Cable and polymer composition comprising a multimodal ethylene copolymer

Abstract

The present invention relates to a cable comprising a conductor surrounded by one or more layers, wherein at least one layer comprises a polymer composition comprising a copolymer of ethylene with one or more comonomers, to a process for producing the cable and to a polymer composition suitable as a cable layer material.

1 . A cable comprising a conductor surrounded by one or more layers, wherein at least one layer comprises a polymer composition comprising a copolymer of ethylene with one or more comonomers, wherein the ethylene copolymer has a density of less than 945 kg/m 3 , an Mz/Mw of at least 2.45 and wherein the ethylene copolymer is obtainable by polymerising ethylene in the presence of a single site catalyst and an activator for said catalyst. 
     
     
         2 . The cable according to  claim 1 , wherein the ethylene copolymer has the Mz/Mw of at least 2.50, preferably of from 2.55 to 15.00, preferably of from 2.60 to 10.00, more preferably of at least 2.65 to 10.00. 
     
     
         3 . The cable according to  claim 1 , wherein the ethylene copolymer has a shear thinning index SHI 2.7/210  of at least 7.0, preferably of at least 8.0, preferably of at least 8.5, preferably of from 8.5 to 50, preferably of from 9.0 to 30, more preferably from 9.5 to 20. 
     
     
         4 . The cable according to  claim 1 , wherein the ethylene copolymer has a Mz of at least 250 000, preferably of at least 260 000, preferably of from 270 000 to 1000 000, and even as high as from 320 000 to 700 000 may be preferred depending on the embodiment. 
     
     
         5 . The cable according to  claim 1 , wherein the ethylene copolymer is a multimodal copolymer which comprises:
 (A) from 30 to 70% by weight, preferably from 45 to 55% by weight, based on the combined amount of components (A) and (B), of a low molecular weight (LMW) ethylene polymer selected from ethylene homopolymer and a copolymer of ethylene and one or more alpha-olefins having from 3 to 20 carbon atoms, and   (B) from 30 to 70% by weight, preferably from 45 to 55% by weight, based on the combined amount of components (A) and (B), of a high molecular weight (HMW) copolymer of ethylene and one or more alpha-olefins having from 3 to 20 carbon atoms.   
     
     
         6 . The cable according to  claim 5 , wherein the LMW polymer (A) is a copolymer of ethylene with one or more alpha-olefins having from 4 to 10 carbon atoms, preferably from 4 to 8 carbon atoms, and the HMW copolymer of ethylene (B) is a copolymer of ethylene with one or more alpha-olefins having from 4 to 10 carbon atoms, preferably from 4 to 8 carbon atoms. 
     
     
         7 . The cable according to  claim 1 , wherein the ethylene copolymer is a multimodal ethylene copolymer which comprises a low molecular weight copolymer of ethylene (A) which is obtainable by polymerising ethylene in the presence of a single site catalyst and an activator for said catalyst, and a high molecular weight copolymer of ethylene (B) which is obtainable by polymerising ethylene in the presence of a single site catalyst and an activator for said catalyst. 
     
     
         8 . The cable according to  claim 1 , characterized in that the ethylene copolymer of the polymer composition has at least one, preferably two or more, in any combination, of the following properties:
 (i) MWD (Mn/Mw) of from 1.5 to 20, preferably of from 2 to 15, preferably of from 2.5 to 10.0 preferably of from 4.5 to 10.0,   (ii) Density of less than 940 kg/m 3 , preferably of less than 935 kg/m 3 , preferably less than 930 kg/m 3 , preferably from 905 to 925 kg/m 3 ,   (iii) Flexural modulus of less than 750 MPa, preferably less than 500 MPa, preferably less than 450 MPa, preferably less than 400 MPa, preferably of less than 330 MPa,   (iv) MFR 2  of from 0.1 to 10.0 g/10 min, preferably from 0.2 to 5.0 g/10 min, more preferably of from 0.2 to 2.5 g/10 min, or   (v) The ethylene copolymer is the multimodal LMW polymer (A) which has a density of less than 945 g/m 3 , preferably from 910 to 943 kg/m 3  
 preferably the ethylene copolymer of the polymer composition has all the above properties (i) to (v). 
   
