Acrylate-olefin copolymer as a high viscosity base fluid

Abstract

The present invention relates to acrylate-olefin copolymers and to a process for preparing these polymers. The present invention further relates to lubricant compositions comprising these copolymers and to the use of these copolymers as lubricant additives or synthetic base fluids in lubricating oil compositions, preferably in gear oil compositions, transmission oil compositions, hydraulic oil compositions, engine oil compositions, marine oil compositions, industrial lubricating oil compositions or in greases.

Description

Technical Field

[0001] This invention relates to acrylate-olefin copolymers and methods for preparing these polymers. The invention also relates to lubricant compositions comprising these copolymers, and the use of these copolymers as lubricant additives or synthetic base fluids in lubricating oil compositions, preferably in gear oil compositions, transmission oil compositions, hydraulic oil compositions, engine oil compositions, marine oil compositions, industrial lubricating oil compositions, or in greases. Background Technology

[0002] This invention relates to the field of lubrication. A lubricant is a composition that reduces friction between surfaces. In addition to allowing free movement between two surfaces and reducing mechanical wear, a lubricant can also inhibit surface corrosion and / or inhibit damage to the surface due to heating or oxidation. Examples of lubricant compositions include, but are not limited to, engine oils, transmission fluids, gear oils, industrial lubricants, greases, and metalworking fluids.

[0003] Lubricants typically contain a base fluid and a variable amount of additives. The common base fluid is a hydrocarbon, such as mineral oil. The terms base oil or base fluid are often used interchangeably. Here, base fluid is used as a general term.

[0004] Depending on the intended use of the lubricant, various additives can be combined with the base fluid. Examples of lubricant additives include, but are not limited to, viscosity index improvers, thickeners, oxidation inhibitors, corrosion inhibitors, dispersants, high-pressure additives, defoamers, and metal passivators.

[0005] Typical non-polymer-based fluids are not very effective as lubricants because of their low viscosity, which decreases further at higher operating temperatures. Therefore, polymer additives are used to thicken base oils and reduce the change in viscosity with temperature. The term viscosity index (VI) is used to describe this change in viscosity with temperature. The lower the VI, the greater the change in viscosity with temperature, and vice versa. Therefore, lubricant formulations require a high VI. To improve the VI, polymer additives or viscosity index improvers (VII) can be added to lubricant formulations.

[0006] It is well known in the art that alkyl acrylates are not recommended for VI modifier applications, and commercial VI modifiers are based on methacrylates. Although there are literature (Rashad et al., J. of Petr. Sci. and Engineering 2012, 173-177; Evin et al., J. of Sol. Chem 1994, 325-338) and patents (WO 96 / 17517), it is generally known that polyacrylates perform worse than polymethacrylates as VI modifiers in those aspects. In particular, WO 96 / 17517 mentions the unexpected finding that poly(alkyl acrylate) esters generally do not adequately reduce the effect of temperature on viscosity when used in hydraulic fluids.

[0007] The disadvantage of adding polymer additives to lubricant formulations is that they will experience shear stress and mechanically degrade over time. Higher molecular weight polymers are better thickeners but will be more susceptible to shear stress, leading to polymer degradation. To reduce the amount of polymer degradation, the molecular weight of the polymer can be reduced, resulting in a more shear-stable polymer. These shear-stable low molecular weight polymers are no longer very effective thickeners and must be used in lubricants at higher concentrations to achieve the desired viscosity. These low molecular weight polymers typically have a molecular weight below 20,000 g / mol and are also known as synthetic high-viscosity base fluids. High-viscosity base fluids are used to enhance viscosity (VI) and thicken lubricant formulations with stringent shear stability requirements. A typical application is gear oils, which have very demanding requirements due to high mechanical stress and a wide temperature range during operation.

[0008] Typical products in this market are high-viscosity polyalphaolefins (PAOs) and metallocene polyalphaolefins (mPAOs), typically sold at 100°C in viscosity ranges from 40 to 300 cSt (Choudary et al., Lubr. Sci. 2012, 23-44). Their key characteristic is good handling performance in terms of viscosity, as these base fluids are polymeric in nature and provide an improved viscosity index. However, their weakness is low polarity. Due to the non-polar nature of PAO base oils, DI packaging materials and aged products exhibit poor solubility in the oil, causing various problems.

[0009] Higher polarity has been described through copolymers of α-olefins with maleic esters (DE3223694), copolymers of α-olefins with acrylates (DE2243064), copolymers of α-olefins with methacrylates (EP0471266), or terpolymers based on the aforementioned monomers (WO2020078770). Alternatively, oil-compatible polyesters (WO0146350), poly(meth)acrylates (DE102010028195), or polyvinyl ethers (US20130165360) can be applied. A major advantage when using a high-viscosity, polar base fluid is that it is not necessary to use low-viscosity, polar fluids such as esters as compatibilizers for polar lubricant additives. Low-viscosity, polar fluids are known to cause problems with coatings and seals, which is less of a problem with high-viscosity fluids.

[0010] Existing products, such as polyalphaolefins (PAOs), do not provide the necessary performance levels for some applications. There is a need for alternative solutions in the industrial gear oil sector, not just for industrial lubricants. In particular, there is a desire to replace existing high-viscosity PAOs, as these products are expensive and do not provide sufficient solubility for key formulation components.

