Comb polymers comprising imide functionality

Abstract

Selected comb polymers include specified amounts of macromonomer and imide functionalization. Further, a method is useful for the preparation of such comb polymers. Lubricant compositions including such comb polymers are useful for reducing wear and fuel consumption of lubricant compositions, especially of engine oil (EO) compositions.

Claims

1. A grafted polyalkyl(meth)acrylate based comb polymer consisting of a base polymer A and units B which are grafted thereon, wherein the base polymer A comprises: (a) 10% to 25% by weight of at least one repeating unit derived from an ester of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene; (b) 0% to 2% by weight of at least one repeating unit derived from methyl (meth)acrylate; (c) 60% to 80% by weight of at least one repeating unit derived from butyl (meth)acrylate; (d) 0% to 16% by weight of at least one repeating unit derived from C.sub.10-20-alkyl (meth)acrylate; and (e) 0% to 2% by weight of at least one repeating unit derived from a styrene monomer having 8 to 17 carbon atoms, wherein an amount of each component (a) to (e) is based on a total composition of the grafted polyalkyl(meth)acrylate based comb polymer; wherein the units B comprise at least one repeating unit prepared from: (f) 1% to 2.5% by weight of at least one repeating unit derived from polar unsaturated monomer selected from the group consisting of maleic acid, maleic acid anhydride, methyl maleic acid anhydride, maleic acid monoester and maleic acid diester; and (g) 2% to 5% by weight of at least one repeating unit derived from a primary amine of general formula (I) ##STR00008## wherein each R′ is independently selected from the group consisting of H and an alkyl radical having 1 to 9 carbon atoms, and wherein the amount of each component (f) and (g) is based on the total composition of the grafted polyalkyl(meth)acrylate based comb polymer.

2. The rafted polyalkyl(meth)acrylate based comb polymer according to claim 1, comprising: (a) 10 to 15% by weight of the ester of (meth)acrylic acid and the hydroxylated hydrogenated polybutadiene; (b) 0% to 2% by weight of the methyl (meth)acrylate; (c) 65% to 76% by weight of the butyl (meth)acrylate; (d) 5% to 16% by weight of C.sub.10-15 alkyl (meth)acrylate; (e) 0% to 2% by weight of the at least one styrene monomer having 8 to 17 carbon atoms; (f) 1% to 2.5% by weight of the at least one polar unsaturated monomer selected from the group consisting of maleic acid, maleic acid anhydride, methyl maleic acid anhydride, maleic acid monoester and maleic acid diester; and (g) 2% to 5% by weight of the primary amine of the following general formula (I) ##STR00009## wherein each R′ independently selected from the group consisting of H and an alkyl radical having 1 to 9 carbon atoms.

3. The grafted polyalkyl(meth)acrylate based comb polymer according to claim 1, wherein the polar unsaturated monomer is maleic acid anhydride.

4. The grafted polyalkyl(meth)acrylate based comb polymer according to claim 1, wherein the primary amine of general formula (I) is N-phenyl-1,4-phenylenediamine.

5. The grafted polyalkyl(meth)acrylate based comb polymer according to claim 1, wherein the grafted polyalkyl(meth)acrylate based comb polymer has a weight-average molecular weight in the range of from 200,000 to 600,000 g/mol.

6. The rafted polyalkyl(meth)acrylate based comb polymer according to claim 1, wherein the hydroxylated hydrogenated polybutadiene has a number-average molecular weight M.sub.n to DIN 55672-1 of 4,000 to 6,000 g/mol.

7. The grafted polyalkyl(meth)acrylate based comb polymer according to claim 6, wherein the number-average molecular weight M.sub.n to DIN 55672-1 is 4,500 to 5,000 g/mol.

8. A method for reducing friction losses of a lubricating oil composition, the method comprising: adding the polyalkyl(meth)acrylate based comb polymer according to claim 1 to the lubricating oil composition.

9. The method according to claim 8, wherein the lubricating oil composition is an engine oil composition.

10. The grafted polyalkyl(meth)acrylate based comb polymer according to claim 1, wherein the butyl (meth)acrylate is n-butyl methacrylate, the C.sub.10-20-alkyl (meth)acrylate is C.sub.12-14-alkyl methacrylate, and the styrene monomer is styrene.

11. An additive composition, comprising: (A) a first base oil selected from the group consisting of API Group III oils and mixtures thereof; (B) a second base oil selected from the group consisting of API Group V base oils and mixtures thereof; and (C) a polyalkyl(meth)acrylate based comb polymer consisting of a base polymer A and units B which is grafted thereon, wherein the base polymer A comprises: (a) 10% to 25% by weight of at least one repeating unit derived from an ester of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene: (b) 0% to 2% by weight of at least one repeating unit derived from methyl (meth)acrylate: (c) 60% to 80% by weight of at least one repeating unit derived from butyl (meth)acrylate; (d) 0% to 16% by weight of at least one repeating unit derived from C.sub.10-20-alkyl (meth)acrylate; and (e) 0% to 2% by weight of at least one repeating unit derived from a styrene monomer having 8 to 17 carbon atoms, wherein an amount of each component (a) to (e) is based on a total composition of the polyalkyl(meth)acrylate based comb polymer; and wherein the units B comprise at least one repeating unit prepared from: (f) 1% to 2.5% by weight of at least one repeating unit derived from a polar unsaturated monomer selected from the group consisting of maleic acid, maleic acid anhydride, methyl maleic acid anhydride, maleic acid monoester and maleic acid diester; and (g) 2% to 5% by weight of at least one repeating unit derived from a primary amine of general formula (I) ##STR00010## wherein each R′ is independently selected from the group consisting of H and an alkyl radical having 1 to 9 carbon atoms, and wherein the amount of each component (f) and (g) is based on the total composition of the polyalkyl(meth)acrylate based comb polymer.

