JP5734777B2 - Cable manufacturing method - Google Patents

Description

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

  Chloroprene rubber is used as a cable sheath because it is excellent in flame retardancy and oil resistance. In the sheath of the cable, not only flame resistance and oil resistance but also water resistance may be required. For this reason, for example, in Patent Document 1 below, a chloroprene rubber composition in which a vulcanizing agent such as hydrotalcite and wet silica is blended at a predetermined ratio with respect to the chloroprene rubber is used to increase the water resistance of the sheath. Proposed.

JP 2008-231248 A

  By the way, when manufacturing a cable using a chloroprene rubber composition, the chloroprene rubber composition is vulcanized under high pressure (2 MPa or more) after extrusion coating the outer periphery of the conductor directly or through another coating; And a method of vulcanizing under a low pressure (0.35 MPa or less). Among these methods, the method of vulcanization under low pressure is desirable from the viewpoints of reduction of energy consumption, safety, and prevention of damage to the cable.

  However, the chloroprene rubber composition described in Patent Document 1 has the following problems when vulcanized under low pressure after coating on a conductor.

  That is, the chloroprene rubber composition has a problem of causing foaming in the resulting cable sheath. Here, foaming in the sheath leads to a significant decrease in the mechanical strength of the sheath.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a cable manufacturing method capable of manufacturing a cable having a sheath in which foaming is sufficiently suppressed even when vulcanized under low pressure. To do.

  As a result of studying the cause of the above problem, the present inventor has found that wet silica is contained in the chloroprene rubber composition described in Patent Document 1, and wet silica is obtained by vulcanizing the chloroprene rubber composition under low pressure. I thought that the water inside would vaporize and cause foaming. Therefore, as a result of further earnest studies, the present inventor has found that the above-described problems can be solved by the following invention, and has completed the present invention.

That is, the present invention provides a cable manufacturing method comprising: a core portion including a conductor ; and a sheath provided on the core portion, the sheath formed by covering the core portion with a chloroprene rubber composition and vulcanizing the chloroprene rubber composition. A preparation step of preparing the core portion and a sheath formation step of forming the sheath on the core portion, wherein the core portion is coated with the chloroprene rubber composition in the sheath formation step. The chloroprene is accommodated in a vulcanized pipe, an inert gas is introduced into the vulcanized pipe, and the unvulcanized cable is pressurized with an inert gas at 0.3 to 0.6 MPa. The sheath is formed by vulcanizing a rubber composition, and the chloroprene rubber composition is a method for producing a cable including chloroprene rubber, a vulcanizing agent, and dry silica .

According to this cable manufacturing method, after the core portion including the conductor is coated with the chloroprene rubber composition, a sheath is formed by vulcanizing the chloroprene rubber composition, and the following effects are obtained when the cable is manufactured. Played. That is, since the amount of water held in the dry silica is sufficiently small, foaming is sufficiently suppressed in the sheath even when vulcanization is performed under low pressure. For this reason, the cable provided with the sheath by which foaming is fully suppressed can be manufactured.

  In the chloroprene rubber composition, the dry silica is preferably obtained by subjecting the surface of silica to a hydrophobic treatment. Since dry silica is formed by subjecting the surface of silica to a hydrophobic treatment, even if the manufactured cable is immersed in water, the dry silica sufficiently suppresses water molecules from being taken into the sheath. . For this reason, the cable provided with the sheath which has the outstanding water resistance can be manufactured.

  In the chloroprene rubber composition, the vulcanizing agent is preferably at least one selected from the group consisting of red lead, hydrotalcite and zinc oxide. In this case, it is possible to manufacture a cable including a sheath having better water resistance than when the vulcanizing agent is a vulcanizing agent such as magnesium oxide.

  The amount of water in the chloroprene rubber composition is preferably 2,500 ppm or less by mass ratio. In this case, even if the cable is manufactured by covering the core containing the conductor with the chloroprene rubber composition and vulcanizing under low pressure to form a sheath, the amount of water in the chloroprene rubber composition exceeds 2,500 ppm. Compared to the case, foaming is more sufficiently suppressed in the sheath. For this reason, the cable provided with the sheath which has much more excellent mechanical strength can be manufactured.

  In the present invention, the “water content” refers to the water content measured with a Karl Fischer moisture meter in accordance with JISK0113 at 125 ° C. for a 1 mm square chloroprene rubber composition cut into a 1 mm square. Let's say quantity.

ADVANTAGE OF THE INVENTION According to this invention, even if it vulcanizes under low pressure, the manufacturing method of the cable which can manufacture the cable provided with the sheath by which foaming is fully suppressed is provided.

