Acrylate-olefin copolymers as high viscosity base fluids

Abstract

Acrylate-olefin copolymers and a method for the preparation of these copolymers are provided. Lubricant compositions can contain the aforementioned copolymers. The copolymers are useful as a lubricant additive or a 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 grease.

Claims

1. A copolymer, comprising: a) 70 to 95% by weight, based on a total weight of the copolymer, of monomer units derived from an acrylate of formula (I), ##STR00007## wherein R.sub.1 means a linear or branched alkyl group having from 4 to 18 carbon atoms and is selected from the group consisting of a C.sub.4 linear alkyl group, a C.sub.6-C.sub.10 linear alkyl group, a C.sub.8-C.sub.18 branched alkyl group, a C.sub.11-C.sub.18 linear alkyl group, and a mixture thereof, and wherein the monomer units derived from the acrylate of formula (I) comprises 0 to 45% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.4 linear alkyl group; 0 to 95% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.6-C.sub.10 linear alkyl group; 0 to 95% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.8-C.sub.18 branched alkyl group; 0 to 45% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.11C.sub.18 linear alkyl group; or a mixture thereof, based on the total weight of the copolymer, b) 5 to 30% by weight, based on the total weight of the copolymer, of monomer units derived from at least one non-functionalized alpha-olefin of formula (II), ##STR00008## wherein R.sub.2 means a linear alkyl group having from 2 to 4 carbon atoms, and wherein the copolymer has a weight-average molecular weight from 5,000 to 35,000 g/mol according to DIN 55672-1.

2. The copolymer according to claim 1, wherein the copolymer comprises from 75 to 95% by weight of monomer units a) derived from the acrylate of formula (I), based on the total weight of the copolymer.

3. The copolymer according to claim 1, wherein the copolymer comprises from 5 to 25% by weight of monomer units b) derived from the at least one non-functionalized alpha-olefin of formula (II), based on the total weight of the copolymer.

4. The copolymer according to claim 1, wherein the copolymer has a kinematic viscosity from 100 to 1,000 mm.sup.2/s at 100? C. according to ASTM D 445.

5. The copolymer according to claim 1, wherein the at least one non-functionalized alpha-olefin of formula (II) is selected from the group consisting of butene, hexene, and a mixture thereof.

6. The copolymer according to claim 1, wherein the amount of the acrylate of formula (I) wherein R.sub.1 is a C.sub.4 linear alkyl group is 0 to 40% by weight, based on the total weight of the copolymer.

7. The copolymer according to claim 1, wherein the acrylate of formula (I) is selected from the group consisting of butyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, 2-propylheptyl acrylate, isononyl acrylate, lauryl acrylate, and a mixture thereof.

8. The copolymer according to claim 1, wherein the copolymer further comprises 0 to 20% by weight of monomer units derived from monomer c) selected from the group consisting of methacrylamides, fumarates, maleates, (meth)acrylates other than the acrylate of formula (I), and a mixture thereof, based on the total weight of the copolymer.

9. The copolymer according to claim 1, wherein the total amount of monomer units derived from monomers a) and b) in the copolymer sums up to 80% by weight or more, based on the total weight of the copolymer.

10. The copolymer according to claim 8, wherein the total amount of monomer units derived from monomers a), b), and c) in the copolymer sums up to 90% by weight or more, based on the total weight of the copolymer.

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

12. The copolymer according to claim 1, wherein the copolymer has a polydispersity index from 1.0 to 3.5.

13. A method for the preparation of the copolymer as defined in claim 1, the method comprising: i) providing a monomer composition, and ii) initiating radical polymerization in the monomer composition to obtain the copolymer.

14. A lubricant composition, comprising: one or more base oil, and at least one copolymer according to claim 1.

15. A method, comprising: adding the copolymer according to claim 1, as a lubricant additive or synthetic base fluid, to a lubricating oil composition.

16. The method according to claim 15, wherein the lubricating oil composition is 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 grease.

17. The copolymer according to claim 4, wherein the copolymer has a kinematic viscosity from 100 to 500 mm.sup.2/s at 100? C. according to ASTM D 445.

18. The copolymer according to claim 8, wherein the copolymer comprises 0 to 10% by weight of the monomer units derived from monomer c), based on the total weight of the copolymer.

19. The copolymer according to claim 9, wherein the total amount of monomer units derived from monomers a) and b) in the copolymer sums up to 90% by weight or more, based on the total weight of the copolymer.

20. The copolymer according to claim 10, wherein the total amount of monomer units derived from monomers a), b), and c) in the copolymer sums up to 100% by weight, based on the total weight of the copolymer.

21. A method according to claim 13, wherein a total amount of radical initiator used relative to the total weight of the monomer composition is 0.01 to 1% by weight.