12. The additive composition according to claim 11, comprising: (A) the first base oil selected from the group consisting of API Group III oils and mixtures thereof: (B) the second base oil selected from the group consisting of API Group V base oils and mixtures thereof; and (C) the polyalkyl(meth)acrylate based comb polymer consisting of the base polymer A and units B which is grafted thereon, wherein the base polymer A comprises: (a) 10% to 15% by weight of at least one repeating unit derived from the an ester of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene; (b) 0% to 2% by weight of at least one repeating unit derived from h methyl (meth)acrylate; (c) 65% to 76% by weight of at least one repeating unit derived from the butyl (meth)acrylate; (d) 5% to 16% by weight of at least one repeating unit derived from the C.sub.10-20-alkyl (meth)acrylate; and (e) 0% to 2% by weight of at least one repeating unit derived from the styrene monomers having 8 to 17 carbon atoms, wherein the amount of each component (a) to (e) is based on the total composition of the polyalkyl(meth)acrylate based comb polymer; and wherein the units B comprise at least one repeating unit prepared from: (f) 1% to 2.5% by weight of at least one repeating unit derived from the polar unsaturated monomer selected from the group consisting of maleic acid, maleic acid anhydride, methyl maleic acid anhydride, maleic acid monoester and maleic acid diester; and (g) 2% to 5% by weight of at least one repeating unit derived from the primary amine of general formula (I) ##STR00011## wherein each R′ is independently selected from the group consisting of H and an alkyl radical having 1 to 9 carbon atoms, wherein the amount of each component (f) and (g) is based on the total composition of the polyalkyl(meth)acrylate based comb polymer.

13. The additive composition according to claim 11, comprising: (A) 0% to 40% by weight of the first base oil selected from the group consisting of API Group III base oils and mixtures thereof; (B) 20% to 80% by weight of the second base oil selected from the group consisting of API Group V base oils and mixtures thereof; and (C) 20% to 40% by weight of the polyalkyl(meth)acrylate based comb polymer, based on a total weight of the additive composition.

14. A method of reducing friction coefficient of a lubricating oil composition, the method comprising: adding the additive composition according to claim 11 to a lubricating oil composition.

15. The additive composition according to claim 11, wherein the second base oil is at least one oil selected from the group consisting of ester oils, diisononyl adipate, dioctylsebacate and mixtures thereof.

16. A lubricating oil composition, comprising: (A) 60% to 99% by weight of a first base oil selected from the group consisting of API Group I, API Group II, API Group III, API Group IV oils and mixtures thereof; (B) 0.25% to 15% by weight of a second base oil selected from the group consisting of API Group V base oils and mixtures thereof; and (C) 0.5% to 10% by weight of a polyalkyl(meth)acrylate based comb polymer consisting of a base polymer A and units B which are grafted thereon, wherein the base polymer A comprises: (a) 10% to 25% by weight of at least one repeating unit derived from an ester of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene: (b) 0% to 2% by weight of at least one repeating unit derived from methyl (meth)acrylate; (c) 60% to 80% by weight of at least one repeating unit derived from butyl (meth)acrylate; (d) 0% to 16% by weight of at least one repeating unit derived from at least one C.sub.10-20-alkyl (meth)acrylate; and (e) 0% to 2% by weight of at least one repeating unit derived from at least one styrene monomer having 8 to 17 carbon atoms, wherein an amount of each component (a) to (e) is based on a total composition of the polyalkyl(meth)acrylate based comb polymer; wherein the units B comprise at least one repeating unit prepared from: (f) 1% to 2.5% by weight of at least one repeating unit derived from a polar unsaturated monomer selected from the group consisting of maleic acid, maleic acid anhydride, methyl maleic acid anhydride, maleic acid monoester and maleic acid diester; and (g) 2% to 5% by weight of at least one repeating nit derived from a primary amine of general formula (I) ##STR00012## wherein each R′ is independently selected from the group consisting of H and an alkyl radical having 1 to 9 carbon atoms, wherein the amount of each component (f) and (g) is based on the total composition of the polyalkyl(meth)acrylate based comb polymer; and (D) 0% to 15% by weight of one or more further additives.

