JPH0481283B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a semiconducting mixture that has good adhesion to metals, and is particularly useful as a mixture for internal semiconducting layers of power cables and the like. <Prior Art> High-voltage CV cables are manufactured by coating a metal conductor with an inner semiconducting layer, an insulating layer, and an outer semiconducting layer by extrusion and then heating to crosslink each layer. <Problems to be Solved by the Invention> However, in the CV cable manufactured in this manner, a phenomenon called shrinkback may occur in which the coating layer shrinks and the conductor protrudes during storage or use. It is presumed that this is because distortion caused by heat during manufacturing remains in the coating layer. When this shrinkback occurs, a small space is created at the interface between the conductor and the coating at the connection or terminal part of the cable, leading to a decrease in cable characteristics and, in some cases, to dielectric breakdown. be. For this reason, conventionally, sufficient heat treatment has been carried out as a countermeasure against shrinkage. This is because sufficient heat treatment with high temperature nitrogen gas, steam, high temperature silicone oil, etc. in the crosslinking step removes distortion in the coating and prevents shrink back to some extent. However, it is difficult to completely prevent shrinkage by this heat treatment alone, leading to an increase in processing (manufacturing) costs. In addition, metal fittings and the like are attached to cable connection parts and terminal parts to prevent shrinkage, but this cannot be said to be perfect. In order to more completely prevent this shrinkback, it is possible to bond the conductor and the internal semiconducting layer more strongly, but at present, it is possible to In addition, no semiconducting mixture has been proposed that has good adhesion to conductors. Therefore, the present inventors conducted intensive research and found that a polymer obtained by grafting maleic anhydride onto an ethylene-vinyl acetate copolymer and/or a polymer obtained by grafting maleic anhydride onto an ethylene-ethyl acrylate copolymer was developed. The base polymer, which contains more than a predetermined weight part, has good adhesion to metal conductors.
It has also been found that the necessary semiconductivity can be obtained. The present invention has been made based on these results. <Means for solving the problems and their effects> In other words, the feature of the present invention is that a polymer or/ and a semiconductive mixture in which 3 parts by weight or more of a polymer obtained by grafting maleic anhydride to an ethylene-ethyl acrylate copolymer, conductive carbon black, and, if necessary, a crosslinking aid or crosslinking agent mixed therein. It is in. The reason why it is necessary to mix at least 3 parts by weight of these grafted polymers with respect to 100 parts by weight of the total base polymer is because if it is less than 3 parts by weight, sufficient adhesion to the conductor cannot be obtained. . The preferred amount is about 5 to 40 parts by weight, and examples of the base polymer include polyolefin. Examples of this polyolefin include low-density polyethylene [Mirason (manufactured by Mitsui Petrochemicals)], linear low-density polyethylene [Urtzex (manufactured by Mitsui Petrochemicals)], high-density polyethylene [Hizex (manufactured by Mitsui Petrochemicals)], and ethylene- Vinyl acetate copolymer [Evaflex (manufactured by Mitsui-Dupont Polychemicals)], ethylene-ethyl acrylate copolymer [Nisseki EEA (manufactured by Nippon Petrochemicals)], ethylene-α-olefin copolymer [Tafmer (Mitsui) (manufactured by Petrochemical Co., Ltd.)], ethylene-α-olefin-diene copolymer, and mixtures thereof. Examples of the conductive carbon black used in the present invention include Denka Black (manufactured by Denki Kagaku Kogyo Co., Ltd.), Toka Black (manufactured by Tokai Carbon Co., Ltd.), and Vulcan XC-
72 (manufactured by Cabot Co., Ltd.), and the blending amount varies depending on the required conductivity, but is generally 10 to 120 parts by weight based on 100 parts by weight of the base polymer.
This is because if it is less than 10 parts by weight, sufficient electrical conductivity cannot be obtained, and if it exceeds 120 parts by weight, workability deteriorates. Although the mixture of the present invention has sufficient adhesion to metals even when uncrosslinked, even greater adhesive strength can be obtained by crosslinking. This crosslinking method is as follows:
Taking the internal semiconductive layer of a cable as an example, the following two methods are possible. A crosslinking agent such as triallyl isocyanurate or triallyl trimellitate is added to this mixture in advance, and this is extruded as an internal semiconductive layer, and at the same time or in a subsequent step, a crosslinking agent such as dicumyl peroxide is added. When extruding something as an insulator and crosslinking this insulator,
A method of crosslinking by transferring a crosslinking agent such as dicumyl peroxide from the insulator side, or a method of adding a crosslinking agent or a crosslinking agent and the above-mentioned crosslinking aid to the mixture in advance and extruding the internal semiconductive layer and crosslinking it. be. Examples of the crosslinking agent include organic compounds such as dicumyl peroxide and 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,1,3-bis(t-butylperoxyisopropyl)benzene. Examples include peroxides. In addition, other additives such as anti-aging agents, processing aids, copper damage inhibitors, stabilizers, etc. can be added to the mixture of the present invention, if necessary. As for the use of the mixture of the present invention, as mentioned above, it is useful as an internal semiconductive layer-like mixture of cables, but it is not limited thereto. For example, it can be used for heating elements, temperature-sensitive resin materials, antistatic materials, electrode materials, etc. that require adhesiveness to metals. <Examples> Examples 1 to 13, Comparative Examples 1 to 5 A 1 mm thick sheet of a semiconductive mixture having the composition shown in Table 1 was made (processing temperature 120° or less). In addition, uncrosslinked polyethylene sheet (2 mm thick) containing dicumyl peroxide and aluminum tape (0.2
mm thick) and copper tape (0.1 mm thick) were prepared. Next, after cleaning the surface of the aluminum tape or copper tape with an organic solvent, this metal tape,
Layer the semiconductive sheet and the polyethylene sheet in that order.
A bonded sheet was produced by pressing for 20 minutes using a pressure press set at 200°. This bonded sheet was cut out to a width of 15 mm, and the adhesive strength between the metal tape and the semiconductive sheet was measured.
The adhesive force was measured by pulling and peeling the metal tape and the semiconductive polyethylene sheet in a 180° direction at a speed of 750 mm/min. The measurement results are also listed in the first vote.