22. The lubricant composition of claim 14, comprising 1 to 95% of the at least one base oil and 5 to 99% by weight of the at least one copolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Copolymer According to the Invention

(2) The present invention relates to a copolymer comprising: a) 70 to 95% by weight, based on the total weight of the copolymer, of monomer units derived from an acrylate of formula (I),

(3) ##STR00003## wherein R.sub.1 means a linear or branched alkyl group having from 4 to 18 carbon atoms and is selected from the group consisting of a C.sub.4 linear alkyl group, a C.sub.6-C.sub.10 linear alkyl group, a C.sub.8-C.sub.18 branched alkyl group, a C.sub.11-C.sub.18 linear alkyl group or a mixture thereof, and wherein the monomer units derived from the acrylate of formula (I) are selected from 0 to 45% by weight of an acrylate of formula (I) wherein R; is a C.sub.4 linear alkyl group, 0 to 95% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.6-C.sub.10 linear alkyl group, 0 to 95% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.8-C.sub.18 branched alkyl group. 0 to 45% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.11-C.sub.18 linear alkyl group, or a mixture thereof, based on the total weight of the copolymer, b) 5 to 30% by weight, based on the total weight of the copolymer, of monomer units derived from at least one non-functionalized alpha-olefin of formula (II),

(4) ##STR00004## wherein R.sub.2 means a linear alkyl group having from 2 to 4 carbon atoms,

(5) and wherein the copolymer has a weight-average molecular weight from 5,000 to 35,000 g/mol according to DIN 55672-1.

(6) The terms polymer and copolymer are used interchangeably to define the copolymer according to the present invention.

(7) According to the present invention, the copolymer of the invention comprises 70 to 95% by weight, based on the total weight of the copolymer, of monomer units a) derived from acrylate monomer of formula (I). According to one aspect of the invention, it is preferred that the copolymer comprises from 75 to 95% by weight, more preferably from 80 to 95% by weight, of monomer units a) derived from acrylate monomer of formula (I), based on the total weight of the copolymer.

(8) The acrylates a) of formula (I) refer to esters of acrylic acid with straight chain or branched alcohols having 4 to 18 carbon atoms. The term encompasses individual acrylic esters with an alcohol of a particular length, and likewise mixtures of acrylic esters with alcohols of different lengths. The acrylates a) of formula (I) are selected from the group consisting of acrylates having a C.sub.4 linear alkyl group, a C.sub.6-C.sub.10 linear alkyl group, a C.sub.8-C.sub.18 branched alkyl group, a C.sub.11-C.sub.18 linear alkyl group or a mixture thereof. The monomer units derived from the acrylate of formula (I) are selected from 0 to 45% by weight, preferably 0 to 40% by weight, more preferably 0 to 30% by weight, of an acrylate of formula (I) wherein R.sub.1 is a C.sub.4 linear alkyl group; 0 to 95% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.6-C.sub.10 linear alkyl group: 0 to 95% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.8-C.sub.18 branched alkyl group; 0 to 45% by weight of an acrylate of formula (I) wherein R.sub.1 is a C.sub.11-C.sub.18 linear alkyl group; or a mixture thereof, based on the total weight of the copolymer.

(9) The acrylate a) of formula (I), wherein R.sub.1 is a C.sub.4 linear alkyl group, corresponds to butyl acrylate.

(10) Most preferred acrylate a) of formula (I), wherein R.sub.1 is a C.sub.6-C.sub.10 linear alkyl group, is n-octyl acrylate.

(11) Most preferred acrylates a) of formula (I), wherein R.sub.1 is a C.sub.8-C.sub.18 branched alkyl group, are 2-ethylhexyl acrylate, 2-propylheptyl acrylate, isononyl acrylate, or a mixture thereof.

(12) Most preferred acrylate a) of formula (I), wherein R.sub.1 is a C.sub.11-C.sub.18 linear alkyl group, is lauryl acrylate.

(13) Particularly preferred acrylates a) of formula (I) are selected from the group consisting of butyl acrylate, n-octyl acrylate. 2-ethylhexyl acrylate, 2-propylheptyl acrylate, isononyl acrylate, lauryl acrylate, or a mixture thereof.

(14) According to the present invention, the copolymer of the invention comprises 5 to 30% by weight, based on the total weight of the copolymer, of monomer units derived from at least one non-functionalized alpha-olefin of formula (II), wherein R.sub.2 means a linear alkyl group having from 2 to 4 carbon atoms. According to one aspect of the invention, it is preferred that the copolymer comprises from 5 to 25% by weight, more preferably from 5 to 20% by weight, of monomer units b) derived from at least one non-functionalized alpha-olefin of formula (II), based on the total weight of the copolymer.

(15) Most preferred non-functionalized alpha-olefins b) of formula (II) are selected from the group consisting of butene, hexene or a mixture thereof.

(16) According to another aspect of the invention, it is preferred that the copolymer has a kinematic viscosity from 100 to 1,000 mm.sup.2 is at 100? C. according to ASTM D 445, more preferably from 100 to 700 mm.sup.2/s at 100? C. according to ASTM D 445, even more preferably from 100 to 500 mm.sup.2/s at 100? C. according to ASTM D 445.

(17) 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 sums up to 80% by weight or more, more preferably sums up to 90% by weight or more, even more preferably sums up to 95% by weight or more, most preferably sums up to 98% by weight or more, most preferably sums up to 100% by weight, based on the total weight of the copolymer.

(18) According to the present invention, the copolymer has a weight-average molecular weight from 5,000 to 35,000 g/mol, preferably from 7,000 to 25,000 g/mol, more preferably from 8,000 to 25,000 g/mol, even more preferably from 10,000 to 25,000 g/mol, according to DIN 55672-1.