17. The lubricating oil composition according to claim 16, comprising: (A) 60% to 99% by weight of the first base oil selected from the group consisting of API Group I, API Group II, API Group III, API Group IV oils and mixtures thereof; (B) 0.25% to 15% by weight of the second base oil selected from the group consisting of API Group V base oils and mixtures thereof; and (C) 0.5% to 10% by weight of the polyalkyl(meth)acrylate based comb polymer consisting of the base polymer A and the units B which are grafted thereon, wherein the base polymer A comprises: (a) 10% to 15% by weight of at least one repeating unit derived from the ester of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene; (b) 0% to 2% by weight of at least one repeating unit derived from the methyl (meth)acrylate; (c) 65% to 76% by weight of at least one repeating unit derived from the butyl (meth)acrylate; (d) 5% to 16% by weight of at least one repeating unit derived from the at least one C.sub.10-20-alkyl (meth)acrylate; and (e) 0% to 2% by weight of at least one repeating unit derived from the styrene monomer having 8 to 17 carbon atoms, wherein the amount of each component (a) to (e) is based on the total composition of the polyalkyl(meth)acrylate based comb polymer; and wherein the units B comprise at least one repeating unit prepared from: (f) 1% to 2.5% by weight of at least one repeating unit derived from the polar unsaturated monomer selected from the group consisting of maleic acid, maleic acid anhydride, methyl maleic acid anhydride, maleic acid monoester and maleic acid diester; and (g) 2% to 5% by weight of at least one repeating unit derived from h primary amine of general formula (I) ##STR00013## wherein each R′ is independently selected from the group consisting of H and an alkyl radical having 1 to 9 carbon atoms, wherein the amount of each component (f) and (g) is based on the total composition of the polyalkyl(meth)acrylate based comb polymer, and (D) 0% to 15% by weight of t one or more further additives.

18. The lubricating oil composition according to claim 16, wherein the one or more further additives is selected from the group consisting of viscosity index improvers, dispersants, defoamers, detergents, antioxidants, pour point depressants, antiwear additives, extreme pressure additives, friction modifiers, anticorrosion additives, dyes and mixtures thereof.

19. A method of reducing friction in an automotive vehicle, the method comprising: applying the lubricating oil composition according to claim 16 to an automotive vehicle.

Description

(1) FIG. 1: MTM test results (50% SRR, 30N, 100° C., 136 min)

(2) The invention has been illustrated by the following non-limiting examples.

EXPERIMENTAL PART

Abbreviations

(3) AMA alkyl methacrylate C.sub.1 AMA C.sub.1-alkyl methacrylate=methyl methacrylate (MMA) C.sub.4 AMA C.sub.4-alkyl methacrylate=n-butyl methacrylate C.sub.14/16/18 AMA typically 5% C14, 30% C16, 65% C18, all linear D dispersity DIOS Dioctylsebacate (CAS: 122-62-3), Group V base oil from Sterinerie Debois with a KV.sub.100 of 3.2 cSt DMAEMA 2-(Dimethylamino)ethyl methacrylate FE fuel economy FM friction modifier Gr III Oil Group III base oil mixture (NB 3043 and NB 3080 from Neste) with a KV.sub.100 of 4.9 cSt HTHS.sub.80 high-temperature high-shear viscosity @80° C., measured according to CEC L-036 HTHS.sub.100 high-temperature high-shear viscosity @100° C., measured according to CEC L-036 HTHS.sub.150 high-temperature high-shear viscosity @150° C., measured according to CEC L-036 KV kinematic viscosity measured according to ASTM D445 KV.sub.40 kinematic viscosity @40° C., measured according to ISO 3104 KV.sub.60 kinematic viscosity @60° C., measured according to ISO 3104 KV.sub.100 kinematic viscosity @100° C., measured according to ISO 3104 LMA lauryl methacrylate, 73% C12, 27% C14, all linear MA maleic anhydride MM macromonomer MMA methyl methacrylate M.sub.n number-average molecular weight M.sub.w weight-average molecular weight MTM mini traction machine NB 3020 Nexbase® 3020, Group III base oil from Neste with a KV.sub.100 of 2.2 cSt NB 3043 Nexbase® 3043, Group III base oil from Neste with a KV.sub.100 of 4.3 cSt PDA N-phenyl-1,4-phenylenediamine OLOA® 55501 DI Package for PCMO commercially available from Oronite PCMO passenger car motor oils PDI polydispersity index Plastomoll DNAdiisononyl adipate, Group V base oil from BASF Sty styrene VI viscosity index, measured according to ISO 2909 Yubase 4 Group III base oil from SK Lubricants with a KV.sub.100 of 4.2 cSt

(4) Test Methods

(5) The comb polymers according to the present invention and the comparative examples were characterized with respect to their molecular weight and PDI.

(6) Molecular weights were determined by size exclusion chromatography (SEC) using commercially available polymethylmethacrylate (PMMA) standards. The determination is effected by gel permeation chromatography with THF as eluent (flow rate: 1 mL/min; injected volume: 100 μl).

(7) The additive compositions including the comb polymers according to the present invention and comparative examples were characterized with respect to their viscosity index (VI) to ASTM D 2270, kinematic viscosity at 40° C. (KV.sub.40) and 100° C. (KV.sub.100) to ASTM D445 and with respect to their shear stability.

(8) To show the shear stability of the additive compositions, the PSSI (Permanent Shear Stability Index) was calculated according to ASTM D 6022-01 (Standard Practice for Calculation of Permanent Shear Stability Index) based on data measured according to ASTM D 2603-B (Standard Test Method for Sonic Shear Stability of Polymer-Containing Oils).

