Conductive jacket

Abstract

The present invention relates to a new semiconductive composition, which comprises 50 to 98 weight percentage (wt %) of a polymer blend, 2 to 50 wt % of a conductive filler and 0.05 to 2 wt % of an antioxidant; wherein said polymer blend comprises 10 to 99 wt % of a multimodal high density polyolefin, which high density polyolefin has a density which is from 930 to 970 kg/m.sup.3 and a melt flow rate (MFR2@190° C.) according to ISO 1133 (190° C., 2.16 kg) which is less than 1.6 g/10 min, and 1 to 90 wt % of a thermoplastic elastomer, a process for producing a semiconductive composition, and a semiconductive jacket comprising the semiconductive composition, and a power cable comprising the semiconductive jacket or comprising the semiconductive composition, or use of a semiconductive jacket or a semiconductive composition in, for example, a power cable.

Claims

1. A semiconductive composition, which semiconductive composition comprises 50 to 98 weight percentage (wt %) of a polymer blend, 2 to 50 wt % of a conductive filler and 0.05 to 2 wt % of an antioxidant; wherein said polymer blend comprises 10 to 99 wt % of a multimodal high density polyolefin, which high density polyolefin has a density which is from 930 to 970 kg/m.sup.3 and a melt flow rate (MFR2@190° C.) according to ISO 1133 (190° C., 2.16 kg) which is less than 1.6 g/10 min, and 1 to 90 wt % of a thermoplastic elastomer.

2. A semiconductive composition according to claim 1, wherein the semiconductive composition comprises 60 to 91 wt % of the polymer blend, 9 to 40 wt % of the conductive filler and 0.1 to 1.0 wt % of the antioxidant; wherein said polymer blend comprises 30 to 90 wt % of the multimodal high density polyolefin and 10 to 70 wt % of the thermoplastic elastomer.

3. A semiconductive composition according to claim 1, wherein the multimodal high density polyolefin is a bimodal high density polyolefin.

4. A semiconductive composition according to claim 1, wherein the multimodal high density polyolefin has a melt flow rate (MFR2@190° C.) according to ISO 1133 (190° C., 2.16 kg) which is 1.2 g/10 min or less.

5. A semiconductive composition according to claim 1, wherein the multimodal high density polyolefin of which Mw is from 500 to 60 kg/mol and Mw/Mn is more than 10.

6. A semiconductive composition according to claim 1, where the multimodal high density polyolefin comprises a multimodal molecular weight distribution α-olefin polymer mixture.

7. A semiconductive composition according to claim 1, where the multimodal high density polyolefin comprises ethylene copolymer of at least one chosen from butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

8. A semiconductive composition according to claim 1, where the multimodal high density polyolefin comprises a mixture of a low-molecular ethylene homopolymer and a high-molecular ethylene copolymer of at least one chosen from butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

9. A semiconductive composition according to claim 1, wherein the conductive filler has a BET nitrogen surface area (according to ASTM D6556), which is less than 700 m.sup.2/g or an Iodine number (according to ASTM D1510), which is less than 700 mg/g.

10. A semiconductive composition according claim 1, which comprises 70 to 90 wt % of a polymer blend, 10 to 30 wt % of a conductive filler and 0.4 to 1.0 wt % of an antioxidant; wherein said polymer blend comprises 45 to 80 wt % of a multimodal high density polyolefin, which high density polyolefin has a melt flow rate (MFR2@190° C.) according to ISO 1133 (190° C., 2.16 kg) which is 0.1 to 1.2 g/10 min, and 20 to 55 wt % of a thermoplastic elastomer, and wherein the conductive filler has a BET nitrogen surface area (according to ASTM D6556), which is 20 to 600 m.sup.2/g or, alternatively, an Iodine number (according to ASTM D1510), which is 20 to 600 mg/g.

11. A semiconductive composition according to claim 1, wherein the conductive filler has a BET nitrogen surface area which is less than 300 m.sup.2/g, or has an Iodine number which is less than 300 mg/g.

12. A semiconductive composition according to claim 1, wherein the conductive filler has a BET nitrogen surface area which is less than 150 m.sup.2/g, or has an Iodine number which is less than 150 mg/g.

13. A semiconductive composition according to claim 1, wherein the conductive filler has a DBP oil absorption (i.e. DBPA) (according to ASTM D 2414), which is less than 320 ml/100 g.

