A MIDDLE-PRESSURE POLYMERIZATION PROCESS FOR LIQUID ETHYLENE COPOLYMERS

Abstract

The present invention relates to a middle-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 mix comprising the ethylene and the acrylate is polymerized at a pressure of 50 to 400 bar and in the presence of at least 2 wt % of a chain transfer agent. The invention further relates to a 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.-16. (canceled)

17. A middle-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 mix comprising the ethylene and the acrylate is polymerized at a pressure of 50 to 400 bar and in the presence of at least 2 wt % of a chain transfer agent.

18. The polymerization process according to claim 17, where the chain transfer agents are saturated or unsaturated hydrocarbons, aliphatic ketones, aliphatic aldehydes, or hydrogen, or mixtures thereof.

19. The polymerization process according to claim 17, where the monomer feed is polymerized in the presence of 4 to 18 wt % of the chain transfer agent.

20. The polymerization process according to claim 17, where the polymerization process is a fed-batch process in which a reactor is partly filled with the ethylene and a solvent, followed by feeding of the acrylate, the chain transfer agent, and an initiator.

21. The polymerization process according to claim 17, where the polymerization process is carried out at a pressure in the range from 70 to 300 bar.

22. The polymerization process according to claim 17, where the monomer mix is polymerized in a polymerization solvent.

23. The polymerization process according to claim 17, where the ethylene copolymer comprises in polymerized form at least 30 wt % of the acrylate.

24. The polymerization process according to claim 17, where the acrylate comprises a polar acrylate selected from C.sub.1-C.sub.5 alkyl (meth)acrylate, and an unpolar acrylate selected from C6-C22 alkyl (meth)acrylate.

25. The polymerization process according to claim 24, where the polar acrylate is methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, or n-butyl (meth)acrylate.

26. The polymerization process according to claim 24, where the unpolar acrylate is selected from C.sub.8-C.sub.18 alkyl (meth)acrylate, in particular from C.sub.8-C.sub.12 alkyl (meth)acrylate.

27. The polymerization process according to claim 24, where the unpolar acrylate is selected from (meth)acrylates of n-octyl, isooctyl, 2-ethylhexyl, n-nonyl, 2-propylheptyl, n-decyl, un-decyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, 2-butyloctyl, 2-pentylnonyl, 2-hexyldecyl, isohexyl, isoheptyl, isooctyl, isononyl, isodecyl, isoundecyl, isododecyl, isotridecyl, isotetradecyl, isopentadecyl, isohexadecyl, isoheptadecyl, isooctadecyl and mixtures thereof.

28. The polymerization process according to claim 24, where the ethylene copolymer comprises in polymerized form 25 to 55 wt % of ethylene, at least 20 wt % of the polar acrylate which is selected from C.sub.1-C.sub.4 alkyl (meth)acrylate, and at least 15 wt % of the unpolar acrylate which is selected from C6-C22 alkyl (meth)acrylate.

29. The polymerization process according to claim 17, where the percentage of the chain transfer agent is based on the sum of the amounts of monomers and the chain transfer agent.

30. A liquid ethylene copolymer obtainable by the polymerization process as defined in claim 17.

31. A lubricant comprising the liquid ethylene copolymer obtainable by the polymerization process as defined in claim 17.

32. A method for reducing friction between moving surfaces comprising the step of contacting the surfaces with the lubricant as defined claim 31.

33. The polymerization process according to claim 17, where the ethylene copolymer comprises in polymerized form at least 50 wt % of the acrylate.

Description

EXAMPLES

[0214] NBA: N-butyl acrylate,

[0215] EHA: 2-Ethylhexyl acrylate, commercially available from BASF SE.

[0216] LA: Lauryl acrylate (60:40 mixture of C.sub.12:C.sub.14 alkyl acrylates)

Preparation of Copolymers

[0217] In an autoclave 720 g cyclohexane was initially added, and then ethylene (“E”) was fed under a pressure of 60 bar. The mixture was heated under stirring to 100° C. and further ethylene were added at a pressure of 100 bar. Feed 1 (26.6 g tert-butylperoxypivalate and 53 g cyclohexane) and Feed 2 (400 g acrylate and 80 g propionaldehyde) were fed to the reaction mixture during two hours. The reaction mixture cooled down and the cyclohexane was destilled off under vacuum. Detailed reaction conditions are summarized in Table 1.

TABLE-US-00001 TABLE 1 Reaction conditions Ethylene Acrylate P T feed Feed Propionaldehyde Ex. Monomers [bar] [° C.] [g] [g] [wt %] 1 E - EHA 100 100 543 400 7.8 wt % 2 E - NBA - 100 100 519 200 NBA 8.0 wt % EHA 200 LA 3 E - NBA - 100 100 539 200 NBA 7.9 wt % LA 200 LA

Characterization of the Liquid Ethylene Copolymers

[0218] 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.

[0219] The Cloud Point CP was determined according to ISO 3015. The Pour Point PP was determined according to ASTM D 97.

[0220] The results demonstrated that all ethylene copolymers were liquid at room temperature and had a pour point below 25° C.

[0221] The results further indicate that all ethylene copolymers tend to have good low temperature characteristics.

[0222] The amounts of monomomers which are present in polymerized form in the polymer was determined by H-NMR and shown in Table 2.

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 - EHA 38.5:61.5 1730 5100 2.9 −24 22 2 E - NBA - EHA 33:31:36 2100 5710 2.7 −21 −48 3 E - NBA - LA 35:33:32 2180 5800 2.7 −18 −9

Viscosity and Appearance of the Liquid ethylene Copolymers

[0223] 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.

[0224] 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 Ex. Monomers [wt %] [mm.sup.2/s] [mm.sup.2/s] VI 1 E - EHA 38.5:61.5 768 64 152 2 E - NBA - EHA 33:31:36 1155 86 153 3 E - NBA - LA 35:33:32 633 61 166

Miscibility with polyalphaolefins

[0225] 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.

[0226] The results demonstrated that the ethylene copolymers are 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 %) Amounts Ex. Monomers [wt %] Miscible 1 E - EHA 38.5:61.5 Yes 2 E - NBA - EHA 33:31:36 Yes 3 E - NBA - LA 35:33:32 Yes