     
     
         9 . The cable according to  claim 1 , wherein said at least one layer is a jacketing layer. 
     
     
         10 . A process for producing a cable comprising applying, preferably coextruding, one or more layers on a conductor, wherein at least one layer is formed from the polymer composition as claimed in  claim 1 . 
     
     
         11 . The process according to  claim 10 , wherein at least a jacketing layer is formed from the polymer composition of any of the preceding claims. 
     
     
         12 . A polymer composition comprising a copolymer of ethylene with one or more comonomers, wherein the ethylene copolymer has a density of less than 945 kg/m 3 , an Mz/Mw of at least 2.45, is obtainable by polymerising ethylene in the presence of a single site catalyst and an activator for said catalyst, and has an MFR 2  of 0.2 to 10 g/10 min. 
     
     
         13 . The polymer composition according to  claim 12 , wherein the copolymer of ethylene is a multimodal copolymer of ethylene and comprises:
 (A) from 30 to 70% by weight, preferably from 45 to 55% by weight, based on the combined amount of components (A) and (B), of a low molecular weight (LMW) ethylene polymer selected from ethylene homopolymer and a copolymer of ethylene and one or more alpha-olefins having from 3 to 16 carbon atoms, and (B) from 30 to 70% by weight, preferably from 45 to 55% by weight, based on the combined amount of components (A) and (B), of a high molecular weight (HMW) copolymer of ethylene and one or more alpha-olefins having from 3 to 16 carbon atoms.   
     
     
         14 . The polymer composition according to  claim 12 , wherein the ethylene copolymer has the MFR 2  of from 0.2 to 5.0 g/10 min, more preferably of from 0.2 to 2.5 g/10 min, the density of less than 940, preferably less than 935, preferably less than 930, preferably from 905 to 925 kg/m 3 , Mz/Mw of at least 2.50, preferably of from 2.55 to 15.00, preferably of from 2.60 to 10.00, more preferably of at least 2.65 to 10.00. 
     
     
         15 . The polymer composition according to  claim 12 , wherein the ethylene copolymer of the polymer composition has at least one, preferably two or more, in any combination, of the following further properties,
 (i) the ethylene copolymer is the multimodal ethylene copolymer, which comprises said LMW polymer (A) which is a copolymer of ethylene with one or more alpha-olefin comonomer(s) having from 4 to 10 carbon atoms, preferably with from 4 to 8 carbon atoms, and said HMW copolymer (B) which is a copolymer of ethylene with one or more alpha-olefin comonomer(s) having from 4 to 10 carbon atoms, preferably from 4 to 8 carbon atoms,   (ii) Mz of at least 250 000, preferably of at least 260 000, preferably of from 270 000 to 1000 000, and even as high as from 320 000 to 700 000 may be preferred depending on the embodiment,   (iii) MWD (Mw/Mn) of 1.5 to 20, preferably of 2 to 16, more preferably of 2.5 to 10, more preferably of from 4.5 to 10,   (iv) SHI 2.7/210  of at least 7.0, preferably of at least 8.0, preferably of at least 8.5, preferably of from 8.5 to 50, preferably of from 9.0 to 30, more preferably of from 9.5 to 20,   (v) Flexural modulus of less than 750 MPa, preferably less than 500 MPa, preferably less than 450 MPa, preferably less than 400 MPa, preferably of less than 330 MPa,   (vi) The ethylene copolymer is said multimodal ethylene copolymer comprising the (LMW) ethylene polymer (A) which has a density of less than 945 g/m 3 , preferably from 910 to 943 kg/m 3 , or   (vii) The ethylene copolymer is said multimodal ethylene copolymer which has a flexural modulus of less than 750 MPa, preferably of less than 500 MPa, more preferably of less than 450 MPa, more preferably of less than 400 MPa preferably of less than 330 MPa and comprises the (LMW) ethylene copolymer (A) which has a density of less than 945 g/m 3 , preferably from 910 to 943 kg/m 3 ;
 preferably the ethylene copolymer has all of the above properties (i) to (vii). 
   
     
     
         16 . The use of the polymer composition according to  claim 13  for producing cables, preferably for producing a cable layer, preferably a jacketing layer.