14. A semiconductive composition according to claim 1, wherein the conductive filler is a carbon black, furnace carbon black, modified furnace carbon black or acetylene carbon black.

15. A semiconductive composition according to claim 1, wherein the thermoplastic elastomer is an unsaturated polyolefin.

16. A semiconductive composition according to claim 1, wherein the thermoplastic elastomer is an ethylene alkyl acrylate copolymer, an ethylene ethyl acrylate copolymer, an ethylene butyl acrylate copolymer or an ethylene methyl acrylate copolymer.

17. A semiconductive composition according to claim 1, where the multimodal high density polyolefine comprises a multimodal molecular weight distribution α-olefin polymer mixture obtained by polymerization of α-olefin in more than two stages, the α-olefin polymer mixture having a density of about 930 to 970 kg/m3 and a melt flow rate (MFR2@190° C.) which is less than 1.6 g/10 min, said α-olefin polymer mixture comprises at least a first and a second α-olefin polymer, of which the first α-olefin polymer has a density of about 930 to 975 kg/m3 and a melt flow rate (MFR2@190° C.) of 50 to 2000 g/10 min, and the density and the melt flow rate of the second α-olefin polymer are chosen so that the resulting α-olefin polymer mixture obtains said density and said melt flow rate.

18. A process for producing a semiconductive composition according to claim 1, wherein the process comprises mixing conductive filler together with the polymer blend during compounding.

19. A semiconductive jacket comprising the semiconductive composition according to claim 1.

20. A power cable comprising the semiconductive jacket according to claim 19.

21. A semiconductive composition according to claim 1, wherein the conductive filler has a DBP oil absorption (i.e. DBPA) (according to ASTM D 2414), which is less than 250 ml/100 g.

Description

EXAMPLES

(1) The invention will now be illustrated by the following non-limiting examples.

(2) Semiconductive composition in accordance with the present invention, and the semiconductive compositions of the comparative examples, were both prepared by first compounding the components followed by extruding the compounded components, using a Buss MDK 46 kneader (Supplier: Buss, reciprocating co-kneader with special screw design).

Examples 1, 2, 3, 4 and 5 (Inventive Examples)

Semiconductive Compositions, Examples 1, 2, 3, 4 and 5, Comprising Multimodal High Density Polyolefin, Thermoplastic Elastomer, Conductive Filler and Antioxidant

(3) Multimodal High Density Polyolefin

(4) For Examples 1, 2, 3, 4 and 5: 47.04, 45.24, 46.92, 52.44, and 47.04 wt %, respectively, of a multimodal high density polyolefin, i.e. a bimodal high density polyethylene, which has a density of 946 kg/m.sup.3 and a melt flow rate (MFR2@190° C.) according to ISO 1133 (190° C., 2.16 kg) which is 0.55 g/10 min, where the multimodal high density polyolefin, i.e. the bimodal high density polyethylene, was prepared as described herein below.

(5) The multimodal high density polyolefin, i.e. a bimodal high density polyethylene, was produced in a polymerisation plant comprising of a first reactor, i.e. a loop reactor, which was connected in series to a second reactor, i.e. a gas-phase reactor, and wherein in the polymerisation a Ziegler-Natta catalyst was utilised.

(6) In the first reactor, i.e. the loop reactor, a first polymer (Polymer 1.1) was produced by the polymerisation of ethylene in the presence of hydrogen (molar ratio of hydrogen to ethylene=roughly 0.70:1). The resulting ethylene homopolymer had an MFR2@190° C. value of about 400 g/10 min and a density of about 0.970 g/cm.sup.3.

(7) In the second reactor, i.e. the gas-phase reactor, a second polymer (Polymer 1.2) was produced by the polymerisation of ethylene with butene (molar ratio of butene to ethylene=roughly 0.20:1, and molar ratio of hydrogen to ethylene=roughly 0.04:1). The resulting copolymer of ethylene and butene was present in the form of an intimate mixture with the ethylene homopolymer from the first reactor, the weight ratio of Polymer 1.1 to Polymer 1.2 being 45:55.

(8) The bimodal mixture of Polymer 1.1 and Polymer 1.2 has a butene content of about 2 wt %.

(9) The weight average molecular weight (M.sub.w) and the number average molecular weight (M.sub.n) are 140 kg/mol and 7 kg/mol, respectively, and thus M.sub.w/M.sub.n is 20.

