A HIGH-PRESSURE POLYMERIZATION PROCESS FOR LIQUID ETHYLENE COPOLYMERS

Abstract

The present invention relates to a continuous high-pressure polymerization process for the preparation of a liquid ethylene copolymer which comprises in polymerized form 20 to 60 wt % of ethylene; and at least 20 wt % of an acrylate, which is selected from C.sub.1-C.sub.22 alkyl (meth)acrylate, where a monomer feed comprising the ethylene and the acrylate is polymerized in the presence of at least 2 wt % of a chain transfer agent. The invention further relates to the liquid ethylene copolymer obtainable by the polymerization process; and to a lubricant comprising the liquid ethylene copolymer obtainable by the polymerization process; and to a method for reducing friction between moving surfaces comprising the step of contacting the surfaces with the lubricant or with the ethylene copolymer.

Claims

1.-17. (canceled)

18. A continuous high-pressure polymerization process for the preparation of a liquid ethylene copolymer which comprises in polymerized form 20 to 60 wt % of ethylene; and at least 20 wt % of an acrylate, which is selected from C.sub.1-C.sub.22 alkyl (meth)acrylate, where a monomer feed comprising the ethylene and the acrylate is polymerized in the presence of at least 2 wt % of a chain transfer agent.

19. The polymerization process according to claim 18, where the chain transfer agents are saturated or unsaturated hydrocarbons, aliphatic ketones, aliphatic aldehydes, or hydrogen, or mixtures thereof.

20. The polymerization process according to claim 18, where the chain transfer agents are propionaldehyde, methyl ethyl ketone, or hydrogen, or mixtures thereof.

21. The polymerization process according to claim 18, where the monomer feed is polymerized in the presence of 4 to 18 wt %, preferably 6 to 15 wt %, and in particular 9 to 13 wt % of the chain transfer agent.

22. The polymerization process according to claim 18 where polymerization is carried out in a stirred high-pressure autoclave.

23. The polymerization process according to claim 18, where the reaction temperature is in the range of 150 to 300° C., preferably 170 to 250° C., and in particular 190 to 230° C.

24. The polymerization process according to claim 18, where the polymerization process is carried out at a pressure in the range from 1000 to 4000 bar, preferably from 1200 to 2500 bar, and particularly 1600 to 2000 bar.

25. The polymerization process according to claim 18, where the ethylene copolymer has a pour point below 25° C., preferably below 20° C., and in particular below 15° C.

26. The polymerization process according to claim 18 where the ethylene copolymer comprises in polymerized form 25 to 55 wt % of the ethylene.

27. The polymerization process according to claim 18 where the ethylene copolymer comprises in polymerized form at least 30 wt %, preferably at least 40 wt %, and in particular at least 50 wt % of the acrylate.

28. The polymerization process according to claim 18 where the ethylene copolymer is free of further monomers beside the ethylene and the acrylate.

29. The polymerization process according to claim 18 where the acrylate comprises a polar acrylate selected from C.sub.1-C.sub.5 alkyl (meth)acrylate, and an unpolar acrylate selected from C.sub.6-C.sub.22 alkyl (meth)acrylate.

30. The polymerization process according to claim 29 where ethylene copolymer comprises in polymerized form 25 to 55 wt % of ethylene, at least 20 wt % of the polar acrylate, and at least 15 wt % of the unpolar acrylate.

31. The polymerization process according to claim 18 where the ethylene copolymer comprises less than 2 mol %, preferably less than 1 mol % of the vinylester of the formula (I) in polymerized form ##STR00004## where R.sup.c, R.sup.d, and R.sup.e are each independently H or C.sub.1-C.sub.4-alkyl, and R.sup.f is C.sub.1-C.sub.20 alkyl.

32. A liquid ethylene copolymer obtainable by the polymerization process as defined in claim 18.

33. A lubricant comprising the liquid ethylene copolymer obtainable by the polymerization process as defined in claim 18.

34. A method for reducing friction between moving surfaces comprising the step of contacting the surfaces with the lubricant as defined claim 33 or with the ethylene copolymer as defined in claim 32.

Description

EXAMPLES

[0202] NBA: N-butyl acrylate, [0203] EHA: 2-Ethylhexyl acrylate, commercially available from BASF SE. [0204] PHA: 2-Propylheptyl acrylate, commercially available from BASF SE. [0205] LA: Lauryl acrylate (60:40 mixture of C.sub.12:C.sub.14 alkyl acrylates) [0206] C17A: Heptadecyl acrylate, based on mixture of branched C17 alcanols, commercially available from BASF SE.

