Crosslinked polyethylene composition

Abstract

The crosslinked polyethylene composition according to the present invention is characterized in that the migration of additives is inhibited due to low oil content of low density polyethylene, and thus, when preparing crosslinked polyethylene using the same, stable extrusion property is exhibited, thus reducing exterior deviation of the crosslinked polyethylene.

Claims

1. A crosslinked polyethylene composition comprising: 100 parts by weight of low density polyethylene(LDPE) having an oil content of 700 ppm or less, 0.1 to 10 parts by weight of a crosslinking agent, and 0.1 to 1.0 parts by weight of an antioxidant, and wherein the oil content is measured and calculated by dividing the mass of the components extracted for 4 hours after putting 500 g of the LDPE in 2 L of water of 100 C., by 500 g.

2. The crosslinked polyethylene composition according to claim 1, wherein the oil content of the low density polyethylene is 300 ppm or less.

3. The crosslinked polyethylene composition according to claim 1, wherein the crosslinking agent is one or more selected from the group consisting of dicumyl peroxide, benzoyl peroxide, lauryl peroxide, t-butyl cumyl peroxide, di(t-butyl peroxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane, and di-t-butyl peroxide.

4. The crosslinked polyethylene composition according to claim 1, wherein the antioxidant is one or more selected from the group consisting of 4,4-thiobis(2-t-butyl-5-methylphenol), 4,6-bis(octylthiomethyl)-o-cresol, 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.

5. The crosslinked polyethylene composition according to claim 1, further comprising 0.1 to 5 parts by weight of a crosslinking accelerator.

6. The crosslinked polyethylene composition according to claim 5, wherein the crosslinking accelerator is 2,4-diphenyl-4-methyl-1-pentene, or 1,4-hydroquinone.

7. The crosslinked polyethylene composition according to claim 1, further comprising 0.1 to 5 parts by weight of a treeing inhibitor.

8. The crosslinked polyethylene composition according to claim 7, wherein the treeing inhibitor is polyethylene glycol.

9. The crosslinked polyethylene composition according to claim 1, wherein the methanol extraction content of the crosslinked polyethylene is 900 ppm or less.

10. A cable comprising the crosslinked polyethylene composition according to claim 1.

11. The cable according to claim 10, wherein the extruded outer diameter deviation of a cable prepared from the crosslinked polyethylene is 0.5 mm or less.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Hereinafter, preferable examples are presented for better understanding of the present invention. However, these examples are presented only as the illustrations of the present invention, and the scope of the present invention is not limited thereby.

Examples 15 and Comparative Examples 12

(2) With the components and contents (parts by weight) described in the following Table 1, each component was kneaded in a Banbury mixer of 120140 C., and then, granulated in the form of pellets. Meanwhile, in order to measure the oil extraction content of each low density polyethylene used, 500 g of low density polyethylene was put in 2 L of water of 100 C. and left for 4 hours, and then, cooled for 2 hours, and the concentration of extracted components was measured, and the results were shown in the following Table 1.

EXPERIMENTAL EXAMPLE

(3) Using the pellets prepared in Examples and Comparative Examples, experiments were conducted as follows.

(4) 1) Methanol Extraction Content

(5) 50 g of the pellets were put in a beaker, and then, 100 mL of methanol was put, and the mixture was stirred for 5 minutes. The methanol solution was filtered with a 10 um PTFE, and vacuum dried to remove methanol, and then, the weight was measured at room temperature. The obtained value was divided by 50 g to calculate the methanol extraction content.

(6) 2) Exterior Deviation

(7) The following 3 kinds of materials were simultaneously extruded in order onto the peripheral part of a conductor (cross section (circular) 630 mm.sup.2), and pressurized and heated at a temperature of 380 C. and a pressure of 10 kg/cm.sup.2, under nitrogen atmosphere, to prepare a cable. Here, the thickness of an insulation layer was controlled to 9 mm, the thickness of the internal semi-conductive layer was controlled 0.6 mm, and the thickness of external semi-conductive layer was controlled to 0.8 mm. The thickness of the insulation layer of the prepared cable was measured with an X-ray outer diameter measuring instrument to measure the thickness deviation.

(8) A. The internal semi-conductive layer was formed using a composition comprising ethylene-acetic acid vinyl copolymer, an organic peroxide crosslinking agent, carbon black, and an antioxidant (semi-conductive resin composition).

(9) B. The insulation layer was formed using the pellets prepared in Examples and Comparative Examples.

(10) C. The external semi-conductive layer was formed using the same semi-conductive resin composition as for the internal semi-conductive layer.

(11) The measurement results were shown in the following Table 1.

(12) TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Example 2 low density 100 100 100 100 100 100 100 polyethylene.sup.1) Crosslinking 2.0 2.0 2.0 2.0 2.0 2.0 2.0 agent.sup.2) antioxidant 1.sup.3) 0.2 0.2 0.1 0.3 0.1 0.2 0.3 antioxidant 2.sup.4) 0.1 0.1 Curing 0.4 0.4 accelerator.sup.5) Treeing 0.5 inhibitor.sup.6) Oil extraction 240 600 600 820 820 920 920 content (ppmw) Methanol 350 800 600 350 500 1,000 1,200 extraction content (ppmw) Extruded outer 0.2 0.4 0.2 0.2 0.2 0.5 0.6 diameter deviation (mm) .sup.1)Example 1(SEETEC BC500, LG Chem., using synthetic oil) Examples 2 and 3(SEETEC BC500, LG Chem., using mineral oil) Examples 4, 5 and Comparative Examples 1, 2(LUTENE CB2030, LG Chem.) .sup.2)dicumyl peroxide .sup.3)4,4-thiobis(2-t-butyl-5-methylphenol) .sup.4)4,6-bis(octylthiomethyl)-o-cresol .sup.5)2,4-diphenyl-4-methyl-1-pentene .sup.6)polyethylene glycol

(13) As shown in Table 1, it was confirmed that, in the case of Example 1 with the smallest oil extraction content of low density polyethylene, the methanol extraction content and extruded outer diameter deviation were also small. And, in the case of Example 2, since the oil extraction content of low density polyethylene is larger than Example 1, the methanol extraction content and extruded outer diameter deviation slightly increased, but by additionally comprising a curing accelerator as in Example 3, they could be lowered. Also, in the case of Examples 4 and 5, although the oil extraction contents of low density polyethylene are rather high, by additionally comprising a curing accelerator or a treeing inhibitor, the methanol extraction content and extruded outer diameter deviation were shown to be low.

(14) To the contrary, in the case of Comparative Examples 1 and 2 wherein the oil extraction content of low density polyethylene is high and additional components other than a crosslinking agent and an antioxidant are not included, the methanol extraction content and extruded outer diameter deviation were shown to be high.