HIGH VISCOSITY POLYACRYLATE BASE FLUIDS

Abstract

Low molecular weight polyalkyl acrylate polymers can be used as high viscosity base fluids. A corresponding method can be used for their preparation. Lubricant compositions may contain such low molecular weight polyalkyl acrylate polymers and the compositions may be used as automatic transmission fluids, manual transmission fluids, continuously variable transmission fluids, gear oil formulations, industrial gear oil formulations, axle fluid formulations, dual clutch transmission fluids, dedicated hybrid transmission fluids, or hydraulic oils.

Claims

1. A lubricant formulation, comprising: a base oil comprising at least one polyalkyl acrylate, wherein the at least one polyalkyl acrylate comprises: (a) 95 to 100% by weight of at least one branched C.sub.8-10-alkyl acrylate; and (b) 0 to 5% by weight of at least one C.sub.1-20-alkyl (meth)acrylate, wherein a weight-average molecular weight of the at least one polyalkyl acrylate is in the range of 7,000 to 25,000 g/mol and a residual monomer content is 0.1% or lower.

2. The lubricant formulation according to claim 1, wherein the at least one polyalkyl acrylate consists of 100% by weight of the at least one branched C.sub.8-10-alkyl acrylate.

3. The lubricant formulation according to claim 1, wherein the at least one branched C.sub.8-10-alkyl acrylate is selected from the group consisting of 2-ethythexyl acrylate and 2-propylheptyl acrylate.

4. A base oil composition, comprising: (A) 70 to 95% by weight of at least one polyalkyl acrylate, comprising: (a) 95 to 100% by weight of at least one branched C.sub.8-10-alkyl acrylate; and (b) 0 to 5% by weight of at least one C.sub.1-20-alkyl (meth)acrylate, wherein a weight-average molecular weight of the at least one polyalkyl acrylate is in the range of 7,000 to 25,000 g/mol and a residual monomer content is 0.1% or lower; and (B) 5 to 30% by weight of a base oil selected from the group consisting of API Group II oils, API Group III oils, API Group IV oils, and mixtures thereof, based on a total weight of the base oil composition.

5. The base oil composition according to claim 4, wherein the at least one polyalkyl acrylate consists of 100% by weight of the at least one branched C.sub.8-10-alkyl acrylate.

6. The base oil composition according to claim 4, wherein the at least one branched C.sub.8-10-alkyl acrylate is selected from the group consisting of 2-ethylhexyl acrylate and 2-propylheptyl acrylate.

7. The base oil composition according to claim 4, wherein the at least one branched C.sub.8-10-alkyl acrylate is ethylhexyl acrylate.

8. The base oil composition according to claim 4, wherein the base oil composition is an industrial gear oil.

9. A polyalkyl acrylate, comprising: a) 95 to 100% by weight of at least one branched C.sub.8-10-alkyl acrylate; and (b) 0 to 5% by weight of at least one C.sub.1-20-alkyl (meth)acrylate, wherein a weight-average molecular weight of the polyalkyl acrylate is in the range of 7,000 to 25,000 g/mol and a residual monomer content is 0.1% by weight or lower.

10. The polyalkyl acrylate according to claim 9, consisting of 100% by weight of the at least one branched C.sub.8-10-alkyl acrylate.

11. The polyalkyl acrylate according to claim 9, wherein the at least one branched C.sub.8-10-alkyl acrylate is selected from the group consisting of 2-ethylhexyl acrylate and 2-propylheptyl acrylate.

12. The polyalkyl acrylate according to claim 9, wherein the at least one branched C.sub.8-10-alkyl acrylate is ethylhexyl acrylate.

13. A lubricating composition, comprising: (A) 20 to 60% by weight of at least one polyalkyl acrylate, comprising: (a) 95 to 100% by weight of at least one branched C.sub.8-10-alkyl acrylate; and (b) 0 to 5% by weight of at least one C.sub.1-20-alkyl (meth)acrylate, based on a total weight of the at least one polyalkyl acrylate, wherein a weight-average molecular weight of the at least one polyalkyl acrylate is in the range of 7,000 to 25,000 g/mol and a residual monomer content is 0.1% by weight or lower; (B) 40 to 80% by weight of a base oil selected from the group consisting of API Group II oils, API Group III oils, API Group IV oils, and mixtures thereof; and (C) 0 to 5% by weight of one or more additives, based on a total weight of the lubricating composition.

14. The lubricating composition according to claim 8, wherein the one or more additives are selected from the group consisting of pour point depressants, dispersants, defoamers, detergents, demulsifiers, antioxidants, antiwear additives, extreme pressure additives, friction modifiers, anticorrosion additives, dyes and mixtures thereof.

