KR102455761B1 - Lubricant composition with improved viscosity characteristics at low operating temperature - Google Patents

Abstract

The present invention relates to a lubricant composition comprising a comb polymer and a synthetic base oil. The lubricant composition has improved viscosity characteristics at low operating temperatures. The invention also relates to the use of comb polymers for the preparation of lubricants having an R-module of 8 or less, wherein the R-module is defined as the ratio of the kinematic viscosity at -20°C and the kinematic viscosity at +20°C. is about

Description

Lubricant composition with improved viscosity characteristics at low operating temperature

The present invention relates to a lubricant composition for use in industrial applications having improved low temperature viscosity characteristics.

Lubricants for use in industrial applications typically include a base oil, such as a mineral oil or synthetic oil, and one or more additives. Additives deliver, for example, reduced friction and wear, increased viscosity, improved viscosity index, and resistance to corrosion, oxidation, aging or contamination.

The ability of a lubricant to reduce friction depends on its viscosity. In general, a minimally viscous fluid is desired, such that the two moving surfaces are still spaced apart. Many lubricant applications require good lubricant properties over a wide temperature range, for example when the engine is at its operating temperature as well as at low temperatures. Accordingly, the viscosity of the lubricant should change as little as possible with temperature in order to provide consistent lubricant properties over a wide temperature range.

The temperature-dependency of the viscosity of a lubricant is measured by the viscosity index (VI). The higher the viscosity index, the less the relative change in viscosity with temperature. The viscosity index is determined from the kinematic viscosity at 40° C. (KV ₄₀ ) and at 100° C. (KV ₁₀₀ ), which well reflects the operating conditions of most engines. Additives that increase the viscosity index are referred to as viscosity index improvers (VII).

Polymers of alkyl (meth)acrylates, and especially comb polymers based on polyalkyl(meth)acrylates, are known in the art to act as good viscosity index improvers in lubricant oils.

For example, US Pat. Nos. 5,565,130 and 5,597,871 disclose the use of comb polymers comprising polybutadiene-derived macromers as viscosity index improvers. No low-temperature properties are disclosed in this document.

WO 2007/003238 A1 describes oil-soluble comb polymers based on polyolefin-based macromers, in particular polybutadiene-based methacrylic acid esters, and C1-C10 alkyl methacrylates. Comb polymers can be used as additives for lubricant oils to improve the viscosity index and shear stability. They present a particularly high viscosity index-improving action in lubricant oils. No low-temperature properties are disclosed in this document.

However, the viscosity index does not adequately reflect the properties of the lubricant at temperatures below 40°C, for example in the low temperature range of -20°C to +20°C. Thus, a lubricant that has good lubricant properties at the operating temperature of the machine or engine does not necessarily have good properties during the cold start phase of the engine as well. However, the cold start properties of the lubricant are an important factor contributing to the improved fuel efficiency of the engine.

The low temperature properties of a lubricant can be measured by the R-factor, which is defined as the ratio of the kinematic viscosity at -20°C to the kinematic viscosity at +20°C. Since the kinematic viscosity at -20°C is generally higher than the kinematic viscosity at +20°C, the R-factor is usually greater than one. Thus, the narrow viscosity difference between -20°C and +20°C is reflected by the low R-coefficient (R-coefficient close to 1).

The problem of providing lubricant compositions with good viscosity properties at low operating temperatures has not been sufficiently addressed in the prior art. Primarily, the prior art reports VI measured between 40°C and 100°C, but does not provide an indication of the viscosity characteristics, for example between -20°C and +20°C.

Accordingly, it is an object of the present invention to provide a lubricant composition having excellent low temperature viscosity properties. In particular, the difference in the kinematic viscosity at -20°C and +20°C of the lubricant composition should be small. It is further an object of the present invention to provide an additive for a lubricant composition for lowering the difference between the kinematic viscosities at -20°C and +20°C.

It has been found that the use of certain comb polymers as additives for lubricant compositions results in surprisingly low R-modules that cannot be achieved using conventional viscosity index improvers. It has also been found that lubricant compositions comprising a synthetic base oil and certain comb polymers exhibit surprisingly good low temperature viscosity characteristics, in particular a surprisingly good R-modulus.

Accordingly, the present invention provides a lubricant composition comprising:

(A) synthetic base oil; and

(B) a comb polymer comprising the following monomers:

(a) esters of (meth)acrylic acid and hydroxylated hydrogenated polybutadiene; and

(b) from 0.2% to 15% by weight of styrene, based on the total weight of the comb polymer;

characterized in that the R-factor, which is the ratio of the kinematic viscosity at -20°C to the kinematic viscosity at +20°C, is 8 or less

It relates to a lubricant composition.

The lubricant composition is preferably defined by an R-module of 8 or less, wherein the R-module is the ratio of the kinematic viscosity of the lubricant composition at -20°C (KV _-20 ) to the kinematic viscosity at +20°C (KV ₊₂₀ ). , that is, KV _-20 /KV ₊₂₀ , and the kinematic viscosity is measured according to ASTM D445.