[0011] Therefore, the object of this invention is to provide highly shear-stable synthetic base fluid or lubricating oil additives that have a positive impact on oil solubility, component solubility, and low-temperature performance in lubricating oil compositions. Furthermore, these new polymers should be able to thicken oils to the desired viscosity. These highly shear-stable polymers should also possess a high viscosity index, a high flash point, and good thermal-oxidative stability. Summary of the Invention Invention Overview

[0013] The inventors of this invention have surprisingly discovered that the acrylate-olefin copolymers as defined in claim 1 can be used as highly shear-stable lubricant additives or synthetic base fluids, depending on their treat rate in lubricating compositions. The acrylate-olefin copolymers according to the invention unexpectedly possess a higher viscosity index than their methacrylate counterparts, as illustrated in the experimental section of this invention. The inventors have also found that the acrylate-derived monomers and the α-olefin-derived side chains of the resulting polymers are crucial for achieving a combination of high viscosity index (VI) and good low-temperature performance.

[0014] The first aspect of the invention is an acrylate-olefin copolymer as defined in claim 1.

[0015] A second aspect of the invention is a method for preparing these copolymers as defined in claim 13.

[0016] A third aspect of the invention is a lubricant composition comprising at least one base oil and at least one copolymer according to the invention, as defined in claim 14.

[0017] A fourth aspect of the invention is the use of these copolymers as lubricant additives or synthetic base fluids in lubricating oil compositions, preferably in gear oil compositions, transmission oil compositions, hydraulic oil compositions, engine oil compositions, marine oil compositions, industrial lubricating oil compositions, or in greases. Invention Details

[0018] copolymers according to the present invention

[0019] This invention relates to copolymers comprising:

[0020] a) Based on the total weight of the copolymer, 65 to 90% by weight of monomer units derived from at least one acrylate of formula (I),

[0021]

[0022] R1 refers to a linear or branched alkyl group containing 6 to 12 carbon atoms.

[0023] b) Based on the total weight of the copolymer, 10 to 35% by weight of monomer units derived from at least one nonfunctionalized α-olefin of formula (II),

[0024]

[0025] R2 refers to a linear alkyl group containing 6 to 16 carbon atoms.

[0026] c) Based on the total weight of the copolymer, 0 to 10% by weight of monomer units derived from at least one monomer, said monomer being selected from a list of methacrylamide, fumarate, maleate, or mixtures thereof, and

[0027] The copolymer described herein has a kinematic viscosity of 80-600 cSt at 100°C according to ASTM D 445, and

[0028] Based on the total weight of the copolymer, the copolymer contains 0 to 22% by weight of monomer units derived from monomers having linear alkyl groups containing more than 8 carbon atoms.

[0029] According to one aspect of the invention, the copolymer preferably comprises 0 to 20% by weight, more preferably 0 to 18% by weight, monomer units derived from monomers having linear alkyl groups having more than 8 carbon atoms, based on the total weight of the copolymer.

[0030] According to another aspect of the invention, the copolymer preferably has a kinematic viscosity at 100°C of 100-500 cSt according to ASTM D 445, more preferably 150-400 cSt according to ASTM D 445, and even more preferably 150-350 cSt according to ASTM D 445.

[0031] According to another preferred aspect of the invention, the total content of monomer units derived from monomers a) and b) in the copolymer of the invention is at most 90% by weight, more preferably at most 95% by weight, even more preferably at most 98% by weight, and most preferably at most 100% by weight, based on the total weight of the copolymer.

[0032] According to another preferred aspect of the invention, the total content of monomer units derived from monomers a), b) and c) in the copolymer of the invention is at most 90% by weight, more preferably at most 95% by weight, even more preferably at most 98% by weight, and most preferably at most 100% by weight, based on the total weight of the copolymer.

[0033] Acrylates of formula (I) a) refer to esters of acrylic acid with straight-chain or branched alcohols containing 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms, more preferably 8 to 10 carbon atoms. The term covers individual acrylates of alcohols having a specific length, and also covers mixtures of acrylates of alcohols having different lengths.

[0034] According to one aspect of the invention, R1 in the acrylate monomer of formula (I) is preferably a linear or branched alkyl group containing 6 to 10 carbon atoms, more preferably a linear or branched alkyl group containing 8 to 10 carbon atoms. Particularly preferred acrylate a) of formula (I) is 2-ethylhexyl acrylate, 2-propylheptyl acrylate, n-octyl acrylate, or a mixture thereof.

[0035] According to the present invention, preferably the copolymer of the present invention comprises 70 to 90% by weight, more preferably 75 to 90% by weight, monomer units of acrylate monomer a) derived from formula (I), based on the total weight of the copolymer.

[0036] According to the present invention, preferably, the copolymer of the present invention comprises 10-30% by weight, more preferably 10-25% by weight, monomer units derived from nonfunctionalized α-olefin (b) of formula (II), based on the total weight of the copolymer. Particularly preferred nonfunctionalized α-olefin (b) of formula (II) is selected from decene, dodecene, tetradecene, hexadecene, or mixtures thereof.

[0037] According to a preferred aspect of the invention, and in accordance with DIN 55672-1, the copolymer has a weight-average molecular weight of 5,000 to 30,000 g / mol, preferably 7,000 to 25,000 g / mol, and even more preferably 8,000 to 20,000 g / mol.

[0038] In this invention, the weight-average molecular weight (Mw) or number-average molecular weight (Mn) of the copolymer is determined by gel permeation chromatography (GPC) using PMMA calibration standards according to DIN 55672-1 under the following measurement conditions:

[0039] Eluent: Tetrahydrofuran (THF)

[0040] Operating temperature: 35℃

[0041] Columns: The column group consists of four columns: two columns SDV. A column SDV A column SDV (PSS Standards Service GmbH, Mainz, Germany), all with a size of 300×8mm and an average particle size of 10μm.

[0042] Flow rate: 1 mL / min

[0043] Injection volume: 100μL

[0044] Instrumentation: Agilent 1100 series consisting of an autosampler, pump, and column oven.