(9) The lubricating oil compositions including the comb polymers according to the present invention and comparative examples were characterized with respect to kinematic viscosity at 40° C. (KV.sub.40), at 60° C. (KV.sub.60) and 100° C. (KV.sub.100) to ASTM D445, the viscosity index (VI) to ASTM D 2270, high-temperature high-shear viscosity at 80° C. (HTHS.sub.80), 100° C. (HTHS.sub.100) and 150° C. (HTHS.sub.150) to CEC L-036, Noack evaporation loss at 250° C. for 1 hour to CEC L-40B and CCS (Cold-Cranking Simulator) apparent viscosity at −35° C. to ASTM D 5293.

(10) Determination of Friction Reduction

(11) The measurement of the coefficient of friction at 100° C. was performed as described in WO 2004/087850. The experiments were carried out on a mini traction machine (MTM, PCS Instruments) under the following conditions:

(12) TABLE-US-00003 TABLE Test parameters and conditions for the MTM frictional tests. Test rig PCS MTM 3 Disk Steel, AISI 52100, diameter = 40.0 mm RMS = 25 to 30 nm, Rockwell C hardness = 63 Elastic modulus = 207 GPa Ball Steel, AISI 52100, diameter = 19.0 mm RMS = 10 to 13 nm, Rockwell C hardness = 58-65 Elastic modulus = 207 GPa Speed 0.005 m/s to 2.5 m/s Temperature 120° C. Sliding/rolling ratio (SRR) 50% Load 30 N = 0.93 GPa max. Hertzian pressure

(13) As a result of a frictional experiment, a Stribeck curve was obtained (coefficient of friction as a function of the rolling/sliding speed).

(14) The evaluation of the friction value measurements is shown in the graph in FIG. 1. The area under the curve corresponds to the “total friction” over the entire speed range examined and is a quantifiable result in which the friction can be expressed as a number. The smaller the area, the greater the friction-reducing effect of the polymer examined.

(15) The areas are determined by integration of the friction value curves in the range of sliding speed 0.005 to 2.0 m/s and 0.0005 to 0.2 m/s and compared to the non-functionalized polymers.

(16) Engine Testing

(17) The fuel economy testing was conducted by using as engine an Insignia 2.0 L General Motors L850 gasoline turbo direct injection, where the engine was set up on a test bench.

(18) The FTP-75 fuel economy cycle was used as a standard fuel economy test in passenger cars to evaluate the fuel economy performance. The EPA Federal Test Procedure, commonly known as FTP-75, for the city driving cycle is a series of tests defined by the US Environmental Protection Agency (EPA) to measure tailpipe emission and fuel economy for passenger cars. The test was repeated 3 times and an average of the three runs was calculated.

(19) As reference was used a SAE 0W16 grade formulation with VPL 3-200 (commercially available from Evonik Industries) as VI improver. The reference was run at the beginning and after every two test formulations.

(20) Synthesis of a Hydroxylated Hydrogenated Polybutadiene

(21) The macroalcohol prepared was a hydroxypropyl-terminated hydrogenated polybutadiene having a mean molar mass M.sub.n=4750 g/mol.

(22) The macroalcohol was synthesized by an anionic polymerization of 1,3-butadiene with butyllithium at 20-45° C. On attainment of the desired degree of polymerization, the reaction was stopped by adding propylene oxide and lithium was removed by precipitation with methanol. Subsequently, the polymer was hydrogenated under a hydrogen atmosphere in the presence of a noble metal catalyst at up to 140° C. and pressure 200 bar. After the hydrogenation had ended, the noble metal catalyst was removed and organic solvent was drawn off under reduced pressure. Finally, the base oil NB 3020 was used for dilution to a polymer content of 70% by weight.

(23) The vinyl content of the macroalcohol was 61%, the hydrogenation level >99% and the OH functionality >98%. These values were determined by .sup.1H-NMR (nuclear resonance spectroscopy).

(24) Synthesis of Macromonomer (MM)

(25) In a 2 L stirred apparatus equipped with saber stirrer, air inlet tube, thermocouple with controller, heating mantle, column having a random packing of 3 mm wire spirals, vapor divider, top thermometer, reflux condenser and substrate cooler, 1000 g of the above-described macroalcohol are dissolved in 450 g of methyl methacrylate (MMA) by stirring at 60° C. Added to the solution are 20 ppm of 2,2,6,6-tetramethylpiperidin-1-oxyl radical and 200 ppm of hydroquinone monomethyl ether. After heating to MMA reflux (bottom temperature about 110° C.) while passing air through for stabilization, about 20 g of MMA are distilled off for azeotropic drying. After cooling to 95° C., 0.30 g of LiOCH.sub.3 is added and the mixture is heated back to reflux. After the reaction time of about 1 hour, the top temperature has fallen to −64° C. because of methanol formation. The methanol/MMA azeotrope formed is distilled off constantly until a constant top temperature of about 100° C. is established again. At this temperature, the mixture is left to react for a further hour. For further workup, the bulk of MMA is drawn off under reduced pressure. Insoluble catalyst residues are removed by pressure filtration (Seitz T1000 depth filter). The content of NB 3020 “entrained” into the copolymer syntheses described further down was taken into account accordingly.