【table】

[Table] According to Examples 1 to 13 in Table 1, if a polymer obtained by grafting maleic anhydride onto an ethylene-vinyl acetate copolymer or a polymer obtained by grafting maleic anhydride onto an ethylene-ethyl acrylate copolymer is used. It can be seen that the adhesion to metal is improved. In addition, adjustment of the blending amount of these polymers,
Adhesive strength can be appropriately selected depending on the presence or absence of crosslinking. Example 14, Comparative Example 8 An internal semiconductive layer of 0.7 mm, an insulating layer of 7 mm, and an external semiconductive layer of 1 mm were coated by extrusion on a single aluminum wire with an outer diameter of 8 mm, and crosslinked to produce a core of a CV cable.
Here, as the internal semiconducting layer, in Example 14, the composition of Example 12 was used, and in Comparative Example 8, the composition of Comparative Example 6 was used. The evaluation results of the CV cable core produced in this way were as shown in Table 2. The dimensional stability shown in Table 2 is based on the amount of conductor protrusion after heating a 30 cm cable core at 121° C. for 20 hours. The shrink back amount is 6m cable core.
It was based on the amount of conductor protrusion after 15 heat cycles. 1 heat cycle is 90℃ heating for 4 hours and room temperature 4 hours
It's time.

【table】

[Table] According to Example 14 in Table 2, it can be seen that the shrink back amount is reduced without deteriorating the characteristics such as volume resistivity and dielectric loss tangent. <Effects of the Invention> As is clear from the above description, according to the present invention, it is semiconductive and satisfies the characteristics required for, for example, a semiconductive layer of a cable, and at the same time has excellent adhesion to metal. A semiconducting mixture can be provided.

Claims (1)

[Claims] 1. In 100 parts by weight of the base polymer, ethylene-
Semiconductor made by dispersing 3 parts by weight or more of a polymer in which maleic anhydride is grafted onto a vinyl acetate copolymer or/and a polymer in which maleic anhydride is grafted into an ethylene-ethyl acrylate copolymer and conductive carbon black. sexual admixture. 2 In 100 parts by weight of the base polymer, ethylene-
Conductive carbon black is dispersed in 3 parts by weight or more of a polymer obtained by grafting maleic anhydride onto a vinyl acetate copolymer or/and a polymer obtained by grafting maleic anhydride onto an ethylene-ethyl acrylate copolymer, and further a crosslinking agent is added. A semiconductive mixture containing a crosslinking agent and/or a crosslinking agent.