15. A process for preparing at least one polyalkyl acrylate, the process comprising: (i) charging a reaction vessel with a base oil; (ii) heating the base oil of (i) to a reaction temperature of 130° C. to 170° C.; (iii) constantly feeding a mixture of at least one branched C.sub.8-10-alkyl acrylate and 0.1 to 1.2% of an initiator, based on an amount of the at least one branched C.sub.8-10-alkyl acrylate, to the reaction vessel over a time of 120 to 240 minutes, to obtain a reaction mixture; (iv) optionally, stirring the reaction mixture obtained under (iii) for another 50 to 90 minutes; and (v) cooling the reaction mixture obtained under (iv) to an ambient temperature and obtaining the at least one polyalkyl acrylate; wherein the at least one polyalkyl acrylate comprises: (a) 95 to 100% by weight of the at least one branched C.sub.8-10-alkyl acrylate; and (b) 0 to 5% by weight of at least one C.sub.1-20-alkyl (meth)acrylate, wherein a weight-average molecular weight of the at least one polyalkyl acrylate is in the range of 7,000 to 25 000 g/mol and a residual monomer content is 0.1% by weight or lower.

16. The lubricant formulation according to claim 1, wherein the lubricant formulation is an industrial gear oil formulation.

Description

[0112] The invention has been further illustrated by the following non-limiting examples.

Experimental Part

Abbreviations

[0113] BV bulk viscosity [0114] BV40 bulk viscosity@40° C. [0115] BV100 bulk viscosity@100° C. [0116] C600R Group II base oil from Chevron with a KV.sub.100 of 12 cSt [0117] DDM dodecyl mercaptane [0118] EHA ethylhexyl acrylate, commercially available from Aldrich [0119] HA hexyl acrylate [0120] Hitec® 307 DI Package commercially available from Afton [0121] IDA iso-decyl acrylate, commercially available from Aldrich [0122] ITDA iso-tridecyl acrylate, commercially available from Aldrich [0123] KV kinematic viscosity measured according to ASTM D445 [0124] KV.sub.40 kinematic viscosity measured@40° C. to ASTM D445 [0125] KV.sub.100 kinematic viscosity measured@100° C. to ASTM D445 [0126] KV.sub.−10 kinematic viscosity measured@−10° C. to ASTM D445 [0127] LA lauryl acrylate, dodecyl acrylate, commercially available from Aldrich [0128] M.sub.n number-average molecular weight [0129] M.sub.w weight-average molecular weight [0130] NB3080 Nexbase® 3080; Group III base oil from Neste with a KV.sub.100 of 7.9 cSt [0131] PAO6 polyalphaolefin base oil with a KV.sub.100 of 6 cSt [0132] PAO8 polyalphaolefin base oil with a KV.sub.100 of 8 cSt [0133] PDI polydispersity index [0134] PHA propylheptyl acrylate, commercially available from Aldrich [0135] PP pour point [0136] VI viscosity index [0137] VPL 1-180 VISCOPLEX® 1-180, pour point depressant commercially available from Evonik [0138] VPL 14-520 VISCOPLEX® 14-520, defoamer commercially available from Evonik [0139] Yubase 6 Group III base oil from SK Lubricants with a KV.sub.100 of 6 cSt

Test Methods

[0140] The polyalkyl acrylates according to the present invention and the comparative examples were characterized with respect to their molecular weight, PDI and bulk viscosity at 40° C. and 100° C. (BV40 and BV100).

[0141] Molecular weights were determined by size exclusion chromatography (SEC) using commercially available polymethylmethacrylate (PMMA) standards. The determination is effected by gel permeation chromatography (GPC) to DIN 55672-1 with THF as eluent (flow rate: 1 mL/min; injected volume: 100 μl).

[0142] The lubricating oil compositions including the polyalkyl acrylates according to the present invention and comparative examples were characterized with respect to kinematic viscosity at −10° C. (KV.sub.−10), 40° C. (KV.sub.40) and 100° C. (KV.sub.100) to ASTM D445, their viscosity index (VI) to ASTM D2270, Brookfield viscosity to ASTM D-2983 and their pour point to ASTM D5950.

[0143] The lubricating compositions were formulated to ISO viscosity grade 220 or 320, within a range of ±10%. The International Standards Organization Viscosity Grade, ISO VG, is recommended for industrial applications.

[0144] The reference temperature of 40° C. represents the operating temperature in machinery.

[0145] This ISO viscosity classification is consequently based on kinematic viscosity at 40° C. (KV.sub.40).

TABLE-US-00002 Midpoint Viscosity Kinematic viscosity limits ISO @40° C. @40° C. Viscosity Grade [mm.sup.2/s] [mm.sup.2/s] 220 220 198 242 320 320 288 352

[0146] Tapered roller bearing measurements to determine the shear loss were run (20 hours, 60° C., 5 kN and 1450 rpm) to CEC L-45-A-99 and corresponding kinematic viscosities measured at 40° C. (KV.sub.40) and 100° C. (KV.sub.100) to ASTM D-445

[0147] In connection with the evaluation of gear oil formulations, foam tests to ASTM D892 were run, air release was determined to DIN ISO 9120.

