JP2014154477A - Power cable production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a power cable which has excellent adhesion and easy peelability, or easiness of peeling an outer semiconductor layer.SOLUTION: A method of producing a power cable which comprises: a conductor 10; an insulator layer 30 coating the outer periphery of the conductor 10; and an outer semiconductor layer 40 comprises: a step of coating the outer periphery of the conductor with a pre-crosslinking insulator layer for formation of the insulator layer; a step of crosslinking the pre-crosslinking insulator layer preliminarily to form a preliminarily crosslinked insulator layer; a step of coating the preliminarily crosslinked insulator layer with a pre-crosslinking outer semiconductor layer for formation of the outer semiconductor layer 40; and a step of carrying out finishing crosslinking of the preliminarily crosslinked insulator layer and the pre-crosslinking outer semiconductor layer.

Description

  The present invention relates to a method for manufacturing a power cable.

  As a method of manufacturing a power cable having three resin layers of an inner semiconductive layer, an insulating layer, and an outer semiconductive layer as an insulating layer on the outer periphery of the conductor, for example, an inner semiconductive layer, an insulating layer on the outer periphery of the conductor. A method is known in which, after extruding three layers of a layer and an external semiconductive layer in one step, these three layers are simultaneously crosslinked (see, for example, Patent Document 1).

  Out of the three resin layers that make up such a power cable, the outer semiconductive layer located on the outermost peripheral side has good electrical and mechanical properties, as well as good terminal processability. Is required. That is, it is required to be easily peeled off from the insulating layer while processing the terminal while being in good contact with the insulating layer. Such an external semiconductive layer is called a free stripping type external conductive layer, and is usually applied to a high voltage power cable of 3.3 kV or higher, particularly a 3.3 to 33 kV power cable.

JP 2011-222324 A

  However, a power cable having a free stripping type external conductive layer as described above can be formed in one process using three layers of an internal semiconductive layer, an insulating layer, and an external semiconductive layer as in the method described in Patent Document 1 described above. When manufacturing by the method of extruding and then simultaneously crosslinking the three layers, it has the following problems. That is, in the method described in Patent Document 1 described above, in order to improve the adhesion between the insulating layer and the external semiconductive layer and the ease of peeling (easy to peel off the external semiconductive layer) In addition, it is necessary to form the insulating layer and the external semiconductive layer with resins having significantly different characteristics, or it is necessary to adjust the composition of the resin and other components constituting each layer with high accuracy. In addition, even when the insulating layer and the external semiconductive layer are formed of resins having significantly different characteristics, or even when the composition is adjusted with high accuracy, if the extrusion conditions or the crosslinking conditions change, the state of crosslinking will change. In some cases, the desired adhesiveness and ease of peeling may not be exhibited, so that it is necessary to manage the manufacturing conditions with high accuracy, resulting in an increase in manufacturing cost.

  The problem to be solved by the present invention is to provide a method for producing a power cable excellent in adhesion and ease of peeling (easy to peel off the external semiconductive layer).

  [1] A method of manufacturing a power cable according to the present invention is a method of manufacturing a power cable including at least a conductor, an insulating layer coated on an outer periphery of the conductor, and an external semiconductive layer, Covering the outer periphery with a pre-crosslinking insulating layer for forming the insulating layer, pre-crosslinking the pre-crosslinking insulating layer to form a pre-crosslinked insulating layer, on the pre-crosslinked insulating layer, A step of covering the pre-crosslinking external semiconductive layer for forming the external semiconductive layer; and a step of subjecting the preliminary cross-linking insulating layer and the pre-crosslinking external semiconductive layer to main cross-linking.

  [2] In the above invention, the pre-crosslinked insulating layer may have a gel fraction in the range of 50 to 65%.

  According to the present invention, by pre-crosslinking the pre-crosslinking insulating layer in advance, the cross-linking sites remaining in the pre-crosslinking insulating layer can be adjusted. As a result, when the pre-crosslinking external semiconductive layer that forms the external semiconductive layer is coated on the precrosslinked insulating layer after the precrosslinking, and these are cross-linked, the insulating layer and the external after the main cross-linking are The ratio of the crosslinking points formed between the semiconductive layers can be adjusted. Therefore, according to the present invention, the adhesion between the insulating layer and the external semiconductive layer and the ease of peeling (ease of peeling off the external semiconductive layer) can be improved.

