JP6708055B2 - Cable manufacturing method - Google Patents

Description

The present invention relates to a cable manufacturing method.

Conventionally, various extruded products have been formed using a silane-crosslinked rubber or a polyolefin resin such as polyethylene. The extruded product is used for sheathing power cables and cabtire cables.

Manufacturing a cable with a sheath made of silane-crosslinked rubber does not require a large amount of heat energy or an expensive heating device, and the desired properties can be obtained by the progress of crosslinking due to moisture in the atmosphere. Is very advantageous.

On the other hand, crosslinking with silane has a problem that the crosslinking speed is slow. If at least the outermost surface layer does not undergo some degree of cross-linking (primary cross-linking) after reaching the winder after coating the rubber sheath, permanent strain remains on the cable surface due to tension and self-weight when aligned and wound. I will end up. Therefore, in the invention described in Patent Document 1, a countermeasure is taken by coating an outer layer having a small permanent deformation rate.

In addition, since the reaction proceeds from the surface to the inside of the cross-linking, in the case of a thick rubber sheath, it takes a very long time to cross-link the inside. Therefore, in the case of a thick rubber sheath cable, it must be stored for many days after being wound with a winder, and the crosslinking is completely completed (secondary crosslinking) and shipped as a product. There is also a problem that it takes a very long time to get there.

Generally, in order to improve the crosslinking rate, it is considered to increase the amount of the silane crosslinking catalyst (mainly organotin catalyst is used).

Further, the grafted polyolefin has a problem of scorch (premature crosslinking) and is troublesome to store and handle. As a method to solve this problem, while supplying the polyolefin base resin to the resin supply port of the extruder, the silane cross-linking catalyst or silane coupling may be performed on the resin supply port side of the extruder or in the middle (cylinder side or screw side). There is a manufacturing method of press-fitting and supplying an agent (see Patent Document 2). The manufacturing method is intended to solve problems such as scorch generation by simultaneously blending all materials without storing the resin and the silane crosslinking catalyst or the silane coupling agent in a mixed state. (Patent Document 2, paragraphs 0018 and 0027).

JP, 2015-146303, A JP, 11-195335, A

However, when the amount of the catalyst is increased, there is a problem that scorching causes burns, resulting in poor appearance of the extruded product. This is because when using pellets pre-compounded with a silane solution or a crosslinking catalyst as the base material, the residence time in the extruder is long, and some of the material stays in flight grooves, breaker plates, screen mesh, etc. This is because excessive heat is applied.

Further, even the technique described in Patent Document 2 is not sufficient to solve the problems such as scorch generation, and, for example, when a large amount of silane crosslinking catalyst is press-fitted and supplied, part of the material adheres to the flight part. However, the burn will occur due to the retention.

As an example, when the relationship between the catalyst amount and the scorch time in a material obtained by kneading a silane liquid for about 3 phr into a rubber material based on chloroprene rubber, the catalyst amount was 0, 0.5, 1.0, 1.5 phr. It was found that the scorch time decreased to 60, 35, 15, and 5 minutes as it increased.

Under general rubber material extrusion conditions, the residence time in the extruder from the material injection to the extrusion and coating of the cable is about 15 minutes. Therefore, in the case of the above example, when a material containing more than 1.0 phr of the catalyst is burnt, it can be said that good extrusion is impossible.

On the other hand, when the amount is a safe amount (for example, the amount of catalyst is 0.5 phr or less) for preventing burns, a crosslinking time of 1 hour or more is essential for primary crosslinking with steam of several atm. For this reason, the line speed must be very slow or the line length (steam can length) must be lengthened.

Therefore, an object of the present invention is to provide a method of manufacturing a cable that can suppress the occurrence of burns due to a scorch in an extruder and that is excellent in deformation resistance even if the crosslinking speed is increased.

In order to achieve the above object, the present invention provides the following cable manufacturing method.

[1] A method for producing a cable having an inner layer sheath containing a silane crosslinking catalyst and an outermost layer sheath containing a larger amount of the silane crosslinking catalyst than the inner layer sheath, wherein the silane crosslinking catalyst is added to 100 parts by mass of the base polymer. In the step of molding each of the inner layer sheath and the outermost layer sheath with an extruder using a composition containing less than 1 part by mass, silane is further added to the composition near the outlet of the extruder for molding the outermost layer sheath. A method for producing a cable, comprising a step of adding a crosslinking catalyst.
[2] The addition amount of the silane crosslinking catalyst further added to the composition in the extruder for forming the outermost sheath is 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the base polymer. The method for manufacturing a cable according to [1] above, characterized in that:
[3] The method for producing a cable according to [1] or [2], wherein the composition contains 1 part by mass or more and 5 parts by mass or less of silane with respect to 100 parts by mass of the base polymer. .
[4] The content of the silane crosslinking catalyst in the composition before the silane crosslinking catalyst is further added is 0.2 parts by mass or more and 0.8 parts by mass or less based on 100 parts by mass of the base polymer. The cable manufacturing method according to any one of the above [1] to [3].
[5] The silane crosslinking catalyst is an organotin-based compound, and the tin element content of the outermost sheath is 2 to 8 times the tin element content of the inner sheath. ] The manufacturing method of the cable as described in any one of [4].