Synthesis 1: General Synthesis of Polyalkyl Acrylates Using a CTA Feed Process

[0148] A round-bottom flask equipped with a glass stir rod, nitrogen inlet, reflux condenser and thermometer was charged with 41.9 g NB3080. 200.0 g EHA, 6.0 g DDM, 0.5 g tert-butylper-2-ethylhexanoate and 4.5 g NB080 were added within 2 hours at 110° C. under nitrogen bubbling. Afterwards, 0.4 g tert-butylper-2-ethylhexanoate and 3.6 g NB3080 were fed to the reaction mixture over 1 hour.

Synthesis 2: General Synthesis of Polyalkyl Acrylates Using ATRP

[0149] 1.88 g of pentamethyldiethylenetriamine, 0.78 g CuBr and 100.0 g of EHA were purged with nitrogen for 30 minutes and heated to 65° C. After addition of 2.12 g of ethylene bis(2-bromoisobutyrate) the reaction mixture was heated to 95° C. After 4 hours 1.10 g DDM were added. The mixture was stirred for 2 h, cooled to room temperature and purified by pressure filtration. After filtration, a clear and slightly yellow colored highly viscous liquid was obtained which was applied without further purification.

Synthesis 3: General Synthesis of Polyalkyl Acrylates Using the Novel Acrylate Process

[0150] 0.85 g (0.5% by weight, based on the amount of EHA) of dicumylperoxide dissolved in 170.0 g of EHA was fed to 26.77 g of NB3080 under nitrogen at 150° C. over 3 hours. Optionally, after this time, the temperature of the mixture was lowered to 110° C. and 0.17 g of tert-butylper-2-ethylhexanoate (0.1% by weight, based on the amount of EHA) dissolved in 3.23 g of NB3080 was added. After stirring for another hour, the resulting clear polymer solution was cooled down and used in subsequent experiments without further purification.

Synthesis 4: General Synthesis of Polyalkyl Methacrylates

[0151] A round-bottom flask equipped with a glass stir rod, nitrogen inlet, reflux condenser and thermometer was charged with 284.4 g EHMA and 8.9 g DDM. 0.75 g tert-butylper-2-ethylhexanoate and 15.0 g EHMA were added within 3 hours at 110° C. under nitrogen bubbling. After holding the temperature for 1 hour, 0.6 g tert-butylper-2-ethylhexanoate were added. After waiting for another hour, a final shot of 0.6 g tert-butylper-2-ethylhexanoate was added and the solution as stirred at 110° C. for one hour. The resulting clear and highly viscous liquid was used without further purification.

TABLE-US-00003 TABLE 1 Initiators used in the different syntheses. Initiator Name A tert-butylper-2-ethylhexanoate B dicumylperoxide C dicetyl peroxydicarbonate D tert-butylperbenzoate E 1,1-di-tert-butylperoxy-3,3,5- trimethyl cyclohexane

[0152] All initiators are commercially available. Diacetyl peroxydicarbonate is commercially available from AkzoNobel.

[0153] The compositions of reaction mixtures used to prepare the working examples and comparative examples are shown in the following Table 2. The amounts of monomer and base oil do always add up to 100%. The amounts of initiator and DDM are given relative to the total amount of monomer.

TABLE-US-00004 TABLE 2 Compositions of reaction mixtures used to prepare the working examples and comparative examples. Initiator A B C D E DDM Example # Monomer Base Oil [%] [%] [%] [%] [%] [%]  1 EHA NB3080 0.25 — — — — 3.00  2 EHA NB3080 0.25 — — — — 1.90  3 EHA NB3080 0.50 — — — — 1.90  4 EHA NB3080 — — — — — —  5 EHA NB3080 1.00 — — — — —  6 EHA NB3080 — 1.25 — — — —  7 EHA NB3080 — — 2.64 — — —  8 EHA NB3080 — 0.90 — — — —  9 EHA NB3080 — 0.90 — — — — 10 EHA NB3080 — 0.90 — — — — 11 EHA NB3080 — 0.90 — — — — 12 EHA NB3080 — 0.90 — — — — 13 EHA NB3080 — 0.90 — — — — 14 EHA NB3080 — 0.50 — — — — 15 EHA NB3080 — 0.90 — — — — 16 EHA NB3080 — 0.90 — — — — 17 EHA NB3080 — 0.50 — — — — 18 EHA NB3080 — 0.30 — — — — 19 EHA NB3080 — 0.20 — — — — 20 EHA NB3080 — 0.05 — — — — 21 EHA NB3080 — 0.50 — — — — 22 HA NB3080 — 0.50 — — — — 23 IDA NB3080 — 0.50 — — — — 24 LA NB3080 — 0.50 — — — — 25 HA NB3080 — 0.50 — — — — 26 ITDA NB3080 — 0.50 — — — — 27 EHA C600R — 0.50 — — — — 28 EHA C600R — 0.50 — — — — 29 EHA C600R — 0.50 — — — — 30 EHA C600R — 0.10 — — — — 31 EHA C600R — 0.20 — — — — 32 EHA C600R — 0.30 — — — — 33 EHA C600R — 0.40 — — — — 34 EHA Yubase 6 — 0.50 — — — — 35 EHA PAO 8 — 0.50 — — — — 36 EHA PAO 8 — 0.50 — — — — 37 PHA PAO 8 — 0.50 — — — — 38 PHA PAO 8 — 0.50 — — — — 39 PHA PAO 8 — 0.20 — — — — 40 PHA PAO 8 — 0.10 — — — — 41 EHA PAO 8 — 0.50 — — — — 42 EHA PAO 8 — 0.90 — — — — 43 EHA PAO 8 — 1.30 — — — — 44 EHA PAO 8 — — — 0.50 — — 45 EHA PAO 8 — — — — 0.50 — 46 EHMA — 0.25 — — — — 2.95

