Hydrogenated Linear Polybutadiene Copolymers as Base Stocks or Lubricant Additives for Lubricant Compositions - Patent application

Abstract

To provide hydrogenated linear copolymers comprising butadiene and isoprene units, and processes for preparing the copolymers; a lubricating oil composition comprising the copolymers; and the use of the copolymers as a lubricant additive for gear oils, transmission oils, hydraulic oils, engine oils, grease, marine oils or industrial lubricating oils.SOLUTION: A hydrogenated linear copolymer, obtainable by polymerizing a monomer composition comprising: a) 10 to 60 mol% of 1,3-butadiene monomer, b) 40 to 90 mol% of isoprene, c) 0 to 40 mol% of one or more of C1-C6 alkyl(meth)acrylates, and d) 0 to 30 mol% of one or more of C7-C24 alkyl(meth)acrylates, based on the total amount of monomers in the monomer composition, wherein the total amount of monomers a) and b) sum up to at least 60 mol% of the total amount of the monomer composition, and the hydrogenated copolymer has a mass-average molecular weight (Mw) in the range of 2,000 g / mol to 30,000 g / mol and a degree of hydrogenation of more than 95%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to hydrogenated linear copolymers comprising monomer units of butadiene and isoprene, and to a process for producing said copolymers. The present invention further relates to lubricating oil compositions containing one or more hydrogenated linear copolymers according to the invention, and to the use of said copolymers as lubricant additives or synthetic base fluids for lubricant compositions, in particular in gear oils, transmission oils, hydraulic oils, engine oils, greases, marine lubricants or industrial lubricants. [Background technology]

[0002] The present invention relates to the field of lubrication. A lubricant is a composition that reduces friction between surfaces. A lubricant allows freedom of movement between two surfaces, reduces mechanical wear of the surfaces, and can also prevent corrosion and / or damage to the surfaces caused by heat or oxidation. Examples of lubricant compositions include, but are not limited to, gear oils, transmission oils, hydraulic fluids, engine oils, greases, marine lubricants, and industrial lubricants.

[0003] A typical lubricant composition contains a base fluid and, optionally, one or more additives. Conventional base fluids are naturally occurring hydrocarbons, such as mineral oil, or synthetic compositions, such as polyalphaolefins, polyalkyl(meth)acrylates, and ethylene-propylene copolymers. The terms base oil and base fluid are generally used interchangeably and are used interchangeably. The general description is base fluid.

[0004] A wide variety of additives can be combined with the base fluid depending on the intended use of the lubricant. Examples of lubricant additives include, but are not limited to, antioxidants, corrosion inhibitors, dispersants, extreme pressure additives, antifoam agents, and metal deactivators. Viscosity index improvers (VII) and thickeners can be used to improve viscosity characteristics. These viscosity modifiers are usually of the polymer type.

[0005] However, one drawback of adding polymeric additives to lubricant formulations is that these additives are subject to shear loading and mechanical degradation over time. High molecular weight polymers are good thickeners but are susceptible to shear loading, which leads to polymer degradation. Reducing the molecular weight of a polymer can result in a polymer with high shear stability. However, these low molecular weight, shear-stable polymers are no longer efficient thickeners and must be used at high concentrations in lubricants to achieve the desired viscosity. These low molecular weight polymers generally have a molecular weight below 20,000 g / mol and are referred to as synthetic high viscosity base fluids.

[0006] Common polymer additives on the market, such as polyalkyl(meth)acrylates (PAMAs), have various drawbacks in various lubricating oil compositions. One example is the large amount of PAMA required in these compositions to achieve the desired viscosity characteristics. Another example is the solubility issues between various types of base oils and PAMA products. Another drawback of conventional PAMA-based lubricant additives is poor traction characteristics.

[0007] Alternatively, lubricant additives based on isoprene and butadiene also exist, as described, for example, in U.S. Pat. No. 7,163,913, which describes linear, radial, and star random copolymers of isoprene and butadiene, in which at least 70 wt. % butadiene is incorporated into the polymer, with the mass ratio of isoprene to butadiene ranging from 90:10 to 70:30, and which are suitable as viscosity index improvers for lubricating oil compositions.

[0008] However, there remains a need to find new lubricant additives that not only combine high thickening effectiveness, good oil solubility, good shear stability, and a high viscosity index in lubricating oil compositions, but also improve the traction properties of the lubricating oil compositions. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 7,163,913 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, it is an object of the present invention to provide a synthetic base fluid or lubricating oil additive for lubricating oil compositions that is highly efficient compared to existing technology. The goal of these novel polymers is to provide superior properties in lubricating oil compositions, particularly in terms of thickening efficiency, shear stability, and traction. These shear-stable polymers described herein should be able to thicken oils to the desired viscosity using lower amounts of polymer compared to commonly used polyalkyl (meth)acrylates. Furthermore, these polymers should exhibit high viscosity index in lubricating oil compositions and excellent solubility in common base fluids. [Means for solving the problem]

[0011] After careful investigation, the inventors of the present invention have surprisingly found that a hydrogenated linear copolymer of butadiene, isoprene, and optionally alkyl (meth)acrylate monomer units as defined in claim 1 provides excellent properties in lubricating oil compositions, particularly in terms of thickening effect and traction performance when added to lubricating oil compositions.

[0012] A first object of the present invention is therefore a hydrogenated linear copolymer as defined in claim 1 and its dependent claims.

[0013] A second object of the present invention relates to a process for the preparation of the hydrogenated linear copolymers according to the invention.

[0014] A third object of the present invention is a lubricating oil composition containing the hydrogenated linear copolymer according to the present invention.

[0015] A fourth object of the present invention is the use of the hydrogenated linear copolymers according to the invention in lubricating oil compositions, in particular gear oil compositions, transmission oil compositions, hydraulic oil compositions, engine oil compositions, marine lubricating oil compositions, industrial lubricating oil compositions or greases, as synthetic base fluids or as lubricant additives in synthetic base fluids.