Preferably, the lubricant composition has an R-factor of 1 to 8.

The composition is preferably formulated to yield a specific kinematic viscosity at 40° C. according to ASTM D445. This can be achieved by adjusting the relative amounts of comb polymer, base oil and optional additives. Preferably, the composition has a kinematic viscosity at 40° C. of 10 to 120 mm ² /s, more preferably 40 to 100 mm ² /s, most preferably 70 to 80 mm ² /s according to ASTM D445.

In a preferred embodiment, the lubricant composition comprises, based on the total weight of the lubricant composition:

(A) 20 to 90% by weight, preferably 30 to 80% by weight, most preferably 35 to 80% by weight of a synthetic base oil, and

(B) 10 to 80% by weight, preferably 20 to 70% by weight, most preferably 20 to 65% by weight of the comb polymer.

Suitable synthetic base oils are selected from API group IV oils. Polyalphaolefins (PAOs) are particularly preferred.

Synthetic base oils are typically characterized by their kinematic viscosity, ie that of a pure base oil without any additives. Preferably, the synthetic base oil is from 1 mm ² /s to 20 mm ² /s, more preferably from 1 to 10 mm ² /s, most preferably from 1 to 5 mm ² /s, particularly preferred according to ASTM D445 It preferably has a kinematic viscosity at 100° C. of 2-3 mm ² /s.

In one embodiment, the synthetic base oil is 1 mm ² /s to 20 mm ² /s, more preferably 1 to 10 mm ² /s, most preferably 1 to 5 mm ² /s, especially according to ASTM D445 It is preferably a polyalphaolefin having a kinematic viscosity at 100° C. of 2 to 3 mm ² /s.

Comb polymers in the context of the present invention comprise a first polymer, also referred to as the backbone or backbone, and a plurality of additional polymers, also referred to as side chains, covalently linked to the backbone. In the case of the present invention, the backbone of the comb polymer is formed by interconnected unsaturated groups of the (meth)acrylates mentioned. The ester group of the (meth)acrylic acid ester, the phenyl radical of the styrene monomer, and the substituents of the additional free-radically polymerizable comonomer form the side chains of the comb polymer. The term "backbone" does not mean that the chain length of the main chain is necessarily longer than that of the side chain.

One important aspect of the present invention is the amount of styrene in the comb polymer. In the context of the present invention, the amount of monomer, such as styrene, is given in weight percent based on the total weight of the monomer mixture. As used herein, the term "total weight of the monomer mixture" refers to the total weight of the monomers, excluding any additives that may be added to the monomer mixture to facilitate polymerization, such as polymerization initiators, polymerization accelerators, chain transfer agents and diluents. . The relative amounts of monomers in the monomer mixture correspond to the relative amounts of the corresponding monomer units in the copolymer, provided that all the different monomers present in the monomer mixture are equally well incorporated into the copolymer.

In one embodiment, the comb polymer (B) comprises, based on the total weight of the comb polymer:

(a) at least 20% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,

(b) 0.2% to 15% by weight of styrene, and

(c) optionally further comonomers.

The hydroxylated hydrogenated polybutadiene used according to the invention has a number-average molar mass M _n of from 4,000 to 6,000 g/mol, preferably from 4,000 to 5,000 g/mol. Because of its high molar mass, the hydroxylated polybutadiene may also be referred to as a macroalcohol in the context of the present invention.

The number-average weight M _n is determined by size exclusion chromatography using commercially available polybutadiene standards. The determination is carried out according to DIN 55672-1 by gel permeation chromatography using THF as eluent.

Preferably, the hydroxylated hydrogenated polybutadiene has a hydrogenation level of at least 99%. An alternative measure of the level of hydrogenation that can be determined for the copolymers of the present invention is the iodine number. The iodine number refers to the number of grams of iodine that can be added onto 100 g of the copolymer. Preferably, the copolymer of the present invention has an iodine number of 5 g or less of iodine per 100 g of copolymer. The iodine number is determined by the Weiss method according to DIN 53241-1:1995-05.

Preferred hydroxylated hydrogenated polybutadiene can be obtained according to GB 2270317.

Some hydroxylated hydrogenated polybutadiene are also commercially available. Commercial hydroxylated hydrogenated polybutadiene includes, for example, Kraton Liquid® L-1203 from Kraton Polymers GmbH (Eschborn, Germany), which has M _n = 4200 g/mol of OH-functionalized hydrogenated polybutadiene (also called olefin copolymer OCP) to an extent of about 98% by weight, each having 1,2 and 1,4 repeating units of about 50%. Additional suppliers of suitable alcohols based on hydrogenated polybutadiene are Cray Valley (Paris), a subsidiary of Total (Paris), or Sartomer Company (Exton, PA, USA). )to be.

Monohydroxylated hydrogenated polybutadiene is preferred. More preferably, the hydroxylated hydrogenated polybutadiene is hydroxyethyl- or hydroxypropyl-terminated hydrogenated polybutadiene. Hydroxypropyl-terminated polybutadiene is particularly preferred.