CONCLUSIONS

[0154] Examples 1 to 4 were prepared according to known processes. Although temperature control and economics were poor, the targeted polymers could be prepared. Examples 1 to 4 are encompassed by claim 1 of the present invention and show good performance as base oils in lubricant compositions (see results presented further down in Table 5). Aside from this, Examples 1 to 3 contain a substantial amount of sulphur which is considered to be detrimental to the compatibility with certain metals and rubber seals. Examples 1 to 3 do further contain high residual monomer contents (see Table 4 further down).

[0155] Example 4 is produced by ATRP which is very challenging in commercial production as lubricants require a product free of contaminants. Removal of the process chemicals from the highly viscous product has proven to be very time-consuming, even on lab-scale.

[0156] To obtain control over temperature, a monomer feed process was used. Attempts to adjust the molecular weight of the polymers to the targeted range below 25,000 g/mol using sulfur-containing chain transfer agents yielded no satisfying residual monomer levels.

[0157] Aside from this, the required amounts of chain transfer agent to be used in this process was quite significant, leading to unwanted high sulfur levels in the product (Examples 1 to 3; 1.90 and 3.00% of DDM are used, respectively). Despite their positive effects on oxidation and wear performance, sulfur components are known to cause problems with yellow metals and rubber sealings (see L. R. Rudnick, Lubricant Additives: Chemistry and Applications, 3rd Edition, 2017, p.197ff).

[0158] Examples 5, 7, 20, 22, 30, 44 and 45 are comparative examples as the molecular weight M.sub.w is outside the claimed range of 7000 to 25,000 g/mol.

[0159] Examples 6, 8-19, 21, 23, 27-29 and 31-43 are in accordance with the present invention.

[0160] Examples 22, 24-26 and 46 are comparative examples as they are prepared from monomers that are not encompassed by claim 1.

[0161] The following Table 3 provides details regarding the preparation method used to synthesize working examples and comparative examples.

TABLE-US-00005 TABLE 3 Process details. Feed Time Temperature Concentration Example # Process [h] [° C.] [%]  1 Synthesis 1 2 110 80  2 Synthesis 1 5 110 60  3 Synthesis 1 5 110 60  4 Synthesis 2 — — 50  5*.sup.) Synthesis 3 4 110 60  6 Synthesis 3 4 160 60  7*.sup.) Synthesis 3 4  84 60  8 Synthesis 3 4 160 60  9 Synthesis 3 4 160 80 10 Synthesis 3 4 160 85 11 Synthesis 3 3 160 85 12 Synthesis 3 3 150 85 13 Synthesis 3 3 150 85 14 Synthesis 3 3 150 90 15 Synthesis 3 3 150 90 16 Synthesis 3 3 150 85 17 Synthesis 3 2 150 85 18 Synthesis 3 3 150 85 19 Synthesis 3 3 150 85 20*.sup.) Synthesis 3 3 150 85 21 Synthesis 3 3 150 85 22*.sup.) Synthesis 3 3 150 85 23 Synthesis 3 3 150 75 24*.sup.) Synthesis 3 3 150 70 25*.sup.) Synthesis 3 3 150 50 26*.sup.) Synthesis 3 3 150 75 27 Synthesis 3 3 150 85 28 Synthesis 3 3 150 80 29 Synthesis 3 3 150 90 30*.sup.) Synthesis 3 3 150 80 31 Synthesis 3 3 150 90 32 Synthesis 3 3 150 90 33 Synthesis 3 3 150 90 34 Synthesis 3 3 150 85 35 Synthesis 3 3 150 85 36 Synthesis 3 3 150 85 37 Synthesis 3 3 150 85 38 Synthesis 3 3 150 80 39 Synthesis 3 3 150 90 40 Synthesis 3 3 150 90 41 Synthesis 3 3 150 80 42 Synthesis 3 3 150 85 43 Synthesis 3 3 150 85 44*.sup.) Synthesis 3 3 140 85 45*.sup.) Synthesis 3 3 125 85 46*.sup.) Synthesis 4 3 110 100 *.sup.)comparative example

[0162] First attempts to prepare the targeted polyacrylates in a batch process similar to poly(EHMA) (Synthesis 4, Example 46) failed due to poor temperature control. Good results were obtained by using the ATRP process (Synthesis 2, Example 4), but due to the poor economics a new process had to be developed.