According to the present invention, it is possible to provide a method of manufacturing a cable that can suppress the occurrence of burns due to scorch in an extruder and that is excellent in deformation resistance even if the crosslinking speed is increased.

It is a cross-sectional view which shows an example of the cable manufactured by the manufacturing method of the cable which concerns on embodiment of this invention. It is the schematic of the manufacturing apparatus used for the manufacturing method of the cable which concerns on embodiment of this invention, (a) shows the whole apparatus, (b) is an enlarged view of the B area|region in (a).

[Cable manufacturing method]
The cable manufacturing method according to the embodiment of the present invention is a method for manufacturing the cable 20 including the inner layer sheath 11 containing the silane crosslinking catalyst and the outermost layer sheath 12 containing a larger amount of the silane crosslinking catalyst than the inner layer sheath 11. Therefore, in the step of molding the inner layer sheath 11 and the outermost layer sheath 12 with an extruder using a composition containing less than 1 part by mass of the silane crosslinking catalyst with respect to 100 parts by mass of the base polymer, the outermost layer sheath 12 is molded. The step of adding a silane crosslinking catalyst 38 to the above composition near the outlet of the extruder 33 is performed.

FIG. 1 is a cross-sectional view showing an example of a cable manufactured by the cable manufacturing method according to the embodiment of the present invention. Further, FIG. 2 is a schematic view of a manufacturing apparatus used for the cable manufacturing method according to the embodiment of the present invention, (a) shows the entire apparatus, and (b) is an enlargement of the B region in (a). It is a figure.

The cable 20 shown in FIG. 1 includes a cable core 10 in which two insulated electric wires 3 are twisted together, an inner layer sheath 11 extruded on the outer periphery of the cable core 10, and an outer layer sheath extruded on the outer periphery of the inner layer sheath 11. 12 (outermost layer sheath). The insulated electric wire 3 may be a single core or a multi-core stranded wire other than two cores.

The insulated wire 3 includes a conductor 1 and an insulator 2 that covers the outer periphery of the conductor 1. The materials of the conductor 1 and the insulator 2 are not particularly limited, and can be formed using known materials. The conductor 1 is not limited to one, and may be a plurality of strands of strands twisted together.

The inner layer sheath 11 contains less than 1 part by mass of the silane cross-linking catalyst, and less than 1 part by mass of the silane cross-linking catalyst with respect to 100 parts by mass of the base polymer on the outer periphery of the cable core 10 delivered by the cable core feeder 31. It is molded by the extruder 32 using the composition containing. The composition used here may be a composition in which the base polymer and the silane crosslinking catalyst are mixed before being charged into the extruder 32, or the base polymer (or the base polymer composition) and the silane crosslinking catalyst are charged into the extruder. It may be a composition which is separately charged into the mouth and mixed in the extruder 32.

The content of the silane crosslinking catalyst in the composition is preferably 0.2 parts by mass or more and 0.8 parts by mass or less, more preferably 0 parts by mass with respect to 100 parts by mass of the base polymer, relative to 100 parts by mass of the base polymer. It is 0.3 parts by mass or more and 0.7 parts by mass or less, and more preferably 0.4 parts by mass or more and 0.6 parts by mass or less with respect to 100 parts by mass of the base polymer.

As the silane cross-linking catalyst, organic tin compounds such as dioctyl tin and dibutyl tin can be used.

The base polymer is preferably a rubber containing a halogen element such as chloroprene rubber or chlorinated polyethylene. In order to satisfy the desired properties, it is preferable to add various additives such as fillers, flame retardants and lubricants to the base polymer.

The content of silane in the composition is preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the base polymer, and more preferably 1.5 parts by mass or more and 4 parts by mass with respect to 100 parts by mass of the base polymer. The amount is 0.5 parts by mass or less, and more preferably 2 parts by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the base polymer. If the amount of silane is less than 1 part by mass relative to 100 parts by mass of the base polymer, the silane crosslinking effect is not obtained in the entire sheath and the strength deteriorates. If the silane liquid exceeds 5 parts by mass with respect to the base polymer, This is because the silane crosslinking proceeds excessively and the elongation deteriorates.

The silane is not particularly limited, but general aminosilane, vinylsilane, etc. can be used.