(19) In the present invention, the weight-average molecular weights (M.sub.w) or number-average molecular weights (M.sub.n) of the copolymers were determined by gel permeation chromatography (GPC) using PMMA calibration standards according to DIN 55672-1 using the following measurement conditions: Eluent: tetrahydrofuran (THF) Operation temperature: 35? C. Columns: the column set consists of four columns: two columns SDV 106 ?, one column SDV 104 ? and one column SDV 103 ? (PSS Standards Service GmbH, Mainz, Germany), all with the size of 300?8 mm and an average particle size of 10 ?m Flow rate: 1 mL/min Injected volume: 100 ?L Instrument: Agilent 1100 series consisting of an autosampler, pump and column oven Detection device: a refractive index detector from Agilent 1100 series.

(20) Preferably, the copolymers of the invention have a very low degree of cross-linking and a narrow molecular weight distribution, which further contributes to the shear resistance. The low degree of crosslinking and the narrow molecular weight are reflected in the polydispersity index of the copolymers. Preferably, the polydispersity index (PDI) of the copolymers according to the invention is in the range of 1.0 to 3.5, more preferably in the range of 1.5 to 3.0. A polydispersity index in the range of 1.0 to 3.5 is considered optimal for most industrial applications with regard to the shear resistance of the copolymers. The polydispersity index is defined as the ratio of weight-average molecular weight to number-average molecular weight (M.sub.w/M.sub.n).

(21) The copolymers of the invention optionally comprise monomer units derived from monomer c), which is selected from the list consisting of methacrylamides, fumarates, maleates, (meth)acrylates other than acrylates a), or a mixture thereof. Preferably, the amount of monomer units derived from monomer c) in the resulting copolymer of the invention is from 0 to 20% by weight, more preferably from 0 to 10% by weight, even more preferably from 0.1 to 5% by weight, most preferably from 0.5 to 3% by weight, based on the total weight of the copolymer. Particularly preferred monomers c) are di-2-ethylhexyl maleate, N-3-dimethylamino propyl methacrylamide, di-2-ethylhexyl fumarate or a mixture thereof.

(22) The term (meth)acrylate refers to esters of acrylic acid, esters of methacrylic acid or a mixture of esters of acrylic acid and methacrylic acid.

(23) 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 sums up to 90% by weight or more, more preferably sums up to 95% by weight or more, even more preferably sums up to 98% by weight or more, most preferably sums up to 100% by weight, based on the total weight of the copolymer.

(24) According to the invention, the copolymer is a statistical copolymer, wherein the monomeric units a), b) and optionally c) are distributed randomly, and sometimes unevenly, in the copolymer.

(25) Surprisingly, it was observed that the combination of monomer units a) of formula (I) with short chain alpha olefin monomer units b) of formula (II) in the copolymer, allows to prepare copolymers with great properties when used as an additive or a base fluid in a lubricant oil formulation. As shown in the experimental part of the present invention, the acrylate-olefin copolymers of the present invention, obtained from a monomer composition combining short olefins with specific acrylate monomers, meet the strict low-temperature requirements of market lubricant formulations, even at low polymer treat rates, without compromising on other performance parameters. Unexpectedly, it was also found that the specific weight ratio combination of acrylate monomers as described with short-chain C.sub.4-C.sub.6 alpha-olefins are crucial to achieve a combination of high VI and good low temperature properties.

(26) Preferable Copolymers of the Invention

(27) According to a preferred aspect of the invention, the copolymer comprises: a) 70 to 95% by weight, based on the total weight of the copolymer, of monomer units derived from an acrylate of formula (I),

(28) ##STR00005## wherein R.sub.1 means a linear or branched alkyl group having from 4 to 18 carbon atoms and the monomer units derived from the acrylate of formula (I) are selected from 0 to 30% by weight of butyl acrylate, 0 to 95% by weight of n-octyl acrylate, 0 to 95% by weight of 2-ethylhexyl acrylate, 2-propylheptyl acrylate, isononyl acrylate or a mixture thereof, and 0 to 45% by weight of lauryl acrylate, or a mixture thereof, based on the total weight of the copolymer, b) 5 to 30% by weight, based on the total weight of the copolymer, of monomer units derived from at least one non-functionalized alpha-olefin of formula (II),

(29) ##STR00006## wherein R.sub.2 means a linear alkyl group having from 2 to 4 carbon atoms, and c) 0 to 10% by weight, based on the total weight of the copolymer, of monomer units selected from the list consisting of methacrylamides, fumarates, maleates, (meth)acrylates other than acrylates a), or a mixture thereof,

(30) and wherein the copolymer has a weight-average molecular weight from 5,000 to 35,000 g/mol, preferably from 7,000 to 25,000 g/mol, even more preferably from 8,000 to 25,000 g/mol, most preferably from 10,000 to 25,000 g/mol, according to DIN 55672-1.

(31) According to a preferred embodiment, the total content of monomer units of monomers a), b) and c) sums up to 95% by weight or more, more preferably 98% by weight or more, even more preferably 100% by weight, based on the total weight of the copolymer.

(32) Method for Preparing the Copolymer According to the Invention

(33) According to the present invention, the above-mentioned polymers are prepared following the method comprising the steps of: i) providing a monomer composition as described above; and ii) initiating radical polymerization in the monomer composition.