[0163] A novel feed process without chain transfer agent was developed which provided polymers with very low residual monomer content (Synthesis 3). Low molecular weights are accessible with good conversion and narrow molecular weight distributions. The process works well, especially at elevated temperatures which are beneficial for reaching high temperatures and good conversions (see e.g. Examples 5, 6, 7, 41, 44 and 45).

[0164] Aside from temperature that needs to be adjusted to the respective initiator system, the molecular weight can be controlled by several measures. Surprisingly low is the influence of the amount of initiator. Very small amounts of initiator result in an increase of the molecular weight, but around 0.5 wt.% variations of the initiator content result in insignificant changes in the molecular weight (Examples 16-20, 29, 31, 32, 33, 42 and 43).

[0165] Feed times have also just minor influence in a reasonable window of 2-4 hours (see Examples 10, 11, 17 and 21).

[0166] The molecular weight can be also influenced by the amount of base oil in the heel at the beginning of the reaction (see Examples 8-10, 22, 25 and 27-29).

[0167] The characteristics of the polyalkyl acrylates prepared in the course of the present invention are disclosed in the following Table 4.

TABLE-US-00006 TABLE 4 Characteristics of the polyalkyl acrylates prepared according to the present invention. Example M.sub.w M.sub.n ReMo BV40 BV100 # [g/mol] [g/mol] PDI [%] [mm.sup.2/s] [mm.sup.2/s] VI  1*.sup.) 13,000 7,060 1.84 0.24 1141 104.4 185  2*.sup.) 16,500 8,440 1.95 0.54 499 54.4 175  3*.sup.) 15,600 8,010 1.95 0.49 480 52.4 173  4*.sup.) 14,400 8,460 1.70 0.01 323 38.3 165  5*.sup.) 34,400 11,300 3.04 0.05 1076 108.1 197  6 7,590 4,730 1.60 0.04 294 31.9 149  7*.sup.) 52,200 15,700 3.32 0.18 1472 148.6 214  8 7,130 4,650 1.53 0.03 287 30.8 147  9 10,500 5,560 1.89 0.01 983 85.4 170 10 12,600 5,960 2.11 0.01 1577 126.3 180 11 11,600 5,750 2.02 0.02 1329 108.6 175 12 16,700 7,060 2.37 0.01 2191 172.1 194 13 13,900 6,430 2.16 <0.01  1798 144.5 187 14 18,600 7,400 2.51 <0.01  3457 252.7 208 15 18,700 7,270 2.57 0.09 3348 244.9 206 16 15,100 6,720 2.25 0.01 1936 153.7 189 17 15,200 7,030 2.16 <0.01  2078 162.0 190 18 16,100 7,240 2.22 0.01 2155 170.0 194 19 17,200 7,500 2.29 0.03 2311 183.0 198 20*.sup.) 30,900 10,300 3.00 0.03 4360 339.2 231 21 15,200 7,190 2.11 0.06 2131 168.6 194 22*.sup.) 53,600 11,800 4.54 0.10 3446 318.3 247 23 15,400 7,490 2.06 — 975 82.9 166 24*.sup.) 15,600 8,530 1.83 — 314 43.0 192 25*.sup.) 14,800 7,570 1.96 — 61 9.6 138 26*.sup.) 14,700 7,270 2.02 — 1320 95.9 157 27 16,300 7,470 2.18 0.02 2723 203.8 198 28 13,700 6,930 1.98 0.06 1872 138.2 176 29 18,800 7,670 2.45 0.05 4441 305.1 212 30*.sup.) 25,100 9,830 2.55 — 6444 434.1 231 31 23,300 9,320 2.50 — — — — 32 20,600 8,640 2.38 — — — — 33 20,800 8,900 2.34 — — — — 34 16,100 7,270 2.21 0.02 2165 172.0 195 35 18,600 8,380 2.22 <0.01  2771 216.1 206 36 17,300 8,060 2.15 0.04 2537 200.4 203 37 14,100 7,270 1.94 <0.01  1671 145.8 197 38 11,500 6,560 1.75 0.09 1016 90.6 175 0.02 39 15,400 7,770 1.98 0.05 2556 201.0 203 40 17,800 8,800 2.02 — — — — 41 14,900 7,600 1.96 0.04 1645 138.0 190 42 20,200 8,530 2.37 — — 229.0 — 43 20,200 8,190 2.47 — 2704 221.8 213 44 30,900 10,200 3.03 <0.01  4587 345.7 229 45*.sup.) 96,700 16,400 5.90 <0.01  13648 993.3 290 46*.sup.) 14,800 7,990 1.85 — — — — *.sup.)comparative example

[0168] It can be seen that all polymers prepared by Synthesis 3 have residual monomer contents of 0.1% or even well below. All working examples which are in accordance with the present invention have bulk viscosities (BV40) well above 320 mm.sup.2/s, i.e. can be easily formulated to ISO viscosity grade 320.