The outer layer sheath 12 (outermost layer sheath) contains a larger amount of silane crosslinking catalyst than the inner layer sheath 11. The outer layer sheath 12 is molded by the extruder 33, except that the above composition containing less than 1 part by mass of the silane crosslinking catalyst is used for 100 parts by mass of the base polymer when molding the outer layer sheath 12. The step of forming is different from the inner layer sheath 11 in that the step of adding the silane crosslinking catalyst 38 to the above composition is added in the vicinity of the outlet of the extruder 33 for molding the outer layer sheath 12. The vicinity of the outlet specifically refers to a distance from the tip (end point) of the screw 41 in the extruder 33 to the outlet of the extruder 33, and preferably from after passing through the screen mesh 42 or the breaker plate 43 to the outlet. In the meantime.

In FIG. 2, a silane cross-linking catalyst charging port 44 is provided immediately after passing through the breaker plate 43 in the extruder 33, and the silane cross-linking catalyst 38 is charged therein by the press-fitting pump 37.

The addition amount of the silane crosslinking catalyst further added to the above composition in the extruder 33 for molding the outer layer sheath 12 is 0.6 parts by mass or more and 3.4 parts by mass or less with respect to 100 parts by mass of the base polymer. The amount is more preferably 0.8 parts by mass or more and 3.2 parts by mass or less based on 100 parts by mass of the base polymer, and further preferably 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the base polymer.

When the amount of silane cross-linking catalyst is small (for example, 0.5 phr or less), until the completion of the primary cross-linking to obtain a predetermined strength by silane cross-linking (crushing width 10% or less in the height direction of the outer sheath 12 cross section) Requires several hours of steam for more than one hour. On the other hand, if the silane crosslinking catalyst is included in an amount of 1 phr, a predetermined strength can be obtained in about 40 minutes, and if the silane crosslinking catalyst is included in an amount of 1.5 phr, a predetermined strength is obtained in about 30 minutes. Therefore, in order to improve the primary crosslinking rate, it is effective to blend a silane crosslinking catalyst in an amount of 1.5 phr or more. Therefore, in the embodiment of the present invention, the amount of silane catalyst is set to be less than 1.0 phr in the inner layer sheath 11 and 1.5 phr or more in the outer layer sheath 12. This makes it possible to suppress burns, improve the primary cross-linking speed (reduce the time required to complete the primary cross-linking), and make pulley contact on the pass line and line winding on the winding drum. Since primary cross-linking can be completed by then, crushing can be suppressed. In addition, according to the embodiment of the present invention, it is possible to solve the problem that the secondary cross-linking completion is slower in the inner sheath of a cable having a thicker sheath thickness. The outer layer sheath 12 preferably has a wall thickness of 50% or less with respect to the wall thickness of the entire sheath.

The tin element content of the outer sheath 12 is preferably 2 to 8 times the tin element content of the inner sheath 11.

The molding temperature of the extruders 32 and 33 is preferably 60° C. or higher and 100° C. or lower.

After the inner layer sheath 11 and the outer layer sheath 12 are extrusion-molded by the crosshead 34, they are passed through a steam can 35 and cross-linked with saturated steam or the like. Then, the cable 20 is wound up by the winder 36.

In the present embodiment, the sheath may have a multilayer structure of three layers or more (for example, another inner layer sheath similar to the inner layer sheath 11 is provided). Furthermore, if necessary, a separator, a braid, a shield tape made of metal foil, or the like may be provided.

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto.

The cable having the structure shown in FIG. 1 was manufactured by the following method and evaluated.

A cable core 10 (outer diameter φ45 mm) in which two insulated electric wires 3 each having a conductor 1 made of a copper wire and an insulator 2 made of ethylene propylene rubber are twisted together, has an inner sheath 11 (thickness 3 mm) and an outer sheath 12 (meat A cable 20 having an outer diameter of 53 mm and having a thickness of 1 mm was coated. Also, in consideration of the actual work, it is better that the compounding type is as small as possible. Therefore, in this study, the same material was used for both the inner layer sheath and the outer layer sheath.

The materials used were chloroprene rubber as the base, aminosilane as the silane: trade name KBM-573 (manufactured by Shin-Etsu Silicone), and dioctyl tin as the silane cross-linking catalyst: trade name Neostan U830 (manufactured by Nitto Kasei) (Table 1 ).

The inner layer sheath 11 was a 90 mm extruder 32, and the outer layer sheath 12 was a 40 mm extruder 33. Three kinds of materials pre-impregnated with 0.5 to 1.5 phr of silane cross-linking catalyst were introduced, and the silane cross-linking catalyst 38 was further added after the breaker plate 43 in the outer layer sheath extruder 33 (see FIG. 2, addition). See Table 2 for the amount).