(34) Standard free-radical polymerization is detailed, inter alia, in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition. In general, a polymerization initiator and optionally a chain transfer agent are used for this purpose.

(35) The polymerization step (ii) can be conducted under standard pressure, reduced pressure or elevated pressure. Preferably, the polymerization is conducted at a pressure range from standard pressure to 50 bar, preferably from standard pressure to 40 bar. In the context of the present invention, the term standard pressure means no added pressure, but ambient or atmospheric pressure.

(36) For the radical copolymerization of olefins with acrylates, the polymerization temperature is critical. In general, the copolymerization temperature is in the range from 110 to 160? C., preferably from 120 to 140? C.

(37) The polymerization step ii) may be performed with or without dilution in oil or any solvent. Preferably, the polymerization step (ii) is made without dilution in oil or any solvent.

(38) Preferably, step (ii) comprises the addition of a radical initiator. Preferably, the radical initiator is selected from di-tert-amyl-peroxide, 2,2-di-(tert-butylperoxy) butane, 1,1-di-tert-butylperoxy-3.3.5-trimethylcyclohexane or di-tert-butyl-peroxide. Preferably, the total amount of radical initiator relative to the total weight of the monomer mixture is 0.01 to 5% by weight, more preferably 0.1 to 1% by weight. Preferably, the total amount of radical initiator is added continuously over the course of the copolymerization reaction (ii).

(39) Preferably, the copolymerization step (ii) is made by feeding the acrylate monomers a), and optionally the monomers c) or any other comonomers, together with the initiator to the non-functionalized alpha-olefin monomers b). Preferably, the total reaction time of the radical polymerization is 2 to 5 hours, more preferably 2 to 4 hours, most preferably 3 hours.

(40) In another preferred aspect of the invention, a third step iii) is optionally performed, corresponding to a distillation step to remove the unreacted alpha-olefin monomer b). Preferably, residual unreacted alpha-olefin monomer b) is removed by distillation at 130C and pressures as low as 15 mbar using a rotary evaporator.

(41) Lubricating Oil Compositions

(42) As indicated above, the present invention also relates to a lubricating oil composition comprising at least one base oil and at least one copolymer as defined in the present invention.

(43) The base oils correspond to lubricant base oils, mineral, synthetic or natural, animal or vegetable oils suited to their use/chosen depending on the intended use.

(44) The base oils used in formulating the lubricating oil compositions according to the present invention include, for example, conventional base stocks selected from API (American Petroleum Institute) base stock categories known as Group I, Group II, Group III, Group IV and Group V. The Group I and II base stocks are mineral oil materials (such as paraffinic and naphthenic oils) having a viscosity index (or VI) of less than 120. Group I is further differentiated from Group II in that the latter contains greater than 90% saturated materials and the former contains less than 90% saturated material (that is more than 10% unsaturated material). Group III is considered the highest level of mineral base oil with a VI of greater than or equal to 120 and a saturates level greater than or equal to 90%. Group IV base oils are polyalphaolefins (PAO). Group V base oils are esters and any other base oils not included in Group I to IV base oils. These base oils can be used individually or as a mixture.

(45) Preferably, the base oil included in the lubricating oil composition of the present invention is selected from the group consisting of an API Group II base oil, an API Group III base oil or a mixture thereof.

(46) Most preferably, the lubricant composition comprises an API Group III base oil or a mixture thereof. In a preferred embodiment of the invention, the lubricating oil composition comprises from 0.1 to 99.9% by weight, preferably from 1 to 95% by weight, of at least one base oil and from 0.1 to 99.9% by weight, preferably from 5% to 99% by weight, of at least one copolymer according to the present invention, based on the total weight of the lubricating composition.

(47) The lubricating oil compositions according to the present invention may also comprise any other additional additives suitable for use in the formulations. These additives include additional viscosity index improvers, pour point depressants, dispersants, demulsifiers, defoamers, lubricity additives, friction modifiers, antioxidants, detergents, dyes, corrosion inhibitors and/or odorants.

(48) Applications for the Copolymer of the Invention

(49) The invention also relates to the use of the copolymer according to the present invention as a lubricant additive or a 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 grease.

(50) Experimental Part

(51) The invention is further illustrated in detail hereinafter with reference to examples and comparative examples, without any intention to limit the scope of the present invention. All percentages in relation to monomers or base fluids given in the tables below are weight percentages (wt %).