It is sectional drawing which shows one Embodiment of the cable of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG.

  FIG. 1 is a cross-sectional view showing an embodiment of a cable according to the present invention. As shown in FIG. 1, a cable 10 is provided on a core portion 2 composed of an inner conductor 1 and the core portion 2, and is formed by covering the core portion 2 with a chloroprene rubber composition and vulcanizing the chloroprene rubber composition. A sheath 3. Here, the chloroprene rubber composition includes chloroprene rubber, a vulcanizing agent, and dry silica.

  According to this cable 10, since the sheath 3 is formed by covering the core portion 2 with the chloroprene rubber composition and vulcanizing the chloroprene rubber composition, foaming is sufficient even when vulcanization is performed under low pressure. A cable 10 with a suppressed sheath 3 is realized.

  The cable 10 is obtained as follows.

[Preparation process]
First, the core portion 2 made of the inner conductor 1 is prepared.

  The inner conductor 1 may be composed of only one strand, or may be configured by bundling a plurality of strands. Further, the inner conductor 1 is not particularly limited with respect to the conductor diameter, the material of the conductor, and the like, and can be appropriately determined according to the application.

[Sheath formation process]
Next, the sheath 3 is formed on the core part 2. The sheath 3 can be obtained as follows.

<Coating process>
First, a chloroprene rubber composition is, for example, extrusion-coated on the core portion 2. As described above, the chloroprene rubber composition includes chloroprene rubber, a vulcanizing agent, and dry silica.

(Vulcanizing agent)
As the vulcanizing agent, for example, metal oxides such as hydrotalcite, magnesium oxide, zinc oxide, or red lead can be used. Especially, since it has the outstanding water resistance, it is preferable to use a red lead, a hydrotalcite, a zinc oxide, or a mixture of these 2 or more types.

  When the vulcanizing agent is Suzutan, the vulcanizing agent is preferably blended at a ratio of 10 to 15 parts by mass with respect to 100 parts by mass of the chloroprene rubber. When the blending ratio of the vulcanizing agent is within the above range, the sheath 3 has more excellent water resistance as compared with the case where it is less than 10 parts by mass. Further, when the blending ratio of the vulcanizing agent is within the above range, the vulcanization time of the chloroprene rubber composition can be shortened as compared with the case where it exceeds 15 parts by mass, and the productivity of the cable 10 is higher. Become.

  Moreover, when a vulcanizing agent is a hydrotalcite, it is preferable that a vulcanizing agent is mix | blended in the ratio of 2-5 mass parts with respect to 100 mass parts of chloroprene rubber. When the blending ratio of the vulcanizing agent is within the above range, the vulcanization time of the chloroprene rubber composition can be shortened as compared with less than 2 parts by mass, and the productivity of the cable 10 is further increased. Further, when the blending ratio of the vulcanizing agent is within the above range, the amount of water in the chloroprene rubber composition is reduced as compared with the case where it exceeds 5 parts by mass, and foaming in the sheath 3 is more sufficiently suppressed.

(Dry silica)
Dry silica is silica obtained by a dry process. Examples of the dry method include a combustion method and an arc method.

  The dry silica is preferably obtained by subjecting the surface of silica obtained by a dry method to a hydrophobic treatment. Since dry silica is obtained by subjecting the surface of silica to a hydrophobic treatment, even if the manufactured cable 10 is immersed in water, the dry silica sufficiently suppresses water molecules from being taken into the sheath 3. Is done. For this reason, the cable 10 provided with the sheath 3 having excellent water resistance can be manufactured.

（式（１）中、Ｒ^１及びＲ^２はそれぞれ独立に、炭素原子数１〜３のアルキル基又は炭素原子数２又は３のアルケニル基を表し、Ｒ^３は、炭素原子数１〜３のアルキル基、炭素原子数２〜３のアルケニル基、又はシリカのＯＨ基と反応する官能基を表し、Ｒ^４は、シリカのＯＨ基と反応する官能基を表す。） What is obtained by subjecting the surface of silica to a hydrophobic treatment means that the surface of silica is treated with a silane compound represented by the following general formula (1).

(In formula (1), R ¹ and R ² each independently represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 or 3 carbon atoms, and R ³ represents one having 1 to 3 carbon atoms. An alkyl group, an alkenyl group having 2 to 3 carbon atoms, or a functional group that reacts with an OH group of silica, and R ⁴ represents a functional group that reacts with an OH group of silica.)

  As the alkyl group, as described above, an alkyl group having 1 to 3 carbon atoms is used. Specifically, a methyl group or an ethyl group can be used as the alkyl group.

  As the alkenyl group, as described above, an alkenyl group having 2 or 3 carbon atoms is used. As the alkenyl group, specifically, a vinyl group or a propenyl group can be used.