[0016] Another object of the present invention is a method for improving the traction coefficient of a lubricating oil composition, which method comprises the step of adding a hydrogenated linear copolymer as defined according to the present invention to the base oil of the lubricating oil composition. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hydrogenated polybutadiene-isoprene copolymers according to the present invention According to a first aspect of the present invention, there is provided a monomer composition comprising the following monomers, based on the total amount of monomers in the monomer composition: a) 1,3-butadiene monomer 10 to 60 mol% b) Isoprene 40 to 90 mol% c) 0 to 40 mol% of one or more C1 to C6 alkyl (meth)acrylates, and d) 0 to 30 mol% of one or more C7 to C24 alkyl (meth)acrylates wherein the combined amount of monomer a) and monomer b) constitutes at least 60 mol % of the total amount of the monomer composition, and the hydrogenated linear copolymer has a weight average molecular weight ranging from 2,000 g / mol to 30,000 g / mol and a degree of hydrogenation greater than 95%.

[0018] In fact, the inventors of the present invention have unexpectedly found that the combination of specific amounts of butadiene and isoprene, as described above, leads to the formation of a hydrogenated linear copolymer with good solubility in oil. According to the present invention, the total amount of butadiene (monomer a) and isoprene (monomer b) in the hydrogenated polybutadiene-isoprene copolymer must constitute at least 60 mol % of the total amount of the monomer composition, and the amount of butadiene should not exceed 60 mol % based on the total amount of the monomer composition. In contrast, as shown in the examples of the present invention, pure hydrogenated polyisoprene or isoprene and butadiene-containing copolymers that do not satisfy the proportions of the monomer units described in claim 1 do not have good overall performance, particularly in terms of having high thickening efficiency while maintaining good traction properties. Therefore, it was unexpected that excellent performance in oil could be achieved when these two dienes are combined together in the ratio described in claim 1.

[0019] According to a preferred embodiment of the present invention, the hydrogenated copolymer has a weight average molecular weight comprised between 3,000 g / mol and 20,000 g / mol, more preferably between 4,000 g / mol and 18,000 g / mol, and most preferably between 5,000 g / mol and 15,000 g / mol. Polymers with this weight average molecular weight have particularly good shear resistance and provide excellent improvement in the viscosity characteristics of lubricant compositions even at low amounts of copolymer.

[0020] The copolymers of the present invention preferably have a very low degree of crosslinking and a narrow molecular weight distribution, which further contributes to shear resistance. The low degree of crosslinking and narrow molecular weight distribution are reflected in the polydispersity index (PDI) of the copolymers of the present invention. The polydispersity index of the copolymers of the present invention is preferably in the range of 1.0 to 4.0, more preferably 1.0 to 3.3. A polydispersity index in the range of 1.0 to 3.3 is believed to be optimal for many industrial applications in terms of copolymer shear resistance. The polydispersity index is defined as the ratio of the weight average molecular weight to the number average molecular weight (Mw / Mn).

[0021] The weight-average and number-average molecular weights are determined by gel permeation chromatography using commercially available polybutadiene calibration standards, preferably carried out in accordance with DIN 55672-1 by gel permeation chromatography using THF as the eluent.

[0022] According to a preferred embodiment of the present invention, the hydrogenated linear copolymer is a random copolymer or a block copolymer, preferably a random copolymer.

[0023] monomer In the present invention, isoprene may also be referred to as 2-methyl-1,3-butadiene.

[0024] In the present invention, butadiene may also be referred to as 1,3-butadiene.

[0025] According to a preferred embodiment, the hydrogenated linear copolymer according to the invention comprises, in addition to the monomers a) and b), optionally a monomer derived from a C1-C6 alkyl (meth)acrylate as monomer c), and a C7-C 24 It may also contain as monomer d) a monomer derived from alkyl(meth)acrylate or a mixture thereof.

[0026] The term "(meth)acrylic acid" refers to acrylic acid, methacrylic acid, and mixtures of acrylic acid and methacrylic acid. Methacrylic acid is preferred. The term "(meth)acrylate" refers to esters of acrylic acid, esters of methacrylic acid, or mixtures of esters of acrylic acid and methacrylic acid. Esters of methacrylic acid are preferred.

[0027] The term "C1-C6 alkyl (meth)acrylate" refers to an ester of a linear or branched alcohol having from 1 to 6 carbon atoms with (meth)acrylic acid. This term includes (meth)acrylic acid esters with alcohols of a particular length individually, as well as mixtures of (meth)acrylic acid esters with alcohols of different lengths. Similarly, "C7-C 24 The term "alkyl (meth)acrylate" refers to an ester of a linear or branched chain alcohol having from 7 to 24 carbon atoms with (meth)acrylic acid.

[0028] Suitable C1-C6 alkyl (meth)acrylates for monomer c) include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-butyl (meth)acrylate. In a preferred embodiment, the preferred C1-C6 alkyl (meth)acrylate is methyl (meth)acrylate, butyl (meth)acrylate, or a mixture of methyl (meth)acrylate and butyl (meth)acrylate. More preferably, the butyl (meth)acrylate is n-butyl (meth)acrylate.

[0029] Suitable for monomer d) C7-C 24 Examples of alkyl (meth)acrylates include 2-butyloctyl (meth)acrylate, 2-hexyloctyl (meth)acrylate, decyl (meth)acrylate, 2-butyldecyl (meth)acrylate, 2-hexyldecyl (meth)acrylate, 2-octyldecyl (meth)acrylate, undecyl (meth)acrylate, 5-methylundecyl (meth)acrylate, dodecyl (meth)acrylate, 2-methyldodecyl (meth)acrylate, 2-hexyldodecyl (meth)acrylate, 2-octyldodecyl (meth)acrylate, tridecyl (meth)acrylate, 5-methyltridecyl (meth)acrylate, tetradecyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, and the like. In a particularly preferred embodiment, the monomer d) comprises one or more C 10 ~C 16 The monomer d) preferably includes alkyl (meth)acrylate, which refers to an ester of a linear or branched alcohol having 10 to 16 carbon atoms with (meth)acrylic acid. The monomer d) is preferably lauryl (meth)acrylate (linear C 12 ~C 15 Contains alkyl (meth)acrylates.

