Cross-linked polyethylene compositions

Patent metadata

Field	Value
Publication number	US-9589700-B2
Application number	US-201214124300-A
Country	US
Kind code	B2
Filing date	Jul 31, 2012
Priority date	Aug 8, 2011
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

A cross-linked polyethylene composition for a power cable insulator including (A) 100 parts by weight of a polyethylene base resin, (B) 0.1 to 0.6 parts by weight of a hindered phenol-based antioxidant, (C) 1 to 4 parts by weight of a crosslinking agent, (D) 0.2 to 1.0 parts by weight of magnesium oxide and (E) 0.1 to 1.0 parts by weight of a scorch inhibitor, which advantageously exhibits superior resistance to water tree generated when a power cable insulator is exposed to outside water and electric field, and superior electrical insulation characteristics.

First claim

What is claimed is:

1. A cross-linked polyethylene composition for a power cable insulator comprising:
(A) 100 parts by weight of a polyethylene base resin;
(B) 0.1 to 0.6 parts by weight of a hindered phenol-based antioxidant;
(C) 1 to 4 parts by weight of a crosslinking agent;
(D) 0.2 to 1.0 parts by weight of magnesium oxide surface treated with silane, which has an average particle size of less than 1 μm; and
(E) 0.1 to 1.0 parts by weight of a scorch inhibitor,
wherein the polyethylene base resin (A) is an ethylene homopolymer polymerized by a free radical initiation reaction at a high pressure of 1,000 bar or more in a high-pressure tubular or autoclave reactor,
wherein the hindered phenol-based antioxidant (B) is the only antioxidant included in the composition, and the hindered phenol-based antioxidant (B) is only one compound selected from the group consisting of 4,4′-thiobis(2-t-butyl-5-methylphenol), 2,2′-thio diethyl bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], pentaerythrityl-tetrakis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 4,4′-thiobis(2-methyl-6-t-butylphenol), 2,2′-thiobis(6-t-butyl-4-methylphenol), octadecyl-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], triethyleneglycol-bis-[3-(3-t-butyl-4-hydroxy-5-methylphenol)propionate], thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 6,6′-di-t-butyl-2,2′-thiodi-p-cresol, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-xylyl)methyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione and dioctadecyl 3,3′-thiodipropionate,
wherein a weight ratio of the scorch inhibitor (E) to the magnesium oxide surface-treated with silane (D) is 1:0.3 to 1:4, and
wherein the cross-linked polyethylene composition has a water tree growth rate of 0.1 or less measured by ASTM D6097.

2. The cross-linked polyethylene composition according to claim 1 , further comprising: a tree inhibitor,
wherein a weight ratio of the magnesium oxide surface-treated with silane to the tree inhibitor is 1:2 to 1:0.1.

3. The cross-linked polyethylene composition according to claim 1 , further comprising: 0.2 to 0.9 parts by weight of polyethylene glycol having a molar mass (g/mol) of 5,000 to 70,000, with respect to 100 parts by weight of the polyethylene base resin.

4. The cross-linked polyethylene composition according to claim 1 , wherein the polyethylene base resin (A) has a density of 0.87 to 0.96 g/cm 3 , a melt index of 0.1 to 50 g/10 min and a weight average molecular weight of 40,000 to 200,000.

5. The cross-linked polyethylene composition according to claim 1 , wherein the crosslinking agent (c) comprises at least one selected from the group consisting of dicumyl peroxide, benzoyl peroxide, lauryl peroxide, tert-butyl cumyl peroxide, di(tert-butyl peroxy isopropyl) benzene, 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane and di-tert-butyl peroxide.

6. The cross-linked polyethylene composition according to claim 1 , wherein the scorch inhibitor comprises at least one selected from the group consisting of 2,4-diphenyl-4-methyl-1-pentene, 1,4-hydroquinone and hydroquinone derivatives.

7. A cable comprising the cross-linked polyethylene composition according to claim 1 , and having a water tree growth rate of 0.1 or less measured by ASTM D6097, upon coating a conductive layer or a semi-conductive layer.

8. A method for preparing a cross-linked polyethylene composition comprising:
a first step of mixing 100 parts by weight of a polyethylene base resin with 0.1 to 0.6 parts by weight of a hindered phenol-based antioxidant, 1 to 4 parts by weight of a crosslinking agent, 0.2 to 1.0 parts by weight of magnesium oxide surface treated with silane which has an average particle size of less than 1 μm, and 0.1 to 1.0 parts by weight of a scorch inhibitor, followed by extrusion; and
a second step of cross-linking the extrudate obtained in the mixing and extrusion step at a temperature higher than a decomposition temperature of the crosslinking agent, to prepare a cross-linked polyethylene composition for a power cable insulator having a water tree growth rate of 0.1 or less measured by ASTM D6097,
wherein the polyethylene base resin is an ethylene homopolymer polymerized by a free radical initiation reaction at a high pressure of 1,000 bar or more in a high-pressure tubular or autoclave reactor,
wherein the hindered phenol-based antioxidant is the only antioxidant included in the composition, and the hindered phenol-based antioxidant is only one compound selected from the group consisting of 4,4′-thiobis(2-t-butyl-5-methylphenol), 2,2′-thio diethyl bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], pentaerythrityl-tetrakis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 4,4′-thiobis(2-methyl-6-t-butylphenol), 2,2′-thiobis(6-t-butyl-4-methylphenol), octadecyl-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], triethyleneglycol-bis-[3-(3-t-butyl-4-hydroxy-5-methylphenol)propionate], thiodiethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 6,6′-di-t-butyl-2,2′-thiodi-p-cresol, 1,3,5-tris(4-t-butyl-3-hydroxy-2,6-xylyl)methyl-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione and dioctadecyl 3,3′-thiodipropionate, and
wherein a weight ratio of the scorch inhibitor to the magnesium oxide surface-treated with silane is 1:0.3 to 1:4.

9. The method according to claim 8 , wherein the first step comprises:
(a) preparing a master batch comprising a combination of the antioxidant and polyethylene glycol, or a combination of the antioxidant, polyethylene glycol and a crosslinking agent; and
(b) adding polyethylene or a combination of polyethylene and a crosslinking agent to an extruder and then adding the master batch obtained in the step (a) to the extruder or directly adding respective additives to the extruder, followed by extrusion.

Assignees

• Sun Ka Ram
• Park In Gyu
• Nam Youn Sun
• Song Young Il
• Do Sang Rok
• Lg Chemical Ltd

Inventors

• Sun Ka Ram
• Park In Gyu
• Nam Youn Sun
• Song Young Il
• Do Sang Rok

Classifications

• Y10T428/2933

  Coated or with bond, impregnation or core · CPC title

• C08K2003/222

  Magnesia, i.e. magnesium oxide · CPC title

• C08K5/01

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

• C08K3/22

  of metals · CPC title

• C08K5/375

  containing six-membered aromatic rings {(C08K5/3725 takes precedence)} · CPC title