  Examples of the functional group that reacts with the OH group of silica include a hydrogen atom, a halogen group, and an alkoxy group.

  Specific examples of the silane compound represented by the general formula (1) include dimethylsilane and trimethylsilane.

  The dry silica is preferably blended at a rate of 5 to 20 parts by mass and more preferably at a rate of 10 to 20 parts by mass with respect to 100 parts by mass of the chloroprene rubber. When the blending ratio of the dry silica is within the above range, the strength is increased because the dry silica as the reinforcing agent is sufficiently blended as compared with the case where it is less than 5 parts by mass. Further, when the blending ratio of the dry silica is within the above range, it is possible to further suppress the dry silica from being aggregated and the rubber from being cracked from the aggregated portion, as compared with the case where it exceeds 20 parts by mass.

  The water content in the chloroprene rubber composition is preferably 2,500 ppm or less. In this case, even if the cable 10 is manufactured by covering the core portion 2 made of the inner conductor 1 with the chloroprene rubber composition and vulcanizing the chloroprene rubber composition under low pressure to form the sheath 3, the chloroprene rubber composition contains Foaming is suppressed more sufficiently in the sheath 3 than in the case where the water content exceeds 2,500 ppm. For this reason, the cable 10 provided with the sheath 3 which has much more excellent mechanical strength can be manufactured.

  The chloroprene rubber composition may further contain additives such as inorganic fillers (clay, carbon black, etc.) other than dry silica, vulcanization accelerators, lubricants, softeners, anti-aging agents, etc., if necessary. .

<Vulcanization process>
Next, the chloroprene rubber composition is vulcanized.

  At this time, an unvulcanized cable formed by coating the core portion 2 with the chloroprene rubber composition is accommodated in the vulcanized pipe, an inert gas is introduced into the vulcanized pipe, and the cable is pressurized with the inert gas. The chloroprene rubber composition is vulcanized.

  Examples of the inert gas include helium gas and nitrogen gas, and nitrogen gas is preferably used. It is preferable that the inert gas be continuously circulated in the vulcanization tube because the inside of the vulcanization tube is maintained in an inert atmosphere and the oxidation of the chloroprene rubber composition is sufficiently suppressed.

  The unvulcanized cable is normally pressurized at a pressure of 0.3 to 0.6 MPa.

  The temperature of vulcanization is usually in the range of 160 to 350 ° C., preferably in the range of 200 to 350 ° C., and is appropriately selected according to the vulcanizing agent in the chloroprene rubber composition.

  The vulcanization time is usually selected in the range of 1 to 40 minutes, preferably in the range of 1 to 15 minutes, depending on the vulcanizing agent in the chloroprene rubber composition.

  In this way, the cable 10 is obtained.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the core portion 2 includes the inner conductor 1, but the core portion 2 may include the inner conductor 1 and an insulating layer that covers the inner conductor 1. May include an inner conductor 1, an insulating layer covering the inner conductor 1, a braid as an outer conductor, and an insulating layer covering the braid. Here, the insulating layer is preferably one obtained by vulcanizing ethylene propylene rubber (EP rubber) from the viewpoint of improving the electrical characteristics of the cable. However, a resin other than EP rubber (for example, butyl rubber or nitrile rubber) is used. Also good.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Examples 1-8 and Comparative Example 1)
First, chloroprene rubber, wet silica, dry silica, clay, carbon black, red lead, hyodotalcite and zinc oxide were prepared and kneaded with the composition shown in Table 1 to prepare a chloroprene rubber composition. In Table 1, unless otherwise indicated, the numerical unit is part by mass. Moreover, the following were used as wet silica and dry silica.
(1) Nipsil VN3 manufactured by wet silica Tosoh Silica
Water content: 63000ppm
(2) Dry silica Nippon Aerosil Co., Ltd. Aerosil R974
Water content: 2500ppm
Silane compound whose surface is treated with silica: Dimethylsilane

  The following characteristics were evaluated for the chloroprene rubber compositions obtained in Examples 1 to 8 and Comparative Example 1 obtained as described above.

[Characteristic evaluation]
(1) Water absorption The chloroprene rubber composition was tested for water absorption as follows.

That is, first, press vulcanization was performed at 160 ° C. for 40 minutes to produce a sheet having a length of 200 mm, a width of 200 mm, and a thickness of 2 mm. Next, a test piece for water absorption test having a length of 35 mm, a width of 35 mm, and a thickness of 2 mm was punched from the sheet. And about this test piece, the weight before immersing in 60 degreeC warm water (fresh water) was measured. In addition, after immersing the test piece in warm water at 60 ° C. for 3 days and after 10 days, each specimen was taken out from the warm water and weighed. And the following formula:
Water absorption (%) = (W2−W1) / W1 × 100
(W1 represents the weight before the test, and W2 represents the weight after the test.)
Based on the above, the water absorption was calculated. The results are shown in Table 1.