[0030] Monomer Composition As described above, the present invention provides a monomer composition comprising the following monomers, based on the total amount of monomers in the monomer composition: a) 1,3-butadiene monomer 10 to 60 mol% b) Isoprene 40 to 90 mol% c) 0 to 40 mol% of one or more C1 to C6 alkyl (meth)acrylates, and d) One or more C7-C 24 Alkyl (meth)acrylate 0 to 30 mol% wherein the combined amount of monomer a) and monomer b) constitutes at least 60 mol % of the total amount of the monomer composition, and the hydrogenated linear copolymer has a weight average molecular weight comprised between 2,000 g / mol and 30,000 g / mol and a degree of hydrogenation greater than 95%.

[0031] In one preferred embodiment, the monomer composition contains the following monomers, based on the total amount of monomers in the monomer composition: a) 1,3-butadiene monomer 10 to 60 mol% b) Isoprene 40 to 90 mol% c) 0 to 20 mol% of one or more C1 to C6 alkyl (meth)acrylates, and d) One or more C7-C 24 Alkyl (meth)acrylate 0 to 20 mol% It consists of:

[0032] According to one preferred embodiment, the above monomer composition may further comprise alkyl (meth)acrylate monomers c) or d) or mixtures thereof.

[0033] In one preferred embodiment, the monomer composition comprises the following monomers, based on the total amount of monomers in the monomer composition: a) 1,3-butadiene monomer 10 to 60 mol% b) Isoprene 40 to 90 mol% c) 1 to 30 mol% of one or more C1 to C6 alkyl (meth)acrylates, and d) One or more C7-C 24 Alkyl (meth)acrylate 0 to 30 mol% It consists of:

[0034] In one preferred embodiment, the monomer composition comprises the following monomers, based on the total amount of monomers in the monomer composition: a) 1,3-butadiene monomer 10 to 60 mol% b) Isoprene 40 to 90 mol% c) 1 to 20 mol% of one or more C1 to C6 alkyl (meth)acrylates, and d) One or more C7-C 24 Alkyl (meth)acrylate 0 to 30 mol% It consists of:

[0035] In one preferred embodiment, the monomer composition comprises the following monomers, based on the total amount of monomers in the monomer composition: a) 1,3-butadiene monomer 10 to 60 mol% b) Isoprene 40 to 90 mol% c) 1 to 20 mol% of one or more C1 to C6 alkyl (meth)acrylates, and d) One or more C7-C 24 Alkyl (meth)acrylate 5 to 20 mol% It consists of:

[0036] According to a preferred embodiment, in the above preferred monomer composition, the one or more C1-C6 alkyl(meth)acrylate monomers c) are selected from methyl(meth)acrylate, butyl(meth)acrylate, or a mixture thereof, and the one or more C7-C 24 The alkyl(meth)acrylate monomer d) is lauryl(meth)acrylate.

[0037] Method for producing the copolymer according to the present invention As explained above, the hydrogenated polybutadiene-isoprene copolymer according to the present invention has the following properties: (i) providing a monomer composition as described above; (ii) conducting solution polymerization on the monomer composition to obtain a copolymer; and (iii) hydrogenating the copolymer obtained in step (ii). It is produced by a method comprising:

[0038] Polymerization step (ii) According to one preferred embodiment, the polymerization in step (ii) is a radical solution polymerization or an anionic solution polymerization, more preferably a radical solution polymerization.

[0039] Radical polymerization Standard radical polymerizations are described in detail, inter alia, in Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition. For this purpose, a polymerization initiator and optionally a chain transfer agent are generally used.

[0040] The copolymer according to the present invention can be obtained by the ATRP method. This reaction mode is described, for example, in J.-S. Wang et al., J. Am. Chem. Soc., Vol. 117, pp. 5614-5615, 1995, and Matyjaszewski, Macromolecules, Vol. 28, pp. 7901-7910, 1995. Furthermore, WO 96 / 30421, WO 97 / 47661, WO 97 / 18247, WO 98 / 40415, and WO 99 / 10387 disclose various specific variations of the above-mentioned ATRP.

[0041] Furthermore, the copolymers according to the invention can also be obtained by the RAFT process, which is described in detail, for example, in WO 98 / 01478 and WO 2004 / 083169.

[0042] According to one preferred embodiment, the random copolymers according to the present invention are prepared by radical solution polymerization, in which case the reaction mixture in step (ii) preferably contains the monomer composition of step (i), one or more radical polymerization initiators, a solubilizing carrier medium as described below, and optionally one or more chain transfer agents.

[0043] Solution polymerization is a preferred method for carrying out the process of the present invention because it allows for more or less control of the concentration of the monomer composition in the reaction mixture by adding a solubilizing carrier medium. By selecting the exact concentration of the monomer composition in the reaction mixture, the molecular weight and polydispersity index of the resulting copolymer can be controlled.

[0044] The total amount of the monomer composition in the reaction mixture is preferably 5 to 95% by weight, more preferably 10 to 70% by weight, even more preferably 20 to 55% by weight, and most preferably 35 to 50% by weight, based on the total weight of the reaction mixture. On an industrial scale, a monomer concentration of more than 20% is usually preferred. A monomer composition concentration in the range of 20 to 55% by weight, preferably 35 to 50% by weight, based on the total weight of the reaction mixture, is considered optimal because it results in random copolymers with low weight-average molecular weights in the range of 2,000 to 30,000 g / mol and low polydispersity indices in the range of 1.0 to 3.3.

[0045] The polymerization is preferably carried out at a temperature of 20°C to 200°C, more preferably 50°C to 150°C, the reaction pressure is preferably 1 bar to 30 bar, more preferably 10 bar to 28 bar, and the total reaction time of the radical polymerization is 1 to 10 hours.

[0046] Preferably, the solubilizing carrier medium used is selected from the group consisting of mineral oils, synthetic oils, ketones, ester solvents, aromatic hydrocarbons, cycloaliphatic hydrocarbons, aliphatic hydrocarbons, and mixtures thereof.

