JP6079673B2 - Cable and manufacturing method thereof - Google Patents

Description

  The present invention relates to a cable and a manufacturing method thereof.

  Conventionally, in a silane-crosslinked polyolefin resin composition, which is also known as a coating material for electric wires and cables, Sn compounds are often used as a catalyst for silanol condensation, which is a reaction that causes silane crosslinking ( For example, Patent Document 1 and Patent Document 2). This is because when a Sn compound is employed as the catalyst, it is possible to ensure a high degree of crosslinking, a crosslinking speed at room temperature, and a good extrusion appearance.

  On the other hand, in recent years, elements such as so-called Pb (lead), Hg (mercury), and Cd (cadmium) have been designated as ROHS prohibited substances. Toxicity to the human body is regarded as a problem not only for the above-mentioned ROHS prohibited substances but also for various metal elements. For example, organic Sn (tin) compounds may fall under environmental hormones. Focusing on this point, the present applicant uses an inorganic tin (Sn) compound as a silanol condensation catalyst, but does not contain Sn as a co-catalyst (hereinafter referred to as “Sn-free”). A technique of using the above has been developed (for example, Patent Document 3).

  Under such circumstances, there is also known a silane cross-linked resin composition using dodecylbenzene sulfonic acid (DDBSA) as a catalyst, which has a sulfo group which is a strong acid group and has a higher cross-linking rate than when an Sn compound is used as a catalyst. (For example, Patent Document 4).

JP 2012-241129 A Special table 2004-526808 gazette JP 2012-197404 A JP-T 9-506915

  However, DDBSA is highly polar and has poor dispersibility for non-polar polyolefin resins. If it becomes so, it will become easy to generate | occur | produce scorch (burn resulting from early vulcanization), and there also exists a possibility that a problem may arise in an external appearance. In addition, there is a risk that the sulfo group, which is a polar group in DDBSA, is eliminated when heating is performed during molding and when the product is used for a long time. In such a case, when DDBSA is used as a catalyst for silanol condensation, if the silane cross-linked resin composition is used as a coating material such as an electric wire or cable, the insulating property may be deteriorated.

  Furthermore, the cross-linking speed is also a major issue in developing Sn-free catalysts. The merit of using the Sn compound as a catalyst is that the crosslinking rate is high. Under normal thinking, even if a Sn-free catalyst is developed, it is not known whether a catalyst capable of obtaining a sufficient crosslinking rate can be developed. On the other hand, there is a possibility of developing Sn-free catalysts that provide moderate crosslinking rates, if not as much as Sn compound catalysts. In that case, however, the catalyst added during the reaction must be increased in order to increase the crosslinking rate. If it becomes so, it will become easy to generate | occur | produce a scorch and there exists a possibility that the rough appearance may arise as a new subject.

  An object of the present invention is to provide a cable that is Sn-free and has good appearance and insulation while being cross-linked quickly and reliably.

The first aspect of the present invention is:
In a cable in which an insulator is provided on the outer peripheral side of the conductor and a sheath is provided on the outer peripheral side of the insulator,
The insulator is a Sn-free silane-crosslinked polyolefin composition. In the silane-crosslinked polyolefin composition, the alkylated naphthalene sulfonic acid is 0.1 to 1 with respect to 100 parts by weight of the polyolefin contained in the silane-crosslinked polyolefin composition. Part by weight,
The sheath is a Sn-free polyvinyl chloride composition, and in the polyvinyl chloride composition, alkylated naphthalene sulfonic acid is 0.1% with respect to 100 parts by weight of polyvinyl chloride contained in the polyvinyl chloride composition. The cable is characterized in that it contains -3 parts by weight, 30-100 parts by weight of a plasticizer having a polar group and a nonpolar group, and 2.5-8 parts by weight of a stabilizer.

A second aspect of the present invention is the aspect described in the first aspect,
The density of the polyolefin is 0.920 g / cm ³ or less.

A third aspect of the present invention is the aspect described in the first or second aspect,
The silane compound is contained in an amount of 1.5 to 5 parts by weight with respect to 100 parts by weight of the polyolefin, and the weight ratio of the silane compound to the free radical generator (silane compound / free radical generator) is 25 to 25 parts. 100.

A fourth aspect of the present invention is the aspect according to any one of the first to third aspects,
The alkylated naphthalene sulfonic acid in the insulator and the sheath is substituted with 1-2 sulfo groups, and is substituted with 1-4 alkyl groups;
The alkyl group is a straight chain or branched chain alkyl group having 5 to 20 carbon atoms,
The total number of carbon atoms in all substituted alkyl groups is 12 to 80;
When there are a plurality of the alkyl groups, the types of the alkyl groups are different from each other.