FIG. 1 is a cross-sectional view of a power cable according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a power cable according to an embodiment of the present invention. As shown in FIG. 1, the power cable 1 of the present embodiment includes a conductor 10, an inner semiconductive layer 20 that covers the conductor 10, an insulating layer 30 that covers the inner semiconductive layer 20, and an insulating layer 30. And an external semiconductive layer 40. Among the layers constituting the power cable 1 of the present embodiment, the outer semiconductive layer 40 is in good contact with the insulating layer 30, but can be easily peeled off from the insulating layer 30 during terminal processing, so-called free stripping type. This is a semiconductive layer. Note that the power cable 1 of the present embodiment may further include a shielding layer, a pressing tape layer, and a sheath outside the external semiconductive layer 40. The thickness of the insulating layer 3 is, for example, 3 to 10 mm, and the thickness of the outer semiconductive layer 4 is, for example, 0.2 to 2 mm. The power cable 1 of the present embodiment is particularly useful for high voltage applications where the working voltage is 3.3 to 33 kV, for example.

<Conductor 10>
As the conductor 10, the metal wire used for electric power cable uses, such as a copper wire, a copper alloy wire, and an aluminum wire, can be used. Further, the surface of such a metal wire plated with tin, silver or the like may be used, and the conductor 10 may be either a single wire or a stranded wire.

<Internal semiconductive layer 20>
The internal semiconductive layer 20 is a semiconductive layer that covers the conductor 10, and is formed by using a resin composition for an internal semiconductive layer and crosslinking it. The resin composition for an internal semiconductive layer usually contains a resin for an internal semiconductive layer, a conductive substance, a crosslinking agent, and an antiaging agent.

  The resin for the internal semiconductive layer is not particularly limited, but usually an ethylene polymer is used. The ethylene polymer may be any polymer containing ethylene as a repeating unit, and is not particularly limited. For example, polyethylene (low density polyethylene, high density polyethylene), ethylene-vinyl acetate copolymer (EVA), ethylene -Ethyl acrylate copolymer (EEA), ethylene-methyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-1-butene copolymer, ethylene-α olefin copolymer, ethylene-propylene diene rubber (EPDM) ). These can be used alone or in combination of two or more. Among these, ethylene-vinyl acetate copolymer (EVA) is preferable from the viewpoint of excellent extrusion processability.

  Although it does not specifically limit as a conductive material, Usually, conductive carbon is used. Examples of the conductive carbon include carbon black, acetylene black, furnace black, ketjen black, thermal black, and graphite. These can be used alone or in combination of two or more. Among these, the content of impurities is small, the electrical characteristics of the resin for internal semiconductive layer are not deteriorated, and no electrical agglomeration is formed at the interface with the resin for internal semiconductive layer without forming a large aggregate. Acetylene black is preferable from the viewpoint that no conductive protrusion is generated.

  The blending ratio of the conductive substance in the internal semiconductive layer resin composition is preferably 60 to 80 parts by weight with respect to 100 parts by weight of the internal semiconductive layer resin. By setting the blending ratio of the conductive material in such a range, stable electrical resistance (conductivity) can be maintained even when the temperature of the power cable 1 rises.

  The cross-linking agent is not particularly limited as long as it can cross-link the above-described resin for the internal semiconductive layer, and a peroxide cross-linking agent is usually used. Examples of peroxide crosslinking agents include t-butyl cumyl peroxide, 2,5-dimethyl-2,5-di-t-butyl peroxyhexine-3, di-t-butyl peroxide, di- (2 -T-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di-t-butylperoxyhexane and the like.

  The blending ratio of the crosslinking agent in the resin composition for the internal semiconductive layer varies depending on the type of the internal semiconductive layer resin used and the type of the crosslinker, but is usually 100 parts by weight of the resin for the internal semiconductive layer. On the other hand, it is 1.0-4.0 weight part, Preferably it is 1.5-3.0 weight part. By setting the blending ratio of the cross-linking agent in such a range, the mechanical properties of the internal semiconductive layer 20 obtained by cross-linking are sufficient while preventing the occurrence of scorch in the resin composition for the internal semiconductive layer. be able to.