These monohydroxylated hydrogenated polybutadiene can be prepared by first converting the butadiene monomer to polybutadiene by anionic polymerization. Subsequently, by reaction of polybutadiene monomer with ethylene oxide or propylene oxide, hydroxy-functionalized polybutadiene can be prepared. Such hydroxylated polybutadiene can be hydrogenated in the presence of a suitable transition metal catalyst.

The esters of (meth)acrylic acid and the described hydroxylated hydrogenated polybutadiene used according to the invention are also referred to in the context of the present invention as macromers, because of their high molar mass.

the term “(meth)acrylic acid” refers to acrylic acid and methacrylic acid and mixtures thereof; Methacrylic acid is particularly preferred. the term “(meth)acrylate” refers to esters of acrylic acid and esters of methacrylic acid and mixtures thereof; Esters of methacrylic acid are particularly preferred.

The macromers used according to the invention can be prepared by transesterification of alkyl (meth)acrylates. Reaction of an alkyl (meth)acrylate with a hydroxylated hydrogenated polybutadiene forms the esters of the present invention. Preference is given to using methyl (meth)acrylate or ethyl (meth)acrylate as reactant.

Such transesterification is well known. For this purpose, for example, a heterogeneous catalyst system, such as a lithium hydroxide/calcium oxide mixture (LiOH/CaO), pure lithium hydroxide (LiOH), lithium methoxide (LiOMe) or sodium methoxide (NaOMe), or a homogeneous catalyst It is possible to use systems such as isopropyl titanate (Ti(OiPr)4) or dioctyltin oxide (Sn(OCt)2O). The reaction is an equilibrium reaction. Thus, the released low molecular weight alcohol is typically removed, for example by distillation.

In addition, the macromers can be prepared by the DCC method (dish acrylic acid, for example from (meth)acrylic acid or (meth)acrylic acid anhydride, preferably under acidic catalysis with p-toluenesulfonic acid or methanesulfonic acid, or from free methacrylic acid by direct esterification with chlorohexylcarbodiimide).

Furthermore, the hydroxylated hydrogenated polybutadiene of the present invention can be converted to an ester by reaction with an acid chloride such as (meth)acryloyl chloride.

Preferably, in the above-mentioned preparation of the esters of the invention, polymerization inhibitors are used, for example the 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl radical and/or hydroquinone monomethyl ether. do.

Some macromers used according to the invention are also commercially available, for example, as Kraton Liquid® L-1253 from Kraton Polymers GmbH (Eschborn, Germany), which is Kraton Liquid® L-1203. methacrylate-functionalized hydrogenated polybutadiene to an extent of about 96% by weight, having about 50% 1,2 repeat units and 1,4 repeat units, respectively. Kraton® L-1253 is also synthesized according to GB 2270317.

Besides macromers and styrene, the monomer mixture may also comprise further comonomers, for example other alkyl (meth)acrylates.

Particular preference is given to alkyl (meth)acrylates (also called C ₁ to C ₂₂ alkyl (meth)acrylates) having 1 to 22 carbon atoms in the alkyl chain.

Suitable alkyl (meth)acrylates are, for example, methyl and ethyl acrylates, propyl methacrylate, butyl methacrylate (BMA) and acrylates (BA), isobutyl methacrylate (IBMA), hexyl and cyclo Hexyl methacrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate (EHA), 2-ethylhexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate (IDMA) , based on a mixture of branched (C10)alkyl isomers), undecyl methacrylate, dodecyl methacrylate (also known as lauryl methacrylate), tridecyl methacrylate, tetradecyl methacrylate ( Also known as myristyl methacrylate), pentadecyl methacrylate, hexadecyl methacrylate (also known as cetyl methacrylate), heptadecyl methacrylate, octadecyl methacrylate (also known as stearyl methacrylate) lactate), nonadecyl methacrylate, eicosyl methacrylate, behenyl methacrylate and combinations thereof.

Suitable C10-15 alkyl (meth)acrylates are, for example, decyl (meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, 2-methyldodecyl (meth)acrylate, tridecyl (meth)acrylate, 5-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate and/or pentadecyl (meth)acrylate .

A particularly preferred C10-15 alkyl (meth)acrylate is the (meth)acrylic acid ester of a linear C12-14 alcohol mixture (C12-14 alkyl (meth)acrylate).

In one embodiment, the comb polymer (B) comprises, based on the total weight of the comb polymer:

(a) from 20% to 50% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,

(b) 0.2% to 15% by weight of styrene, and

(c) up to 70% by weight of alkyl (meth)acrylates having from 1 to 22 carbon atoms in the alkyl chain.

In one embodiment, the comb polymer comprises, based on the total weight of the comb polymer:

(a) from 20% to 35% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,

(b) 0.2% to 15% by weight of styrene;

(c) 0.2% to 20% by weight of an alkyl (meth)acrylate having 12 to 15 carbon atoms in the alkyl chain, and

(d) 50% to 70% by weight of an alkyl (meth)acrylate having from 1 to 4 carbon atoms in the alkyl chain.