According to a fifth aspect of the present invention,
An insulator coating step of coating a conductor with a Sn-free insulator containing a polyolefin, a silane compound, a free radical generator, and an alkylated naphthalenesulfonic acid;
After the insulator coating step, a sheath coating step of covering the insulator with a Sn-free sheath containing polyvinyl chloride and alkylated naphthalenesulfonic acid;
After the sheath covering step, an insulator crosslinking step for performing silane crosslinking on the insulator;
Have
In the insulator coating step, the insulator is prepared by adding 0.1 to 1 part by weight of alkylated naphthalenesulfonic acid to 100 parts by weight of polyolefin,
In the sheath coating step, a plasticizer having a polar group and a nonpolar group is added to polyvinyl chloride, and alkylated naphthalenesulfonic acid is added in an amount of 0.1 to 3 with respect to 100 parts by weight of the polyvinyl chloride. A method for producing a cable, characterized in that the sheath is prepared by adding 30 to 100 parts by weight of a plasticizer having parts by weight, a polar group and a nonpolar group and 2.5 to 8 parts by weight of a stabilizer. is there.

  According to the present invention, it is possible to provide a cable that is Sn-free and has good appearance and insulation while being cross-linked quickly and reliably.

It is the cross-sectional schematic of the cable which used the silane crosslinked polyolefin resin composition in this embodiment as a coating | coated material.

The present inventor has studied a means for solving the above-described problems.
First, in terms of dispersibility, as described above, DDBSA is highly polar and dispersible with respect to non-polar polyolefin resins. In view of the fact that the polyolefin resin is nonpolar, the present inventor has sought a compound having a balance between polarity and nonpolarity relative to the polyolefin resin as a catalyst for silanol condensation. As a result, the present inventor has obtained knowledge that the use of alkylated naphthalene sulfonic acid as a catalyst for silanol condensation is one configuration for solving the above-mentioned problems.

  Next, the present inventor has examined the crosslinking rate. As a result, the following phenomenon peculiar to cable manufacture was discovered.

  Generally, a polyvinyl chloride (PVC) composition is applied as the sheath of the cable. This PVC composition is usually produced by adding a plasticizer to a PVC resin (PVC resin, hereinafter also referred to simply as “PVC”). When this inventor examined, the compound which has a polar group and a nonpolar group was used as a plasticizer. As the insulator, a silane-crosslinked polyolefin resin composition using alkylated naphthalenesulfonic acid as a catalyst for silanol condensation was used. And this inventor performed the process of forming a sheath by coat | covering the said PVC with the PVC composition to which the plasticizer was added.

  In this process, when the present inventor coats the outer layer of the silane-crosslinked polyolefin composition applied to the insulator, the plasticizer contained in the sheath, which is the outer layer of the insulator, is allowed to enter the silane-crosslinked polyolefin composition. I found out that I would migrate.

  The present inventor has come up with a technique for improving the crosslinking rate in the silane-crosslinked polyolefin composition constituting the insulator by utilizing this phenomenon. It is the following method.

  First, an alkylated naphthalene sulfonic acid is used as a crosslinking catalyst used for preparing a silane-crosslinked polyolefin composition. Alkylated naphthalene sulfonic acid is a non-Sn compound. In addition, alkylated naphthalene sulfonic acids are hydrolyzable with strong acids. Therefore, the crosslinking rate is higher than that of the Sn compound catalyst. In addition, as described above, since the alkylated naphthalenesulfonic acid has a polar group and a nonpolar group, the polarity and nonpolarity are balanced with respect to the polyolefin resin used as the raw material of the silane-crosslinked polyolefin composition. Yes. Therefore, alkylated naphthalenesulfonic acid has good dispersibility with respect to the olefin resin.

In addition, alkylated naphthalene sulfonic acid is added to PVC as a raw material for the PVC composition used for the sheath. Thereby, the alkylated naphthalenesulfonic acid in the sheath also exhibits affinity for the plasticizer in the sheath. As described above, the plasticizer in the sheath moves to the insulator which is the inner layer. Like the plasticizer, the alkylated naphthalene sulfonic acid in the sheath has polar and non-polar groups. As a result, the alkylated naphthalene sulfonic acid also moves into the insulator together with the plasticizer. After transfer, the alkylated naphthalene sulfonic acid acts as a silanol catalyst inside the insulator.
The present invention has been created based on the above findings.