(2) Moisture content of chloroprene rubber composition About 0.5 g of chloroprene rubber composition was cut into 1 mm squares, and the moisture content of this chloroprene rubber composition was measured at 125 ° C. using a Karl Fischer moisture meter. did. The results are shown in Table 1.

(3) Existence of foaming in the sheath First, a cable was manufactured as follows. That is, first, an internal conductor made of a twisted wire in which 12 strands having an outer diameter of 0.665 mm were twisted was prepared. Next, 5 parts by mass of vulcanization accelerator, 3.5 parts by mass of carbon black, 1.5 parts by mass of anti-aging agent, 1 part by mass of lubricant, 10 parts by mass of softener, 80 parts by mass of talc with respect to 100 parts by mass of ethylene propylene rubber. An insulating layer-forming composition prepared by partially blending was prepared. Subsequently, the composition for forming an insulating layer was extrusion coated on the inner conductor to form a first unvulcanized insulating layer. Next, the first unvulcanized insulating layer was covered with a braid made of tin-plated copper wire. Subsequently, the braid was covered with the above composition for forming an insulating layer to form a second unvulcanized insulating layer. Thereafter, the chloroprene rubber compositions of Examples 1 to 8 and Comparative Example 1 were put into an extruder and heated to 70 ° C., and then the second unvulcanized insulating layer was extrusion-coated with this chloroprene rubber composition. A vulcanized cable was obtained. Next, the unvulcanized cable was accommodated in a vulcanized tube having an inner diameter of 20 cm and a length of 20 m. Then, nitrogen gas was continuously introduced into the vulcanizing tube, and the unvulcanized cable was pressurized with nitrogen gas at 0.35 MPa for 2 minutes at 345 ° C. (linear speed: 10 m / min). The vulcanized insulation layer, the second unvulcanized insulation layer and the chloroprene rubber composition are vulcanized together, and the first vulcanized insulation layer is provided inside the braid, and the second vulcanized insulation layer is provided just outside the braid. A sheath was formed on the second vulcanized insulating layer. A cable was thus obtained. The cable thus obtained was cut and the cut surface was visually observed. And in the cut surface, when foaming was not seen, it was set as the pass, and when foaming was seen, it was set as the failure. The results are shown in Table 1. In Table 1, the pass is represented by “◯”, and the fail is represented by “x”.

  From the results shown in Table 1, it was found that the water absorption rate of the chloroprene rubber compositions of Examples 1 to 8 was sufficiently reduced as compared with the chloroprene rubber composition of Comparative Example 1. Moreover, even if the chloroprene rubber compositions of Examples 1 to 8 were vulcanized under low pressure, no foaming was observed in the obtained cable sheath. On the other hand, when the chloroprene rubber composition of Comparative Example 1 was vulcanized under low pressure, foaming was observed in the resulting cable sheath.

From this, it was confirmed that the cable manufacturing method of this invention can manufacture the cable provided with the sheath by which foaming is fully suppressed.

DESCRIPTION OF SYMBOLS 1 ... Internal conductor 2 ... Core part 3 ... Sheath 10 ... Cable

Claims (4)

A core including a conductor;
  A sheath that is provided on the core part, covers the core part with a chloroprene rubber composition, and vulcanizes the chloroprene rubber composition;
A method of manufacturing a cable comprising:
  A preparation step of preparing the core portion;
  A sheath forming step of forming the sheath on the core portion,
  In the sheath forming step,
  An unvulcanized cable formed by coating the chloroprene rubber composition on the core portion is accommodated in a vulcanized tube, an inert gas is introduced into the vulcanized tube, and the unvulcanized cable is inerted with the inert gas. Vulcanizing the chloroprene rubber composition while pressurizing at 0.3 to 0.6 MPa to form the sheath,
  A method for producing a cable, wherein the chloroprene rubber composition comprises chloroprene rubber, a vulcanizing agent, and dry silica. The method for producing a cable according to claim 1, wherein the dry silica is obtained by subjecting a surface of silica to a hydrophobic treatment . The cable manufacturing method according to claim 1 or 2, wherein the vulcanizing agent is at least one selected from the group consisting of red lead, hydrotalcite, and zinc oxide. The manufacturing method of the cable as described in any one of Claims 1-3 whose moisture content in the said chloroprene rubber composition is 2500 ppm or less by mass ratio .

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