Preparation of Copolymers

[0207] A high-pressure autoclave, of the type described in the literature (M. Buback et al., Chem. Ing. Tech. 1994, 66, 510-513) was used for continuous copolymerization

[0208] Ethylene was fed continuously into a first compressor until approx. 250 bar. Separately from this, the amount of the acrylate was also compressed continuously to an intermediate pressure of 250 bar and was mixed with the ethylene fed. The ethylene acrylate mixture was further compressed using a second compressor. The reaction mixture is brought to a 1 liter autoclave with pressure and temperatures given also according to Table 1. The desired temperature is controlled depending on the amount of initiator tert-amyl peroxypivalate in isodecane, which is introduced to the autoclave separately from the monomer feed (about 1000-1500 ml/h).

[0209] Separately from this, the amount of chain transfer agent propionaldehyde (PA) or methylethyl ketone (MEK) was first compressed to an intermediate pressure of 250 bar and then fed continuously into the high-pressure autoclave with the aid of a further compressor under the reaction pressure.

[0210] The output of the reactions in Table 1 was usually around 5-6 kg/h at a conversion of 30 to 45 wt % (based on ethylene feed). Details of the reaction conditions were summarized in Table 1 and the analytical data of the liquid ethylene copolymers are summarized in Table 2. The regulator feed in Table 1 refers to propionaldehyde if nothing else is indicated.

TABLE-US-00001 TABLE 1 Preparation of liquid ethylene copolymers P T Ethylene Acrylate Regulator Ex. Monomers [bar] [° C.] Feed Feed Feed 1 E-MA 1700 220 11820 g/h 5035 g/h 2600 g/h 60.8 wt % 25.9 wt % 13.4 wt % 2 E-EA 1700 220 11950 g/h 3080 g/h 2460 g/h 68.3 wt % 17.6 wt % 14.1 wt % 3 E-NBA 1700 220 11970 g/h 4986 g/h 2049 g/h 63 wt % 26.2 wt % 10.8 wt % 4 E-EHA 1700 220 12040 g/h 5961 g/h 2576 g/h 58.5 wt % 29 wt % 12.5 wt % 5 E-PHA 1700 220 12000 g/h 5510 g/h 2317 g/h 60.5 wt % 27.8 wt % 11.7 wt % 6 E-LA 1700 220 11920 g/h 6130 g/h 1500 g/h 59.8 wt % 31.4 wt % 7.6 wt % 7 E-EHA- 1800 220 12020 g/h EHA: 2930 g/h 1500 g/h NBA 60.3 wt % 14.7 wt % 7.6 wt % NBA: 2790 g/h 14.5 wt % 8 E-LA- 1800 220 12180 g/h LA: 3250 1510 g/h NBA 60.7 wt % 16.2 g/h 7.5 wt % 16.2 wt % NBA: 3130 g/h 15.6 wt % 9 E-LA- 1800 220 12030 g/h LA: 2470 g/h 1540 g/h EHA- 61.6 wt % 12.6 wt % 7.9 wt % NBA EHA: 500 g/h 2.6 wt % NBA: 3000 g/h 15.4 wt % 10 E-LA- 1900 200 11890 g/h LA: 1510 g/h MEK: 350 g/h NBA 76.3 wt % 9.7 wt % 2.2 wt % NBA: 1480 g/h PA: 350 g/h 9.5 wt % 2.2 wt % 11 E-LA- 1900 200 12120 g/h LA: 1540 g/h MEK: 910 g/h NBA 74.6 wt % 9.5 wt % 5.6 wt % NBA: 1480 g/h PA: 200 g/h 9.1 wt % 1.2 wt % 12 E-PHA- 1700 220 11960 g/h PHA: 3020 g/h MEK: NBA 59.9 wt % 15.1 wt % 1520 g/h NBA: 3050 g/h 7.6 wt % 15.3 wt % PA: 400 g/h 2.0 wt % 13 E-C17A- 1700 220 11970 g/h C17: 2010 g/h 1210 g/h NBA 62.5 wt % 10.5 wt % 6.3 wt % NBA: 3960 g/h 20.7 wt % 14 E-LA- 2100 200 12030 g/h LA: 1400 g/h MEK: 300 g/h NBA 77.4 wt % 9.0 wt % 1.9 wt % NBA: 1510 g/h PA: 300 g/h 9.7 wt % 1.9 wt %

Characterization of the Liquid Ethylene Copolymers

[0211] The molecular weight number distribution Mn and the molecular weight weight distribution Mw were determined via GPC. The polydispersity was calculated as PD=(Mw/Mn). The GPC analysis was made with a RI detector, a PLgel MIXED-B column (column temperature 35° C.) and THF with 0.1% trifluor acetic acid as elution medium. The calibration was done with very narrow distributed polystyrene standards from the Polymer Laboratories with a molecular weights M=from 580 until 6.870.000 g/mol.

