JPH04311742A - Insulating composition - Google Patents

Abstract

PURPOSE:To obtain a composition consisting of a specific polyethylene, specific random terpolymer and crosslinking agent, excellent in resistance to water treeing and heat resistance and suitable as an insulating material for power cable. CONSTITUTION:The objective composition obtained by blending (A) polyethylene selected from crystalline high-pressure-processed low-density polyethylene and crystalline low-pressure-processed straight-chain low-density polyethylene with (B) ethylene-ethylene acrylate-maleic anhydride random tercopolymer and (C) organic peroxide crosslinking agent or blending the polyethylene of the component A with the component B, (D) ethylene-alpha-olefin copolymer and the component C. A polyethylene having 0.918-0.928 MFR or 1-butene copolymer having 0.915-0.925 MFR is preferably used as the component A. A copolymer having 5.0-30 MFR, 0.935-0.952 density and 2-4wt.% maleic anhydride content is preferably used as the component B.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition having excellent water resistance and heat resistance, and particularly suitable as a material for forming an insulating layer for power cables.

0002

BACKGROUND OF THE INVENTION Cross-linked polyethylene insulated power cables are widely used from the viewpoints of electrical performance, heat resistance, cost, etc. However, with the recent increase in working voltage, when cross-linked polyethylene insulated power cables are used in wet conditions,
The possibility of water tree deterioration has been raised as a problem.

[0003] Water tree deterioration is a phenomenon in which when a cross-linked polyethylene insulator is electrically charged in a wet state for a long period of time, partial dielectric breakdown occurs in the insulator, eventually leading to complete circuit breakdown. One of the reasons for this is said to be that polyethylene is hydrophobic, so water tends to concentrate in areas where the electric field is abnormal.

[0004] As a countermeasure against such water tree deterioration, methods of mixing, for example, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, or polyethylene glycol with polyethylene are known. However, since the effect on water tree deterioration is not necessarily sufficient, recently, compositions in which polyethylene is blended with resins such as saponified ethylene-vinyl acetate copolymers and polyethylene hydroxide have been proposed (Japanese Patent Application Laid-Open No. 1983-1979-1). Publication No. 246946, Japanese Unexamined Patent Publication No. 56-34738
Publication No.).

[0005] However, even the above compositions are not sufficiently effective against water tree deterioration, and these compositions also have shortcomings in heat resistance, resulting in deterioration of the insulator in harsh and rapidly changing natural environments. It has the disadvantage of being easy to progress.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an insulating composition that has excellent water tree resistance, that is, less water tree deterioration even when applied with electricity in a wet state, and has excellent heat resistance. That's true.

[0007]

[Means for solving the problem] The above problem can be solved as follows (I
) and (II). (I) At least one member selected from the group consisting of ■crystalline high-pressure low-density polyethylene and crystalline low-pressure straight-chain low-density polyethylene containing an olefin having 4 to 10 carbon atoms as a comonomer, ■ethylene-ethyl acrylate- An insulating composition comprising a maleic anhydride ternary random copolymer and (1) an organic peroxide crosslinking agent. (II) Insulating composition consisting of ■crystalline high-pressure low-density polyethylene, ■ethylene-ethyl acrylate-maleic anhydride ternary random copolymer, ■ethylene-α-olefin copolymer, and ■organic peroxide crosslinking agent. .

The insulating composition of the present invention will be explained in detail below. In this specification, melt flow rate (hereinafter referred to as M
(abbreviated as FR) is a value measured at 190°C in accordance with ASTM D1238.

The crystalline high-pressure low density polyethylene (hereinafter also referred to as LDPE) used in the present invention has an MFR of 0.5 to 2.5, preferably 0.7 to 2.0.
Density is 0.910-0.930, preferably 0.9
A range of 18 to 0.928 is preferable. Examples of such LDPE include Yucalon ZF-30, EH-30, EF-30, and ZF-51 manufactured by Mitsubishi Yuka Co., Ltd.
, ZE-41, YF-30, Mirason 9,5S manufactured by Mitsui Petrochemical Co., Ltd., and the like.