[0047] Examples of mineral oils are paraffin oils, naphthenic oils, solvent-refined oils, isoparaffin-containing high VI oils, and hydrocracked high VI oils. Examples of synthetic oils are organic esters, diesters and polyesters such as carboxylic acid esters and phosphate esters, silicone oils, organic ethers such as perfluorinated alkyl ethers and polyalkylene glycols, and synthetic hydrocarbons, particularly polyolefins and gas-to-liquid oils (GTL). Examples of ketones are butanone and methyl ethyl ketone. Examples of ester solvents are aliphatic oils and synthetic ester lubricants (e.g., di-C 4~12 Alkyl C 4~12 Dicarboxylic acid esters, such as dioctyl sebacate and dioctyl adipate, polyol Poly-C 4~12 -alkanoates, such as pentaerythritol tetracaproate, and tri-C 4~12 Hydrocarbyl phosphates, such as tri-2-ethylhexyl phosphate, dibutylphenyl phosphate, di-2-ethylhexylphenyl phosphate, 2-ethylhexyldiphenyl phosphate, and tricresyl phosphate. Examples of aromatic hydrocarbons are benzene, toluene, xylene, ethylbenzene, trimethylbenzene, ethyltoluene, and mixtures thereof. Examples of cycloaliphatic hydrocarbons are cyclohexane, methylcyclohexane, and cycloaliphatic terpenes. Examples of aliphatic hydrocarbons are n-pentane, n-hexane, n-heptane, 1-decene, and aliphatic terpenes.

[0048] In one preferred embodiment, the solubilizing carrier medium is a cycloaliphatic or aliphatic or aromatic hydrocarbon, preferably cyclohexane or toluene.

[0049] Step (ii) involves the addition of a radical initiator.

[0050] Suitable radical initiators include, for example, azo initiators such as azobis-isobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile) (AMBN) and 1,1-azobiscyclohexanecarbonitrile, and peroxy compounds such as methyl ethyl ketone peroxide, acetylacetone peroxide, dilauryl peroxide, ketone peroxide, t-butyl peroctoate, methyl isobutyl ketone peroxide, cyclohexanone peroxide, dibenzoyl peroxide, t-butyl peroxide, methyl ethyl ketone ... peroxybenzoate, t-butylperoxyisopropyl carbonate, 2,5-bis(2-ethylhexanoylperoxy)-2,5-dimethylhexane, t-butylperoxy-3,5,5-trimethylhexanoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, cumyl hydroperoxide, t-butyl hydroperoxide, and bis(4-t-butylcyclohexyl)peroxydicarbonate.

[0051] Preferably, the radical initiator is selected from the group consisting of 2,2'-azobis(2-methylbutyronitrile), 2,2-bis(t-butylperoxy)butane, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butylperoxybenzoate, and t-butylperoxy-3,5,5-trimethylhexanoate. In a particularly preferred embodiment, the radical initiator is 2,2-bis(t-butylperoxy)butane.

[0052] The total amount of the radical initiator relative to the total mass of the monomer mixture is preferably 0.01 to 5 mass %, more preferably 0.02 to 1 mass %, and most preferably 0.05 to 0.5 mass %.

[0053] The total amount of radical initiator can be added in one step, or the radical initiator can be added in multiple steps during the polymerization reaction. For example, one portion of the radical initiator can be added to initiate the radical polymerization, and then a second portion of the radical initiator can be added over 0.5 to 3.5 hours after the first dose. Preferably, the radical initiator is added in one step.

[0054] Step (ii) optionally comprises the addition of a chain transfer agent. Examples of chain transfer agents are sulfur-containing compounds such as thiols, e.g., n- or t-dodecanethiol, 2-mercaptoethanol, and mercaptocarboxylic acid esters, e.g., methyl-3-mercaptopropionate, or longer-chain alkenes. Preferred chain transfer agents are alkenes having up to 20 carbon atoms, particularly alkenes having up to 15, more preferably up to 12, carbon atoms.

[0055] After completion of the radical polymerization, the product is preferably filtered to remove impurities present in the reaction mixture, and then the volatile solvent is evaporated.

[0056] Anionic polymerization An alternative route for carrying out step (ii) is by producing polybutadiene-isoprene polymers according to the invention by living anionic polymerization of butadiene and isoprene monomers.

[0057] This type of reaction is well established and is described in detail in Anionic Polymerization. Principles and Practical Applications, by HL Hsieh and RP Quirk, 1996, Marcel Dekker, Inc. (New York).

[0058] According to the present invention, a batch or semi-batch process is preferred for the living anionic polymerization of 1,3-butadiene and isoprene. A continuous process for the living polymerization can also be considered.

[0059] The polymerization is generally carried out in an aliphatic, cycloaliphatic, or aromatic hydrocarbon solvent. Examples of an aliphatic hydrocarbon solvent are hexane or heptane. Examples of a cycloaliphatic hydrocarbon solvent are cyclohexane or methylcyclohexane. Examples of an aromatic hydrocarbon solvent are benzene or toluene. Polar heteroaliphatic solvents, such as tertiary amines and / or ethers and / or cyclic ethers, can also be used as solvents or co-solvents. Examples of tertiary amines are tetramethylenediamine or N,N,N'N",N",-pentamethyldiethylenediamine. Examples of ethers or cyclic ethers are diethyl ether and tetrahydrofuran. It is also common to use solvent mixtures of an aliphatic, cycloaliphatic, or aromatic hydrocarbon solvent and a polar heteroaliphatic solvent.

[0060] Conventional initiators are organometallic reactants in which the metal is from the group of alkali metals or alkaline earth metals. Typical examples are monofunctional or difunctional organosodium, organolithium, or organopotassium initiators, such as n-butyllithium, s-butyllithium, t-butyllithium, 1,1-diphenylhexyllithium, diphenylmethyllithium, 1,1,4,4-tetraphenyl-1,4-dilithiumbutane, lithium naphthalene, and their sodium and potassium analogs. Preferably, organolithium initiators are used, and more preferably n-butyllithium initiators.