First, the manufacturing method of the cable in this embodiment is demonstrated. In the middle, the characteristics of each component of the cable will be described, and the cable produced last will be described.
In addition, a publicly known technique may be adopted for matters not specifically mentioned in the present embodiment. For example, the contents described in Patent Document 1 and Patent Document 3 published by the present applicant may be incorporated as appropriate.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Overview)
As shown in FIG. 1, the cable 10 according to this embodiment has an insulator 2 provided on the outer periphery side of a long conductor 1 and a sheath 3 provided on the outer periphery side of the insulator 2. As the conductor 1, a known material may be used. For example, copper, aluminum, or an alloy thereof can be used. The conductor may be plated with various metals such as tin or tin alloy. The configuration of the conductor may be a single wire or a stranded wire.

(Insulator coating process)
In this step, the long conductor 1 is covered with a Sn-free insulator 2 containing a polyolefin, a silane compound, a free radical generator, and an alkylated naphthalene sulfonic acid.

The polyolefin used in this step preferably has a density of 0.920 g / cm ³ or less, which is excellent in moisture permeability. If the density is 0.920 g / cm ³ or less, the polymer chains in the polyolefin are not too dense, and therefore a sufficient crosslinking rate can be maintained even under normal temperature and normal humidity (23 ° C. and 50%). In addition, the kind of polyolefin is not specifically limited, 1 type may be sufficient and 2 or more types may be blended.

  There is no restriction | limiting in particular in the compound used as this polyolefin. An example is polyethylene. Examples of the polyethylene include those produced by copolymerizing ethylene and an α-olefin, as described in Patent Document 1, for example. As the α-olefin, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like are used, and one or a combination of two or more may be produced. . In the present embodiment, these polyethylenes may be used alone or in combination of two or more. The melt index (MI) is not particularly limited.

  The numerical values (for example, the density and the number of weight parts) in the present specification are also numerical values in the raw material used when the insulator 2 and the sheath 3 of the cable 10 according to the present embodiment are manufactured, and constitute the cable 10 It is also a numerical value in the insulator 2 and the sheath 3. Hereinafter, it will be described based on that.

  The silane compound is preferably added in an amount of 1.5 to 5 parts by weight based on 100 parts by weight of the polyolefin contained in the composition. If the silane compound is 1.5 parts by weight or more with respect to 100 parts by weight of the polyolefin, a sufficient degree of crosslinking can be obtained, and thus a sufficient crosslinking rate can be maintained. On the other hand, if the silane compound is 5 parts by weight or less with respect to 100 parts by weight of the polyolefin, the reaction between the silane compounds can be suppressed during graft copolymerization. As a result, it is possible to suppress the generation of foreign matters due to the reaction between silane compounds. As a result, it can suppress that the said foreign material sticks in a reactor, and can also suppress generation | occurrence | production of the external appearance defect of a molding.

  The silane compound must have both a group capable of reacting with the polymer and an alkoxy group that forms a crosslink by silanol condensation. Specifically, vinylsilane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltrissilane are preferable.

  The free radical generator is preferably in a weight ratio of (silane compound / free radical generator) = 25-100. If the weight ratio is 25 or more, occurrence of rough appearance can be suppressed. On the other hand, if the weight ratio is 100 or less, a sufficient degree of crosslinking can be obtained, and thus a sufficient crosslinking rate can be maintained. This means that the higher the ratio of the free radical generator to the silane compound (the lower the weight ratio), the more crosslinking points of the polymer and the faster the crosslinking formation rate at the initial stage of the reaction. However, when the amount of free radical generators is excessive, the polymers become polymerized and become particles due to the difference in viscosity, which causes a rough appearance. As the free radical generator, an organic peroxide that decomposes by heat to generate free radicals is used. Specifically, dicumyl peroxide, benzoyl peroxide, 1,1-bis (t-butyl peroxy) -3,3,5-trimethylcyclohexane, t-butyl peroxyisopropyl carbonate, t-butyl peroxy Benzoate or the like is desirable.

  The catalyst used in the silanol condensation is one of the major features in this embodiment. In this embodiment, alkylated naphthalene sulfonic acid is used as the catalyst. As described above, the alkylated naphthalenesulfonic acid is a compound that has a balance between polar and nonpolar with respect to the polyolefin resin. Therefore, the alkylated naphthalenesulfonic acid (that is, the catalyst in the silanol condensation reaction) is excellent in compatibility with the polyolefin resin, and consequently the dispersibility of the catalyst in the polyolefin resin is good.