[0045] Detection device: A refractive index detector from the Agilent 1100 series.

[0046] Preferably, the copolymers of the present invention have very low crosslinking degree and narrow molecular weight distribution, which further contributes to their shear resistance. Low crosslinking degree and narrow molecular weight are reflected in the polydispersity index (PDI) of the copolymers. Preferably, the polydispersity index (PDI) of the copolymers according to the present invention is in the range of 1.0 to 4.0, more preferably 1.5 to 3.5. In terms of the shear resistance of the copolymers, a polydispersity index in the range of 1.0 to 3.5 is considered optimal for most industrial applications. The polydispersity index is defined as the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn).

[0047] According to a preferred aspect of the invention, the copolymer of the invention has a COC flash point of over 250°C according to ASTM D92.

[0048] The copolymers of the present invention may optionally contain monomer units derived from monomer c), said monomer c) being selected from a list consisting of methacrylamide, fumarate, maleate, or mixtures thereof. Preferably, the amount of monomer units derived from monomer c) in the copolymers obtained according to the present invention is 0 to 10% by weight, preferably 0 to 7% by weight, more preferably 0 to 5% by weight, and even more preferably 0 to 3% by weight, based on the total weight of the copolymer. Particularly preferred monomer c) is di-2-ethylhexyl maleate, N-3-dimethylaminopropylmethacrylamide, di-2-ethylhexyl fumarate, or mixtures thereof.

[0049] It has been surprisingly observed that the introduction of monomer units c) into the copolymer allows for the complete conversion of nonfunctionalized α-olefins b) and therefore eliminates the need for a final distillation step at the end of the copolymerization.

[0050] According to a preferred aspect of the invention, in addition to monomer units derived from monomers a), b), and unnecessarily c), the acrylate-olefin copolymer of the invention further comprises 0 to 10% by weight, more preferably 0 to 6% by weight, monomer units derived from at least one monomer selected from (meth)acrylates, vinyl esters, or mixtures thereof, based on the total weight of the copolymer. Particularly preferred monomer d) is lauryl methacrylate (LMA), stearyl methacrylate (SMA), or vinyl lauryl acrylate (VLA).

[0051] According to another preferred aspect of the invention, the total content of monomer units of monomers a), b), c) and d) is 95% by weight, more preferably 98% by weight, and even more preferably 100% by weight.

[0052] According to another preferred aspect of the invention, when the copolymer consists of monomer units derived from monomers a), b), optional c), and optional d), the copolymer contains 0 to 22% by weight, more preferably 0 to 20% by weight, and even more preferably 0 to 18% by weight of monomer units derived from monomers a), b), c), and d), having linear alkyl groups having more than 8 carbon atoms, based on the total weight of the copolymer.

[0053] According to the present invention, the copolymer is a statistical copolymer having a sequential distribution of monomer units derived from monomers a) and b) and optional monomers c) and d).

[0054] Preferred copolymers of the present invention

[0055] According to a preferred aspect of the invention, the copolymer comprises:

[0056] a) 65 to 90% by weight, more preferably 70 to 90% by weight, even more preferably 75 to 90% by weight, of monomer units derived from at least one acrylate of formula (I), based on the total weight of the copolymer.

[0057]

[0058] R1 refers to a linear or branched alkyl group containing 8 to 10 carbon atoms.

[0059] b) 10 to 35% by weight, more preferably 10 to 30% by weight, even more preferably 10 to 25% by weight of monomer units derived from at least one nonfunctionalized α-olefin of formula (II), based on the total weight of the copolymer.

[0060]

[0061] R2 refers to a linear alkyl group containing 8 to 12 carbon atoms.

[0062] c) 0 to 10% by weight, more preferably 0 to 5% by weight, even more preferably 0 to 3% by weight, monomer units derived from at least one monomer selected from the list of free methacrylamide, fumarate, maleate, or mixtures thereof, based on the total weight of the copolymer, and

[0063] The copolymer described herein has a kinematic viscosity of 80-600 cSt at 100°C according to ASTM D 445, and

[0064] The copolymer contains 0 to 22% by weight, preferably 0 to 18% by weight, monomer units derived from monomers having linear alkyl groups containing more than 8 carbon atoms, based on the total weight of the copolymer.

[0065] According to a preferred embodiment, the total content of monomer units of monomers a), b) and c) is at most 95% by weight, more preferably 98% by weight, and even more preferably 100% by weight, based on the total weight of the copolymer.

[0066] According to a preferred embodiment, the copolymer further comprises 0 to 10% by weight, more preferably 0 to 6% by weight, monomer units derived from at least one monomer (d) selected from alkyl methacrylates, vinyl esters, or mixtures thereof, based on the total weight of the copolymer. Particularly preferred monomer (d) is lauryl methacrylate (LMA), stearyl methacrylate (SMA), or vinyl lauryl methacrylate (VLA).

[0067] According to a preferred embodiment, the total content of monomer units of monomers a), b), c) and d) is at most 95% by weight, more preferably 98% by weight, and even more preferably 100% by weight.

[0068] Preparation method of copolymer according to the present invention

[0069] According to the present invention, the above polymer is prepared by a method comprising the following steps:

[0070] i) Provide the monomer composition as described above; and

[0071] ii) Initiate free radical polymerization in the monomer composition.

[0072] Standard free radical polymerization is described in particular detail in Ullmann's Encyclopedia of Industrial Chemistry, sixth edition. Typically, polymerization initiators and unnecessary chain transfer agents are used for this purpose.

[0073] Polymerization can be carried out under standard pressure, reduced pressure, or high pressure.

[0074] For free radical copolymerization of olefins and acrylates, the polymerization temperature is critical. Typically, the copolymerization temperature is 140 to 180°C, preferably 150 to 170°C.