[0061] Under the exclusion of oxygen and protic reagents, the living nature of anionic polymerization results in excellent control of the resulting molecular weight and polydispersity index (PDI).

[0062] The polymerization reaction is generally terminated using a protic reagent, such as methanol, ethanol, 2-propanol, or water, to neutralize the macroanion.

[0063] Typical reaction temperatures range from 10° C. to 120° C., and typical reaction pressures range from 1 to 100 bar.

[0064] Hydrogenation step (iii) On an industrial scale, the present invention requires obtaining hydrogenated copolymers free of double bonds, since this reduces the reactivity of the copolymer to chemical oxidation, crosslinking or other undesired side reactions. Therefore, in step (iii), the inventors of the present invention carry out selective hydrogenation of the diene units, as described below.

[0065] According to the present invention, the monomer units derived from butadiene and isoprene are hydrogenated. A high degree of hydrogenation of more than 95% of the polymerized units derived from butadiene and isoprene in the polyisoprene-butadiene copolymer is desired to improve stability against oxidation. The hydrogenation is selective and does not affect any of the monomer units c) and d) derived from (meth)acrylic acid esters.

[0066] The selectivity of hydrogenation can be, for example, quantitative 1 H nuclear magnetic resonance ( 1 The degree of hydrogenation can be determined by H NMR spectroscopy or infrared (IR) spectroscopy. The degree of hydrogenation is defined as the degree of saturation (mol) of carbon-carbon bonds of polymerized units derived from conjugated dienes by addition of hydrogen relative to the unhydrogenated starting material. The degree of hydrogenation of the random copolymer according to the present invention can be determined by saturation in a deuterated chloroform solution using dimethyl terephthalate as a standard substance. 1 It is measured by H NMR spectroscopy. The chemical shifts are calibrated using the solvent signal. To determine the degree of hydrogenation, the signal integrals of each of the standards are correlated with the signal integrals of the olefin protons. For each sample, it is necessary to repeat the measurement and determination using an unhydrogenated reference sample to define a degree of hydrogenation of 0%.

[0067] The selective hydrogenation of the copolymers of the present invention is typically carried out as a heterogeneous reaction using an insoluble metal or metal complex supported catalyst, or as a homogeneous reaction using a soluble organometallic catalyst, in the presence of at least one solubilizing carrier medium, using hydrogen gas or other hydrogen sources as a reducing agent. Detailed descriptions of homogeneous catalytic hydrogenation can be found, for example, in U.S. Pat. No. 3,541,064 and British Patent No. 1,030,306. Heterogeneous catalysts, in which insoluble supported metals are used as catalysts, offer economic advantages and are therefore widely used for industrial selective hydrogenation processes, and are generally preferred over other methods. The selective hydrogenation process is preferably a heterogeneous catalytic reaction process using an insoluble supported metal as the catalyst.

[0068] Typical catalytically active metals for heterogeneously catalyzing selective hydrogenation according to the present invention include, but are not limited to, Ru, Rh, Pd, Ir, Pt, Mn, Cr, Fe, Co, Ni, U, Cu, Nd, In, Sn, Zn, Ag, Cr, and alloys of one or more of these metals.

[0069] Typical catalyst supports include, but are not limited to, oxides (Al2O3, TiO2, SiO2, etc.), carbon, silica gel or other supports.

[0070] Additionally, the heterogeneous catalyst may be used in the form of, for example, pellets or powder.

[0071] In a preferred embodiment, the selective hydrogenation process is carried out using a carbon-supported Pd catalyst, preferably in powder form, as the heterogeneous catalyst. The use of a carbon-supported Pd catalyst is preferred because it carries out the hydrogenation of the double bonds derived from butadiene and isoprene with high selectivity and conversion.

[0072] The amount of catalytically active metal supported on the support is preferably 0.1 to 10 mass %, more preferably 1 to 10 mass %, based on the total mass of the supported catalyst.

[0073] When hydrogen gas is used as the reducing agent, the reaction pressure is preferably 5 to 1500 bar, which may be constant or may have a pressure gradient. More preferably, the reaction pressure is 5 to 500 bar, even more preferably 5 to 250 bar, and most preferably 10 to 90 bar.

[0074] The concentration of the random copolymer in the solubilizing carrier medium in the hydrogenation step (iii) is typically 5 to 95% by weight. Preferably, the concentration of the random copolymer in the solubilizing carrier medium is 10 to 70% by weight of the random copolymer, based on the total weight of the copolymer and carrier medium.

[0075] In one preferred embodiment, the hydrogenation is carried out in the presence of a cycloaliphatic or aliphatic hydrocarbon, preferably cyclohexane.

[0076] The reaction temperature in the hydrogenation step (iii) is preferably 0 to 200°C, more preferably 20 to 150°C, and even more preferably 20 to 120°C.

[0077] In a particularly preferred embodiment, the hydrogenation is carried out in the presence of a carbon-supported Pd catalyst at a temperature of 20-120°C, a pressure of 10-90 bar, and using cyclohexane as the solubilizing carrier medium. These conditions have been found to be optimal for producing the copolymers described above, as they lead to high reactivity and selectivity in the selective hydrogenation of the double bonds derived from the conjugated dienes.

[0078] lubricating oil composition The present invention provides (x) one or more base oils; (y) one or more of the above hydrogenated linear copolymers according to the present invention; and a composition comprising:

[0079] Lubricant compositions according to the present invention preferably have a viscosity index greater than 140. Viscosity index can be measured according to ASTM D2270.

[0080] The lubricating oil composition preferably contains 0.5 to 80 mass %, more preferably 1 to 50 mass %, even more preferably 1 to 30 mass %, and most preferably 1 to 15 mass % of one or more hydrogenated linear copolymers, and 20 to 99.5 mass %, more preferably 50 to 99 mass %, even more preferably 70 to 99 mass %, and most preferably 85 to 99 mass % of one or more base oils, based on the total amount of the lubricating oil composition.

