacol ester and the mixture was diluted to a solids content of <NUM>% with NB3043.

A solution of <NUM> wt. % of <NUM>-aminophenylboronic acid pinacol ester in dioctylsebacate was prepared. Then an apparatus with a <NUM>-neck flask, precision glass saber stirrer and condenser was charged with <NUM> of the polymer mixture prepared as described under step (<NUM>) or (<NUM>). After heating to <NUM> under nitrogen, <NUM> of the <NUM>-aminophenylboronic acid pinacol ester solution was added within <NUM> hour. The post-grafting reaction was finished <NUM> hours after the addition of the <NUM>-aminophenylboronic acid pinacol ester and the mixture was diluted to a solids content of <NUM>% with NB3043.

The net compositions of the resulting boronic ester-modified polyalkyl (meth)acrylates A are shown in the following Table <NUM>.

A solution of a monomer mixture (compositional details of the examples of the used monomer mixtures are given in Table <NUM>) and <NUM>% (based to the total amount of monomers) of initiator <NUM>,<NUM>-bis(tert-butylperoxy)butane was prepared at room temperature. An apparatus with <NUM>-neck flask and precision glass saber stirrer was initially charged with <NUM> butyl acetate. After heating to <NUM> under nitrogen, <NUM> of the monomer-initiator-mixture was added within <NUM> hours. Then the reaction mixture was cooled down to <NUM> and <NUM>% (based to the total amount of monomers) of <NUM>,<NUM>-bis(tert-butylperoxy)butane was added and the mixture was stirred at <NUM> overnight. <NUM> of a <NUM>% solution of polymer in butyl acetate was obtained. The solvent was then exchanged by adding NB3043 to the solution of polymer in butyl acetate. Subsequently, the butyl acetate was removed by vacuum distillation resulting in a <NUM>% solution of polymer in NB3043.

Table <NUM> shows the net compositions of the working examples and comparative examples. The monomer components will add up to <NUM>%. As the residual monomer content in the retrieved polymers is significantly below <NUM>%, the net compositions of the polymers correspond to the used monomer compositions.

The properties of the boronic ester-modified polyalkyl (meth)acrylates A and the polyalkyl (meth)acrylate B are presented in the following Table <NUM>.

The resulting polymers were characterized by their molecular weight and PDI. The results are shown in the following Table <NUM>.

The weight-average molecular weights are in the range of <NUM>,<NUM>/mol (Example 4b) and <NUM>,<NUM>/mol (Example 2c). The number-average molecular weights are in the range of <NUM>,<NUM>/mol (Example 5c) and <NUM>,<NUM>/mol (Examples 1c and 6c).

The thickening efficiency of a VI improver is specified by its KV100 (kinematic viscosity at <NUM>) at a given treat rate.

The single polymers were dissolved in a base oil and the retrieved solutions were characterized by their KV40, KV100 and VI. The results are shown in the following Table <NUM>.

It can be seen that the KV40-values are between <NUM> and <NUM><NUM>/s, the KV100-values are between <NUM> and <NUM><NUM>/s and the viscosity indices are in the range of <NUM> (Example <NUM>) and <NUM> (Example <NUM>).

To show the associative effect of the polymers, mixtures comprising equal parts of an AMBER polymer and a diol-polymer, compositions comprising <NUM>% of a <NUM>:<NUM> polymer mixture in a base oil were prepared and, subsequently, KV40, KV100 and viscosity indices were measured.

The corresponding values are outlined in the following Table <NUM>.

Claim 1:
Lubricating oil composition, comprising at least:
- more than <NUM>% by weight, based on the total weight of the lubricating composition, of a base oil,
- a boronic ester-modified polyalkyl (meth)acrylate copolymer A, comprising <NUM> mol% to <NUM> mol% of maleic acid anhydride, and <NUM> mol% to <NUM> mol% of an aminophenylboronic acid ester of general formula (I)
<CHM>
wherein n denotes an integer from <NUM> to <NUM>,
R<NUM> and R<NUM> are independently selected from the group consisting of hydrogen and C1-<NUM> alkyl, or
R<NUM> together with R<NUM> form a ring of general formula (IIa)
<CHM>
wherein R<NUM>, R<NUM>, R<NUM> and R<NUM> are independently selected from the group consisting of H and C1-<NUM> alkyl and the stars "*" represent the bonds to the oxygen atoms, or
R<NUM> together with R<NUM> form a ring of general formula (IIb)
<CHM>
wherein R<NUM> and R<NUM> are independently selected from the group consisting of H and C1-<NUM> alkyl and the stars "*" represent the bonds to the oxygen atoms, or
R<NUM> together with R<NUM> form a ring of general formula (IIc)
<CHM>
wherein R<NUM> denotes a hydrogen atom or C1-<NUM> alkyl and the stars "*" represent the bonds to the oxygen atoms,
and
- a diol functionalized polyalkyl (meth)acrylate copolymer B comprising from <NUM>% to <NUM>% molar of C1-<NUM> alkyl (meth)acrylates, and from <NUM>% to <NUM>% molar of a C2-<NUM>α,β-di-hydroxyalkyl (meth)acrylate.