[0075] The polymerization step (ii) can be carried out with or without dilution in the oil. Preferably, the polymerization step (ii) is carried out without diluting the oil or any solvent.

[0076] Preferably, step (ii) includes adding a free radical initiator. Preferably, the free radical initiator is selected from di-tert-butyl peroxide or dicumyl peroxide. Preferably, the total amount of the free radical initiator is 0.01 to 5% by weight, more preferably 0.1 to 1% by weight, relative to the total weight of the monomer mixture. Preferably, the total amount of the free radical initiator is added continuously during the copolymerization reaction (ii).

[0077] Preferably, the copolymerization step (ii) is carried out by feeding the acrylate monomer (a) and the unnecessary monomer (c) or any other comonomer together with the initiator into the nonfunctionalized α-olefin monomer (b). Preferably, the total reaction time for the free radical polymerization is 2 to 5 hours, more preferably 3 hours.

[0078] In another preferred aspect of the invention, a third step iii) is not necessarily performed, which corresponds to a distillation step to remove unreacted α-olefin monomer b). Preferably, residual unreacted α-olefin monomer b is removed by distillation using a rotary evaporator at 150°C and a pressure as low as 5 mbar. Advantageously, when the copolymer of the invention contains monomer units derived from monomer c), distillation step iii) is not required. It has been surprisingly observed that a small amount of monomer c (less than 10% by weight, more preferably less than 5% by weight, based on the total weight of the copolymer) increases the conversion of olefins during copolymerization (less than 1% by weight of residual unreacted α-olefin b) so that distillation step iii is not required.

[0079] Lubricating oil composition

[0080] As described above, the present invention also relates to lubricating oil compositions comprising at least one base oil and at least one copolymer as defined in the present invention.

[0081] Base oil refers to the lubricant base oil selected according to its use / intended use, such as mineral oil, synthetic or natural oil, animal or vegetable oil.

[0082] Base oils used to formulate lubricating oil compositions according to the present invention include, for example, conventional base oils selected from API (American Petroleum Institute) base oil categories, referred to as Group I, Group II, Group III, Group IV, and Group V. Group I and Group II base oils are mineral oil materials (e.g., alkane and naphthenic oils) with a viscosity index (or VI) less than 120. A further distinction between Group I and Group II is that the latter contains more than 90% saturated material, while the former contains less than 90% saturated material (i.e., more than 10% unsaturated material). Group III is considered to be the highest level of mineral base oils with a VI greater than or equal to 120 and a saturation level greater than or equal to 90%. Preferably, the base oils included in the lubricating oil compositions of the present invention are selected from API Group II and Group III base oils. Most preferably, the lubricant composition comprises API Group III base oil. Group IV base oils are polyalphaolefins (PAO). Group V base oils are esters and any other base oils not included in Groups I through IV. These base oils can be used alone or as mixtures.

[0083] In a preferred embodiment of the invention, the lubricating oil composition comprises 0.1 to 99.9% by weight, preferably 1 to 95% by weight, of at least one base oil and 0.1 to 99.9% by weight, preferably 5 to 99% by weight, of at least one copolymer according to the invention, based on the total weight of the lubricating composition.

[0084] The lubricating oil composition according to the present invention may further comprise any other additional additives suitable for the formulation. These additives include additional viscosity index improvers, pour point depressants, dispersants, demulsifiers, antifoaming agents, lubricating additives, friction improvers, antioxidants, detergents, dyes, preservatives and / or flavoring agents.

[0085] Use of the copolymer of the present invention

[0086] The present invention also relates to the use of the copolymer according to the present invention as a lubricant additive or synthetic base fluid in a lubricating oil composition, preferably in a gear oil composition, a transmission oil composition, a hydraulic oil composition, an engine oil composition, a marine oil composition, an industrial lubricating oil composition or in a grease.

[0087] Experimental part

[0088] The present invention will be further described in detail below with reference to the examples and comparative examples, without intending to limit the scope of the present invention. All percentages given in the following table for monomers or base fluids are weight percentages (wt%).

[0089] Abbreviations

[0090] BF-26 Brookfield viscosity measured at -26 °C

[0091] BF-30 Brookfield viscosity measured at -26 °C

[0092] BV Kinematic viscosity [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0104] EHA 2-Ethylhexyl Acrylate

[0105] EHMA 2-Ethylhexyl Methacrylate

[0106] HA Hexyl acrylate

[0107] HexDec hexadecene

[0108] Defoamers available from Afton in 2030

[0109] 307 DI packaging materials available from Afton

[0110] 3250 DI packaging material available from Afton

[0111] IDA Isodecyl Acrylate

[0112] IDMA isodecyl methacrylate

[0113] Ini initiator

[0114] ITDA isotridecyl acrylate is available from Aldrich.

[0115] KV kinematic viscosity as measured by ASTM D445

[0116] KV 40 Kinematic viscosity at 40°C as measured according to ASTM D445

[0117] KV 100 Kinematic viscosity at 100°C as measured according to ASTM D445

[0118] LA lauryl acrylate, dodecyl acrylate

[0119] LMA (Lauryl Methacrylate), 73% C12, 27% C14, fully linear

[0120] Mn number-average molecular weight

[0121] MO methyl oleate

[0122] Mw weight-average molecular weight

[0123] nm was not measured.

[0124] nOA (n-octyl acrylate)

[0125] NB3080 3080; derived from Neste KV100 Group III base oil with a viscosity grade of 7.9 cSt.

[0126] PAO100 is derived from Chevron Phillips' KV100 polyalphaolefin base oil with a viscosity grade of 100 cSt.

[0127] PAO4 is a polyalphaolefin base oil with 4 cSt and KV100 content.