[0081] When the lubricant composition according to the present invention is used as an engine oil, it preferably contains 0.5 to 20% by mass of the copolymer according to the present invention, based on the total mass of the lubricant composition, so that the kinematic viscosity at 100°C according to ASTM D445 is 3 mm or less. 2 / s~10mm 2 The range is / s.

[0082] When the lubricant composition according to the present invention is used as an automotive gear oil, it preferably contains 2% by mass to 35% by mass of the copolymer according to the present invention, based on the total mass of the lubricant composition, so that the kinematic viscosity at 100°C according to ASTM D445 is 2mm or less. 2 / s~15mm 2 The range is / s.

[0083] When the lubricant composition according to the present invention is used as an automotive transmission oil, it preferably contains 1% by mass to 25% by mass of the copolymer according to the present invention, based on the total mass of the lubricant composition, so that the kinematic viscosity at 100°C according to ASTM D445 is 2 mm or less. 2 / s~9mm 2 The range is / s.

[0084] When the lubricant composition according to the invention is used as an industrial gear oil, it preferably contains 15% to 80% by weight of the copolymer according to the invention, based on the total weight of the lubricant composition, so that the kinematic viscosity at 100°C according to ASTM D445 is 10 mm or less. 2 / s~130mm 2 The range is / s.

[0085] When the lubricant composition according to the invention is used as a hydraulic oil, it preferably contains 1% to 20% by weight of the copolymer according to the invention, based on the total weight of the lubricant composition, so that the kinematic viscosity at 100°C according to ASTM D445 is 3mm or less. 2 / s~20mm 2 The range is / s.

[0086] The amounts of (x) and (y) preferably total 100% by mass, based on the total mass of the lubricant composition.

[0087] base oil The base oil used in the composition preferably comprises one or more oils of lubricating viscosity, which may represent lubricant base fluids, mineral oils, synthetic oils or natural oils, animal oils or vegetable oils, suitable and / or selected for the intended use.

[0088] Base fluids used in preparing lubricating oil compositions according to the present invention include conventional base stocks selected from the API (American Petroleum Institute) base stock categories known as Group I, Group II, Group III, Group IV, and Group V. Group I and II base stocks are mineral oil materials (e.g., paraffinic and naphthenic oils) with a viscosity index (or VI) of less than 120. Group I further differs from Group II in that Group II contains more than 90% saturates, and Group I contains less than 90% saturates (i.e., 10% or more unsaturates). Group III is considered the highest level of mineral oil base fluids, with a VI of 120 or greater and 90% or greater saturates. Group IV base fluids are polyalphaolefins (PAOs). Group V base fluids are esters and other base fluids not included in Groups I-IV. These base fluids can be used individually or in mixtures.

[0089] Preferably, the one or more base oils (x) are selected from polyalphaolefin base oils, API Group III base oils or mixtures thereof.

[0090] Other additives The lubricating oil composition according to the present invention may further contain other additional additives (z) suitable for use in the formulation. These additives are selected from the group consisting of viscosity index improvers, pour point improvers, dispersants, demulsifiers, lubricity additives, detergents, antifoam agents, corrosion inhibitors, friction modifiers, antioxidants, antiwear agents, extreme pressure agents, antioxidants, dyes, fragrances, or mixtures thereof. Preferably, the lubricating oil composition according to the present invention contains a pour point depressant (PPD) to lower the minimum temperature at which the fluid will flow or can be poured. These additives are well known. Typical examples of these PPDs include ethylene-vinyl acetate copolymers, chlorinated paraffin-naphthalene condensates, chlorinated paraffin-phenol condensates, polymethacrylates, and polyalkylstyrenes. Polymethacrylates having a weight average molecular weight of 5,000 to 200,000 g / mol are preferred.

[0091] Preferably, the amounts of compounds (x), (y) and (z) total 100 mass %, based on the total mass of the lubricating oil composition.

[0092] Applications of the Hydrogenated Linear Copolymers According to the Invention The present invention relates to the use of the hydrogenated linear copolymers according to the invention as lubricating oil additives or synthetic base fluids, depending on the treat rate in lubricating oil compositions, preferably gear oil compositions, transmission oil compositions, hydraulic oil compositions, engine oil compositions, marine lubricating oil compositions, industrial lubricating oil compositions or greases.

[0093] As shown in the experimental section below, the use of hydrogenated linear copolymers according to the present invention in lubricating oil compositions can improve the traction coefficient of the lubricating oil composition while maintaining excellent thickening effect and shear stability in the lubricating oil composition.

[0094] The present invention also relates to a method for improving the traction coefficient of a lubricating oil composition, which method comprises the step of adding to a base oil a hydrogenated linear copolymer according to the present invention, as described in detail above.

[0095] As shown in the experimental section below, the positive effects of the hydrogenated linear copolymers of the present invention result in significant improvements in the traction coefficient and thickening effect of lubricating oil compositions. Furthermore, the hydrogenated linear copolymers defined in the present invention provide high viscosity index, good shear stability, excellent low temperature properties, and excellent solubility in typical base fluids. [Example]

[0096] The present invention will be described in detail below with reference to examples and comparative examples, but these are not intended to limit the scope of the present invention in any way.

[0097] Abbreviation PMMA Polyalkyl(meth)acrylate MMA C1-Alkyl methacrylate = Methyl methacrylate BMA C4-Alkyl methacrylate = n-Butyl methacrylate LMA C 12 / 14 Alkyl methacrylate = Lauryl methacrylate KRL Tapered roller bearing KV 40 Kinematic viscosity at 40°C, measured according to ASTM D445 KV 100 Kinematic viscosity at 100°C, measured according to ASTM D445 M n number average molecular weight M w mass average molecular weight NB3030 Nexbase® 3030, Neste Group III base oil, KV 100 3.0 cSt NB3043 Nexbase® 3043, Neste Group III base oil, KV 100 4.3 cSt PDI polydispersity coefficient, M w / M n The molecular weight distribution calculated by PSSI100 Permanent Shear Stability Index (KV before and after shear) 100 (calculated based on VI Viscosity Index, measured according to ASTM D2270 GPC Gel Permeation Chromatography MTM Mini Traction Device PP Pour Point, Measured According to ASTM D97 T g Glass transition temperature, measured by differential scanning calorimetry BF Brookfield Viscosity measured at -40°C according to ASTM D2983