  The anti-aging agent is not particularly limited, and anti-aging agents used in the field of resin compositions and rubber compositions can be used without limitation. For example, 2,6-di-tert-butylphenol, 2 Hindered phenols such as 4,6-di-tert-butyl-4-ethylphenol; thiobisphenols such as 4,4′-thiobis- (6-tert-butyl-3-methylphenol); phosphite, tris ( Phosphorous systems such as mixtures-and-nonyl-phenyl) phosphites; Imidazole systems such as 2-mercaptobenzimidazole and 2-methylmercaptobenzimidazole; Tris (nonylphenyl), dilauryl thiodipropionate, distearyl thiodipro Pionate, distearyl-β, β-thiodibutyrate, lauryl steari Thiodipropionate, sulfur ester-based compounds, amyl - thioglycolate, 1,1'-thiobis - (2-naphthol), etc. hydrazine derivatives can be used.

<Insulating layer 30>
The insulating layer 30 is an insulating layer that covers the inner semiconductive layer 20, and is formed by crosslinking the insulating layer resin composition. The resin composition for insulating layers usually contains a resin for insulating layers, a crosslinking agent, and an anti-aging agent.

  Although it does not specifically limit as resin for insulating layers, Usually, an ethylene-type polymer is used. Specific examples of the ethylene polymer include those similar to the resin for the internal semiconductive layer described above. Among the ethylene polymers, the insulating layer resin is preferably low-density polyethylene and high-density polyethylene, more preferably low-density polyethylene, from the viewpoint of insulation.

  The cross-linking agent is not particularly limited as long as it can cross-link the above-described insulating layer resin, and a peroxide cross-linking agent is usually used. Specific examples of the peroxide crosslinking agent include those similar to the above-described resin composition for an internal semiconductive layer.

  The blending ratio of the crosslinking agent in the insulating layer resin composition varies depending on the type of the insulating layer resin and the type of the crosslinking agent used, but is usually 1.0 with respect to 100 parts by weight of the insulating layer resin. It is -4.0 weight part, Preferably it is 1.5-2.5 weight part. By setting the blending ratio of the crosslinking agent in such a range, the mechanical properties of the insulating layer 30 obtained by crosslinking can be made sufficient while preventing the occurrence of scorch of the resin composition for insulating layers.

  Moreover, as an anti-aging agent, although it does not specifically limit, the thing similar to the resin composition for internal semiconductive layers mentioned above can be used.

<External semiconductive layer 40>
The external semiconductive layer 40 is a semiconductive layer that covers the insulating layer 30, and is formed by using a resin composition for an external semiconductive layer and crosslinking it. In the present embodiment, the external semiconductive layer 40 is a so-called free stripping type semiconductive layer that is in good contact with the insulating layer 30 but can be easily peeled off from the insulating layer 30 during terminal processing. The resin composition for an external semiconductive layer for forming the external semiconductive layer 40 usually contains a resin for the external semiconductive layer, a conductive substance, a crosslinking agent, and an antiaging agent.

  The resin for the external semiconductive layer is not particularly limited, but usually an ethylene polymer is used. Specific examples of the ethylene polymer include those similar to the resin for the internal semiconductive layer described above. Among the ethylene-based polymers, an ethylene-vinyl acetate copolymer (EVA) is preferable as the resin for the external semiconductive layer from the viewpoint of excellent extrusion processability.

  Although it does not specifically limit as a conductive material, Usually, conductive carbon is used. Specific examples of the conductive carbon include those similar to the resin for the internal semiconductive layer described above, and the blending amounts thereof can also be the same.

  The cross-linking agent is not particularly limited as long as it can cross-link the above-described resin for the external semiconductive layer, and a peroxide cross-linking agent is usually used. Specific examples of the peroxide crosslinking agent include those similar to the above-described resin composition for an internal semiconductive layer.