The crystalline low pressure linear low density polyethylene (hereinafter also referred to as L-LDPE) containing an olefin having 4 to 10 carbon atoms as a comonomer used in the present invention has an MFR of
is 0.5-2.5, preferably 0.7-2.0
, the density is 0.910-0.930, preferably 0.910-0.930.
A range of 915 to 0.925 is preferred. Here, the olefin having 4 to 10 carbon atoms refers to 1-butene,
1-hexene, 1-octene, ethyl-hexene-1,
Preferred are n-decene-1 and the like. As an example of such L-LDPE, commercially available products include Yucalon LLF3 manufactured by Mitsubishi Yuka Co., Ltd.
0F (MFR=1.0, density=0.920), M-
40F (MFR=0.7, density=0.922), F
-30H (MFR = 2.0, density = 0.920), Mitsui Petrochemicals Ultzex UZ2020L (MFR
= 1.0, density = 0.920), NZ-2006 (M
FR=0.8, density=0.923), NUCG-5210 manufactured by Nippon Unicar Co., Ltd. (MFR=1.0, density=0.9
20) etc.

The ethylene-ethyl acrylate-maleic anhydride ternary random copolymer used in the present invention has M
FR is 3.0-70, preferably 5.0-30,
Density is 0.920-0.960, preferably 0.9
35 to 0.952, the comonomer content is 14 to 35% by weight, of which the maleic anhydride content is 2 to 4% by weight, and the melting point measured by differential scanning calorimeter is 65 to 35% by weight. Polymers in the 96°C range are preferred. As an example of such ethylene-ethyl acrylate-maleic anhydride ternary random copolymer, commercially available products include:
Bondine TX8030, HX829 manufactured by Sumitomo Chemical Co., Ltd.
0, HX8140, HX8020, AX8060, AX
8390, etc.

The ethylene-α olefin copolymer used in the present invention has an MFR of 0.5 to 40, preferably
2.0 to 20, with a density of 0.880 to 0.918, preferably 0.884 to 0.910. Ethylene-α olefin copolymers in this range are usually referred to as very low density polyethylene (hereinafter referred to as VLDPE).
A resin commercially available under the name (also referred to as "C") falls under this category, and is a copolymer produced by copolymerization of ethylene and an alpha olefin having 4 to 8 carbon atoms. Here carbon number is 4 ~
The α-olefins of No. 8 include 1-butene, 1-octene, ethyl-hexene-1, hexene-1, n-decene-1,
1st class is preferred. Examples of such ethylene-α olefin copolymers include ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, ethylene-decene-1 copolymer, etc. It will be done. Commercially available products include the following: Manufactured by Mitsui Petrochemical Co., Ltd.: Tafmar A4085 (MFR=3.
6, density = 0.88), A4090 (MFR = 3.6
, density=0.89), A20090 (MFR=18,
Density = 0.890) Manufactured by Sumitomo Chemical Co., Ltd.: Excellen VL200 (MFR = 2
．． 0, density = 0.900), VL400 (MFR = 5
．． 0, density = 0.900), VL700 (MFR = 1
0, density = 0.905), VL800 (MFR = 20
, density = 0.905) Manufactured by Sumitomo Chemical Co., Ltd.: EUL430
(MFR=4.0, density=0.890), EUL7
30 (MFR=10, density=0.890), EUL7
31 (MFR=10, density=0.895) manufactured by Nippon Unicar: DEFD-1209 (MFR=1.0, density=0
．． 900), DEFD-1210 (MFR=1.0,
Density = 0.890) Manufactured by Mitsubishi Yuka Co., Ltd.: X139 (MFR
= 2.26, density = 0.901), X141 (MFR =
7.62, density=0.903), X140(MFR
= 18.7, density = 0.901)

[0013] In the composition of the present invention, the blending ratio of each of the above resin components is as follows. In composition (I), the blending ratio of the low density polyethylene component and the ethylene-ethyl acrylate-maleic anhydride ternary random copolymer is 99.5 by weight.
-60:0.5 -40, preferably 99-70:1
~30. In composition (II), the amount of the ethylene-ethyl acrylate-maleic anhydride ternary random copolymer per 100 parts by weight of the low-density polyethylene component is 0.5 to 40 parts by weight, preferably 1 to 30 parts by weight, and ethylene. -The blending amount of α-olefin copolymer is 1 to 40
Parts by weight, preferably 5 to 20 parts by weight.