[0098] Sample preparation Polymer synthesis Using the monomer compositions shown in Table 1 below, copolymers 1 to 8 according to the present invention and comparative examples 10 to 12 were prepared by radical solution polymerization. In a 5 L autoclave, at a temperature of 20°C and a pressure of 10 bar, the monomers were mixed with toluene so that the concentration of the monomers relative to the total mass of the mixture was 40% by weight. The temperature was increased to 130°C using a heating rate of 5.5°C / min, and then the initiator, 2,2-bis(t-butylperoxy)butane (50% by weight in liquid paraffin), was added. The radical polymerization was carried out at a reaction temperature of 130°C, the reaction pressure was approximately 20 bar, and the reaction time was 3 hours. The effluent was filtered, and the volatile solvents were evaporated. The resulting copolymers were then selectively hydrogenated.

[0099] Hydrogenation of copolymers For the selective hydrogenation, 1.5 L of a 40% by weight solution of the unsaturated copolymer in cyclohexane was placed in a 2 L autoclave and 5% Pd / C catalyst powder (0.15% by weight Pd per polymer) was added. The hydrogenation was carried out under stirring at a reaction temperature of 90 °C and a reaction pressure of 90 bar H2 until a degree of hydrogenation of 95% or more was achieved. The effluent was filtered and volatile components were evaporated. All polymerized units other than those derived from conjugated dienes (butadiene and isoprene) were not converted during the selective hydrogenation. Copolymers 1 to 8 according to the present invention and comparative examples 10 to 12 were all hydrogenated according to the following procedure.

[0100] Examples (also listed in Table 1 below): Examples 1-4 according to the invention are based on a monomer composition of butadiene and isoprene.

[0101] Examples 5 and 6 according to the invention are based on a monomer composition of butadiene, isoprene and methyl (meth)acrylate.

[0102] Examples 7 and 8 according to the invention are based on a monomer composition of butadiene, isoprene, methyl (meth)acrylate, butyl (meth)acrylate and lauryl (meth)acrylate.

[0103] Comparative Example 9, PAMA, was synthesized according to Example 1 of U.S. Patent Application Publication No. 2013 / 0229016. 12~15 It is a copolymer of methacrylate.

[0104] Comparative Example 10 is a copolymer of 80 mole % (76 wt %) butadiene and 20 mole % (24 wt %) isoprene, as disclosed in US Pat. No. 7,163,913.

[0105] Comparative Example 11 is based on the monomer composition of butadiene, methyl (meth)acrylate, butyl (meth)acrylate and lauryl (meth)acrylate. This product is synthesized using the same method as the examples according to the present invention.

[0106] Comparative Example 12 is based on pure polyisoprene and is synthesized using the same method as the example according to the invention.

[0107] Bulk Polymer Properties Test Method The weight average molecular weight Mw and polydispersity index PDI of the hydrogenated linear copolymers according to the present invention were determined using a Tosoh EcoSEC GPC system HLC-8320 equipped with a PSS SDV 5 μm precolumn and a 30 cm linear S separation column of PSS SDV 5 μm, and an RI detector, at a temperature of 40° C., a flow rate of 0.3 mL / min, and tetrahydrofuran (THF) as the eluent against polybutadiene calibration standards.

[0108] The weight average molecular weight of the polyalkyl(meth)acrylate of Comparative Example 9 was determined by gel permeation chromatography (GPC) using polymethyl methacrylate calibration standards and THF as the eluent.

[0109] The composition, hydrogenation degree, and selectivity of the hydrogenation process of the copolymer of the present invention are 1 Determined in deuterated chloroform using 1 H-NMR spectroscopy.

[0110] The glass transition temperature was measured by differential scanning calorimetry (DSC) on a Mettler-Toledo DSC1. The Mettler-Toledo STARe 10.00 software was used for the analysis. Indium and cyclohexane were used as standards. In two heating / cooling cycles, 8–10 mg of sample was cooled to −80°C at a cooling rate of 20 K / min. After 10 min, the sample was heated to 200°C at a heating rate of 10 K / °C. The glass transition temperature was obtained from the second heating cycle.

[0111] The bulk properties of the hydrogenated linear copolymers according to the invention are all very satisfactory with low PDI values, Mw and glass transition temperatures, as shown in Table 1. Furthermore, a high level of control is observed during synthesis, as the PDI values ​​of the hydrogenated copolymers according to the invention are all below 3.3.

[0112] Furthermore, all of the hydrogenated linear copolymers obtained according to the present invention have a high degree of hydrogenation (greater than 96% of the isoprene and butadiene are hydrogenated), which degree of hydrogenation is calculated as described above for hydrogenation.

[0113] [Table 1]

[0114] Evaluation of lubricant compositions The use of the copolymers according to the invention as lubricant additives is demonstrated in two different lubricant formulations using different hydrogenated linear copolymers according to the invention.

[0115] Test Method The target value for KV100 is 7.0 cSt for the formulations in Table 3. Viscosity loss at 100°C was measured after 40 hours at 80°C against the kinematic viscosity of the fresh oil at 100°C in a tapered roller bearing test (KRL) according to CEC-L-45-A-99.

[0116] The formulations in Table 4 have a fixed VI-KV40 target of 26 cSt and a KV100 target of 5.5 cSt. Traction coefficients were measured with a Mini Traction Apparatus using a 3 / 4 inch ball loaded against a disk under the conditions listed in Table 2 below: [Table 2]

[0117] Kinematic viscosity was measured according to ASTM D445.

[0118] Viscosity index was measured according to ASTM D2270.

[0119] The Brookfield viscosities reported in the lubricant formulation examples in Table 3 were measured at a temperature of -40°C according to ASTM D2983.

[0120] The pour points (PP) of the examples shown in Table 3 were measured according to ASTM D97.