  The blending ratio of the crosslinking agent in the resin composition for the external semiconductive layer varies depending on the type of the resin for external semiconductive layer and the type of the crosslinker used. On the other hand, it is 1.0-4.0 weight part, Preferably it is 1.5-3.0 weight part. By setting the blending ratio of the crosslinking agent in such a range, the mechanical properties of the external semiconductive layer 40 obtained by cross-linking can be made sufficient while preventing the occurrence of scorch of the resin for the external semiconductive layer. it can.

  Moreover, as an anti-aging agent, although it does not specifically limit, the thing similar to the resin composition for internal semiconductive layers mentioned above can be used.

<Manufacturing method of power cable 1>
Next, a method for manufacturing the power cable 1 of the present embodiment will be described.
First, on the conductor 10, an internal semiconductive layer resin composition for forming the internal semiconductive layer 20 and an insulating layer resin composition for forming the insulating layer 30 are extruded by coextrusion, A layer made of a resin composition for an internal semiconductive layer (hereinafter referred to as “pre-crosslinking internal semiconductor layer”) and a layer made of a resin composition for an insulating layer (hereinafter referred to as “pre-crosslinking insulating layer”) on the conductor 10. Are obtained in this order to obtain a pre-crosslinking laminate.

  Next, the pre-crosslinking insulating layer that forms the pre-crosslinking laminate thus obtained is pre-crosslinked to obtain a pre-crosslinked laminate. Here, in the present embodiment, “preliminary crosslinking” refers to a layer made of a resin composition for an insulating layer after preliminary crosslinking (hereinafter referred to as “preliminary crosslinking insulating layer” while the crosslinking of the insulating layer before crosslinking proceeds to some extent. )), Which is carried out under conditions such that unreacted crosslinking sites remain to some extent, and the crosslinking is not sufficiently progressed or crosslinked under substantially the same conditions as this crosslinking. It doesn't include anything to let you. In this case, although depending on the pre-crosslinking conditions and the type of the cross-linking agent, in general, the pre-cross-linking internal semiconductor layer is also pre-cross-linked in addition to the pre-cross-linking insulating layer (hereinafter referred to as such). The layer thus formed is referred to as a “preliminarily crosslinked internal semiconductor layer”). The specific conditions for the pre-crosslinking will be described later.

  Next, on the pre-crosslinked insulating layer forming the pre-crosslinked laminate thus obtained, a layer comprising a resin composition for an external semiconductive layer for forming the external semiconductive layer 40 (hereinafter referred to as “before cross-linking”). After that, the cross-linking is performed on the pre-crosslinked internal semiconductor layer, the pre-cross-linked insulating layer, and the external semi-conductive layer before cross-linking, whereby the conductor 10 shown in FIG. The power cable 1 including the conductive layer 20, the insulating layer 30, and the outer semiconductive layer 40 can be obtained.

  Here, in this embodiment, as described above, before the pre-crosslinking external semiconductive layer for forming the external semiconductive layer 40 is formed, the pre-crosslinking insulating layer is preliminarily crosslinked in advance. By reacting the crosslinking sites contained in the pre-crosslinking insulating layer to some extent (crosslinking is advanced to some extent), the crosslinkability on the outer surface of the precrosslinked insulating layer obtained by precrosslinking and in the vicinity of the outer surface is moderately reduced. is there. As a result, the pre-crosslinking external semiconductive layer for forming the external semiconductive layer 40 is formed on the pre-crosslinked insulating layer thus formed, and after the main crosslink is performed, the main crosslink The degree of cross-linking at the interface between the subsequent insulating layer 30 and the external semiconductive layer 40 can be controlled, whereby the adhesion between the insulating layer 30 after the main cross-linking and the external semiconductive layer 40 and ease of peeling (external semiconductive layer 40) can be controlled. It is possible to satisfactorily balance the ease of peeling of the conductive layer.

  That is, when the insulating layer 30 is formed, the remaining crosslinking sites are adjusted in advance by pre-crosslinking, and in this state, the external semiconductive layer resin composition for forming the external semiconductive layer 40 is formed. The cross-linking point formed between the insulating layer 30 after the main cross-linking and the external semiconductive layer 40 is adjusted by carrying out the main cross-linking together with the product. As a result, the ratio of cross-linking points formed between the insulating layer 30 after the main cross-linking and the external semiconductive layer 40 is set to an appropriate range, and as a result, the insulating layer 30 and the external semi-conductive layer after the main cross-linking are obtained. The adhesiveness of 40 and the ease of peeling are made favorable.