Abbreviations

(52) Anglamol 6043 additive package BA butyl acrylate But 1-butene BF-40 Brookfield viscosity measured at ?40? C. in accordance with ASTM D2983 BV bulk viscosity BV100 bulk viscosity @100? C. in accordance with ASTM D445 C.sub.2 Acr C.sub.2 alkyl acrylate C.sub.4 Acr C.sub.4 linear alkyl acrylate C.sub.6-C.sub.10 Acr C.sub.6-C.sub.10 linear alkyl acrylate C.sub.8-C.sub.18 b-Acr C.sub.8-C.sub.18 branched alkyl acrylate C.sub.11-C.sub.18 Acr C.sub.11-C.sub.18 linear alkyl acrylate cSt centistokes corresponding to mm.sup.2/s in SI units cP centipoise corresponding to mPa.Math.s in SI units DAPO di-tert-amyl peroxide DBPO di-tert-butyl peroxide Dec 1-decene EA ethyl acrylate EHA 2-ethylhexyl acrylate Hex 1-hexene INA isononyl acrylate Ini initiator KRL Tapered Roller Bearing Shear Stability Test according to CEC L-45-A-99 KV kinematic viscosity measured according to ASTM D445 KV.sub.40 kinematic viscosity measured @40? C. to ASTM D445 KV.sub.100 kinematic viscosity measured @100? C. to ASTM D445 LA lauryl acrylate or dodecyl acrylate M.sub.n number-average molecular weight M.sub.w weight-average molecular weight n.m. not measured nOA n-octyl acrylate PDI polydispersity index PPD pour point depressant SL shear loss determined at 100? C. after KRL (20 hours run at 60? C.) VI viscosity index VPL 1-300 Evonik VISCOPLEX? 1-300, polyalkylmethacrylate pour point depressant Yubase 4 Group III base oil from SK Lubricants with a KV.sub.100 of 4 mm.sup.2/s Yubase 6 Group III base oil from SK Lubricants with a KV.sub.100 of 6 mm.sup.2/s Yubase 8 Group III base oil from SK Lubricants with a KV.sub.100 of 8 mm.sup.2/s

(53) Test Methods KV ASTM D445 VI ASTM D2270 KRL CEC L-45-A-99 BF ASTM D2983

(54) In the present invention, the bulk viscosity (BV) of the polymer (product obtained from polymerization reaction) corresponds to the kinematic viscosity (KV) of the resulting product of the polymerization measured in accordance with ASTM D445. Thus, the bulk viscosity of the polymers (BV100) as shown in Table 2 below, were measured as kinematic viscosity at 100? in accordance with ASTM D445.

(55) The solubility of each polymer in oil was tested by mixing 20% by weight of polymer in 80% by weight of Yubase 4 base oil. A polymer is considered not to be soluble when a hazy or two-phase mixture is obtained. The result of this solubility test in oil for each polymer is also shown in Table 2 below.

EXAMPLES

Synthesis 1: Acylate-Hexene Copolymer (Ex. 1)

(56) 6.99 g of DAPO (1.0 wt % relative to the acrylate in the feed) mixed with 707.8 g EHA was slowly fed to 486.2 g of 1-hexene in 170.4 g heptane (25:75 solvent to olefin monomer) under nitrogen at 130? C. for 3 hours. After stirring for another hour, the resulting clear and colorless polymer was cooled down and filtered under pressure using a filter aid. Subsequently, the residual hexene was removed by distillation at 130? C. and at a pressure of less than 15 mbar using a rotary evaporator. The amount of monomer incorporated in the polymer is determined by NMR analysis.

(57) Inventive examples 3 and 4, as well as comparative examples 2* to 5*, were prepared in the same way as inventive example 1, except that the amounts of reactants and/or other reaction conditions were changed as listed in Tables 1 and 2. For inventive example 4 and comparative example 5*, the reaction mixtures after the feed and stirring steps were heated at 140? C. for 30 minutes before cooling. Furthermore, comparative example 4* was prepared with 2,2-di-(tert-butylperoxy) butaneas initiator and comparative example 3* with 1,1-di-tert-butylperoxy-3,3,5-trimethylcyclohexane as initiator.

Synthesis 2: Acrylate-Butene Copolymer (Ex.2)

(58) 2.3 g of DAPO (0.3 wt % relative to the acrylate in the feed) mixed with 766 g EHA was slowly fed to 457 g of 1-butene under nitrogen at 130? C. for 3 hours. After stirring for another hour, the resulting clear and colorless polymer was cooled down and filtered under pressure using a filter aid. Subsequently, the residual monomer was removed by distillation at 130? and at a pressure of less than 15 mbar using a rotary evaporator. The amount of monomer incorporated in the polymer is determined by NMR analysis.

Synthesis 3: Acrylate-Hexene Copolymer with Acrylate Mixture (Ex.5)

(59) 4.63 g of DAPO (0.7 wt % relative to the acrylate in the feed) mixed with 335.7 g EHA and 323.7 g LA was slowly fed to 511.4 g of 1-hexene in 184.9 g heptane (25:75 solvent to olefin monomer) under nitrogen at 130? C. for 3 hours. After stirring for another hour, the resulting clear and colorless polymer was cooled down and filtered under pressure using a filter aid. Subsequently, the residual hexene was removed by distillation at 130? C. and at a pressure of less than 15 mbar using a rotary evaporator. The amount of monomer incorporated in the polymer is determined by NMR analysis.

(60) Inventive examples 5 to 11, as well as comparative examples 6* to 9* were prepared in the same way as inventive example 5, except that the amounts of reactants and/or other reaction conditions were changed as listed in Tables 1 and 2. For inventive examples 9 to 11, the reaction mixtures after the feed and stirring steps were heated at 140? C. for 30 minutes before cooling. Furthermore, inventive example 9 was prepared with 2,2-di-(tert-butylperoxy) butane as initiator.

