High-pressure polymerization process for liquid ethylene copolymers
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 1 -C 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.
1. 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 1 -C 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 selected from propionaldehyde, methyl ethyl ketone, or hydrogen, or mixtures thereof.
2. The polymerization process according to claim 1 , where the monomer feed is polymerized in the presence of 4 to 18 wt % of the chain transfer agent.
3. The polymerization process according to claim 1 where polymerization is carried out in a stirred high-pressure autoclave.
4. The polymerization process according to claim 1 , where the reaction temperature is in the range of 150 to 300° C.
5. The polymerization process according to claim 1 , where the polymerization process is carried out at a pressure in the range from 1000 to 4000 bar.
6. The polymerization process according to claim 1 , where the ethylene copolymer has a pour point below 25° C.
7. The polymerization process according to claim 1 where the ethylene copolymer comprises in polymerized from 25 to 55 wt % of the ethylene.
8. The polymerization process according to claim 1 where the ethylene copolymer comprises in polymerized form at least 30 wt % of acrylate.
9. The polymerization process according to claim 1 where the ethylene copolymer is free of further monomers beside ethylene and acrylate.
10. The polymerization process according to claim 1 where the acrylate comprises
a polar acrylate selected from C 1 -C 5 alkyl (meth)acrylate, and
an unpolar acrylate selected from C 6 -C 22 alkyl (meth)acrylate.
11. The polymerization process according to claim 10 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.
12. The polymerization process according to claim 1 where the ethylene copolymer comprises less than 2 mol % the vinylester of the formula (I) in polymerized form
where R c , R d , and R e are each independently H or C 1 -C 4 -alkyl, and R f is C 1 -C 20 alkyl.
13. A liquid ethylene copolymer obtainable by the polymerization process as defined in claim 1 .
14. A lubricant comprising the liquid ethylene copolymer obtainable by the polymerization process as defined in claim 1 .
15. A method for reducing friction between moving surfaces comprising the step of contacting the surfaces with the lubricant as defined claim 14 .