[0212] The Cloud Point CP was determined according to ISO 3015. The Pour Point PP was determined according to ASTM D 97.

[0213] The results demonstrated that all ethylene copolymers were liquid at room temperature and had a pour point below 25° C.

[0214] The results further indicate that all ethylene copolymers tend to have good low temperature characteristics because of their low cloud point.

[0215] The amounts of monomomers which are present in polymerized form in the polymer was determined by H-NMR.

TABLE-US-00002 TABLE 2 Analytical data of copolymers Amounts Mn Mw PP CP Ex. Monomers [wt %] [g/mol] [g/mol] PD [° C.] [° C.] 1 E-MA 34-66 2250 4900 2.2 3 −25 2 E-EA 32-68 2380 5210 2.3 −12 −42 3 E-NBA 33-67 2760 5290 2.2 −30 −19 4 E-EHA 34-66 1990 4050 2.0 −33 −60 5 E-PHA 35-65 1920 3850 2.0 −33 5 6 E-LA 37.5-62.5 3630 7940 2.2 6 18 7 E-EHA-NBA 32-35-33 2670 6520 2.4 −27 −54 8 E-LA-NBA 35-32-33 2740 7490 2.7 −9 −9 9 E-LA-EHA- 36-18-12-34 2540 6500 2.6 −21 −11 NBA 10 E-LA-NBA 42-29-29 6380 22900 3.6 9 −4 11 E-LA-NBA 44-27-29 4440 15000 3.4 9 6 12 E-PHA-NBA 34-22-44 4470 12900 2.9 −18 −49 13 E-C17A-NBA 35-22-43 2910 8060 2.8 −24 −50 14 E-LA-NBA 42-29-29 5660 23600 4.2 9 6

Viscosity and Appearance of the Liquid Ethylene Copolymers

[0216] The Kinematic Viscosity at 40° C. (V40) and at 100° C. (V100) were determined according to ASTM D 445. The Viscosity Index (VI) was determined according to ASTM D 2270. The appearance of the liquid ethylene copolymers was determined visually.

[0217] The results demonstrated that the ethylene copolymers have a desired high kinematic viscosity, as well as a desired high viscosity index.

TABLE-US-00003 TABLE 3 Viscosity data Amounts V40 V100 Appearance Ex. Monomers [wt %] [mm.sup.2/s] [mm.sup.2/s] VI of the liquid 1 E-MA 34-66 17038 372 129 Clear 2 E-EA 32-68 3925 185 150 Clear 3 E-NBA 33-67 1622 126 177 Clear 4 E-EHA 34-66 738 63 154 Turbid 5 E-PHA 35-65 544 50 150 Turbid 6 E-LA 36-60 1517 147 209 Turbid 7 E-EHA-NBA 32-35-33 2202 162 184 Clear 8 E-LA-NBA 35-32-33 1536 138 197 Clear 9 E-LA-EHA-NBA 36-18-12-34 1545 132 183 Clear 12 E-PHA-NBA 34-22-44 7701 493 233 Clear 13 E-C17A-NBA 35-22-43 2746 195 191 Clear
Miscibility with Polyalphaolefins

[0218] The liquid ethylene copolymers were mixed with polyalphaolefine having a kinematic viscosity at 100° C. of about 6 cSt in a weight ratio of 50:50 at room temperature and mixed at room temperature by rolling for 12 hours. The mixtures' appearance was observed after homogenization and again after 24 hours. The copolymer is deemed compatible with the polyalphaolefine when no phase separation was observed after 24 hours.

[0219] The results demonstrated that several of the ethylene copolymers a miscible with very unpolar low viscosity polyalphaolefines (typically based on poly(1-decen)).