(10) Thermoplastic Elastomer

(11) For Examples 1, 2, 3, 4 and 5: 31.36, 30.16, 31.28, 34.96, and 31.36 wt %, respectively, of a grade of a thermoplastic elastomer, i.e. ethylene butyl acrylate (EBA) copolymer, having a melt flow rate (MFR2@190° C.) according to ISO 1133 (190° C., 2.16 kg) which is 4.5 g/10 min and the content of butyl acrylate which is 7.5 mol % or 27 wt % with regard to the total amount of monomers in EBA. The saturated polyolefin were prepared by a high pressure polymerisation process.

(12) Conductive Filler

(13) For examples 1, 2 and 3: 21, 24, and 21 wt %, respectively, of a conductive filler, i.e. a commercially available standard grade of a modified furnace carbon black having a BET nitrogen surface area (according to ASTM D6556) which is 65 m.sup.2/g, and a DBPA oil absorption (according to ASTM D2414): 190 ml/100 g,

(14) for Example 4: 12 wt % of a conductive filler, i.e. a commercially available special grade of a modified furnace carbon black having a BET nitrogen surface area (according to ASTM D6556) which is 770 cm.sup.3/g, and a DBPA oil absorption (according to ASTM D2414): 320 ml/100 g, of which paremeters are similar level to typical values of Ketjenblack,
for Example 5: 21 wt % of a commercially available grade of a conductive filler, i.e. a carbon black having an Iodine number (according to ASTM D1510) which is 587 mg/g, and a DBPA oil absorption (according to ASTM D2414): 131 ml/100 g.

(15) Antioxidant

(16) For Examples 1, 2, 4 and 5: 0.6 wt % of a commercially available grade of an antioxidant being 2,2,4-trimethyl-1,2-dihydroquinoline (CAS 26780-96-1) and for Example 3: 0.8 wt % of a commercially available grade of an antioxidant being 4,4′-bis(1,1′-dimethylbenzyl) diphenylamine (CAS 10081-67-1).

Examples 6, 7 and 8 (Comparative Examples)

Semiconductive Compositions, Examples 6, 7 and 8, Comprising Multimodal High Density Polyolefin, Thermoplastic Elastomer, Conductive Filler and Antioxidant

(17) Multimodal High Density Polyolefin

(18) For Examples 6, 7 and 8: 41.5, 46.44 and 50.31 wt %, respectively, of a multimodal high density polyolefin, i.e. a bimodal high density polyethylene, having a density of 944 kg/m.sup.3 and a melt flow rate (MFR2@190° C.) according to ISO 1133 (190° C., 2.16 kg) which is 1.7 g/10 min; the multimodal high density polyolefin, i.e. the bimodal high density polyethylene, was prepared using the same polymerisation plant that was used for the preparation of the bimodal high density polyethylene of the inventive Examples 1, 2, 3, 4 and 5, but with the below conditions;

(19) In the first reactor, i.e. the loop reactor, a first polymer (Polymer 2.1) was produced by the polymerisation of ethylene in the presence of hydrogen (molar ratio of hydrogen to ethylene=roughly 0.60:1). The resulting ethylene homopolymer had an MFR2@190° C. value of about 400 g/10 min and a density of about 0.970 kg/cm3.

(20) In the second reactor, i.e. the gas-phase reactor, a second polymer (Polymer 2.2) was produced by the polymerisation of ethylene with butene (molar ratio of butene to ethylene=roughly 0.35:1, and molar ratio of hydrogen to ethylene=roughly 0.07:1). The resulting copolymer of ethylene and butene was present in the form of an intimate mixture with the ethylene homopolymer from the first reactor, the weight ratio of Polymer 2.1 to Polymer 2.2 being 45:55.

(21) The bimodal mixture of Polymer 2.1 and Polymer 2.2 has a butene content of about 3 to 4 wt %.

(22) The weight average molecular weight (M.sub.w) and the number average molecular weight (M.sub.n) are 120 kg/mol and 7 kg/mol, respectively, and thus M.sub.w/M.sub.n is 17.

(23) Thermoplastic Elastomer

(24) For Examples 6, 7 and 8: 44.7, 30.96 and 27.09 wt %, respectively, of the thermoplastic elastomer, i.e. of the same ethylene butyl acrylate (EBA) copolymer which was used for inventive Examples 1, 2, 3, 4 and 5.