The pre-crosslinking conditions for pre-crosslinking of the insulating layer before cross-linking are as follows. The cross-linking sites of the pre-cross-linking insulating layer obtained by pre-crosslinking are moderately lowered, and thereby the insulating layer 30 after the main cross-linking The pre-cross-linking insulation after pre-crosslinking may be used as long as it can satisfactorily balance the adhesion with the external semi-conductive layer 40 and the ease of peeling (ease of peeling off the external semi-conductive layer). The condition is such that the gel fraction of the layer is in the range of 50 to 65%, and more preferably in the range of 50 to 60%. In the present embodiment, by performing pre-crosslinking under conditions such that the gel fraction of the pre-crosslinked insulating layer after pre-crosslinking is in the above range, the space between the insulating layer 30 after the main cross-linking and the external semiconductive layer 40 is The degree of cross-linking can be made more appropriate, whereby the adhesion between the insulating layer 30 after the main cross-linking and the external semiconductive layer 40 and the ease of peeling can be more highly balanced. The gel fraction of the pre-crosslinked insulating layer is, for example, based on JIS C3005, a solvent that can dissolve the insulating layer resin contained in the insulating layer resin composition for forming the insulating layer 30 (specifically The resin for insulating layer before crosslinking can be dissolved, and the pre-crosslinked insulating layer is immersed in a solvent that does not dissolve the resin for insulating layer after crosslinking), and the weight of the pre-crosslinked insulating layer before and after immersion is measured And it can obtain | require according to a following formula from the obtained result.
Gel fraction (%) of pre-crosslinked insulating layer = (weight of pre-crosslinked insulating layer after immersion / weight of pre-crosslinked insulating layer before immersion) × 100

  The pre-crosslinking conditions can be controlled by adjusting the pre-crosslinking temperature and the cross-linking time, but the insulating layer resin contained in the insulating layer resin composition for forming the insulating layer 30 can be controlled. Appropriately set according to the type, the type and amount of the crosslinking agent, and the type of resin for the external semiconductive layer contained in the resin composition for the external semiconductive layer that will form the external semiconductive layer 40 do it. However, on the other hand, if the pre-crosslinking temperature is too low or the pre-crosslinking time is too short, the advance of the pre-crosslinking is insufficient and the desired ease of peeling cannot be obtained. On the other hand, if the pre-crosslinking temperature is too high or the pre-crosslinking time is too long, it becomes substantially the same as the main cross-linking and the desired adhesion cannot be obtained. The preliminary crosslinking is performed when the resin composition for the internal semiconductive layer for forming the internal semiconductive layer 20 and the resin composition for the insulating layer for forming the insulating layer 30 are extruded by coextrusion molding. It may be carried out or after extrusion by coextrusion molding.

  Further, the conditions for carrying out the main crosslinking for the pre-crosslinked inner semiconductor layer, the pre-crosslinked insulating layer and the pre-crosslinking outer semiconductive layer are not particularly limited, but the temperature at which the cross-linking sites contained in these layers sufficiently react The cross-linking time may be set to 200 to 260 ° C. and 2 to 10 minutes in cable production. However, these conditions differ depending on methods such as vapor crosslinking and dry crosslinking, and appropriate ones may be employed.

  According to the present embodiment, as described above, the pre-crosslinking insulating layer that will form the insulating layer 30 is preliminarily cross-linked, thereby adjusting the cross-linking sites remaining in the pre-crosslinking pre-crosslinking insulating layer. can do. And according to this embodiment, after pre-crosslinking, when the pre-crosslinking external semiconductive layer that forms the external semiconductive layer is coated on the pre-crosslinked insulating layer after pre-crosslinking and these are cross-linked, The ratio of cross-linking points formed between the insulating layer 30 and the external semiconductive layer 40 can be adjusted. Thereby, according to this embodiment, the adhesiveness between the insulating layer 30 and the external semiconductive layer 40 and the ease of peeling (easy peeling of the external semiconductive layer) can be improved.