TABLE-US-00004 TABLE 4 Miscibility with PAO-6 (50:50 vol %) Ex. Monomers Amounts [wt %] Miscible 1 E-MA 34-66 No 2 E-EA 32-68 No 3 E-NBA 33-67 No 4 E-EHA 34-66 No 5 E-PHA 35-65 Yes 6 E-LA 36-60 Yes 7 E-EHA-NBA 32-35-33 Yes 8 E-LA-NBA 35-32-33 Yes 9 E-LA-EHA-NBA 36-18-12-34 Yes 12 E-PHA-NBA 34-22-44 Yes 13 E-C17A-NBA 35-22-43 Yes

Hydraulic Oil

[0220] The liquid ethylene copolymers can be used in typical hydraulic oils as demonstrated by the following compositions in Table 5. The Lubricants A to D are formulated with commercially available base oils and additives like typical hydraulic oils. [0221] Nexbase® 3043: API Group III base oil, KV40 20 mm.sup.2/s, KV100 4.3 mm.sup.2/s, pour point −18° C., commercially available from Neste N.V., Belgium. [0222] Nexbase® 3060: API Group III base oil, KV40 32 mm.sup.2/s, KV100 6 mm.sup.2/s, pour point −15° C., commercially available from Neste N.V., Belgium. [0223] Irgaflo® 942 P: Pour point depressant for lubricants, commercially available from BASF Corp, USA. [0224] Irgalube® 8080: Ashless anti-wear hydraulic fluid package, commercially available from BASF Corp, USA. [0225] Additin® RC 9200 N: Zinc containing hydraulic fluid package for antiwear corrosion protection and antioxidant, commercially available from Lanxess, Germany.

TABLE-US-00005 TABLE 5 Hydraulic oil composition [wt %] A B C D Nexbase ® 3043 20 20 15 15 Nexbase ® 3060 74.9 74.5 80.2 79.7 Copolymer from Ex. 10 4.0 4.0 — — Copolymer from Ex. 14 — — 3.7 3.8 Irgaflo ® 942 P 0.7 0.7 0.7 0.7 Irgalube ® 8080 0.4 — 0.4 — Additin ® RC 9200 N — 0.8 — 0.8 KV40 [mm.sup.2/s] 46.5 46.7 45.8 47.2 KV100 [mm.sup.2/s] 8.5 8.6 8.3 8.6 Viscosity Index VI 160 163 157 162 Pour point −36° C. −36° C. −36° C. −36° C. KRL [%] 5.5 5.5 — —

[0226] The data showed, that the hydraulic oils of the compositions A to D [0227] have a high viscosity index; [0228] have a low pour point; and [0229] have a low shear loss, calculated by the KV100 before and after the test according to CEC L45-99 (20 h) (termed “KRL”).

Industrial Oil

[0230] The liquid ethylene copolymers can be used in typical industrial oils, especially gear oil, as demonstrated by the following compositions in Table 6. The Lubricants A to E are formulated with commercially available base oils and additives like typical industrial oils.

[0231] The data showed that the industrial oils have an advantagous combination of high viscosity index, low pour point, low shear loss, and good oxidation stability. [0232] PAO 6: a commercially available polyalphaolefine having a kinematic viscosity at 100° C. of about 6 cSt. [0233] Group III oil: a commercially available group III base oil with KV100 of 6 cSt. [0234] Ester base stock: Synative® ES DPHA from BASF SE. [0235] Additive Package 1: mixture of commercially available anti-wear additive, metal deactivator, antioxidants, corrosion inhibitor and defoamer. [0236] Ox-Stab.: The oxidation stability was tested according to ASTM D2893 at 121° C., where a sample is subjected to a temperature of 121° C. for 312 h in the presence of dry air, and then the oil is tested for increase in kinematic viscosity. Table 6 shows the increase in kinematic viscosity in percent.

TABLE-US-00006 TABLE 6 Industrial oil compositions [wt %] A B C D E Copolymer from Ex. 7 53.0 53.0 56.4 Copolymer from Ex. 8 55.9 Copolymer from Ex. 9 56.9 PAO 6 40.5 39.5 43.4 30.4 Group III Oil 43.4 Ester base stock 9.6 Additive Package 1 3.6 3.6 3.6 3.6 3.6 KV40 [mm.sup.2/s] 343 336 305 314 326 KV100 [mm.sup.2/s] 41 39 35 36 38 Viscosity Index VI 174 168 161 159 167 Pour point −21° C. −30° C. −33° C. −27° C. −39° C. Ox-Stab. 4% 5% 6% 5% 6% KRL [%] 8.2 3.6 2.8 3.4 3.7