(25) Conductive Filler

(26) For Example 6: 13 wt % of a conductive filler, i.e. the commercially available special grade of the highly conductive carbon black used in the inventive Example 4, and

(27) for both Examples 7 and 8: 22 wt % of a conductive filler, i.e. a commercially available standard grade of the modified furnace carbon black used in the inventive Examples 1, 2 and 3; and

(28) Antioxidant

(29) For Examples 6, 7 and 8: 0.8, 0.6 and 0.6 wt %, respectively, of an antioxidant, i.e. a commercially available grade of an antioxidant being 2,2,4-trimethyl-1,2-dihydroquinoline (CAS 26780-96-1).

(30) Further, during the compounding step the temperature zones of the Buss MDK 46 kneader were ranging from 140 to 180° C., and during the extrusion the extrusion temperature was around 160° C. The obtained melted mix was then pelletized, and pellets of each example were used for measuring the relevant properties, as described herein, by using the methods disclosed in “Methods”.

(31) Table 1 shows the properties of the inventive Examples 1, 2, 3, 4 and 5, and of the comparative Examples 6, 7 and 8. When a multimodal high density polyolefin having a high MFR2@190° C., i.e. as in the comparative Examples 6, 7 and 8, is used in the base resin blend, i.e. the polymer blend, a high Shore D, a low VR (or high conductivity) and appropriate MFR21@190° C. can be obtained for different grades of conductive fillers. However, when using the multimodal high density polyolefin having a high MFR2@190° C., a good ESCR and a good resistance of bending cracking test could only be achieved for high conductive grades of conductive fillers having a BET nitrogen surface area (according to ASTM D6556) which is 770 m.sup.2/g, or a DBPA oil absorption (according to ASTM D2414) which is 320 ml/100 g. When a commercially available standard grade of conductive filler, having a BET nitrogen surface area (according to ASTM D6556) which is 65 m.sup.2/g, or having a DBPA oil absorption (according to ASTM D2414) which is 190 [ml/100 g], was used, the semiconductive composition could only be appropriately semiconductive when the conductive filler content is at least about 22 wt %. The high loading of the conductive filler gives a low ESCR. Although ESCR could be improved by increasing the content of the multimodal high density polyolefin, the resulting semiconductive composition would then be too brittle for bending.

(32) However, when a multimodal high density polyolefin having a low MFR2@190° C., i.e. as in the inventive Examples 1, 2, 3, 4 and 5, is used in the base resin blend, i.e. the polymer blend, the resulting semiconductive composition exhibited excellent performance of both mechanical flexibility and ESCR while VR was maintained at a low level, surprisingly, also when non high conductive grades of conductive fillers were used. Thus, in Examples 1, 2, 3 and 5, the resulting semiconductive composition exhibited excellent performance of both mechanical flexibility and ESCR while VR was maintained at a low level, when the following non high conductive grades of conductive fillers were used: in Examples 1, 2, and 3: a commercially available standard grade of conductive filler having a BET nitrogen surface area (according to ASTM D6556) which is 65 m.sup.2/g, or a DBPA oil absorption (according to ASTM D2414) which is 190 ml/100 g, or in Example 5: a commercial available conductive filler having an Iodine number (according to ASTM D1510) which is 587 m.sup.2/g, or a DBPA oil absorption (according to ASTM D2414) which is 131 ml/100 g was used, which requires a high content (21 wt %) of the conductive filler to maintain the low VR value. Furthermore, when 4,4′-bis(1,1′-dimethylbenzyl) diphenylamine (CAS 10081-67-1) was used as the antioxidant (as in Example 3) instead of the antioxidant 2,2,4-trimethyl-1,2-dihydroquinoline (CAS 26780-96-1), VR, MFR21@190° C. and, even, Shore D were improved. Thus, 4,4′-bis(1,1′-dimethylbenzyl) diphenylamine (CAS 10081-67-1) may advantageously be used in the semiconductive composition of the present invention.

(33) TABLE-US-00001 TABLE 1 Performance of inventive Examples 1-5 and comparative Examples 6-8 ESCR Bend F0 cracking Shore VR@90° C. MFR21@190° C. Example [h] test D [ohm cm] [g/10 min] 1 >3000 No 54 88 14 cracking 2 >3000 No 58 18 8.28 cracking 3 >3000 No 57 25 22 cracking 4 >3000 No 53 41 32.75 cracking 5 >3000 No 57 158 6.89 cracking 6 1600 No 50 19 55.62 cracking 7 20 No 57 41 32 cracking 8 170 Small 59 22 29 cracking