  In addition, the silane crosslinked polyolefin resin composition in this embodiment needs to be Sn free. Therefore, in this embodiment, at least the Sn salt of alkylated naphthalene sulfonic acid is not used. Of course, other metal salts may be used, but it is preferable to use alkylated naphthalene sulfonic acid itself because it is preferable not to include a metal in the insulator 2 as much as possible.

  Further, it is necessary that 0.1 to 1 part by weight of alkylated naphthalene sulfonic acid is contained with respect to 100 parts by weight of polyolefin contained in the composition. If it is 0.1 parts by weight or more, a sufficient degree of crosslinking can be obtained, and thus a sufficient crosslinking rate can be maintained. On the other hand, if the amount is 1 part by weight or less, the polymer is moderately polymerized, a large difference in viscosity does not occur, and the generation of grains that causes a rough appearance is suppressed.

In addition, the alkylated naphthalene sulfonic acid satisfying the following conditions is preferable in terms of balancing the polarity.
・ Substituted with 1 to 2 sulfo groups.
・ Substitute with 1 to 4 alkyl groups.
-The alkyl group is a linear or branched alkyl group having 5 to 20 carbon atoms.
-The sum total of carbon number in all the substituted alkyl groups is 12-80.
-When there are a plurality of the alkyl groups, the types of the alkyl groups are different from each other.
Specific alkylated naphthalene sulfonic acids include didodecyl naphthalene monosulfonic acid, tridodecyl naphthalene monosulfonic acid, tetradodecyl naphthalene monosulfonic acid, and combinations thereof.

  In addition to the above, a known additive may be added as necessary within the range not impairing the effects of the present invention. For example, process oil, processing aid, flame retardant, flame retardant aid, crosslinking aid, antioxidant, UV absorber, copper damage inhibitor, lubricant, inorganic filler, compatibilizer, plasticizer, stabilizer, It is also possible to add additives such as carbon black and colorant. In addition, you may add said additive to the sheath 3 described below. However, plasticizers and stabilizers used in the sheath coating process are used.

  In addition, as a specific method of this process, you may use the method as described in patent document 1 or patent document 3. As an example, this process is performed using a single screw extruder, a twin screw extruder, a kneader, a Banbury mixer, a roll, or the like. The “sheath covering step” described below may be performed simultaneously using this step and a single screw extruder.

(Sheath coating process)
In this process, after the insulator coating process, the insulator 2 is coated with a Sn-free sheath 3 containing polyvinyl chloride (PVC) and alkylated naphthalene sulfonic acid. That is, the sheath 3 of the cable 10 of the present embodiment is made of a polyvinyl chloride composition.

In this embodiment, alkylated naphthalene sulfonic acid is added not only to the insulator 2 but also to the sheath 3. This is one of the major features of this embodiment.
In the sheath 3 of the present embodiment, PVC is used and no silane compound is added, so that the alkylated naphthalenesulfonic acid does not act as a catalyst in the sheath 3. However, by performing the insulator cross-linking step, which is the next step, the alkylated naphthalene sulfonic acid in the sheath 3 moves into the insulator 2 together with the plasticizer. When the alkylated naphthalenesulfonic acid moves into the insulator 2, the alkylated naphthalenesulfonic acid functions as a catalyst in silanol condensation.

  In the PVC composition forming the sheath 3, 0.1 to 3 parts by weight of alkylated naphthalene sulfonic acid is added to 100 parts by weight of PVC. If it is 0.1 parts by weight or more, when the alkylated naphthalenesulfonic acid migrates into the insulator 2 together with the plasticizer, the alkylated naphthalenesulfonic acid can sufficiently function as a catalyst in silanol condensation, and the crosslinking rate of the insulator 2 Can be improved. If it is 3 parts by weight or less, the insulation of the sheath 3 can be maintained in a good state.

  As the PVC in the PVC composition of this step, it is preferable to use a PVC having a polymerization degree in the range of 1000 to 2500. If the degree of polymerization is 1000 or more, sufficient heat resistance as a wire covering material can be ensured. On the other hand, if it is 2500 or less, kneading at an appropriate temperature is sufficient, and moldability is improved.

  It is preferable to further add a plasticizer or a stabilizer to the PVC in the PVC composition in this step. Hereinafter, the plasticizer and the stabilizer in this embodiment will be described.

  The plasticizer in this step needs to have a polar group and a nonpolar group. Because of this configuration, the alkylated naphthalene sulfonic acid together with the plasticizer moves from the sheath 3 into the insulator 2.