Synthesis 4: Acrylate-Hexene Copolymer Synthesis with 2-Step Addition of the Initiator Ex.12)

(61) 5.94 g of DAPO (0.7 wt % relative to the acrylate in the feed) were used in total. ?.sup.th of the initiator was mixed with 536.3 g 1-hexene and charged to the reactor. The remaining ?.sup.th of the initiator mixed with 842.0 g INA was then slowly fed to the reactor under nitrogen at 130? C. for 3 hours. After stirring for another hour, the reaction mixture was heated at 140? C. for 30 minutes. Then, the resulting clear and colorless polymer was cooled down and filtered under pressure using a filter aid. Subsequently, the residual hexene was removed by distillation at 130? C. and at a pressure of less than 15 mbar using a rotary evaporator. The amount of monomer incorporated in the polymer is determined by NMR analysis.

(62) Inventive example 13 was prepared in the same way as inventive example 12, except that the amounts of reactants and other reaction conditions were changed as listed in Tables 1 and 2.

Synthesis 5: Acrylate-Long-Chain Olefin Copolymer (Ex. 1*)

(63) 18 g of DBPO (0.3 wt % relative to the acrylate in the feed) dissolved in 6,000 g EHA was slowly fed to 1,500 g of 1-decene under nitrogen at 160? C. within 3 hours. After the feed had been finalized and stirring for 2 hours at 160? C., the resulting clear and colorless polymer was cooled down. Subsequently, the residual olefin was removed by distillation at 160? C. and pressures as low as 10 mbar using a rotary evaporator. The amount of decene incorporated in the polymer is determined gravimetrically assuming that no residual acrylate monomer is present.

(64) Further details regarding the synthetic procedures of the individual examples are provided in Tables 1 and 2 together with basic properties of the polymers. In the context of the invention, the term Solvent to olefin monomer describes the approximate volume ratio between the solvent and all non-functionalized alpha-olefin monomers b). The term Olefin eq is defined as the molar equivalent of olefin to acrylate. The alpha-olefin monomers are always first charged to the reactor. The acrylate monomers and the initiator are then fed over a set period of time. For acrylate-olefin copolymers with acrylate mixtures, all acrylates were mixed with the initiator before feeding to the olefin. The temperatures given in Table 1 correspond to the reaction temperature during the acrylate/initiator feed.

(65) Formulations comprising the inventive and comparative polymers of Table 2 were then prepared with the amounts of components as shown in Tables 3 and 4. The properties of the different formulations such as viscosity index, kinematic, viscosity, Brookfield viscosity and shear loss are also shown in Tables 3 and 4. The target was to get formulations fulfilling SAE 75W-90 standard (SAE is the organization Society of Automotive Engineers). Table 5 shows the properties of some formulations prepared using some comparative polymers of Table 2, which do not meet the requirements of 75W-90 formulations.

(66) TABLE-US-00001 TABLE 1 Polymerization conditions for the preparation of acrylate-olefin copolymers Ini T Solvent to Olefin Ex# Acrylate Olefin [wt %] [? C.] olefin monomer eq Inventive Ex. 1 EHA Hex 1.0 130 25:75 1.5 Examples Ex. 2 EHA But 0.3 130 0:100 2 Ex. 3 nOA Hex 0.7 130 25:75 2 Ex. 4 nOA Hex 0.7 130 25:75 2 Ex. 5 EHA + LA Hex 0.7 130 25:75 2 Ex. 6 EHA + LA Hex 0.7 130 25:75 2 Ex. 7 EHA + LA Hex 0.7 130 25:75 2 Ex. 8 BA + EHA + LA Hex 0.7 130 25:75 2 Ex. 9 BA + EHA + LA Hex 0.5 125 0:100 2 Ex. 10 nOA + EHA Hex 0.7 130 25:75 2 Ex. 11 nOA + EHA Hex 0.7 130 25:75 2 Ex. 12 INA Hex 0.7 130 0:100 1.5 Ex. 13 INA Hex 1.0 130 25:75 1.5 Comparative Ex. 1* EHA Dec 0.3 160 0:100 0.33 Examples Ex. 2* EA Hex 0.7 130 25:75 2 Ex. 3* BA Hex 1.0 130 25:75 1.5 Ex. 4* BA Hex 0.7 125 0:100 2 Ex. 5* LA Hex 0.7 130 25:75 2 Ex. 6* EA + EHA Hex 1.0 130 25:75 2 Ex. 7* BA + EHA Hex 0.7 130 25:75 2 Ex. 8* BA + LA Hex 0.5 130 50:50 2 Ex. 9* EHA + LA Hex 0.5 130 50:50 2