Synthesis of Working Examples

(26) (1) Base Polymer Synthesis

(27) An apparatus with 4-neck flask and precision glass saber stirrer is initially charged with a 300 g mixture of low molecular weight monomers and macromonomer (compositional details are shown in Table 1), and with 200 g of a base oil mixture of Plastomoll DNA/NB3020=92.3:7.7. After heating to 115° C. under nitrogen, 1.8 g of 2,2-bis(tert-butylperoxy)butane (50% in mineral oil) is added and the temperature is maintained. Another 500 g of the monomer-oil mixture and 1.8 g 2,2-bis(tert-butylperoxy)butane (50% in mineral oil) is added within 3 hours. Then the reaction is maintained at 115° C. for another 2 h. Subsequently, the reaction mixture is diluted to 40% solids with Plastomoll DNA and 0.2% 2,2-bis(tert-butylperoxy)butane within 3 hours. Then the reaction is maintained at 115° C. for another 2 h and after this another 0.2% 2,2-bis(tert-butylperoxy)butane is added and the mixture is stirred at 115° C. overnight. 1500 g of a 40% solution of comb polymer in mineral oil are obtained. The monomer components will add up to 100%. The amounts of initiator and dilution oil are given relative to the total amount of monomers.

(28) (2) Grafting Step

(29) Maleic anhydride is heated up at 90° C. An apparatus with a 4-neck flask and precision glass saber stirrer is charged with 1400 g of the base polymer mixture as prepared in step (1) and heated up to 110° C. under nitrogen. Then 7 g of molten maleic anhydride are added. 1.4 g of tert-butyl perbenzoate is added. Subsequently, the reaction temperature is increased to 130° C. After 1 h, 2 h and 3 h another 0.71 g tert-butyl perbenzoate are each added to the reaction mixture. The grafting reaction is finished 2 hours after the last initiator addition.

(30) (3) Amine Reaction Step

(31) A solution of 15% by weight of PDA in Plastomoll DNA is prepared at 90° C. Then an apparatus with a 4-neck flask and precision glass saber stirrer and condenser is charged with 503 g of the grafted polymer mixture prepared as described under step (2). After heating to 120° C. under nitrogen 31.5 g PDA solution (15% in Plastomoll DNA) is added within 4 hours. During the reaction water is formed and distilled off the reaction mixture. The post-grafting reaction is finished 2 hours after PDA addition.

Description of the Examples

(32) Table 1 summarizes the monomer components of the examples and comparative examples as used in the synthesis of the polymers.

(33) The following variations of the above described procedure were made: Ex 4: double of the amount of maleic anhydride and PDA were used in steps (2) and (3) Ex 5 and Ex 6: Plastomoll DNA was replaced by DIOS in all reaction steps CE-1 and CE-2: no grafting and amine reaction step CE-3: no grafting and amine reaction step; instead the functional monomer DMAEMA was added with the other monomers in step (1) CE-5: 2.3 times the amount of maleic anhydride and PDA were used in steps (2) and (3)

(34) TABLE-US-00004 TABLE 1 Monomer mixtures (40% of reaction mixture) used to prepare working examples and comparative examples (CE). Polymer C4 C1 Example MM LMA AMA Sty AMA MA PDA # [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] 1 11.58 8.39 74.87 1.40 0.24 1.22 2.30 2 11.58 11.28 71.98 1.40 0.24 1.22 2.30 3 11.58 15.14 68.12 1.40 0.24 1.22 2.30 4 14.33 9.16*.sup.) 68.09 1.34 0.19 2.39 4.50 5 11.58 8.39 74.87 1.40 0.24 1.22 2.30 6 11.58 11.28 71.98 1.40 0.24 1.22 2.30 CE-1 12.0 11.7 74.6 1.45 0.25 — — CE-2 15.0 5.0 68.0 12.0 — — — CE-3 11.76 8.53 76.06 1.42 0.24 — 1.99**.sup.) CE-4 14.47 4.82 65.61 11.58 — 1.22 2.30 CE-5 9.47 68.14 — — 14.21  2.84 5.34 CE-6 9.95 71.60 — — 14.93  1.22 2.30 CE-7 10.61 4.82 81.05 — — 1.22 2.30 CE-8 22.19 20.94 51.71 1.40 0.24 1.22 2.30 *.sup.)C.sub.14/16/18 AMA was used instead of LMA **.sup.)DMAEMA was used instead of PDA and randomly copolymerized

(35) The net compositions of the resulting comb polymers including the macromonomer conversion rate MM.sub.conv. are given in the following Table 2.