In one embodiment, the comb polymer (B) comprises, based on the total weight of the comb polymer:

(a) 25% to 30% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,

(b) 0.2% to 15% by weight of styrene;

(c) 0.2% to 15% by weight of an alkyl methacrylate having 12 to 14 carbon atoms in the alkyl chain,

(d) from 50% to 65% by weight of butyl methacrylate, and

(e) 0.1% to 0.2% by weight of methyl methacrylate.

The comb polymer based on polyalkyl(meth)acrylate according to the present invention can preferably be obtained by radical polymerization. However, comb polymers can also be obtained by polymer-like reactions and/or graft copolymerization.

In one embodiment, the comb polymer can be obtained by radical polymerization involving the following steps:

a) providing a monomer mixture comprising the indicated monomers; and

b) initiating radical polymerization in the monomer mixture.

The polymerization reaction is preferably initiated by mixing the monomer mixture with a radical initiator. In some cases, it may be necessary to heat the reaction mixture to the reaction temperature specified below to initiate polymerization.

Radical initiators include any of the well known free-radical-generating compounds such as peroxy, hydroperoxy and azo initiators such as, for example, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, tert-butyl peroxy Isobutyrate, caproyl peroxide, cumene hydroperoxide, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, azobisisobutyronitrile and tert-butyl peroctoate ( also known as tert-butylperoxy-2-ethylhexanoate). Preferred radical initiators are benzoyl peroxide, lauroyl peroxide, tert-butyl peroxyisobutyrate, azobisisobutyronitrile and tert-butyl peroctoate. Particular preference is given to tert-butyl peroctoate. The initiator concentration is typically from 0.025 to 1 wt-%, preferably from 0.05 to 0.75 wt-%, more preferably from 0.1 to 0.5 wt-%, most preferably from 0.2 to 0.4 wt, based on the total weight of the monomers. -%to be.

The polymerization is preferably carried out at a temperature below the boiling point of the reaction mixture. Preferably, the temperature is in the range of 60 to 150 °C, more preferably 85 to 130 °C and most preferably 90 to 110 °C.

One or more polymerization promoters may also be added to the monomer mixture. Suitable accelerators include, for example, quaternary ammonium salts such as benzyl(hydrogenated-tallow)-dimethylammonium chloride and amines. Preferably the accelerator is soluble in hydrocarbons. These accelerators, if used, are present at a level of 1 to 50 wt-%, preferably 5 to 25 wt-%, based on the total weight of the initiator.

Chain transfer agents may also be added to control the molecular weight of the copolymer. Preferred chain transfer agents are alkyl mercaptans such as lauryl mercaptan (also known as dodecyl mercaptan, DDM). The amount of chain transfer agent is preferably 5 wt-% or less, more preferably 2 wt-% or less, based on the total weight of the monomers.

Diluents may also be added to the monomer mixture. Preferably, the first and second reaction mixtures each comprise at most 60 wt-%, more preferably 5-60 wt-%, most preferably 10-60 wt-% of diluent.

Among the diluents suitable for use in the process of the invention in the case of non-aqueous solution polymerization are aromatic hydrocarbons (such as benzene, toluene, xylene and aromatic naphtha), chlorinated hydrocarbons (such as ethylene dichloride, chlorobenzene and dichlorobenzene), esters ( such as ethyl propionate or butyl acetate), (C6-C20)aliphatic hydrocarbons (such as cyclohexane, heptane and octane), mineral oils (such as paraffinic and naphthenic oils) or synthetic base oils such as poly([alpha]- olefin) oligomeric (PAO) lubricating oils such as [alpha]-decene dimers, trimers and mixtures thereof).

The lubricant composition according to the present invention may further comprise auxiliary additives selected from the group consisting of pour point depressants, antiwear agents, antioxidants, dispersants, detergents, friction modifiers, defoamers, extreme pressure additives and corrosion inhibitors. The auxiliary additive is preferably added in an amount of 0.1 to 25 weight-%, based on the total weight of the lubricant composition.

Suitable pour point depressants include ethylene-vinyl acetate copolymers, chlorinated paraffin-naphthalene condensates, chlorinated paraffin-phenol condensates, polymethacrylates, polyalkylstyrenes, and the like. Polymethacrylates having a mass-average molecular weight of 5,000 to 50,000 g/mol are preferred.

Preferred antiwear and extreme pressure additives are sulfur-containing compounds such as zinc dithiophosphate, zinc di-C3-12-alkyldithiophosphate (ZnDTP), zinc phosphate, zinc dithiocarbamate, molybdenum dithiocarbamate. , molybdenum dithiophosphate, disulfide, sulfurized olefins, sulfurized oils and fats, sulfurized esters, thiocarbonates, thiocarbamates, polysulfides and the like; phosphorus-containing compounds such as phosphites, phosphates such as trialkyl phosphates, triaryl phosphates such as tricresyl phosphate, amine-neutralized mono- and dialkyl phosphates, ethoxylated mono- and dialkyl phosphates, phospho nates, phosphines, amine salts or metal salts of these compounds, and the like; sulfur and phosphorus-containing antiwear agents such as thiophosphites, thiophosphates, thiophosphonates, amine salts or metal salts of these compounds, and the like.