[0128] PAO6 has a KV of 6cSt 100 Polyalphaolefin base oil

[0129] PAO8 has a KV of 7.8 cSt. 100 INEOS Durasyn 168 polyalphaolefin base oil

[0130] PAO8 I is an INEOS Durasyn 128 polyalphaolefin base oil with a KV100 of 7.8 cSt.

[0131] PDI (Polydispersity Index)

[0132] PHA 2-propylheptyl acrylate

[0133] PP Pour Point

[0134] Priolube 3970 is an ester-based fluid available from Croda.

[0135] RC9420 is a DI packaging material available from Rheinchemie.

[0136] ReMo residual monomer content

[0137] SMA stearyl methacrylate, 35% C16, 65% C18, fully linear

[0138] Shear loss of SL KRL20 after 20 hours of KRL measurement at 100℃

[0139] Shear loss after 100 hours of KRL measurement, measured at 100°C using SL KRL100.

[0140] TetDec tetradecene

[0141] VI Viscosity Index

[0142] VLA Vinyl Laurate

[0143] VPL 1-180 Evonik 1-180, Pour Point Decreasing Agent

[0144] VPL 1-300 Evonik 1-300, Pour Point Decreasing Agent

[0145] Yubase 4 is derived from SK Lubricants' KV with 4cSt. 100 Group III base oils

[0146] Test methods

[0147] KV ASTM D445

[0148] VI ASTM D2270

[0149] PP ASTM D5950

[0150] Copper corrosion ASTM D130

[0151] Steel corrosion DIN ISO 7120

[0152] TOST ASTM D2893

[0153] RPVOT ASTM D2272

[0154] Foam (ASTM D892)

[0155] KRL CEC L-45-A-99

[0156] BF ASTM D2983

[0157] COC ASTM D92

[0158] In this invention, the bulk viscosity (BV) of the product (the product obtained from the polymerization reaction) corresponds to the kinematic viscosity (KV) of the resulting polymer product as measured according to ASTM D445. Therefore, according to ASTM D445, the bulk viscosity of the polymer is measured as the kinematic viscosity at 40°C and 100°C, respectively (BV40 and BV100 as shown in Tables 1, 2, 3 and 4 below). Example

[0159] Synthesis 1: Pure acrylate (Ex. 39*)

[0160] 1.62 g of DBPO (0.6 wt% relative to acrylate) dissolved in 270.0 g of EHA was slowly fed into 30.0 g of PAO8 at 160 °C under nitrogen for 3 hours. After stirring for another hour, the resulting clear and colorless polymer solution was cooled and used for further experiments without further purification.

[0161] Synthesis 2: (meth)acrylate / olefin copolymer with distillation step (Ex. 8)

[0162] 3.6 g of DBPO dissolved in 1200 g of EHA (0.3 wt% relative to monomer in the feed) was slowly fed into 300 g of 1-decene (0.33 molar equivalents relative to (meth)acrylate) at 160 °C under nitrogen for 3 hours. After stirring for another hour, the resulting clear and colorless polymer was cooled. Subsequently, residual decene was removed by distillation using a rotary evaporator at 150 °C and pressures as low as 5 mbar.

[0163] Synthesis 3: Acrylate / olefin copolymer without distillation step (Ex. 54)

[0164] 0.77 g of DBPO dissolved in 249.3 g of EHA and 5.7 g of DEHF (0.3 wt% relative to monomers in the feed) was slowly fed into 45.0 g of 1-tetradecene at 160 °C under nitrogen for 3 hours. After stirring for another hour, the resulting clear and colorless polymer was cooled and used without further purification.

[0165] Examples 1 to 28 were prepared in the same manner as Synthesis 2, except that the amounts of reactants or other reaction conditions were varied as listed in Table 1. The α-olefin monomer was always first charged into the reactor, and the (meth)acrylate monomer and initiator were fed over a set time period.

[0166] Examples 38 to 43 were prepared in the same manner as Synthesis 1, except that the amounts of reactants or other reaction conditions were changed as listed in Table 3.

[0167] Examples 44 to 61 were prepared in the same manner as Synthesis 3, except that the amounts of reactants or other reaction conditions were changed as listed in Table 4.

[0168] Since the molar ratios in the reaction do not represent the final composition, the final proportion of olefins in the polymer after distillation is given as % by weight (olefins Inc.). This proportion is determined by gravimetric analysis in cases where the (meth)acrylate conversion is complete or its boiling point is too high to be removed by distillation. For example, Example 8 had a residual EHA content of less than 0.01% by weight prior to the distillation step.

[0169] In some embodiments, up to three polymers with similar viscosities are blended. For the blending process, the products are stirred together at 80°C for 1 hour. The blends are listed in Table 2 (see Examples 29 to 37). The amount of olefin introduced is calculated from the values ​​measured for the individual components. Other values, such as molecular weight or viscosity, are measured for the blends.

[0170] Good high-viscosity base fluids require a combination of several properties. A key indicator of high-performance gear oils is low-temperature performance. Besides the low viscosity dependence on temperature (which is also reflected in VI), it is important that the polymer does not exhibit strong intermolecular interactions that lead to poor low-temperature performance.

[0171] The polymers according to the invention have an advantageous combination of viscosity, viscosity index, and shear stability, as illustrated in Examples 5, 6, or 8. In contrast, it can be observed that the acrylate-olefin copolymer containing 22.6% by weight of linear side chains with more than 8 carbon atoms, as in Comparative Example 7*, exhibits good VI (236), but performs poorly at low temperatures (BF-26 = 192,000 cP), as shown in its lubricant formulation (Example F-21*). In contrast, the acrylate-olefin copolymer of Example 50 of the invention, containing only 15% by weight of linear side chains with more than 8 carbon atoms, combines high VI (220) and, as shown in its lubricant formulation (Example F-28), performs very well even under more demanding low-temperature conditions (BF-30 = 102,000 cP) (BF-30 replaces BF-26 in Comparative Example F-21*).