[0121] Lubricating oil formulation 1 (KV100=7.0cSt) Lubricating oil compositions were prepared containing an API Group III base fluid (Nexbase 3030), a commercially available additive package, and any of the copolymers 1-8 according to the present invention, or comparative polymers 9 or 10, as set forth in Table 3 below. For comparison of the individual lubricating oil compositions, the kinematic viscosity at 100°C was adjusted to 7.0 cSt.

[0122] For each composition, viscosity properties as well as shear stability (KRL) and low temperature properties were measured.

[0123] One advantage of the present invention is that low amounts (treat rates) of copolymers 1-8 according to the present invention are sufficient to achieve good kinematic viscosity and good viscosity index, whereas the formulation containing the PAMA additive of Comparative Example 9 achieves similar results to the formulation according to the present invention, but at a treat rate of over 20% by weight (twice the amount of the formulation according to the present invention).

[0124] Thus, surprisingly, even though the additives according to the invention have a low molecular weight, they are very effective thickeners even at low concentrations in lubricant formulations.

[0125] In Comparative Example 10, similar results are observed as in the examples according to the invention in terms of treat rate and VI, but the low temperature properties of Comparative Example 10 do not satisfy the requirements for industrial application, thus indicating that copolymers with a high ratio of butadiene to isoprene are not suitable for the production of good lubricant additives.

[0126] [Table 3]

[0127] [Table 4]

[0128] Lubricant formulation (fixed VI) A second type of lubricant formulation was prepared, as shown above in Table 4, and the traction coefficients of each formulation containing copolymers 1-8 according to the invention or comparative polymers 9-12 were measured. All of the lubricant formulations in Table 4 were based on a mixture of Group III base fluids (Nexbase 3030 and Nexbase 3043), a commercially available additive package, and either a copolymer according to the invention or a comparative example.

[0129] To directly compare the individual lubricating oil compositions, the kinematic viscosity of each composition at 100°C was adjusted to 5.5 cSt and the kinematic viscosity of each composition at 40°C was adjusted to 26.0 cSt.

[0130] Viscosity characteristics and traction coefficients were determined for each composition (see Table 4 above). The lubricant composition containing the PAMA additive exhibited poorer traction performance and was therefore used as a reference point for comparing the different traction results of the other lubricant compositions.

[0131] As shown in Table 4 above, the traction coefficients of the examples according to the invention are superior to the comparative examples, demonstrating the additional positive effect of using a lubricant additive according to the invention.

[0132] In conclusion, the hydrogenated copolymers according to the invention have been shown to meet the demands of the lubricant technology sector by providing a low treat rate, which is always desirable in order to avoid thickening of the lubricant formulation, and by providing a low risk of incompatibility with other components in the lubricant formulation. Furthermore, there is a clear positive effect on the traction properties of lubricant formulations containing the lubricant additive according to the invention.

Claims

1. A monomer composition consisting of the following monomers, based on the total amount of monomers in the monomer composition: a) at least 10 mole percent 1,3-butadiene monomer b) at least 40 mole % isoprene c) one or more C １ ~C ６ 1 to 30 mol % of an alkyl (meth)acrylate, and d) one or more C ７ ~C ２４ Alkyl (meth)acrylate 0 to 30 mol% wherein the combined amount of monomer a) and monomer b) constitutes at least 60 mol % of the total amount of the monomer composition, and said hydrogenated linear copolymer has a weight average molecular weight comprised between 2,000 g / mol and 30,000 g / mol and a degree of hydrogenation greater than 95%, and said hydrogenated linear copolymer is a random copolymer.

2. 10. The hydrogenated linear copolymer of claim 1, wherein the hydrogenated linear copolymer has a weight average molecular weight comprised between 3,000 g / mol and 20,000 g / mol.

3. 3. The hydrogenated linear copolymer of claim 1, wherein the hydrogenated linear copolymer has a polydispersity index PDI of 1.0 to 4.

0.

4. The monomer composition contains the following monomers, based on the total amount of monomers in the monomer composition: a) at least 10 mole percent 1,3-butadiene monomer b) at least 40 mole % isoprene c) one or more C １ ~C ６ 1 to 20 mol % of an alkyl (meth)acrylate, and d) one or more C ７ ~C ２４ Alkyl (meth)acrylate 5 to 20 mol% 4. The hydrogenated linear copolymer of claim 1, consisting of:

5. The one or more C １ ~C ６ 5. The hydrogenated linear copolymer of claim 1, wherein the alkyl (meth)acrylate monomer c) is selected from methyl (meth)acrylate, butyl (meth)acrylate, or mixtures thereof.

6. The one or more C ７ ~C ２４ 6. The hydrogenated linear copolymer of claim 1, wherein the alkyl (meth)acrylate monomer d) is lauryl (meth)acrylate.

7. 10. A method for producing the hydrogenated linear copolymer of claim 1, comprising the steps of: (i) providing a monomer composition according to any one of claims 1 to 6; (ii) conducting solution polymerization on the monomer composition to obtain a copolymer; and (iii) hydrogenating the copolymer obtained in step (ii).

1. A method for producing a hydrogenated linear copolymer, comprising:

8. 8. The method of claim 7, wherein the solution polymerization in step (ii) is radical solution polymerization or anionic solution polymerization.

9. (x) one or more base oils; and (y) one or more hydrogenated linear copolymers according to any one of claims 1 to 6. A lubricating oil composition comprising:

10. 10. The lubricating oil composition of claim 9, wherein the one or more base oils are selected from a polyalphaolefin base oil, an API Group III base oil, or a mixture thereof.

11. 11. The lubricating oil composition according to claim 9 or 10, wherein the lubricating oil composition contains 0.5 to 80 mass % of one or more hydrogenated linear copolymers (y) and 20 to 99.5 mass % of one or more base oils (x), based on the total amount of the lubricating oil composition.

12. 10. Use of the hydrogenated linear copolymer of any one of claims 1 to 6 as a lubricant additive or synthetic base fluid in a lubricating oil composition or grease.

13. 12. A method for improving the traction coefficient of a lubricating oil composition according to any one of claims 9 to 11, comprising adding one or more hydrogenated linear copolymers (y) to one or more base oils (x).

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