Suitable antioxidants include, for example, phenol-based antioxidants and amine-based antioxidants.

Phenol-based antioxidants include, for example, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-bis(2,6-di-t-butylphenol); 4,4'-bis(2-methyl-6-t-butylphenol); 2,2'-methylenebis(4-ethyl-6-t-butylphenol); 2,2'-methylenebis(4-methyl-6-t-butyl phenol); 4,4'-butylidenebis(3-methyl-6-t-butylphenol); 4,4'-isopropylidenebis(2,6-di-t-butylphenol); 2,2'-methylenebis(4-methyl-6-nonylphenol); 2,2'-isobutylidenebis(4,6-dimethylphenol); 2,2'-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-t-butyl-4-methylphenol; 2,6-di-t-butyl-4-ethyl-phenol; 2,4-dimethyl-6-t-butylphenol; 2,6-di-t-amyl-p-cresol; 2,6-di-t-butyl-4-(N,N'-dimethylaminomethylphenol); 4,4'thiobis(2-methyl-6-t-butylphenol); 4,4'-thiobis(3-methyl-6-t-butylphenol); 2,2'-thiobis(4-methyl-6-t-butylphenol); bis(3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide; bis(3,5-di-t-butyl-4-hydroxybenzyl) sulfide; n-octyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate; n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate; 2,2′-thio[diethyl-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] and the like. Of these, bis-phenol-based antioxidants and ester group-containing phenol-based antioxidants are particularly preferred.

Amine-based antioxidants include, for example, monoalkyldiphenylamines such as monooctyldiphenylamine, monononyldiphenylamine and the like; dialkyldiphenylamines such as 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4 '-dioctyldiphenylamine, 4,4'-dinonyldiphenylamine, etc.; polyalkyldiphenylamines such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraoctyldiphenylamine, tetranonyldiphenylamine and the like; Naphthylamines, in particular alpha-naphthylamine, phenyl-alpha-naphthylamine and further alkyl-substituted phenyl-alpha-naphthylamines such as butylphenyl-alpha-naphthylamine, pentylphenyl-alpha-naphthylamine amine, hexylphenyl-alpha-naphthylamine, heptylphenyl-alpha-naphthylamine, octylphenyl-alpha-naphthylamine, nonylphenyl-alpha-naphthylamine, and the like. Among these, diphenylamine is preferable to naphthylamine from the viewpoint of its antioxidant effect.

Suitable antioxidants are further sulfur and phosphorus containing compounds such as metal dithiophosphates such as zinc dithiophosphate (ZnDTP), “OOS triesters” = olefins of dithiophosphoric acid, cyclopentadiene, norbornadi reaction products with activated double bonds from ene, α-pinene, polybutene, acrylic acid esters, maleic acid esters (ashless on combustion); organosulfur compounds such as dialkyl sulfides, diaryl sulfides, polysulfides, modified thiols, thiophene derivatives, xanthates, thioglycols, thioaldehydes, sulfur-containing carboxylic acids; heterocyclic sulfur/nitrogen compounds, especially dialkyldimercaptothiadiazole, 2-mercaptobenzimidazole; zinc bis(dialkyldithiocarbamate) and methylene bis(dialkyldithiocarbamate); organophosphorus compounds such as triaryl and trialkyl phosphites; organocopper compounds and overbased calcium- and magnesium-based phenoxides and salicylates.

Suitable dispersants include poly(isobutylene) derivatives such as poly(isobutylene)succinimide (PIBSI), such as borated PIBSI; and ethylene-propylene oligomers having N/O functional groups.

Preferred detergents include metal-containing compounds such as phenoxides; salicylate; thiophosphonates, especially thiopyrophosphonates, thiophosphonates and phosphonates; sulfonates and carbonates. These compounds may contain as metals, in particular calcium, magnesium and barium. These compounds may preferably be used in neutral or overbased form.

Friction modifiers used include mechanically acting compounds, for example molybdenum disulfide, graphite (including graphite fluoride), poly(trifluoroethylene), polyamide, polyimide; compounds which form the adsorption layer, for example long-chain carboxylic acids, fatty acid esters, ethers, alcohols, amines, amides, imides; compounds that form layers through tribological reactions, such as saturated fatty acids, phosphoric and thiophosphoric esters, xanthogenates, sulfurized fatty acids; Compounds which form polymer-like layers, for example ethoxylated dicarboxylic acid partial esters, dialkyl phthalates, methacrylates, unsaturated fatty acids, sulfurized olefins or organometallic compounds, such as molybdenum compounds (molybdenum dithiophosphate and molybdenum dithiocarbamate MoDTC) and its combination with ZnDTP, copper-containing organic compounds.