[0172] Surprisingly, even longer side chains (e.g., in Examples 48 (C12 side chains) or 51 (C14 side chains) of the invention) exhibit the same level as Example 50 (C10 side chains) because the total amount of monomer units derived from monomers having a total of more than 8 carbon atoms in the copolymer is less than 22% by weight, based on the total weight of the copolymer. Long linear side chains (more than 8 carbon atoms) can be any monomer unit of the copolymer (any monomer a), b), c), d), or other comonomers), as shown in Comparative Example 13*, which has 81% by weight of linear side chains containing more than 8 carbon atoms due to the high content of lauryl acrylate. As shown in Comparative Formulation F-38*, the high content of long linear side chains containing more than 8 carbon atoms in the acrylate monomer units results in extremely poor low-temperature performance (PP at -18°C), despite a high VI (195), thus failing to achieve a good combination of high VI and good low-temperature performance. The amounts of these side chains are provided in Tables 1 to 4 as >C8 SC".

[0173] While polymethacrylates are known to be excellent VI modifiers, they are surprisingly outperformed by their acrylate counterparts in the lower molecular weight range. This is illustrated in Table 5, where F-2 and F-3* are based on very similar polymers (EHA for Example 29 of the present invention and EHMA for Comparative Example 20*), but the much higher VI of the EHA-based polymer (Example 29 of the present invention) results in a higher VI and better low-temperature viscosity in the final formulation.

[0174] F-2 exhibits similar performance levels to the PAO100 base formulation F-1*. Compared to pure polyolefins, the polar ester functional groups in the acrylate-olefin copolymers of this invention benefit the overall compatibility of different formulation components (to allow for direct comparison with PAO100, the formulations in Table 4 were prepared without additional additives). Unlike PAO, which must be prepared via cationic or coordination polymerization, the free radical polymerization method used to prepare the acrylate-olefin copolymers of this invention provides an easy route to obtain higher viscosity products with good shear stability in a commercially attractive manner.

[0175]

[0176]

[0177]

[0178]

[0179] Table 5. Lubricant formulations with a high-viscosity base fluid of 100 cSt.

[0180] Preparation Ex. F-1* F-2 F-3* PAO100 [wt%] 22.3 Ex.29 [wt%] 31.5 Ex.20* [wt%] 29.8 PAO4 [wt%] 77.7 68.5 70.2 KV40 [cSt] 46.0 46.1 45.9 KV100 [cSt] 8.4 8.5 8.1 VI 162 164 151 BF-40 [cP] 11,000 12,200 14,000 PP [℃] -66 -66 -66

[0181] (*) refers to the comparative embodiment.

[0182] Examples of formulations containing EHA homopolymers are shown in Tables 6 and 7. For process reasons, the pure acrylates shown in Table 3 were prepared as solutions in oil, preventing these polymers from acquiring their bulk properties. To avoid affecting the comparison of the copolymers, the oil used for polymerization was the same as that subsequently used in the formulations. It can be seen that the mentioned EHA homopolymers (Comparative Examples 38* and 39*) provide lower VI and exhibit worse low-temperature performance in the formulations. As shown in Table 8, the comparative polyacrylate examples with longer side chains, which are EHA homopolymers, also perform worse than the inventive acrylate-olefin copolymers of this invention.

[0183] Table 6. Lubricant formulations with a high-viscosity base fluid of 150 cSt

[0184] Preparation Ex. F-4* F-5 F-6* F-7* F-8* Ex.38* [wt%] 35.2 Ex.30 [wt%] 28.5 Ex.19* [wt%] 28.2 Ex.34* [wt%] 25.2 Ex.37* [wt%] 23.1 VPL 1-300 [wt%] 0.3 0.3 0.3 0.3 0.3 Yubase 4 [%] 64.5 71.2 71.5 74.5 76.6 KV40 [cSt] 49.7 48.6 49.2 46.2 46.7 KV100 [cSt] 8.9 8.9 8.6 8.2 8.8 VI 161 166 152 153 172 BF-40 [cP] 90,000 55,000 83,000 77,000 solid PP [℃] -42 -39 -42 -39 -39

[0185] (*) refers to the comparative embodiment.

[0186] Table 7. Lubricant formulations with a high-viscosity base fluid of 450 cSt

[0187] Preparation Ex. F-9* F-10 F-11* F-12* F-13* F-14 F-15* F-16* Ex.39* [wt%] 55.0 55.1 Ex.6 [wt%] 47.0 47.4 Ex.18* [wt%] 45.0 43.6 Ex.35* [wt%] 43.0 42.1 RC9420 [wt%] 2.0 2.0 2.0 2.0 Hitec 307 [wt%] 2.7 2.7 2.7 2.7 VPL 1-180 [wt%] 0.7 0.7 0.7 0.7 NB3080 [wt%] 41.6 43.4 53.1 54.6 PAO8 [wt%] 43.0 51.0 53.0 55.0 KV40 [cSt] 312.9 320.3 325.3 318.9 314.9 326.5 312.6 312.7 KV100 [cSt] 36.4 39.5 34.5 34.5 36.3 39.6 33.4 33.8 VI 164 176 150 153 163 174 149 152 BF-26 [cP] 74,000 49,000 74,000 77,000 n.m. n.m. n.m. n.m. PP [℃] -39 -45 -42 -45 -36 -39 n.m. -39

[0188] (*) refers to the comparative embodiment.