(36) TABLE-US-00005 TABLE 2 Net Polymer compositions of the resulting comb polymers. Polymer C4 C1 Example MM.sub.conv. MM LMA AMA Sty AMA MA PDA # [%] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] 1 90 10.42 8.50 75.85 1.42 0.24 1.24 2.33 2 88 10.19 11.46 73.11 1.42 0.24 1.24 2.34 3 94 10.89 15.26 68.66 1.41 0.24 1.23 2.32 4 90 12.90 9.31*.sup.) 69.23 1.36 0.19 2.43 4.58 5 93 10.77 8.47 75.56 1.41 0.24 1.23 2.32 6 93 10.77 11.38 72.64 1.41 0.24 1.23 2.32 CE-1 88 10.56 11.89 75.82 1.47 0.25 — — CE-2 88 13.20 5.11 69.44 12.25 — — — CE-3 88 10.35 8.67 77.28 1.44 0.24 — 2.02**.sup.) CE-4 88 12.73 4.92 66.94 11.82 — 1.24 2.35 CE-5 94 8.90 68.57 — — 14.30  2.86 5.37 CE-6 94 9.35 72.07 — — 15.03  1.23 2.32 CE-7 87 9.23 4.89 82.30 — — 1.24 2.34 CE-8 93 20.64 21.36 52.74 1.43 0.24 1.24 2.35 *.sup.)C.sub.14/16/18 AMA was used instead of LMA **.sup.)DMAEMA was used instead of PDA and randomly copolymerized

(37) Examples 1 to 6 are in accordance with the present invention and show varying amounts of macromonomer (MM) as well as varying ratios of LMA/nBMA which are within the claimed ranges. Example 4 contains a higher functionalization with MA and PDA than the other examples which all contain the same percentage of the functional monomers MA and PDA. Examples 5 and 6 were prepared with DIOS instead of Plastomoll DNA in the reaction mixture.

(38) The comparative examples (CE) were either prepared without functional monomers (CE-1 and CE-2) or contain a different amine functionality like DMAEMA instead of MA and PDA (CE-3) or have different monomer compositions, e.g. do not contain Sty, nBMA or MMA or show monomer contents which are outside the claimed ranges (CE-4, CE-5, CE-6, CE-7, CE-8).

(39) Table 3 summarizes the characteristics of additive compositions comprising examples and comparative examples (15% by weight of polymer in base oil). As base oil was used a Group III base oil mixture (NB 3043 and NB 3080 from Neste) with KV.sub.100 of 4.9 cSt.

(40) TABLE-US-00006 TABLE 3 Typical properties of the examples and comparative examples (CE). Polymer KV.sub.100 KV.sub.40 Example KV.sub.100 KV.sub.40 M.sub.w shear loss shear loss # [mm.sup.2/s] [mm.sup.2/s] VI [g/mol] PDI [%] [%] 1 6.82 27.49 224 482.000 4.57 — 2.58 2 6.98 27.94 228 316.000 4.36 0.16 2.02 3 7.75 28.30 266 320.000 3.6 — — 4 6.42 30.42 171 348.000 4.05 0.49 19.75  5 6.62 27.31 214 359.000 3.85 — 3.29 6 7.05 27.64 236 348.000 3.66 — 2.14 CE-1 7.66 28.22 262 309.000 4.26 — — CE-2 6.57 27.53 208 198.000 3.25 — — CE-3 6.66 27.05 219 295.000 4.46 1.04 1.18 CE-4 6.21 27.14 190 214.000 3.29 0.30 0.17 CE-5 *.sup.) *.sup.) *.sup.) 437.000 4.23 *.sup.) *.sup.) CE-6 12.41  50.28 255 526.000 5.34 64.05  61.14  CE-7 6.36 27.48 196 283.000 3.92 — 0.85 CE-8 9.82 34.01 294 330.000 4.16 22.25  12.98  *.sup.) This product was not soluble in Group III base oil.

(41) Table 3 shows that all polymers except for CE-5 were soluble in the Group III testing oil (which contains 22% by weight of API Group V oil selected from Plastomoll DNA or DIOS). CE-5 could not be dissolved in Group III oil or GTL4 oil. The high amount of polar monomers, like methyl methacrylate, and functional groups (MA and PDA) in this sample is probably the reason why the solvency of Group III oil might not be high enough for this product. As Group III oils and GTL oils are typically used for modern engine oils this candidate was considered to be not applicable in typical modern engine oil formulations.

(42) The data in Table 3 further show that very high viscosity indexes (171-294) are obtained with the described comb polymer products and that the weight-average molecular weight ranged from 300.000 to 500.000 g/mol. For most samples, except for CE-6 and CE-8, very good shear stabilities were obtained as well.

(43) In order to evaluate the properties of the examples and comparative examples in lubricating oil compositions, typical engine oil formulations without DI package were prepared and characterized. The detailed results of formulations which were adjusted to a HTHS.sub.150 of 2.6 cSt are given in Table 4 below.