The organic peroxide crosslinking agent used in the present invention is not particularly limited as long as it is used in ordinary polymerization. Specifically, the following compounds are exemplified. Dicumyl peroxide (DCP), 1,3-bis(tert-butylperoxy-isopropyl)benzene [for example, Percadox 14 manufactured by Kayaku Nouri Co., Ltd.], 2,5-dimethyl-2,5-di(tert-butylperoxy) ) Hexane (for example, Kayahexa YD manufactured by Kayaku Nouri Co., Ltd.). The blending amount of the organic peroxide crosslinking agent is 100% of the resin component.
The amount per part by weight is usually 0.2 to 6.0 parts by weight, preferably 1.0 to 4.0 parts by weight.

The insulating composition of the present invention may also contain various antioxidants such as hindered phenol-based, amine-based, quinone-based, and phosphorus-based antioxidants, stabilizers such as stearic acid, and ultraviolet absorbers such as benzophenone derivatives. Additives such as additives, plasticizers such as phthalate esters, other processing aids, reinforcing fillers, and flame retardants may also be blended. In particular, it is preferable to incorporate a hindered phenol antioxidant. The following compounds are exemplified as the hindered phenolic antioxidant. 2,6-di-tert-butyl-4-ethylphenol (e.g. M-17 manufactured by Ouchi Shinko Co., Ltd.), 2,
6-di-tert-butyl-4-methylphenol (for example, manufactured by Ouchi Shinko Co., Ltd.: N-200), 2,2-methylenebis(4-ethyl-6-tert-butylphenol) (for example, manufactured by Ouchi Shinko Co., Ltd.: NS -5) ,2,2
-methylenebis(4-methyl-6-tert-butylphenol) (for example, manufactured by Ouchi Shinko Co., Ltd.: NS-6), 2,
5-di-tert-butylhydroquinone (for example, Ouchi Shinko Co., Ltd.: NS-7), 4,4'-thiobis(6-t
ert-butyl-3-methylphenol) (for example, N-300 manufactured by Ouchi Shinko Co., Ltd.). When blending a hindered phenol antioxidant, the blending amount is 100% of the resin component.
The amount per part by weight is usually 0.1 to 5.0 parts by weight, preferably 1.0 to 3.0 parts by weight.

The composition of the present invention is useful, for example, as a material for forming an insulating layer for power cables. Usually, the composition is crosslinked by heating at 160 to 250°C for 5 to 60 minutes to form an insulating layer.

[0017]