The pass/fail was judged by the appearance inspection of the extruded cable (extrusion time: 0 to 60 minutes or more) and the deformation amount after 30 minutes. Passed when the appearance of the cable did not appear rough even after extrusion for 60 minutes or more (○), and when the appearance did not occur immediately after extrusion (0 minutes), the appearance began to become rough during extrusion (less than 60 minutes). The case where the appearance was rough (immediately after extrusion (0 minutes)) was designated as failure (x). In addition, for acceptable products that did not cause surface roughening, they were crosslinked with steam of 2 atm for 30 minutes, and the amount of deformation under 1N load was less than 10% of the wall thickness (less than 0.4 mm) and passed (○). Those with 10% or more (0.4 mm or more) were regarded as rejects (x). In both evaluations, the case of passing (◯) was judged as passing (see Table 2).

In Comparative Example 1 in which the silane cross-linking catalyst was not added to the material of the outer sheath after the breaker plate 43 and the catalyst content of the inner and outer sheaths was 0.5 parts by mass, the appearance was not roughened. The amount of deformation after a minute was large. In Comparative Example 2 in which the silane cross-linking catalyst was not added to the material of the outer sheath after the breaker plate 43 and the catalyst content of the inner and outer sheaths was 1.0 part by mass, the appearance immediately after extrusion was good, but in the middle. Rough appearance occurred. Further, in the comparative example 3 in which the silane crosslinking catalyst was not added to the material of the outer sheath after the breaker plate 43 and the catalyst content of the inner and outer sheaths was 1.5 parts by mass, the appearance was already roughened at the start of extrusion. Occurred. From these results, it was found that the amount of the catalyst, which is less than 1.0 part by mass, is 0.5 parts by mass, but the appearance is not roughened, but the crosslinking rate is slow. On the other hand, it was found that when the amount of the catalyst was 1.0 part by mass or more, the crosslinking rate was too fast and the appearance was roughened due to burns immediately after the extrusion or during the extrusion.

Therefore, in Examples 1 to 3, the amount of the silane catalyst contained in the material was set to 0.5 parts by mass, and the silane catalyst was further added in the vicinity of the outlet of the extruder 33 for the outer layer sheath.

When the amount of silane added was 0.5 part by mass, the outer sheath 12 did not show any rough appearance. When the amount of silane added was 1.0 to 3.0 parts by mass, the appearance was good, and the amount of deformation after 30 minutes was small and passed.

Further, using SEM-EDX, the amount of tin (Sn) element (%) relative to chloroprene (Cr) in the examples and comparative examples was measured, and the inner and outer layer ratios thereof were obtained. As a result, in Examples 1 to 3, it was found that the outer layer contained about 2 to 8 times more Sn than the inner layer.

1: Conductor, 2: Insulator, 3: Insulated wire, 10: Cable core 11: Inner layer sheath, 12: Outer layer sheath, 20: Cable 31: Cable core feeder 32: Extruder (inner layer), 33: Extruder (Outer layer)
34: Crosshead, 35: Steam can, 36: Winder 37: Press-fit pump, 38: Silane cross-linking catalyst 41: Screw, 42: Screen mesh 43: Breaker plate

Claims (5)

A method for producing a cable comprising an inner layer sheath containing a silane crosslinking catalyst and an outermost layer sheath containing a larger amount of the silane crosslinking catalyst than the inner layer sheath,
In the step of molding each of the inner layer sheath and the outermost layer sheath with an extruder using a composition containing less than 1 part by mass of a silane crosslinking catalyst with respect to 100 parts by mass of a base polymer,
A method for producing a cable, further comprising the step of adding a silane crosslinking catalyst to the composition in the vicinity of the outlet of the extruder for molding the outermost layer sheath. The addition amount of the silane crosslinking catalyst further added to the composition in the extruder for forming the outermost layer sheath is 1 part by mass or more and 3 parts by mass or less based on 100 parts by mass of the base polymer. The method for manufacturing a cable according to claim 1. The said composition contains 1 mass part or more and 5 mass parts or less of silane with respect to 100 mass parts of said base polymer, The manufacturing method of the cable of Claim 1 or Claim 2 characterized by the above-mentioned. The content of the silane crosslinking catalyst in the composition before the silane crosslinking catalyst is further added is 0.2 parts by mass or more and 0.8 parts by mass or less with respect to 100 parts by mass of the base polymer. The method for manufacturing a cable according to claim 1, wherein the cable is manufactured. The silane crosslinking catalyst is an organotin-based compound, and the tin element content of the outermost sheath is 2 to 8 times the tin element content of the inner layer sheath. The method for manufacturing the cable according to any one of items.

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