(44) TABLE-US-00007 TABLE 4 Characteristics of Formulation Examples A in a 0W20 engine oil formulation using Yubase 4 as base oil. Formu- Friction***.sup.) Friction***.sup.) lation Polymer Treat Rate KV.sub.100 KV.sub.40 CCS-35 Noack HTHS.sub.100 HTHS.sub.150 (5-2000 (5-200 # Ex. # [wt %] [mm.sup.2/s] [mm.sup.2/s] VI [mPas] [%] [mPas] [mPas] mm/s) mm/s) A-1 1 12.4 6.97 22.60 304 2223 14.1 4.19 2.80 32.9 4.8 A-2 2 12.1 6.97 23.08 295 2255 14.1 4.32 2.76 33.4 5.0 A-3 3 9.9 6.94 22.35 306 2187 13.9 4.22 2.73 38.6 6.0 A-4 4 16.8 6.93 24.86 265 2366 14.4 4.85 2.70 30.8 4.3 A-5 5 12.7 6.96 22.74 300 2279 13.8 4.25 3.01 35.1 5.8 A-6 6 11.3 6.91 22.40 304 2238 13.7 4.22 2.83 33.5 5.5 A-7*.sup.) CE-1 10.7 6.91 22.15 308 2198 14.5 4.41 2.72 50.5 7.8 A-8*.sup.) CE-2 14.2 6.91 23.27 288 2306 14.6 4.82 3.03 53.2 9.0 A-9*.sup.) CE-3 13.1 6.99 22.56 306 2162 14.8 4.42 2.86 60.0 10.1  A-10*.sup.) CE-4 15.7 6.90 23.68 280 2317 13.7 4.83 3.09 40.0 7.8 A-11*.sup.) CE-5 **.sup.) **.sup.) **.sup.) **.sup.) **.sup.) **.sup.) **.sup.) **.sup.) **.sup.) **.sup.) A-12*.sup.) CE-6 8.6 9.62 35.19 276 2477 12.9 4.99 2.59 31.1 4.9 A-13*.sup.) CE-7 14.3 6.90 24.28 271 2276 14.6 4.36 2.99 41.1 7.3 A-14*.sup.) CE-8 8.5 7.89 25.11 318 2295 13.4 4.82 2.59 30.3 4.6 *.sup.)comparative example **.sup.) This product was not soluble in Yubase 4. ***.sup.)The area under the curve (traction coefficient versus mean speed) corresponds to the “total friction” or “friction” over the entire speed range examined and is a quantifiable result in which the friction can be expressed as a number.

(45) From Table 4 it is clearly visible that formulations comprising the inventive comb polymers and most of the comparative comb polymers have low KV.sub.40 and low high-temperature high-shear viscosities at 100° C. (see Formulations A-1 to A-10 and A-13).

(46) The KV.sub.40 values are between 22 and 25 mm.sup.2/s and the HTHS.sub.100 values are between 4.0 and 4.9 mPas; especially for the examples according to the present invention.

(47) Low values of KV.sub.40 and HTHS.sub.100 are known to be indicators of very good fuel economy (see US 2010/0190671, page 1, paragraph [0005]). That means that the lubricating oil formulations according to the present invention can also be used to decrease fuel consumption.

(48) Formulations A-12 and A-14 comprising polymer examples CE-6 and CE-8 do not show the advantageously low values of KV.sub.40 and HTHS.sub.100. Instead, it is shown that KV.sub.40 and HTHS.sub.100 are significantly higher for these samples and, therefore, no fuel economy advantage can be predicted for these additives.

(49) Polymer Example CE-5 was not soluble in Yubase 4 and corresponding Formulation A-11 could therefore not be evaluated. As Yubase 4 or similar Group III oils are used for engine oil formulations polymer CE-5 is not suited for typical engine oil formulations. As already mentioned further above, the high amount of polar monomers, like methyl methacrylate, and functional groups (MA and PDA) in this sample is probably the reason why the solvency of Yubase 4 oil might not be high enough for this product.

(50) In addition, it was found that by using the inventive comb polymers with grafted imide functionality surprisingly low values of friction loss can be achieved with corresponding formulations. Low friction loss as determined by MTM measurements means that with these formulations an additional benefit on fuel economy is expected because of the positive impact on the friction in the engine.

(51) From Table 4 it is visible that all formulations comprising examples with imide functionality give very low friction losses (A-1 to A6 as well as A-12 and A-14) while the formulations comprising examples without dispersant functionality (A-7 and A-8) or with DMAEMA as dispersant functionality (A-9) show significantly higher friction losses. Surprisingly, also other formulations comprising polymers with imide functionality but different monomer compositions than the inventive examples could not obtain such low friction losses (A-10 and A-13).

(52) Formulation example A-4 further shows that a higher amount of imide functionality leads to excellent friction data but KV.sub.40 and HTHS.sub.100 are raising as well.

(53) The MTM results are further illustrated in FIG. 1.

(54) A comparison of the inventive examples with the comparative examples shows that only in the formulations where the inventive comb polymers were used both low KV.sub.40 and HTHS.sub.100 values as well as low friction losses can be achieved. What means that superior fuel economy is expected for formulations wherein both mechanisms come to work: beneficial viscometric properties and low friction loss.

(55) Engine Testing Results

(56) Engine tests were conducted to show the fuel economy advantage of the friction reducing comb polymers and to therefore proof the expectations as mentioned further above. The formulations were adjusted to SAE 0W16 grade with Yubase 4+ as base oil (details listed in Table 5). In order to show the friction reducing effect of the invention a DI package without friction modifier (OLOA 55501 without FM) was chosen. One example using a polymer in accordance with the present invention (Formulation B-3 comprising polymer example 1) was compared with an example using a comparative polymer without friction reducing functionality (Formulation B-2, comprising polymer example CE-1).