Suitable antifoaming agents are silicone oils, fluorosilicone oils, fluoroalkyl ethers and the like.

The above-mentioned additives are, inter alia, those described in T. Mang, W. Dresel (eds.): “Lubricants and Lubrication”, Wiley-VCH, Weinheim 2001; R. M. Mortier, S. T. Orszulik (eds.): "Chemistry and Technology of Lubricants".

Lubricating compositions according to the present invention may be, to name a few, industrial gear oils, lubricants for wind turbines, compressor oils, hydraulic fluids, paper machine lubricants, engine or motor oils, transmission and/or drivetrain fluids, machine tools It can be useful in a variety of applications including lubricants, metalworking fluids and transformer oils.

In a further aspect, the present invention is also the use of a comb polymer as described above as an additive to a base oil for preparing a lubricant composition, which is preferably characterized as having an R-module of 8 or less, wherein R- The modulus relates to the use wherein the modulus is defined as the ratio of the kinematic viscosity of the lubricant composition at -20°C to the kinematic viscosity at +20°C, measured according to ASTM D445. Preferably, the lubricant composition has an R-factor of 1 to 8.

Preferably, the lubricant composition comprises a synthetic base oil. The base oil is preferably selected from the group consisting of polyalphaolefins, naphthenic base oils and mixtures thereof. More preferably, the lubricant composition is 1 mm ² /s to 20 mm ² /s, more preferably 1 to 10 mm ² /s, most preferably 1 to 5 mm ² /s, particularly preferred according to ASTM D445 preferably a polyalphaolefin base oil having a kinematic viscosity at 100° C. of 2-3 mm ² /s.

The lubricant composition preferably has a kinematic viscosity at 40°C of from 10 to 120 mm ² /s, more preferably from 40 to 100 mm ² /s, most preferably from 70 to 80 mm ² /s according to ASTM D445.

In a further aspect, the present invention provides a method for preparing a lubricant composition having an R-modulus of 8 or less, preferably 1 to 8, wherein the R-modulus is determined according to ASTM D445 of the lubricant composition at -20°C. Defined as the ratio of kinematic viscosity to kinematic viscosity at +20° C., the method comprising adding a comb polymer according to the present invention to a synthetic base oil, the synthetic base oil preferably being 1 mm ² / according to ASTM D445 a kinematic viscosity at 100° C. of s to 20 mm ² /s, more preferably 1 to 10 mm ² /s, most preferably 1 to 5 mm ² /s, particularly preferably 2 to 3 mm ² /s It relates to a method which is a polyalphaolefin base oil having

The method preferably comprises dissolving the comb polymer at 40° C. of 10 to 120 mm ² /s, more preferably 40 to 100 mm ² /s, most preferably 70 to 80 mm ² /s according to ASTM D445. It is characterized in that it is added in an amount to obtain a lubricant composition having a kinematic viscosity.

experimental part

Synthesis of Hydroxylated Hydrogenated Polybutadiene

The macroalcohol produced was a hydroxypropyl-terminated hydrogenated polybutadiene having an average molar mass M _n = 4750 g/mol.

The macroalcohol was synthesized by anionic polymerization of 1,3-butadiene using butyllithium at 20-45°C. Upon achievement of the desired degree of polymerization, the reaction was stopped by addition of propylene oxide and lithium was removed by precipitation with methanol. Subsequently, the polymer is hydrogenated under a hydrogen atmosphere in the presence of a noble metal catalyst at a pressure of up to 140° C. and 200 bar. After the hydrogenation was completed, the noble metal catalyst was removed, and the organic solvent was taken out under reduced pressure. Finally, it was diluted with the base oil NB 3020 to a polymer content of 70% by weight.

The macroalcohol had a vinyl content of 61%, a hydrogenation level >99% and an OH functionality >98%. These values were determined by H-NMR (nuclear resonance spectroscopy).

Synthesis of macromers (MM)

In a 2 L stirring apparatus equipped with saber stirrer, air inlet tube, thermocouple with controller, heating mantle, column with random packing of 3 mm wire helix, vapor distributor, top thermometer, reflux condenser and base cooler, 1000 g of the above The described macroalcohol was dissolved in 450 g of methyl methacrylate (MMA) by stirring at 60°C. To the solution was added 20 ppm of 2,2,6,6-tetramethylpiperidine-1-oxyl radical and 200 ppm of hydroquinone monomethyl ether. After heating the MMA to reflux while passing air for stabilization (bottom temperature about 110° C.), about 20 g of MMA was distilled off for azeotropic drying. After cooling to 95° C., 0.30 g of LiOCH 3 were added and the mixture heated again to reflux. After a reaction time of about 1 hour, the top temperature dropped to ˜64° C. due to methanol formation. The methanol/MMA azeotrope formed was continuously distilled until a constant top temperature of about 100° C. was re-established. At this temperature, the mixture was allowed to react for an additional hour. For further work-up, the MMA bulk was withdrawn under reduced pressure. Insoluble catalyst residues were removed by pressure filtration (Seitz T1000 depth filter). The content of NB 3020 "incorporated" into the copolymer synthesis described further below was taken into account accordingly.