[Example] Examples 1 to 24 The compositions of the present invention shown in Tables 1 to 4 were mixed in a roll mill (
120℃, 10 minutes), then hot press at 180℃,
Cross-linking molding was performed for 30 minutes to obtain a sample sheet with a thickness of 3 mm. A water tree test was conducted using this sheet and the electrode system shown in FIG. After applying AC 10 KV, 1 KHz for 200 hours and 400 hours under room temperature and submersion with 2.0 mol/l saline, the sample sheet was cut into slices of 0.1 mm and the maximum length of the generated water tree was measured. Furthermore, for heat resistance evaluation, a 1m thick sample made under the same conditions
The tensile strength retention (%) and elongation retention (%) after 7 days at 150° C. were determined using the crosslinked sheet of No. m in accordance with ASTM D573. The results are summarized in Tables 1 to 4.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022] The abbreviations in the table represent the following. ZF-30: LDPE, manufactured by Mitsubishi Yuka Co., Ltd., Yucalon ZF
-30UZ2020L: L-LDPE, Mitsui Petrochemical Co., Ltd., Urtozex UZ2020L (MFR=1.0
, density = 0.920) NUCG5210: L-LDPE
, manufactured by Nippon Unicar Co., Ltd., NUCG-5210 (MFR=1
．． 0, density = 0.920) F-30F: L-LDPE, Mitsubishi Yuka Co., Ltd., Yucalon LLF-30F (MFR = 1.0, density = 0.920) M-40F: L-LDPE, Mitsubishi Yuka Co., Ltd. manufactured by Yucalon LLM-40F (MFR=0.7, density=0.922) EH-30: LDPE, manufactured by Mitsubishi Yuka Co., Ltd., Yucalon EH
-30ZF-51: LDPE, manufactured by Mitsubishi Petrochemical Co., Ltd., Yucalon ZF-515S: LDPE, manufactured by Mitsui Petrochemical Co., Ltd., Mirason 5SVL200: VLDPE, manufactured by Sumitomo Chemical Co., Ltd., Excellen VL200 (MFR = 2.0,
Density = 0.900) VL400: VLDPE, manufactured by Sumitomo Chemical Co., Ltd., Excellen VL400 (MFR = 5.0, density = 0.900
) EUL430: VLDPE, manufactured by Sumitomo Chemical Co., Ltd., EU
L430 (MFR=4.0, density=0.890) EUL731: VLDPE, manufactured by Sumitomo Chemical Co., Ltd., EU
L731 (MFR = 10, density = 0.895) A4085: VLDPE, manufactured by Mitsui Petrochemicals, Tafmar A4085 (MFR = 3.6, density = 0.88) A4090: VLDPE, manufactured by Mitsui Petrochemicals, Tafmar A4090 ( MFR=3.6, density=0.89
) X139: VLDPE, manufactured by Mitsubishi Yuka Co., Ltd., X139
(MFR=2.26, density=0.901) X140: VLDPE, manufactured by Mitsubishi Yuka Co., Ltd., X140
(MFR=18.7, density=0.901) DEFD1209: VLDPE, manufactured by Nippon Unicar Co., Ltd., D
EFD-1209 (MFR=1.0, density=0.900
) DEFD1210: VLDPE, manufactured by Nippon Unicar Co., Ltd., D
EFD-1210 (MFR=1.0, density=0.890
) AX8390: Manufactured by Sumitomo Chemical Co., Ltd., Bondine AX83
90AX8060: Manufactured by Sumitomo Chemical Co., Ltd., Bondine AX
8060 H
-300NS-6: Manufactured by Ouchi Shinkosha, NS-6NS-
5: manufactured by Ouchi Shinko Co., Ltd., NS-5M-17: manufactured by Ouchi Shinko Co., Ltd., M-17DCP: dicumyl peroxide, YD manufactured by Mitsui Petrochemical Co., Ltd.: manufactured by Kayaku Nouri Co., Ltd., Kayahexa YDP-14: manufactured by Kayaku Nouri Co., Ltd. Made by company,
Parkadox 14

[0023]

Effects of the Invention In the composition of the present invention, the ethylene-ethyl acrylate-maleic anhydride ternary random copolymer effectively disperses and retains the water that has entered the polymer matrix, so that the water can be absorbed into the abnormal part of the electric field. This prevents water trees from concentrating on water. Therefore, the water resistance is significantly improved compared to conventional polyethylene compositions. It also has excellent heat resistance, with no decrease in tensile strength or elongation even after exposure to heating conditions, and has very excellent properties as an insulating layer material for power cables.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an electrode system used in a water tree test.

[Explanation of symbols]

1 Copper electrode 2 Polyethylene 3 Sample sheet 4 Salt solution 5 Conductive paint layer

Claims (2)

[Claims] [Claim 1] ■Crystalline high pressure low density polyethylene;
and at least one member selected from the group consisting of crystalline low-pressure linear low-density polyethylene containing an olefin having 4 to 10 carbon atoms as a comonomer, ■ ethylene-ethyl acrylate-maleic anhydride ternary random copolymer, and ■ organic An insulating composition comprising a peroxide crosslinking agent. [Claim 2] ■Crystalline high-pressure low-density polyethylene;
An insulating composition comprising: (1) an ethylene-ethyl acrylate-maleic anhydride ternary random copolymer, (2) an ethylene-α-olefin copolymer, and (2) an organic peroxide crosslinking agent.