  In particular, in the present embodiment, the pre-crosslinking insulating layer that will form the insulating layer 30 is preliminarily crosslinked to adjust the crosslinking site when the external semiconductive layer 40 is formed thereon. Therefore, the insulating layer 30 after the main cross-linking can be sufficiently cross-linked and have excellent mechanical strength and the like. That is, for example, when the amount of the crosslinking agent in the insulating layer resin composition that forms the insulating layer 30 is reduced, or when the insulating layer resin itself has a low crosslinkability, the crosslinking site However, in such a case, there is a problem that the crosslink density of the insulating layer 30 after the main crosslink is lowered, resulting in a decrease in mechanical strength and the like. According to the present embodiment, the adhesion between the insulating layer 30 and the external semiconductive layer 40 and the ease of peeling can be improved without causing such a problem.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, in the above-described embodiment, the power cable 1 including the conductor 10, the inner semiconductive layer 20, the insulating layer 30, and the outer semiconductive layer 40 is illustrated. However, the power cable of the present invention has such a configuration. It is not limited, For example, the structure which does not have the internal semiconductive layer 20 may be sufficient.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Example 1>
First, an insulating layer resin composition for forming the insulating layer 30 and an external semiconductive layer resin composition for forming the external semiconductive layer 40 were prepared. Specifically, the insulating layer resin composition was prepared by blending the insulating layer resin, the crosslinking agent, and the antiaging agent in the proportions shown in Table 1, and kneading at 120 ° C. The resin composition for the external semiconductive layer was prepared by blending the resin for the external semiconductive layer, the conductive material, the crosslinking agent and the antiaging agent in the proportions shown in Table 1, and kneading at 120 ° C. In Table 1, the following components were specifically used as each component.
(1) Resin for insulating layer: Low density polyethylene (LDPE) (trade name “UBEC530”, manufactured by Ube Maruzen Polyethylene Co., Ltd.)
(2) Crosslinker: Dicumyl peroxide (trade name “Park Mill D”, manufactured by NOF Corporation)
(3) Anti-aging agent: 4,4′-thiobis- (6-tert-butyl-3-methylphenol) (trade name “NOCRACK 300”, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
(4) Resin for outer semiconductive layer: ethylene-vinyl acetate copolymer (EVA) (trade name “EV260”, manufactured by Mitsui DuPont Polychemical Co., Ltd.)
(5) Conductive substance: Acetylene black (trade name “Denka Black”, manufactured by Denki Kagaku Kogyo Co., Ltd.)

  Subsequently, the resin composition for insulating layer prepared above is press-molded at 120 ° C. to obtain a preform having a width of 25 mm, a length of 100 mm, and a thickness of 3 mm. By preliminarily crosslinking under conditions of a precrosslinking temperature of 170 ° C. and a precrosslinking time of 9 minutes, a precrosslinked insulating layer sample was obtained.

The pre-crosslinked insulating layer sample thus obtained was subjected to gel fraction measurement by the following method in accordance with JIS C3005. That is, first, the obtained pre-crosslinked insulating layer sample was immersed in xylene at a temperature of 110 ° C. for 24 hours. Next, the gel-like sample obtained after the immersion is filtered, the filtration residue is dried by heating at 80 ° C. for 12 hours, and the weight after drying is measured, whereby the insoluble resin not dissolved in xylene is measured. The weight of the ingredients was obtained. And according to the following formula, the gel fraction of the pre-crosslinked insulating layer sample was determined.
Gel fraction (%) of pre-crosslinked insulating layer sample = (weight of insoluble resin component / weight of resin component in pre-crosslinked insulating layer sample before xylene immersion) × 100

  Next, separately from the above, the resin composition for the external semiconductive layer prepared above is press-molded at 120 ° C. to obtain an uncrosslinked external semiconductive layer sample having a width of 25 mm, a length of 100 mm, and a thickness of 2 mm. Obtained.