In addition, the following are mentioned as a kind of plasticizer to be used.
“DOP (di-2-ethylhexyl phthalate), DOIP (di-2-ethylhexyl isophthalate), DOTP (di-2-ethylhexyl terephthalate), n-DOP (dinormal octyl phthalate), n-DOIP (isophthalate) Dinormal octyl acid), n-DOTP (dinormal octyl terephthalate), DINP (diisononyl phthalate), DINIP (diisononyl isophthalate), DINTP (diisononyl terephthalate), n-DNP (dinormal nonyl phthalate), n -DNIP (dinormal nonyl isophthalate), n-DNTP (dinormal nonyl terephthalate), DIDP (diisodecyl phthalate), DIDIP (diisodecyl isophthalate), DIDTP (diisodecyl terephthalate), DPHP (di-2 phthalate) The Bilheptyl), DPHIP (di-2-propylheptyl isophthalate), DPHTP (di-2-propylheptyl terephthalate), n-DDP (dinormaldecyl phthalate), n-DDIP (dinormaldecyl isophthalate), n -DDTP (dinormaldecyl terephthalate), TOTM (tri-2-ethylhexyl trimellitic acid), n-TOTM (trinormal octyl trimellitic acid), TINTM (triisononyl trimellitic acid), n-TNTM (trimellitic acid trimethyl) Normalnonyl), TIDTM (triisodecyl trimellitic acid), n-TDTM (trinormaldecyl trimellitic acid), DOA (di-2-ethylhexyl adipate), DINA (diisononyl adipate), DIDA (diisodecyl adipate), DO (Di-2-ethylhexyl sebacate), DOZ (di-2-ethylhexyl azelate), a polyester plasticizer adipic acid, these singly or two or more of the blend. "

  In addition, as addition amount of a plasticizer, it is the range of 30-100 weight part of addition amount with respect to 100 weight part of PVC. In this embodiment, when covering the insulator 2 with the sheath 3, it is preferable that the extrusion temperature exceeds 150 ° C. in order to obtain smooth moldability. At that time, some of the plasticizer present in the PVC composition is transferred to the inside of the insulator 2. At this time, an alkylated naphthalenesulfonic acid having both a polar group and a nonpolar group is added to the PVC composition in the same manner as the plasticizer. Then, since the alkylated naphthalene sulfonic acid has an affinity with the plasticizer, the alkylated naphthalene sulfonic acid moves into the insulator 2 together with the plasticizer. As a result, the crosslinking rate of the silane-crosslinked polyolefin composition used for the insulator 2 can be improved. If the added amount of the plasticizer is 30 parts by weight or more, the plasticizer is sufficiently transferred into the insulator 2 and the crosslinking speed of the insulator 2 is improved. If the addition amount of the plasticizer is 100 parts by weight or less, the insulation in the sheath 3 can be kept good.

  On the other hand, as a stabilizer in this embodiment, what is necessary is just to give shaping | molding stability and durability with respect to a PVC composition. In the present embodiment, it is preferable to use a Ca—Zn-based non-lead stabilizer as the stabilizer. As an amount of the stabilizer, 2.5 to 8 parts by weight is added to 100 parts by weight of PVC. If it is 2.5 parts by weight or more, sufficient lubricity can be secured. If the amount is 8 parts by weight or less, the appearance of the sheath 3 can be improved without excessive lubricity.

  In addition, as a specific technique of this process, the technique described in Patent Document 1 or Patent Document 3 may be used, or the technique described in the insulator coating process may be used.

(Insulator cross-linking process)
In this step, silane crosslinking is performed on the insulator 2 after the sheath coating step.
In addition, as a specific method of this process, you may use the method as described in patent document 1 or patent document 3. For example, there is a method in which the sheath 3 is left in a high humidity environment at room temperature or a temperature lower than the melting point of polyolefin.

  By passing through the insulator cross-linking step, as described above, the plasticizer in the sheath 3 moves to the insulator 2 that is the inner layer thereof. Like the plasticizer, the alkylated naphthalene sulfonic acid in the sheath 3 has a polar group and a nonpolar group. As a result, the alkylated naphthalenesulfonic acid also moves into the insulator 2 together with the plasticizer. The alkylated naphthalenesulfonic acid after the migration acts as a silanol catalyst inside the insulator 2. That is, it is possible to efficiently bring the catalyst to the inside of the insulator 2 without adding an excessive amount of the catalyst. If it becomes so, it will become unnecessary to add an excess catalyst and it will become possible to improve a silane bridge | crosslinking speed | velocity | rate, while a scorch does not deteriorate an external appearance.