(57) TABLE-US-00008 TABLE 5 Details of the 0W16 formulations B used in fuel economy testing and fuel consumption results. The Formulations were blended a) with an inventive example (Ex 1) or b) with one of the Comparative Examples (CE-1, VPL ® 3-200 or Lubrizol ® 7077). SAE 0W-16 B-1*.sup.) B-2*.sup.) B-3 B-4*.sup.) VI improver VPL ® 3-200 [wt %] 5.2 — — — Polymer Example CE-1 [wt %] — 7.2 — — Polymer Example 1 [wt %] — — 5.8 — Lubrizol 7077 [wt %] — — — 4.3 VPL ® 1-254 [wt %] — — — 0.1 OLOA 55501 without FM [wt %] 8.9 8.9 8.9 8.9 Yubase 4 Plus [wt %] 85.9 83.9 85.3 86.7 Total [wt %] 100 100 100 100 KV.sub.100 [mm.sup.2/s] 6.58 6.17 6.19 6.84 KV.sub.40 [mm.sup.2/s] 26.05 25.95 26.15 33.73 VI 226 201 199 168 KV.sub.60 [mm.sup.2/s] 14.2 13.97 14.17 17.43 CCS −35° C. [mPas] 3336 3431 3266 4107 Noack 1h @250° C. [%] 12.3 12.3 12.2 12.3 HTHS.sub.80 [mPas] 6.71 6.65 6.71 7.38 HTHS.sub.100 [mPas] 4.56 4.44 4.51 4.94 HTHS.sub.150 [mPas] 2.35 2.37 2.42 2.37 Yield Stress @−40° C. [Pas] <35 <35 <35 <35 MRV @−40° C. [mPas] 17400 30200 8800 33600 After Bosch pump (30 cycles) KV.sub.100 [mm.sup.2/s] 6.57 6.16 6.17 6.54 KV.sub.40 [mm.sup.2/s] 26.03 25.93 26.12 31.98 VI 225 200 199 165 HTHS.sub.150 [mPas] 2.35 2.39 2.35 2.24 After Bosch pump (90 cycles) KV.sub.100 [mm.sup.2/s] 6.55 6.15 6.17 6.47 KV.sub.40 [mm.sup.2/s] 26.03 25.93 26.14 31.64 VI 224 200 198 163 HTHS.sub.150 [mPas] 2.36 2.4 2.37 2.21 Fuel Consumption L/100 km 8.958 8.943 8.932 9.046 Fuel consumption change [%] 0 −0.17 −0.28 0.98 Fuel Savings L/100 km 0 −0.015 −0.026 0.088 *.sup.)= comparative example

(58) As standard was used a formulation comprising the commonly used viscosity index improver VPL® 3-200 which is a commercially available comb polymer from Evonik Industries AG (Formulation B-1).

(59) It can be seen that by using a formulation which comprises an imide comb polymer in accordance with the present invention (B-3 comprising Polymer Example 1) significantly higher fuel economy is obtained (0.28% reduced fuel consumption) than by using a formulation comprising a conventional non-functionalized comb polymer (B-2 comprising CE-1, 0.17% reduced fuel consumption). These results show that the friction reducing functionality contributes to the fuel economy result and even increases fuel economy in comparison to the non-functionalized comb.

(60) To show the superior fuel economy performance of the comb polymers an additional formulation containing Lubrizol® 7077, an olefin copolymer having an ethylene content of about 50 weight percent (commercially available from Lubrizol Corporation), as VI improver was evaluated (Formulation B-4). In this case 0.98% decreased fuel economy was observed in comparison to the viscosity improver VPL® 3-200 (commercially available from Evonik Industries AG).

CONCLUSION

(61) Functionalizing selected polyalkyl(meth)acrylate based comb polymers with imide functions by grafting maleic anhydride on the base polymer followed by the reaction with the aromatic amine PDA the friction coefficient of lubricating oil compositions, especially 0W20 engine oil formulations, can be significantly reduced (see formulation examples A-1 to A-6). This effect is not observed when other base polymers are used or other functionalities are introduced to the comb polymers (see formulation examples A-7 to A-14). It was observed that only a low degree of branching of the comb polymer together with a small amount of imide functionality results in a significant reduction of friction. To balance the friction reducing effect good viscometric properties and solubility in Group III base oils like Nexbase 3043 or Yubase 4+ is necessary. It was further found that all 3 properties are only met when small amounts of imide are introduced and the polarity of the polymer backbone is increased. However, when the imide content is increased the solubility in the above-named oils is not guaranteed anymore (see additional example 1).

(62) It was surprisingly found that those polymers which had the best viscometric properties in the formulations also exhibited the lowest traction coefficients, especially in the low speed regime. The imide functionalization therefore did not only lead to the targeted lower traction but in addition enabled the development of combs with improved viscometric performance which in the end resulted in improved FE in the engine.

(63) It could be shown that adding dispersant property to a comb polymer has advantageous effects on fuel consumption due to the following features: 1) reducing friction, 2) improving viscometric properties like lowering KV.sub.40 and HTHS.sub.100.

(64) These findings do especially mean that the addition of friction reducing property into a comb polymer enables the formulation of engine oils with at least reduced or even no friction modifier in the DI package of the engine oil formulation what at the end leads to cost savings.