(67) TABLE-US-00002 TABLE 2 Polymer properties of the prepared acrylate-olefin copolymers incorpo- incorporated acrylate [wt %] rated C.sub.2 C.sub.4 C.sub.6-C.sub.10 C.sub.8-C.sub.18 C.sub.11-C.sub.18 olefin Mw Mn BV100 Oil Ex# Acrylate Olefin Acr Acr Acr b-Acr Acr [wt %] [g/mol] [g/mol] PDI [mm.sup.2/s] solubility Inventive Ex. 1 EHA Hex 84.4 15.6 15,500 6,890 2.26 440.1 soluble Examples Ex. 2 EHA But 92.8 7.2 16,600 6,940 2.32 427.3 soluble Ex. 3 nOA Hex 84.8 15.2 22,200 9,040 2.45 266.4 soluble Ex. 4 nOA Hex 81.4 18.6 16,600 7,300 2.27 182.2 soluble Ex. 5 EHA + LA Hex 44.6 39.9 15.5 17,600 7,810 2.25 206.3 soluble Ex. 6 EHA + LA Hex 69.7 15.5 14.8 15,800 7,070 2.24 300.7 soluble Ex. 7 EHA + LA Hex 75.3 7.9 16.8 14,700 6,620 2.22 307.3 soluble Ex. 8 BA + Hex 18.9 28.1 38.5 14.5 19,100 8,190 2.34 239.0 soluble EHA + LA Ex. 9 BA + Hex 13.4 39.6 28.2 18.7 16,300 7,210 2.26 245.1 soluble EHA + LA Ex. 10 nOA + EHA Hex 41.8 41.3 16.8 15,600 6,940 2.25 244.9 soluble Ex. 11 nOA + EHA Hex 58.7 25.7 15.6 15,300 6,770 2.26 275.1 soluble Ex. 12 INA Hex 86.9 13.1 19,400 7,850 2.47 363.6 soluble Ex. 13 INA Hex 87.5 12.5 14,600 6,440 2.26 252.0 soluble Compar- Ex. 1* EHA Dec 82.0 18.0 15,600 6,190 2.52 279.3 soluble ative Ex. 2* EA Hex 78.7 21.3 19,000 7,580 2.51 n.m. not soluble Examples Ex. 3 BA Hex 78.7 21.3 15,200 6,430 2.37 n.m. not soluble Ex. 4* BA Hex 77.1 22.9 16,800 6,330 2.65 471.8 not soluble Ex. 5* LA Hex 85.6 14.4 18,300 8,980 2.04 150.9 soluble Ex. 6* EA + EHA Hex 17.0 65.2 17.9 16,000 6,810 2.35 492.3 soluble Ex. 7* BA + EHA Hex 46.9 34.9 18.2 18,200 6,960 2.61 454.1 soluble Ex. 8* BA + LA Hex 30.5 56.3 13.2 20,700 8,590 2.41 171.7 soluble Ex. 9* EHA + LA Hex 27.1 59.1 13.8 15,100 6,470 2.33 141.4 soluble

(68) TABLE-US-00003 TABLE 3 75W-90 formulations of acrylate-olefin copolymers Comparative Inventive Examples Example Form. Ex. F-1 F-2 F-3 F-4 F-5 F-1* Ex. 1 [wt %] 29.7 Ex. 2 [wt %] 29.5 Ex. 3 [wt %] 24.3 Ex. 4 [wt %] 26.4 Ex. 12 [wt %] 26.2 Ex. 1* [wt %] 32.0 Anglamol 6043 [wt %] 6.5 6.5 6.5 6.5 6.5 6.5 VPL 1-300 [wt %] 0.5 0.5 0.5 0.5 0.5 0.5 Yubase 4 [wt %] 31.3 33.5 16.8 21.0 Yubase 6 [wt %] 32.0 30.0 68.7 51.6 50.0 40.0 Yubase 8 [wt %] 15.0 KV40 [mm.sup.2/s] 90.9 91.9 88.1 89.2 91.2 90.7 KV100 [mm.sup.2/s] 14.4 14.4 14.7 14.4 14.6 14.4 VI 164 163 174 167 167 164 BF-40 [mPa .Math. s] 115,000 131,000 136,000 130,000 120,000 122,000 SL 100? C. [%] 5.3 5.7 6.7 5.0 6.7 5.0

(69) TABLE-US-00004 TABLE 4 75W-90 formulations comprising inventive acrylate- olefin copolymers prepared with acrylate mixtures Form. Ex. F-6 F-7 F-8 F-9 F-10 F-11 F-12 Ex. 5 [wt %] 29.5 Ex. 6 [wt %] 28.7 Ex. 7 [wt %] 29.4 Ex. 8 [wt %] 28.1 Ex. 9 [wt %] 27.8 Ex. 10 [wt %] 29.0 Ex. 11 [wt %] 29.4 Anglamol 6043 [wt %] 6.5 6.5 6.5 6.5 6.5 6.5 6.5 VPL 1-300 [wt %] 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Yubase 4 [wt %] 23.5 21.3 21.0 24.9 15.2 14.0 13.6 Yubase 6 [wt %] 40.0 43.0 42.6 40.0 50.0 50.0 50.0 KV40 [mm.sup.2/s] 86.1 89.0 89.6 86.1 87.9 89.9 93.0 KV100 [mm.sup.2/s] 14.3 14.2 14.1 14.4 14.1 14.4 14.7 VI 173 164 162 174 166 167 165 BF-40 [mPa .Math. s] 133,000 122,000 122,000 121,000 119,000 120,000 132,000 SL 100? C. [%] 4.3 3.6 3.4 5.4 3.8 5.6 7.0