[0169] It is further visible that polymers having a weight-average molecular weight of around 7,000 g/mol show borderline bulk viscosities at 40° C. (see Examples 6 and 8), i.e. they can only be formulated to an ISO viscosity grade of 220 or below.

[0170] Different acrylate monomers were used to generate homopolymers for the evaluation as high viscosity base fluids. Hexyl acrylate has proven to be completely unsuitable as the bulk viscosity of the synthesized polymers was too low to be of any use (Example 25). Even with a massive boost in molecular weight, high treat rate and the expected lack of shear stability are so poor that no further investigation was done (Example 22).

Lubricating Compositions

[0171] To proof the performance of the acrylate polymers prepared in accordance with the present invention, lubricating compositions were prepared by using the acrylate polymers as a base fluid and mixing them together with other base oil(s) to reach ISO viscosity grades of 220 and 320. The results for typical formulation parameters like KV100, VI, PP and Brookfield viscosity are presented in the following Tables 5 to 9.

[0172] While acrylates and methacrylates are often regarded interchangeable in the field of VI improvers, the results presented in the present invention clearly show a difference when using them as high viscosity base stocks. While the EHMA homopolymer (Example 46) showed very poor miscibility with Nexbase 3080 (an API Group III oil), and phase separation was observed, no such issues were found for EHA homopolymers in any of the used solvents and concentrations.

[0173] Poly(lauryl acrylate, LA) (Example 24) showed poor performance in treat rate and low temperature properties in a fully formulated ISO 320 formulation. Poly(isodecylacrylate) (Example 23) and poly(isotridecylacrylate) (Example 26) both showed insufficient performance at low temperatures compared to poly(EHA).

[0174] Improved low temperature performance was observed for poly(propylheptylacrylate) (Examples 37-40) at the cost of a slightly increased treat rate compared to poly(EHA).

[0175] Due to the high conversion of the monomers and as no other volatile components are used in the process such as chain transfer agents, the flashpoints of the acrylate polymers are very high. Data are given for Example 27 and the measured flashpoint (COC method ASTM D92) was the same as specified for the dilution oil Chevron 600R used in the process (Example 27).

[0176] For the use of Example 30, precipitation was observed in an ISO 220 formulation in API Group III base oil. As this was not observed for other samples at lower molecular weight, it can be concluded that the in all other experiments observed perfect oil compatibility even in extremely poor solvency base oils is limited to molecular weights below 25,000 g/mol for EHA homopolymers.

TABLE-US-00007 TABLE 5 Formulation data of compositions A formulated to ISO 320 (KV.sub.40 = 320 ± 10%) Composition A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 Example 1 [%] 65.70 — — — — — — — — Example 2 [%] — 80.90 — — — — — — — Example 3 [%] — — 81.80 — — — — — — Example 4 [%] — — — 46.9 — — — — — Example 9 [%] — — — — 69.00 — — — — Example 10 [%] — — — — — 63.00 — — — Example 12 [%] — — — — — — 58.00 — — Example 13 [%] — — — — — — — 60.20 — Example 21 [%] 58.00 Viscoplex 1-180 [%] 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 NB3080 [%] 30.95 15.75 14.85 49.75 27.65 33.65 38.65 36.45 38.65 Blend Total [%] 100.0 100.0 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Polymer content [%] 52.6 48.5 49.1 46.9 55.2 53.55 49.3 51.8 49.3 KV.sub.40 [mm.sup.2/s] 326.1 322.9 319.4 317.8 321.2 322.2 322.0 320.9 317.1 KV.sub.100 [mm.sup.2/s] 37.45 37.71 37.03 36.73 35.27 35.71 36.65 36.07 36.21 VI 164 167 165 164 156 157 162 159 162 KV.sub.−10 [mm.sup.2/s] 14,020 14,270 14,618 14,828 14,913 14,661 14,713 Brookfield (Air) 184,000 510,000 244,000 140,000 152,000 216,000 160,000 [mPas] 188,000 498,000 240,000 140,000 152,000 200,000 152,000 PP [° C.] −33 −36 −30 −39 −33 −36 −33 KRL @20 hours KV.sub.40 [mm.sup.2/s] 320.5 314.7 317.5 KV.sub.100 [mm.sup.2/s] 36.78 36.74 35.93 shear loss 1.8 2.6 0.8 @100° C. [%] RL 209 reference 9.9 9.9 10.2 oil value [%]