Synthesis of comb polymer

A comb polymer according to the present invention was prepared according to the following free radical polymerization procedure.

In a glass beaker, 100 g of a mixture of all monomers (eg as detailed in Table 1) at 90° C. in ester oil (eg diisononyl adipate) to reach an approximate 60% w/w dilution diluted. Thereafter, 35% of this diluted mixture was continuously charged to a stirred glass reactor, followed by addition of 0.105 g of the initiator t-butylperoxy 2-ethylhexanoate. The remaining monomer mixture was slowly added to the glass reactor at a constant flow rate for 3 h, while at the same time an additional 0.195 g of the initiator t-butylperoxy 2-ethylhexanoate was added, which was also introduced at a constant flow rate for 3 h. . The reaction temperature was kept constant at 90°C. After 3 hours, an additional 2x0.2 g of initiator t-butylperoxy 2-ethylhexanoate is added 2 and 5 hours after the end of the monomer feed to ensure the completion of polymerization, during which time the reaction is carried out at 90° C. was maintained in When the reaction is complete, additional dilute ester oil may be added.

Lauryl methacrylate is a mixture of linear C ₁₂ and C ₁₄ alkyl methacrylates with a C ₁₂ to C ₁₄ alkyl methacrylate ratio of approximately 73/27.

The composition of the monomer mixture used to prepare exemplary copolymers according to the present invention is given in Table 1 below. The amount of monomer is given as weight-% based on the total weight of the comb polymer.

Table 1: Net composition of comb polymers prepared to support the present invention

CE = Comparative Example

Comb polymers A and B are examples of the invention and have the styrene content claimed by the invention. Comb polymer C is a comparative example and contains a higher amount of styrene. This was prepared to suggest that higher amounts of styrene lead to higher R-modules.

The following polyalkylmethacrylates are known as viscosity index improvers and have been used in comparative lubricant compositions. They are prepared to suggest that R-modules within the claimed range of 1-8 can only be reached by using comb polymers comprising certain amounts of esters of (meth)acrylic acid and hydroxylated hydrogenated polybutadiene. became

Comparative Copolymer D is a polyalkylmethacrylate prepared from 89.97 wt% dodecyl pentadecyl methacrylate and 10.03 wt% methyl methacrylate via a similar above-mentioned free radical polymerization procedure.

dodecyl pentadecyl methacrylate is 16 to 26 weight % C ₁₂ alkyl methacrylate, 24 to 34 weight % C ₁₃ alkyl methacrylate, 24 to 34 weight % C ₁₄ alkyl methacrylate, and 16 to a mixture of branched and linear C ₁₂ to C ₁₅ alkyl methacrylates having an average composition of 26 wt % C ₁₅ alkyl methacrylate, and approximately 80% linear alkyl methacrylate.

Comparative Copolymer E has 99.80 wt % C ₁₂ to C ₁₅ alkyl methacrylate (20% C ₁₂ alkyl methacrylate, 34% C ₁₃ alkyl methacrylate, 29% C ₁₄ alkyl methacrylate, and A polyalkylmethacrylate prepared via a similar above-mentioned free radical polymerization procedure from 17% C ₁₅ alkyl methacrylate, along with approximately 40% linear alkyl methacrylate) and 0.20 weight percent methyl methacrylate. It is acrylate.

A poly-alpha-olefin base oil (PAO2) having a kinematic viscosity at 100° C. of 2 mm ² /s according to ASTM D445 and the indicated amount of the copolymer according to the table below as viscosity index improver was added to a KV of 76 mm ² /s A lubricant composition was obtained by mixing targeting ₄₀ .

Table 2: Lubricant composition comprising comb polymer and base oil

* ⁾ based on the total weight of the comb polymer

** ⁾ based on the total weight of the lubricant composition

CE: Comparative Example

The lubricant compositions were tested by determining the kinematic viscosity, viscosity index and R-modulus at various temperatures. The kinematic viscosity was determined according to ASTM D445, the viscosity index was determined according to ASTM D2270, and the R-modulus was calculated as the ratio of the kinematic viscosity at -20°C to the kinematic viscosity at +20°C. The results are given in Table 3 below.

Table 3: Viscosity data of lubricant compositions

CE: Comparative Example

The data demonstrate that the lubricant compositions according to the invention (compositions 1 and 2 comprising comb polymers A and B, respectively) have a high viscosity index as well as a low R-modulus. The composition according to the invention thus ensures good viscosity characteristics at low operating temperatures, defined as an R-factor of less than 8. In contrast, comparative lubricant compositions (compositions 3, 4 and 5 comprising comb polymers with higher amounts of styrene or conventional polyalkylmethacrylates D and E) exhibit good viscosity indexes, but good at low operating temperatures. does not show performance. They present an R-factor greater than 8.

The data thus suggest that the use of comb polymers according to the present invention has surprising advantages over the use of conventional viscosity index improvers in improving the viscosity characteristics of lubricants not only at normal operating temperatures but also at low operating temperatures. .

