Polymer composition for cable applications with advantageous electrical properties

Patent metadata

Field	Value
Publication number	US-10934420-B2
Application number	US-201515522725-A
Country	US
Kind code	B2
Filing date	Oct 27, 2015
Priority date	Oct 27, 2014
Publication date	Mar 2, 2021
Grant date	Mar 2, 2021

Abstract

The invention relates to a polymer composition comprising polyolefin (a), which is other than low density polyethylene (LDPE), and polyolefin (b), which is an LDPE polymer and obtainable by a high pressure process which process comprises the steps: (i) compressing one or more monomer(s) under pressure in a compressor, using a compressor lubricant for lubrication, (ii) polymerising a monomer optionally together with one or more comonomer(s) in a polymerisation zone, (iii) separating the obtained polyolefin (b) from the unreacted products and recovering the separated polyolefin in a recovery zone, wherein in step (i) the compressor lubricant comprises a non-mineral oil; a power cable, e.g. of a direct current (DC) power cable, use of a polymer composition and a process for producing a DC power cable.

First claim

The invention claimed is:

1. A polymer composition comprising polyolefin (a), which is other than low density polyethylene (LDPE),
wherein the amount of polyolefin (a) is 1.0 to 30 wt %, based on the combined weight of the polyolefin (a) and a polyolefin (b), and polyolefin (b), which is an LDPE polymer and obtainable by a high pressure process which process comprises the steps:
(i) compressing one or more monomer(s) under pressure in a compressor, using a compressor lubricant for lubrication,
(ii) polymerising a monomer optionally together with one or more comonomer(s) in a polymerisation zone,
(iii) separating the obtained polyolefin (b) from the unreacted products and recovering the separated polyolefin in a recovery zone,
wherein in step (i) the compressor lubricant comprises a non-mineral oil,
wherein the polyolefin (a) is a low-pressure polyethylene produced in the presence of an olefin polymerisation catalyst, selected from a MDPE polymer or a HDPE polymer,
wherein the amount of polyolefin (b) is 99.0 to 70.0 wt % based on the combined weight of the polyolefin (a) and a polyolefin (b), and
wherein the combined amount of polyolefins (a) and (b) in the composition is from 80 to 100 wt %, based on the total weight of the polymer component(s) present in the polymer composition.

2. A polymer composition according to claim 1 , wherein the nonmineral oil is polyalkylene glycol (PAG).

3. A polymer composition according to claim 1 , wherein the polyolefin (b) being an LDPE polymer is, for example, an, optionally, unsaturated LDPE homopolymer or an, optionally, unsaturated LDPE copolymer of ethylene with one or more comonomer(s).

4. A polymer composition according to claim 1 , wherein the polymer composition further comprises a peroxide in an amount of less than 37 mmol —O—O-/kg polymer composition, for example, less than 35 mmol —O—O-/kg polymer composition, e.g. 0.1 to 34 mmol —O—O-/kg polymer composition, for example 0.5 to 33 mmol —O—O-/kg polymer composition, e.g. 5.0 to 30 mmol —O—O-/kg polymer composition, for example 7.0 to 30 mmol —O—O-/kg polymer composition, e.g. from 10.0 to 30 mmol —O—O-/kg polymer composition.

5. A polymer composition according to claim 1 , wherein the polymer composition has an electrical conductivity of 160 fS/m or less, for example 150 fS/m or less, e.g. 140 fS/m or less, for example 130 fS/m or less, e.g. 120 fS/m or less, for example 110 fS/m or less, e.g. 100 fS/m or less, for example 90 fS/m or less, e.g. 0.01 to 80 fS/m, for example 0.01 to 70 fS/m, e.g. 0.05 to 60 fS/m, for example 0.05 to 50 fS/m, for example 0.05 to 40 fS/m, e.g. 0.05 to 30 fS/m, for example 0.05 to 20.0 fS/m, e.g. 0.05 to 15.0 fS/m, for example 0.05 to 10.0 fS/m, when measured according to DC conductivity method using a 1 mm thick plaque sample as described under “Determination Methods”.

6. A polymer composition according to claim 1 , wherein the amount of the polyolefin (b) is for example 75 to 99.0 wt %, e.g. 80 to 99.0 wt %, based on the combined weight of the polyolefin (a) and the polyolefin (b).