TABLE-US-00008 TABLE 6 Formulation data of compositions A formulated to ISO 320 (KV.sub.40 = 320 ± 10%) Composition A-10 A-11 A-12 A-13 A-14 A-15 A-16 A-17 Example 23 [%] 67.50 — — — — — — — Example 24 [%] — 96.65 — — — — — — Example 26 [%] — — 62.00 — — — — — Example 35 [%] — — — 54.70 — — — — Example 36 [%] — — — — 56.00 — — — Example 37 [%] — — — — — 62.40 — — Example 41 [%] — — — — — — 61.20 — Example 46 [%] 30.55 Viscoplex 1-180 [%] 0.70 0.70 0.70 — — — — 0.70 Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 NB3080 [%] 29.15 — 34.65 — — — — 66.10 PAO 8 — — — 42.65 41.35 34.95 36.15 — Blend Total [%] 100.0 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Polymer content [%] 50.63 67.66 46.50 46.50 47.60 53.04 48.96 30.55 KV.sub.40 314.5 315.5 313.6 325.3 325.1 328.1 323.2 309.8 [mm.sup.2/s] KV.sub.100 35.20 42.94 33.06 38.02 37.86 38.13 37.09 31.54 [mm.sup.2/s] VI 158 193 147 167 166 166 163 141 KV.sub.−10 15,695 solid 16,180 solid [mm.sup.2/s] Brookfield (Air) 220,000 solid 200,000 108,000 94,000 82,000 110,000 solid [mPas] 216,000 solid 212,000 112,000 96,000 81,000 106,000 solid PP [° C.] −39 −6 −36 −36 −39 −45 −36 ??? KRL @20 hours KV.sub.40 315.3 317.0 324.5 311.0 [mm.sup.2/s] KV.sub.100 36.86 36.79 37.69 35.76 [mm.sup.2/s] shear loss 3.1 2.8 1.2 3.6 @100° C. [%] RL 209 reference 9.7 9.7 9.7 8.3 oil value [%]

TABLE-US-00009 TABLE 7 Formulation data of compositions A formulated to ISO 320 (KV.sub.40 = 320 ± 10%) Composition A-18 A-19 A-20 A-21 A-22 A-23 A-24 A-25 A-26 A-27 Example 34 [%] 57.80 61.00 62.70 — — — — — — — Example 27 [%] — — — 42.0 — — — — — — Example 35 [%] — — — — 54.70 — — — — — Example 36 [%] — — — — — 56.00 — — — — Example 37 [%] — — — — — — 62.40 — — Example 39 [%] — — — — — — — 57.60 — Example 40 [%] — — — — — — — — 54.70 — Example 41 [%] 61.20 Viscoplex 1-180 [%] 0.70 0.70 — 0.80 — — — — — — Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 Chevron 600R [%] — — — 54.50 — — — — — — NB3080 [%] 38.85 — — — — — — — — — Yubase 6 [%] — 35.65 — — — — — — — — PAO 6 [%] — — 34.65 — — — — — — — PAO 8 [%] — — — — 42.65 41.35 34.95 39.75 42.65 36.15 Blend Total [%] 100.0 100.0 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Polymer content [%] 49.13 51.85 53.30 35.70 46.50 47.60 53.04 51.84 49.23 48.96 top treat 2000 2000 2000 — — — — — — — Viscoplex 14-520 [ppm] KV.sub.40 324.7 324.6 322.7 319.2 325.3 325.1 328.1 323.7 317.0 323.2 [mm.sup.2/s] KV.sub.100 37.37 37.89 38.31 32.37 38.02 37.86 38.13 38.06 38.05 37.09 [mm.sup.2/s] VI 164 167 169 142 167 166 166 168 170 163 Brookfield (Air) 128,000 95,000 143,970 108,000 94,000 82,000 80,000 74,000 110,000 [mPas] 130,000 96,000 112,000 96,000 81,000 80,000 72,000 106,000 PP [° C.] −36 −36 −39 −33 −36 −39 −45 −48 −45 −36 KRL @20 hours KV.sub.40 310.8 309.6 313.3 309.3 315.3 317.0 324.5 311.0 [mm.sup.2/s] KV.sub.100 35.69 36.13 37.21 31.69 36.86 36.79 37.69 35.76 [mm.sup.2/s] shear loss 4.5 4.6 2.9 2.1 3.1 2.8 1.2 3.6 @100° C. [%] RL 209 reference 10.1 10.1 10.1 9.7 9.7 9.7 8.3 oil value [%] water content Karl 0.02 0.02 0.02 Fischer [%] flash point 238 232 234 [° C.]

[0177] For ISO 320 formulations, the data disclosed in Tables 5 to 6 show that for EHA and PHA polymers the required polymer content is 40 to 60% by weight. The polymers in accordance with the present invention show good solubility in the used base oils (i.e. Group III and IV oils as well as mixtures thereof) at all temperatures down to the PP (pour point) of the formulation.