[0189] Table 8. Lubricant formulations with a high viscosity base fluid of pure polyacrylate.

[0190] Preparation Ex. F-17* F-18* F-190* F-20* Ex.40* [wt%] 62.4 Ex.41* [wt%] 67.5 Ex.42* [wt%] 96.6 Ex.43* [wt%] 62.0 Viscoplex 1-180 [wt%] 0.7 0.7 0.7 0.7 Hitec 307 [wt%] 2.7 2.7 2.7 2.7 Nexbase 3080 [wt%] 29.1 34.6 PAO8 [wt%] 34.9 KV40 [cSt] 328.1 314.5 315.5 313.6 KV100 [cSt] 38.1 35.2 42.9 33.1 VI 166 158 193 147 BF-26 [cP] 81,000 220,000 solid 212,000 PP [℃] -45 -39 -6 -36

[0191] (*) refers to the comparative embodiment.

[0192] Residual monomers of the polymers described in Tables 9 and 4 (all amounts are in weight percent).

[0193]

[0194] High-performance lubricants also need to meet many requirements. Exceptionally good low-temperature performance, high flash point, and good aging behavior are directly influenced by the choice of high-viscosity base fluid.

[0195] As shown in Table 10 below, the inventive acrylate-olefin copolymer of the present invention has a high flash point, which meets the requirements for gear oil applications.

[0196] The effects of different PAO viscosity grades are shown in Table 11 below (PAO4, PAO6, PAO8). Lower grades, such as PAO4, allow for the use of higher amounts of the acrylate-olefin copolymer of the present invention, which further improves the VI and low-temperature performance of the resulting formulation. For formulation F-23 of the present invention, other performance parameters important for industrial gear oil formulations are provided. Strong performance in TOST and RPVOT tests demonstrates good stability against severe thermal-oxidative stress. The low foaming tendency and low corrosivity of the formulation enhance the suitability of the acrylate-olefin copolymer of the present invention in gear oil formulations.

[0197] Table 10: Flash Points of Some High-Viscosity Base Fluids

[0198] Example COC [℃] 256 Ex.53 271 Ex.61 260

[0199] Table 11 320cSt Lubricant Formulations with Base Oils of Different Viscosities

[0200]

[0201] (*) refers to the comparative embodiment.

[0202] (**) Add at the top

[0203] The properties of the polymer without the distillation step are shown in Tables 12 and 13 below, and are at a similar level to the distilled samples (Table 1). When using two different samples, care should be taken to compare the different formulations in PAO8. While "PAO8" exhibits excellent low-temperature performance, "PAO8I" shows slightly inferior low-temperature performance at the improved VI level.

[0204] Table 12: 320cSt Lubricant Formulations with Different High-Viscosity Base Fluids

[0205] Ex.5 F-26 F-27 F-28 F-29 F-30 F-31 F-32 F-33 F-34 F-35 Preparation Ex 53.2 Ex.5 [wt%] 54.2 Ex.49 [wt%] 54.0 Ex.50 [wt%] 53.0 Ex.51 [wt%] 52.4 Ex.54 [wt%] 52.6 Ex.46 [wt%] 52.6 Ex.44 [wt%] 53.6 Ex.45 [wt%] 54.4 Ex.47 [wt%] 53.4 Ex.48 [wt%] 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Hitec �250 [wt%] 44.8 43.8 44.0 45.0 45.6 45.4 45.5 44.4 43.4 44.4 PAO8 I [wt%] 318.8 320.2 322.1 317.7 317.7 316.6 321.1 323.9 322.5 323.3 KV40 [cSt] 39.3 38.6 39.1 39.1 39.2 39.2 38.9 37.7 39.3 39.6 KV100 [cSt] 175 172 173 175 176 176 173 178 174 175 VI 89k 116k 102k 102k 96k 97k 114k 124k 102k 93k BF-30 [cP] -39 -39 -39 -39 -39 -39 -39 -36 -39 -39 [[ID=8l]]PP [℃] 6.3 2.4 3.1 4.7 5.0 5.7 4.8 2.8 3.4 4.3

[0206] “k” refers to thousand (10 3 For example, BF-30[cP]89k cP=89,000cP Table 13 320cSt lubricant formulations with different high viscosity base fluids.

[0207] SL KRL100 100℃ [%] F-36 F-37* F-38* F-39 F-40 F-41 F-42 Preparation Ex. 60.0 Ex.31 [wt%] 50.0 Ex12* [wt%] 71.8 Ex13* [wt%] 53.8 Ex.32 [wt%] 63.5 Ex.33 [wt%] 57.7 Ex.52 [wt%] 52.1 Ex.8 [wt%] 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Hitec 3250 [wt%] 38.0 48.0 26.2 44.2 34.5 40.3 45.9 PAO8 [wt%] 323.0 322.0 323.2 323.6 322.8 322.8 319.6 KV40 [cSt] 41.1 36.6 44,2 39.5 41.7 38.7 38.1 KVl00 [cSt] 182 162 195 174 185 171 170 VI 95,000 140,000 BF-3 [cP] 96,000 84,000 104,000 104,000 solid -48 -42 -18 -45 -48 -48 -45 PP [℃] 2.7 SL KRL20 100℃ [%] n.m. 1.6 5.2 2.2 3.6 3.5

Claims

1. Copolymer, comprising: a) Based on the total weight of the copolymer, 65 to 90% by weight of monomer units derived from at least one acrylate of formula (I), R1 refers to a linear or branched alkyl group containing 6 to 12 carbon atoms. b) Based on the total weight of the copolymer, 10 to 35% by weight of monomer units derived from at least one nonfunctionalized α-olefin of formula (II), R2 refers to a linear alkyl group containing 6 to 16 carbon atoms. and c) Based on the total weight of the copolymer, 0 to 10% by weight of monomer units derived from at least one monomer, said monomer being selected from a list of methacrylamide, fumarate, maleate, or mixtures thereof, and The copolymer described herein has a kinematic viscosity of 80 to 600 cSt at 100°C according to ASTM D 445, and Based on the total weight of the copolymer, the copolymer contains 0 to 22% by weight of monomer units derived from monomers having linear alkyl groups containing more than 8 carbon atoms.