7. A polymer composition according to claim 1 , wherein the polyolefin (a) is a low-pressure polyethylene polymerised in the presence of an olefin polymerisation catalyst and selected from an ethylene homopolymer or a copolymer of ethylene with one or more comonomer(s).

8. A polymer composition according to claim 1 , wherein the polyolefin (b) is an unsaturated LDPE polymer, which is selected from an unsaturated LDPE homopolymer or an unsaturated LDPE copolymer of ethylene with one or more comonomer(s), and comprises vinyl groups in total amount of, for example, more than 0.20/1000 carbon atoms, e.g., more than 0.30/1000 carbon atoms, and, for example, more than 0.40/1000 carbon atoms.

9. A polymer composition according to claim 1 , wherein the polyolefin (b) is an unsaturated LDPE copolymer of ethylene with at least one polyunsaturated comonomer and optionally with one or more other comonomer(s), the polyunsaturated comonomer consists of, for example, a straight carbon chain with at least 8 carbon atoms and at least 4 carbons between the non-conjugated double bonds, of which at least one is terminal, said polyunsaturated comonomer is, e.g. a diene, for example a diene which comprises at least eight carbon atoms, the first carbon-carbon double bond being terminal and the second carbon-carbon double bond being non-conjugated to the first one, for example, a diene which is selected from C8- to C14-non-conjugated diene or mixtures thereof, e.g. selected from 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, 7-methyl-1,6-octadiene, 9-methyl-1,8-decadiene, or mixtures thereof, for example from 1,7-octadiene, 1,9-decadiene, 1,11-dodecadiene, 1,13-tetradecadiene, or any mixture thereof.

10. A polymer composition according to claim 1 , wherein the polymer composition comprises crosslinking agent, for example, a peroxide in an amount of up to 110 mmol —O—O-/kg polymer composition, e.g. up to 90 mmol —O—O-/kg polymer composition (corresponds 0 to 2.4 wt % of dicumyl peroxide based on the polymer composition), for example 1.0 to 75 mmol —O—O-/kg polymer composition, e.g. less than 50 mmol —O—O-/kg polymer composition, for example less than 40 mmol —O—O-/kg polymer composition, e.g. less than 37 mmol —O—O-/kg polymer composition, for example less than 35 mmol —O—O-/kg polymer composition, e.g. 0.1 to 34 mmol —O—O-/kg polymer composition, for example 0.5 to 33 mmol —O—O-/kg polymer composition, for example 5.0 to 30 mmol —O—O-/kg polymer composition, e.g. 7.0 to 30 mmol —O—O-/kg polymer composition, for example 10.0 to 30 mmol —O—O-/kg polymer composition.

11. A power cable, for example a direct current (DC) power cable, comprising a conductor which is surrounded by, at least, an inner semiconductive layer, an insulation layer and an outer semiconductive layer, in that order, wherein at least one layer, for example at least the insulation layer, comprises, e.g. consists of, a polymer composition according to claim 1 .

12. A method for producing at least one layer, for example at least an insulation layer, of a power cable, e.g. of a direct current (DC) power cable, comprising a conductor surrounded by at least an inner semiconductive layer, an insulation layer and an outer semiconductive layer, in that order comprising the use of a polymer composition according to claim 1 .

13. The method according to claim 12 for producing a DC cable, wherein the inner semiconductive layer comprises a first semiconductive composition, the insulation layer comprises an insulation composition and the outer semiconductive layer comprises a second semiconductive composition and wherein the insulation composition of the insulation layer comprises a polymer composition, according to claim 1 .

14. A process for producing a power cable, comprising the steps of applying on a conductor, for example, by (co)extrusion, an inner semiconductive layer comprising a first semiconductive composition, an insulation layer comprising an insulation composition and an outer semiconductive layer comprising a second semiconductive composition, in that order, wherein the insulation composition of the insulation layer comprises, for example, consists of, a polymer composition according to claim 1 .

Assignees

• Borealis Ag

Inventors

• Englund Villgot
• Hagstrand Per-Ola
• Smedberg Annika
• Nilsson Ulf

Classifications

• C08K5/01

  Hydrocarbons {(C08K5/0091 takes precedence)} · CPC title

• C08K5/14

  Peroxides · CPC title

• C08L2207/066

  LDPE (radical process) · CPC title

• C08L23/0815

  with aliphatic 1-olefins containing one carbon-to-carbon double bond · CPC title

• C08L2203/202

  use in electrical wires or wirecoating · CPC title