The cable 10 in this embodiment is created through the above steps. The cable 10 in this embodiment is a cable 10 in which an insulator 2 is provided on the outer peripheral side of the long conductor 1 and a sheath 3 is provided on the outer peripheral side of the insulator 2. The insulator 2 is a Sn-free silane-crosslinked polyolefin composition, and 0.1 to 1 part by weight of alkylated naphthalene sulfonic acid is contained with respect to 100 parts by weight of polyolefin contained in the silane-crosslinked polyolefin composition. . On the other hand, the sheath 3 is a Sn-free polyvinyl chloride composition, and 0.1 to 3 parts by weight of alkylated naphthalene sulfonic acid is contained with respect to 100 parts by weight of polyvinyl chloride contained in the polyvinyl chloride composition. Yes.
In addition, the technical significance about each said structure, composition, the number of weight parts, and the effect which they bring about are as above-mentioned. Further, other preferable examples such as the density and weight ratio of the polyolefin (silane compound / free radical generator) can also be applied to the cable 10 itself in this embodiment.

  According to the present embodiment, “alkylated naphthalene sulfonic acid”, which is less polar than DDBSA, which is a silanol condensation catalyst described in Patent Document 4, is used as a catalyst. Therefore, compatibility with the resin can be improved. In addition, as described above, the alkylated naphthalene sulfonic acid is included in the insulator 2 as a catalyst, and the alkylated naphthalene is also present in the sheath 3 existing on the outer peripheral side of the insulator 2. Sulfonic acid is contained. By performing the insulator cross-linking step in this state, the alkylated naphthalene sulfonic acid in the sheath 3 moves into the insulator 2. By doing so, silanol condensation can be caused without requiring a large amount of catalyst in the silane crosslinking in the insulator 2. As a result, it is possible to provide a silane-crosslinked polyolefin resin composition that is Sn-free and has good appearance and insulation while being rapidly and reliably crosslinked.

An outline of the present embodiment will be described.
First, silane-crosslinked polyolefin resin compositions were prepared using the composition of the amount described in Table 1 (Examples 1 to 14) and Table 2 (Comparative Examples 1 to 11) described later as raw materials. Specifically, the following steps were performed.
(Step A) Step of copolymerizing a silane compound with polyolefin (Step B) Step of preparing a catalyst masterbatch (Step C) Step of kneading alkylated naphthalene sulfonic acid with polyolefin obtained by graft copolymerization of silane compound (Step D) Kneading A step of coating the conductor 1 with a later compound (insulator coating step)
(Step E) Step of kneading alkylated naphthalene sulfonic acid to PVC (Step F) Step of coating compound 2 after kneading on insulator 2 (Sheath coating step)
(Step G) Silane cross-linking step by silanol condensation (insulator cross-linking step)

Thereafter, an evaluation test was performed on each sample. Specifically, the following tests were conducted.
(Evaluation Test 1) Confirmation of Extrusion Appearance for Confirming Roughness of Appearance (Evaluation Test 2) Hot Set Test for Confirming Cross-Linking Quickly and Certainly (Evaluation Test 3) For Confirming Insulation Degree Volume resistivity measurement test Hereinafter, this example will be described in detail.

[Production of Cable 10]
(Step A) Step of copolymerizing a silane compound with polyolefin Using a 40 mm extruder (L / D = 24), polyolefins having compositions and quantities described in Table 1 (Examples) and Table 2 (Comparative Examples) described later are used. The hopper was put into the container. At the same time, a solution in which a free radical generator was dissolved in the silane compounds shown in Table 1 (Example) and Table 2 (Comparative Example) was injected into the container with a liquid pump. Strand extrusion was performed by setting the cylinder temperature to 200 ° C. and the residence time in the extruder to 100 to 150 seconds. Thereafter, a polyolefin in which a silane compound was graft-copolymerized was formed into pellets having a diameter of 2 to 3 mm using a pelletizer.

(Step B) Catalyst masterbatch production step On the other hand, the catalyst masterbatch (catalyst MB) used for silanol condensation is the raw materials (composition and quantity) listed in Table 1 (Examples) and Table 2 (Comparative Examples). Based on the above. Specifically, a 6 inch open roll was used. Then, an alkylated naphthalenesulfonic acid (manufactured by NACURE CD-2180 King) is added to a separately prepared non-copolymerized polyolefin (that is, a polyolefin before the step A), and the mixture is added at 160 ° C. for 5 minutes. Kneading was performed. Thereafter, using a pelletizer, a catalyst MB having a size of 3 mm × 3 mm × 0.5 mm was prepared in accordance with each example and comparative example.