When formulated at a given KV ₄₀ of 76 mm ² /s, the data in Table 3 suggests that the kinematic viscosity of the formulation increases with decreasing temperature.

By using the polymers of the invention (Examples 1 and 2), the viscosity increase is much less compared to the use of standard polymers (Examples 4 and 5) or polymers with higher styrene content (Example 3).

When formulated with a given KV ₄₀ of 76 mm ² /s, a lubricant composition comprising a comb polymer according to the invention exhibits a KV ₂₀ in the range of 130 to 140 and a KV _-20 in the range of 640 to 870.

It is further suggested that the definition of VI is not suitable for estimating viscosities at temperatures below 40°C, for example up to -20°C.

Claims (16)

A lubricant composition comprising:
(A) 20 to 90% by weight of a synthetic base oil, the synthetic base oil being a polyalphaolefin having a kinematic viscosity at 100°C of 1 to 10 mm ² /s according to ASTM D445; and
(B) 10 to 80% by weight of a comb polymer comprising, based on the total weight of the comb polymer, the following monomers:
(a) 20 to 35% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,
(b) 0.2% to 15% by weight of styrene;
(c) 0.2 to 20% by weight of an alkyl methacrylate having 12 to 15 carbon atoms in the alkyl chain, and
(d) 50 to 70% by weight of an alkyl (meth)acrylate having 1 to 4 carbon atoms in the alkyl chain. The lubricant composition according to claim 1 , wherein the lubricant composition has a ratio of kinematic viscosity at -20°C (KV _-20 ) to kinematic viscosity at +20°C (KV ₊₂₀ ) of 8 or less, i.e. KV- ₂₀ /KV ₊₂₀ wherein the kinematic viscosity is measured according to ASTM D445. The lubricant composition according to claim 1 or 2, wherein the synthetic base oil (A) is a polyalphaolefin having a kinematic viscosity at 100° C. of 1 to 5 mm ² /s according to ASTM D445. The lubricant composition according to claim 1 or 2, wherein the synthetic base oil (A) is a polyalphaolefin having a kinematic viscosity at 100° C. of 2-3 mm ² /s according to ASTM D445. 3. The composition according to claim 1 or 2, characterized in that it comprises from 30 to 80% by weight of the synthetic base oil (A) and from 20 to 70% by weight of the comb polymer (B), based on the total weight of the lubricant composition. lubricant composition. The lubricant composition according to claim 1 or 2, wherein the hydroxylated hydrogenated polybutadiene of component (a) has a number-average molecular weight M _n according to DIN 55672-1 of 4,000 to 5,000 g/mol. The lubricant composition according to claim 1 or 2, wherein the comb polymer (B) comprises, based on the total weight of the comb polymer:
(a) 25 to 30% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,
(b) 0.2 to 15% by weight of styrene;
(c) 0.2 to 15% by weight of an alkyl methacrylate having 12 to 14 carbon atoms in the alkyl chain,
(d) 50 to 65% by weight of butyl methacrylate, and
(e) 0.1 to 0.2% by weight of methyl methacrylate. A comb polymer comprising, based on the total weight of the comb polymer, as an additive to a base oil for preparing a lubricant composition having an R-factor of 8 or less:
(a) 20 to 35% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,
(b) 0.2 to 15% by weight of styrene;
(c) 0.2 to 20% by weight of an alkyl methacrylate having 12 to 15 carbon atoms in the alkyl chain,
(d) from 50 to 65% by weight of an alkyl (meth)acrylate having from 1 to 4 carbon atoms in the alkyl chain,
wherein the R-module is defined as the ratio of the kinematic viscosity of the lubricant composition at -20°C to the kinematic viscosity at +20°C, measured according to ASTM D445, wherein the base oil is from 1 to 10 mm ² /s according to ASTM D445 It is a polyalphaolefin base oil having a kinematic viscosity at 100°C of
Comb polymer. The comb polymer according to claim 8, wherein the base oil is a polyalphaolefin base oil having a kinematic viscosity at 100°C of 1 to 5 mm ² /s according to ASTM D445. The comb polymer according to claim 8, wherein the base oil is a polyalphaolefin base oil having a kinematic viscosity at 100°C of 2-3 mm ² /s according to ASTM D445. The comb polymer according to any one of claims 8 to 10, characterized in that the lubricant composition has an R-modulus of 1 to 8. The comb polymer according to any one of claims 8 to 10, characterized in that the comb polymer comprises, based on the total weight of the comb polymer:
(a) 25 to 30% by weight of an ester of (meth)acrylic acid and hydrogenated polybutadiene,
(b) 0.2 to 15% by weight of styrene;
(c) 0.2 to 15% by weight of an alkyl methacrylate having 12 to 14 carbon atoms in the alkyl chain,
(d) 50 to 65% by weight of butyl methacrylate, and
(e) 0.1 to 0.2% by weight of methyl methacrylate. delete delete delete delete