2. The copolymer of claim 1, wherein, based on the total weight of the copolymer, the copolymer comprises 0 to 20% by weight of monomer units derived from monomers having linear alkyl groups having more than 8 carbon atoms.

3. The copolymer of claim 2, wherein, based on the total weight of the copolymer, the copolymer comprises 0 to 18% by weight of monomer units derived from monomers having linear alkyl groups having more than 8 carbon atoms.

4. The copolymer of claim 1, wherein the copolymer has a kinematic viscosity of 100 to 500 cSt at 100°C according to ASTM D 445.

5. The copolymer of claim 4, wherein the copolymer has a kinematic viscosity of 150 to 400 cSt at 100°C according to ASTM D 445.

6. The copolymer of claim 4, wherein the copolymer has a kinematic viscosity of 150 to 350 cSt at 100°C according to ASTM D 445.

7. The copolymer of claim 1, wherein the copolymer comprises 10 to 30% by weight of monomeric units b) of a nonfunctionalized α-olefin derived from formula (II), based on the total weight of the copolymer.

8. The copolymer of claim 7, wherein the copolymer comprises 10 to 25% by weight of monomeric units b) of nonfunctionalized α-olefins derived from formula (II), based on the total weight of the copolymer.

9. The copolymer according to claim 1, wherein the nonfunctionalized α-olefin (b) of formula (II) is selected from decene, dodecene, tetradecene, hexadecene, or mixtures thereof.

10. The copolymer of claim 1, wherein R1 in the acrylate of formula (I) is a linear or branched alkyl group containing 6 to 10 carbon atoms.

11. The copolymer of claim 10, wherein R1 in the acrylate of formula (I) is a linear or branched alkyl group containing 8 to 10 carbon atoms.

12. The copolymer of claim 10, wherein the acrylate of formula (I) is selected from 2-ethylhexyl acrylate, 2-propylheptyl acrylate, n-octyl acrylate or mixtures thereof.

13. The copolymer of claim 1, wherein the copolymer comprises 0 to 7% by weight of monomer units derived from monomer c), based on the total weight of the copolymer.

14. The copolymer of claim 13, wherein the copolymer comprises 0 to 5% by weight of monomer units derived from monomer c), based on the total weight of the copolymer.

15. The copolymer of claim 13, wherein the copolymer comprises 0 to 3% by weight of monomer units derived from monomer c), based on the total weight of the copolymer.

16. The copolymer of claim 1, wherein, based on the total weight of the copolymer, the total amount of monomer units derived from monomers a) and b) in the copolymer is at most 90 by weight.

17. The copolymer of claim 16, wherein, based on the total weight of the copolymer, the total amount of monomer units derived from monomers a) and b) in the copolymer is at most 95% by weight.

18. The copolymer of claim 16, wherein, based on the total weight of the copolymer, the total amount of monomer units derived from monomers a) and b) in the copolymer is at most 98 by weight.

19. The copolymer of claim 1, wherein, based on the total weight of the copolymer, the total amount of monomer units derived from monomers a), b) and c) in the copolymer is at most 90% by weight.

20. The copolymer of claim 19, wherein, based on the total weight of the copolymer, the total amount of monomer units derived from monomers a), b) and c) in the copolymer is at most 95% by weight.

21. The copolymer of claim 19, wherein, based on the total weight of the copolymer, the total amount of monomer units derived from monomers a), b) and c) in the copolymer is at most 98 by weight.

22. The copolymer of claim 19, wherein, based on the total weight of the copolymer, the total amount of monomer units derived from monomers a), b) and c) in the copolymer is at most 100 by weight.

23. The copolymer of claim 1, wherein the copolymer has a weight-average molecular weight of 5,000 to 30,000 g / mol according to DIN 55672-1.

24. The copolymer of claim 23, wherein the copolymer has a weight-average molecular weight of 7,000 to 25,000 g / mol according to DIN 55672-1.

25. The copolymer of claim 23, wherein the copolymer has a weight-average molecular weight of 8,000 to 20,000 g / mol according to DIN 55672-1.

26. The copolymer of claim 1, wherein the copolymer has a PDI of 1 to 4.

27. The copolymer of claim 26, wherein the copolymer has a PDI of 1.5 to 3.

5.

28. The copolymer of claim 1, wherein the copolymer has a COC flash point greater than 250°C according to ASTM D92.

29. A method for preparing a copolymer as defined in any one of claims 1-28, wherein the method comprises the following steps: i) Provide monomer compositions, ii) Initiate free radical polymerization in the monomer composition to obtain the copolymer.

30. A lubricant composition comprising one or more base oils and at least one copolymer according to any one of claims 1-28.

31. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or a synthetic base fluid in a lubricating oil composition.

32. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or a synthetic base fluid in gear oil compositions.

33. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or a synthetic base fluid in a transmission fluid composition.

34. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or a synthetic base fluid in a hydraulic oil composition.

35. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or synthetic base fluid in an engine oil composition.

36. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or synthetic base fluid in marine oil compositions.

37. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or a synthetic base fluid in industrial lubricating oil compositions.

38. Use of the copolymer according to any one of claims 1-28 as a lubricant additive or a synthetic base fluid in greases.

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