(70) TABLE-US-00005 TABLE 5 Formulations of comparative acrylate-olefin copolymers with poor low temperature properties, not fulfilling 75W-90 formulation requirements Form. Ex. F-2* F-3* F-4* F-5* F-6* Ex. 5* [wt %] 34.5 Ex. 6* [wt %] 32.0 Ex. 7* [wt %] 31.2 Ex. 8* [wt %] 33.7 Ex. 9* [wt %] 36.6 Anglamol 6043 [wt %] 6.5 6.5 6.5 6.5 6.5 VPL 1-300 [wt %] 0.5 0.5 0.5 0.5 0.5 Yubase 4 [wt %] 58.5 61.0 61.8 59.3 56.4 KV40 [mm.sup.2/s] 79.7 88.3 86.8 78.9 79.4 KV100 [mm.sup.2/s] 14.4 14.1 14.2 14.3 14.2 VI 190 165 170 189 185 BF-40 [mPa .Math. s] solid 700,000 178,000 solid solid

(71) As shown in Table 2 above, the inventive polymers according to the invention are all soluble in oil. In contrast, some comparative polymers are not soluble in oil, such as comparative Ex.2* to 4* with high amounts of C.sub.4 linear alkyl acrylate, or with shorter alkyl acrylates such as ethyl acrylate. Therefore, these comparative examples were not tested in formulations as they do not fulfill the requirement of solubility in oil.

(72) As shown in Tables 3 and 4 above, the 75W-90 formulations comprising the inventive acrylate-olefin copolymers according to the invention deliver optimized viscosity-temperature properties. The inventive copolymers according to the invention used in the formulations have a favorable combination of viscosity (KV40 and KV100), viscosity index (VI), low temperature properties (BF) and shear stability (SL). For some inventive formulations, a reduced treat rate is achieved without negative effects on other formulation properties, especially low temperature viscosity (BF-40) and shear stability (SL 100? C.) which are the most important parameters of the 75W-90 specification. To fulfill the 75W-90 formulation requirements, it is observed that less polymer is required in the formulations using short chain olefin hexene- or butene-containing polymers as thickeners (F-1 and F-2) compared to a formulation comprising a longer chain alpha olefin decene-containing copolymer (F-1*).

(73) Interestingly, the combination of three different alkyl acrylates from Ca linear alkyl group, a C.sub.8-C.sub.18 branched alkyl group, a C.sub.11-C.sub.18 linear alkyl group, such as the polymers of inventive Ex.8 and Ex.9, the copolymers with only one alkyl acrylate with a C.sub.6-C.sub.10 linear alkyl group, such as the inventive polymers Ex.3 and Ex.4, as well as the copolymer with only one alkyl acrylate with a C.sub.8-C.sub.18, branched alkyl group, such as inventive polymer Ex.12, show very low treat rates in 75W-90 formulations (F-9 and F-10, F-3 and F-4, as well as F-5, respectively).

(74) A good high viscosity base fluid needs to combine several properties. An important criterion for high-performance gear oils is the low temperature performance. Aside from a low dependency of the viscosity on the temperature, which is also reflected in the VI, it is important that the polymers do not show strong intermolecular interactions, leading to poor low temperature performance.

(75) Regarding the composition of the copolymers, acrylate-olefin copolymers with acrylate mixtures, combining short- and long-chain as well as branched acrylates, allow to tailor the solubility in the base oil and the low temperature properties (Ex. Table 2). Thereby, the requirements of the 75W-90 specification can be met (Table 4). As aforementioned, combinations of short chain olefins with high amounts of short-chain acrylates (Ex.2*-4*) tend to lead to insolubility in the base oil (Yubase 4) Thus, the defined ranges for the C.sub.4 and C.sub.11-C.sub.18 alkyl acrylates according to the invention need to be met to ensure the fulfilment of the 75W-90 specification. For example, the copolymer with EA/EHA and hexene (Ex.6*) is oil soluble but was not able to fulfill the low temperature requirements of the 75W-90 formulation as shown in Table 5 (F-3*, BF-40=700,000 mPa-s). Furthermore, comparative Ex.7* demonstrate that an amount of an acrylate with C.sub.4 linear alkyl group in the copolymer higher than 45% by weight, more specifically 46.9% by weight, lead to a copolymer which is oil soluble, but does not perform well at low temperature (F-4*. BF-40=178,000 mPa.Math.s).

(76) Comparative acrylate-olefin copolymers comprising high amounts of long chain linear acrylates (C.sub.11-C.sub.18 linear alkyl acrylate), such as lauryl acrylate, show poor low temperature properties as these copolymers are prone to crystallization (comparative Ex.5* and F-2*). Even in combination with short-chain or branched alkyl acrylates, the incorporation of more than 45% by weight of lauryl acrylate in the copolymer lead to extremely poor low temperature properties in the corresponding 75W-90 formulations. As shown in comparative formulations F-5* and F-6* in Table 5, the high content of long linear side chains having more than 8 carbon atoms in the acrylate monomer units result in extremely poor low temperature performance (solid at BF ?40? C.) despite a high VI (>185). Thus, no good combination of high VI and good low temperature performance is achieved. Surprisingly, copolymers with lauryl acrylate contents according to the invention fulfill the requirements of a 75W-90 formulation (see for example inventive polymers Ex.5 to Ex.7 and corresponding formulations examples F-6 to F-8) which shows that the ranges of acrylates as described are essential to get a polymer with good properties.