(Step C) Step of kneading the catalyst into the polyolefin in which the silane compound is graft-copolymerized Next, using the 130 mm extruder (L / D = 24), the “silane compound was graft-copolymerized” prepared in the above (Step A). “Polyolefin” and “Catalyst MB” prepared in (Step B) were simultaneously charged from the hopper at a ratio of a predetermined composition. And extrusion was performed by setting the cylinder temperature to 200 ° C. and the residence time in the extruder to 100 to 150 seconds.

(Step D) Step of coating conductor 1 with compound after kneading (insulator coating step)
When extruding, the conductor 1 having a cross-sectional area of 100 SQ was coated. In this way, the conductor 1 was covered with the insulator 2 to produce an electric wire. The thickness of the insulator 2 was 1.5 mm.

(Step E) Step of kneading alkylated naphthalenesulfonic acid in PVC On the other hand, in order to produce a PVC composition used as the sheath 3, the following steps were performed.
The composition and amount of PVC (resin), plasticizer, stabilizer, alkylated naphthalene sulfonic acid catalyst or dibutyltin dilaurate shown in Table 3 below were charged into a 50 liter pressure kneader. The degree of polymerization of PVC was 1300. DINP was used as the plasticizer. A lead-free Ca—Zn-based stabilizer was used as the stabilizer.
Then, kneading was performed at a start temperature of 130 ° C. and an end temperature of 170 ° C. Thereafter, the PVC composition was pelletized.
In addition, as shown in Table 3, the symbols a to k are given to the respective compositions. In addition, about the composition ek, it deviates from either of the prescription | regulations regarding the cable 10 described in this embodiment.

(Step F) Step of coating insulator 2 with compound after kneading (sheath coating step)
Thereafter, the prepared pellets were put into the hopper of a 130 mm extruder (L / D = 24), the cylinder temperature was set to 180 ° C., and the residence time in the extruder was set to 100 to 150 seconds. For 2), the sheath 3 was covered to produce a cable 10. The thickness of the sheath 3 was 1.5 mm.

(Step G) Silane cross-linking step by silanol condensation (insulator cross-linking step)
The cable 10 obtained in (Step F) was left for 36 to 72 hours under normal temperature and normal humidity conditions of a temperature of 23 ° C. (± 1) and a humidity of 50% (± 5).
The following evaluation tests were performed on each sample obtained through the above steps.

[Evaluation test]
(Evaluation Test 1) Confirmation of Extrusion Appearance i) Confirmation of Extrusion Appearance in Insulator 2 For the insulator 2 at the end of (Step D), the smoothness of the surface is evaluated by “hand touch” and “presence of granular protrusions”. did. Smooth touch and no grainy protrusions are “particularly good”, smooth touch and slightly melt fractured, but no grainy protrusions are “good ○” The case where the roughness was understood, the grainy protrusion was present, and the appearance was rough was designated as “x”.
ii) Confirmation of Extrusion Appearance in Sheath 3 The surface smoothness of the sheath 3 at the end of (Step F) (ie before silane crosslinking) was evaluated by “hand touch” and “presence of granular protrusions”. A sample having a smooth feel and having no granular protrusions was evaluated as “Good”, and a sample having rough texture and having a granular protrusion and having a rough appearance was evaluated as “X”.
Since it was considered that the extrusion appearance had little relation to the presence or absence of silane cross-linking, the test was performed on the cable 10 in the middle of production of this example (that is, before silane cross-linking).

(Evaluation Test 2) Hot Set Test In this test, it was confirmed whether or not the elongation of the sample was moderately suppressed even after the sample was heated, that is, whether “crosslinking was performed quickly and reliably”. Each sample is silane-crosslinked under the same conditions. Therefore, if the crosslinking speed is high, crosslinking is sufficiently performed even within a predetermined time, and the result of this test is naturally good. As a result, the crosslinking rate can be evaluated by this test.
The specific method of this test is as follows.

The sheath 3 and the insulator 2 were peeled off from the cable 10 after the silane crosslinking was performed through (Step G), and the insulator 2 was subjected to a hot set test indicated by 9 of JISC3660-2-1. A dumbbell-shaped test piece was hung in a thermostat having an air temperature of 200 ° C., and the elongation (elongation under load) after applying a load of 20 N / cm ² for 15 minutes was measured. Then, after removing a load and 5 minutes passed, the test piece was taken out from the tank. And the elongation (permanent elongation) after leaving to stand at normal temperature for 5 minutes was measured with respect to the said test piece. In this example, a material satisfying the standards of elongation under load ≦ 175% and permanent elongation ≦ 15% was determined to be acceptable. In addition, the above test was done about each when bridge | crosslinking time was 36h, 48h, and 72h.