  Then, the pre-crosslinked insulating layer sample obtained above and the uncrosslinked external semiconductive layer sample were bonded together and sandwiched between a pair of press plates using a spacer having a thickness of 4.8 mm at 170 ° C. The laminate sample (width 25 mm, length 100 mm) composed of the insulating layer 30 and the external semiconductive layer 40 was obtained by performing press crosslinking (main crosslinking) under the conditions of 15 minutes. At this time, a mylar sheet was sandwiched from the end in the length direction to a position of 40 mm, and this portion was used as a lead-out portion for measuring peel strength.

  And about the laminated body sample obtained in this way, using a tensile tester, the peel strength is measured by pulling at a speed of 200 mm / min. did. In this example, when peeling was performed with the interface between the insulating layer 30 and the external semiconductive layer 40 appearing as it was, the tensile strength at the time of peeling was defined as the peel strength. Further, when peeling did not occur at the interface between the insulating layer 30 and the external semiconductive layer 40 and the insulating layer 30 or the external semiconductive layer 40 was broken, it was determined that “peeling is impossible”. If the peel strength is preferably in the range of 20 to 40 N / 12.5 mm, more preferably in the range of 25 to 35 N / 12.5 mm, it can be determined that adhesion and ease of peeling are highly balanced. desirable. The results are shown in Table 2.

<Examples 2-4, Comparative Examples 1-6>
The conditions shown in Table 2 for the pre-crosslinking temperature and pre-crosslinking time conditions during pre-crosslinking when pre-crosslinking the preform obtained by using the resin composition for an insulating layer to obtain a pre-cross-linked insulating layer sample Except that, a pre-crosslinked insulating layer sample and a laminate sample composed of the insulating layer 30 and the external semiconductive layer 40 were obtained in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 2.

<Evaluation>
From the results shown in Table 2, Examples 1 to 4 (170 ° C., 9 minutes to 12 minutes, or 190 ° C., 1.4 minutes to 1.9 minutes) in which the pre-crosslinking conditions of the pre-crosslinking insulating layer are appropriate are shown. In each case, the peel strength was in the range of 25 to 35 N / 12.5 mm, and the adhesion between the insulating layer 30 and the external semiconductive layer 40 and the ease of peeling were good. In Examples 1 to 4, the gel fraction of the pre-crosslinked insulating layer sample obtained by pre-crosslinking was in the range of 50 to 65%.

  On the other hand, in Comparative Examples 1 and 4 in which the pre-crosslinking time of the insulating layer before cross-linking is short and the pre-crosslinking is not sufficiently progressed, between the insulating layer 30 and the external semiconductive layer 40 The adhesiveness became too high, and “peeling was impossible”. In Comparative Examples 1 and 4, the gel fractions of the pre-crosslinked insulating layer samples obtained by pre-crosslinking were all less than 50%.

  In addition, in Comparative Examples 2, 3, 5, and 6 in which the pre-crosslinking time of the insulating layer before cross-linking was too long and pre-cross-linking was performed under the same cross-linking conditions as the main cross-linking, the insulating layer 30 and the external semiconductive The adhesiveness between the layers 40 was too low, resulting in extremely low peel strength. In Comparative Examples 2, 3, 5 and 6, the gel fractions of the pre-crosslinked insulating layer samples obtained by pre-crosslinking were all over 65%.

DESCRIPTION OF SYMBOLS 1 ... Electric power cable 10 ... Conductor 20 ... Internal semiconductive layer 30 ... Insulating layer 40 ... External semiconductive layer

Claims (2)

A method for producing a power cable comprising at least a conductor, and an insulating layer and an outer semiconductive layer coated on the outer periphery of the conductor,
Coating the outer periphery of the conductor with a pre-crosslinking insulating layer for forming the insulating layer;
Pre-crosslinking the pre-crosslinking insulating layer to form a pre-crosslinked insulating layer;
Coating the pre-crosslinking external semiconductive layer to form the external semiconductive layer on the pre-crosslinked insulating layer;
And a step of subjecting the preliminary cross-linking insulating layer and the pre-crosslinking external semiconductive layer to a main cross-linking step.   The method for producing a power cable according to claim 1, wherein the pre-crosslinked insulating layer has a gel fraction in a range of 50 to 65%.

Images