[0178] The polymers of the present invention further show good low temperature behavior (see KV.sub.−10 and BF-26 values) and pour points what is remarkable for polymers having such high polarities.

[0179] The formulations comprising the polymers of the present invention have high VIs of around 160. This means that the KV.sub.100 of the formulations is higher than the KV.sub.100 of a regular mineral oil-based ISO 460 formulation. This allows the combination of high protection of the equipment and good flow properties at low temperatures.

[0180] Formulation A17 provides the surprising result that the EHMA polymer is different to the EHA polymers; the EHMA polymer is not compatible with the base oils at low temperatures even though the treat rate is substantially lower. Such a difference between acrylates and methacrylates has not been reported before as oil soluble VI improvers are not pushed that hard to the solubility limits. The combination of high treat rates and a rather thick apolar base oil with poor solvency is a special case not covered by the state of the art so far.

[0181] When comparing different acrylate homopolymers, poly-LA (A-11) is obviously unsuitable as the formulation becomes solid at temperatures above −10° C. While poly-IDA performs only slightly inferior in terms of VI and low-temperature properties compared to EHA and PHA polymers the gap is larger for poly-ITDA. Also, the polarity of poly-ITDA is lower which does not make it a promising candidate compared to the other options.

TABLE-US-00010 TABLE 8 Foam test Composition A-18 A-19 A-20 sequence I Foam after Blowing Period @24° C. 0 0 0 [mL] sequence I Foam after 10 min @24° C. 0 0 0 [mL] sequence I Collapse time @24° C. 0 0 0 [s] sequence II Foam after Blowing Period @94° C. 210 40 50 [mL] sequence II Foam after 10 min @94° C. 0 0 0 [mL] sequence II Collapse time @94° C. 334 129 134 [s] sequence III Foam after Blowing Period @24° C. 0 0 0 [mL] sequence III Foam after 10 min @24° C. 0 0 0 [mL] sequence III Collapse time @24° C. 0 0 0 [s]

[0182] Due to the high polarity of some of the polymer blocks an impact on performance tests involving interfaces was expected. For the air release and foam tests no strong effect was observed.

[0183] Filtration of the fluid is no problem at all which confirms the visual observation that the polymer and the additives are completely dissolved in the oil phase.

TABLE-US-00011 TABLE 9 Formulation data of compositions B formulated to ISO 220 (KV.sub.40 = 220 ± 10%) Composition B-1 B-2 B-3 B-4 B-5 B-6 Example 28 [%] 35.00 — — — — — Example 29 [%] — 28.00 — — — — Example 30 [%] — — 25.00 — — — Example 32 [%] — — — 27.10 — — Example 33 [%] — — — — 27.10 — Example 31 [%] — — — — — — Hitec 307 [%] 2.65 2.65 2.65 2.65 2.65 2.65 Chevron 600R [%] 62.35 69.35 72.35 70.25 70.25 — Blend Total [%] 100.0 100.0 100.00 100.00 100.00 100.00 Polymer content [%] 28.00 25.20 20.00 24.39 24.39 — KV.sub.40 [mm.sup.2/s] 218.7 217.9 219.8 220.9 219.8 — KV.sub.100 [mm.sup.2/s] 23.51 23.67 24.14 24.00 23.93 — VI 133 134 137 135 136 — KRL @20 hours KV.sub.40 [mm.sup.2/s] 216.5 209.2 KV.sub.100 [mm.sup.2/s] 23.23 22.80 shear loss @100° C. [%] 1.2 3.7 RL209 shear loss @100° C. [%] 10.1 10.1

[0184] For ISO 220 formulations, the data disclosed in Table 9 show that the required minimum polymer content is about 20% by weight. The polymers in accordance with the present invention show good solubility in the used base oils (i.e. Group III and IV oils as well as mixtures thereof) at all temperatures down to the pour point of the formulation. The resulting formulations have high VIs of around 130.

[0185] Different to the previously described formulations, the ISO220 formulations in Table 9 are more focused on formulation cost optimization rather than performance. For this reason, the treat rate of the acrylate polymers was minimized by choosing the lower viscosity grade and a Group II base fluid. The Group II base fluid does not only offer an economic advantage due to the simpler refinery process, it also has a higher viscosity than Group III and IV base fluids used in the previous examples which allows the reduction of the polymer treat rate below 30% by weight while maintaining excellent shear stability.

[0186] At such low treat rates, the positive influence on the VI is less pronounced, but still quite substantial. Not visible in the provided data, but apparent during formulation and investigation of the formulations is that the function of the inventive polymers as compatibilizer between additives and apolar base oils is in no way impaired at the reduced treat rates. Taking into account that an addition of 10% by weight of a polar low viscosity base stock with strong dissolving power is not uncommon in industrial gear oils based on apolar base stocks, this is an excellent result for the polyacrylates.