  In this example, among the cases where the cross-linking time is set to 36h, 48h, 72h, even if it is rejected in the case of 36h, 48h, the one that passed in the case of 72h is determined as a practical cable 10. And it was a good evaluation.

(Evaluation Test 3) Volume Resistivity Measurement Test In this test, the degree of insulation was confirmed. Specific methods are as follows.
The device shown in JISK6723-6-8 is peeled off each sheath 3 and each insulator 2 from each cable 10 that has undergone (Step F) (the time required for silane crosslinking is 72 h). And according to the method, the volume resistivity at 500V charge at room temperature for 1 minute was measured.
i) Determination of Volume Resistivity in Insulator 2 In the determination of volume resistivity in insulator 2, a sample with a measurement result of “volume resistivity ≧ 10 ¹⁶ Ω · cm” is “excellent in insulation ( That is, ○) ”. On the other hand, a sample having a measurement result of “volume resistivity <10 ¹⁶ Ω · cm” was defined as “inferior in insulation (ie, x)”.
ii) Determination of Volume Resistivity in Sheath 3 On the other hand, in determination of volume resistivity in sheath 3, a sample having a measurement result of “volume resistivity ≧ 10 ¹² Ω · cm” is evaluated as “excellent in insulation (that is, ○ ) ”. On the other hand, a sample with a measurement result of “volume resistivity <10 ¹² Ω · cm” was defined as “inferior in insulation (ie, x)”.

[Evaluation results]
The results of the above evaluation tests are shown in Table 1 (Examples) and Table 2 (Comparative Examples).

  Table 3 shows a list of compositions of the sheath 3 used in the examples and comparative examples.

Table 1 (Example) and Table 2 (Comparative Example) revealed the following. That is, in the (evaluation tests 1 to 3), the samples satisfying the conditions of “evaluation of ◯ or higher” and “pass” were shown to satisfy the following conditions.
“Insulator 2 is a Sn-free silane-crosslinked polyolefin composition. In the silane-crosslinked polyolefin composition, alkylated naphthalenesulfonic acid is 0.1 to 100 parts by weight of polyolefin contained in the silane-crosslinked polyolefin composition. 1 part by weight,
The sheath 3 is a Sn-free polyvinyl chloride composition. In the polyvinyl chloride composition, the alkylated naphthalene sulfonic acid is 0.1% with respect to 100 parts by weight of the polyvinyl chloride contained in the polyvinyl chloride composition. -3 parts by weight, 30-100 parts by weight of a plasticizer having a polar group and a nonpolar group, and 2.5-8 parts by weight of a stabilizer. ]

Hereinafter, the result obtained by each Example or each comparative example is explained in full detail.
First, Example 4 and Comparative Example 2 are compared. These samples have the same composition and amount of raw materials except for the catalyst used in the silanol condensation contained in the insulator 2 and the catalyst contained in the sheath 3. The catalyst of Example 4 is alkylated naphthalene sulfonic acid and is contained in both the insulator 2 and the sheath 3. On the other hand, the catalyst of Comparative Example 1 is a conventional Sn catalyst.
For example, Example 4 (that is, Sn-free example) showed a better result in the hot set test, that is, an improvement in the crosslinking rate, as compared with Comparative Example 2 (that is, Sn-containing example). The reason for this is considered that the hydrolyzability of the strong acid promotes the silanol condensation reaction, and as a result, the hydrolyzability of the strong acid contributes to the early progress of crosslinking.

Moreover, Example 4 and Comparative Examples 1-3 are compared. Comparative Examples 1 to 3 are Sn-containing examples in which alkylated naphthalenesulfonic acid is contained only in the sheath 3 or Sn-containing examples in which alkylated naphthalenesulfonic acid is not contained in either the insulator 2 or the sheath 3. is there.
Example 4 (that is, Sn-free example) had a good result in the hot set test, that is, an improvement in the crosslinking rate, as compared with Comparative Examples 1 to 3 (that is, Sn-containing example). In Comparative Example 1 and Comparative Example 2, a sufficient crosslinking rate was not obtained. In Comparative Example 3, although the sheath 3 contains alkylated naphthalene sulfonic acid, the insulator 2 uses Sn compound as a catalyst in excess of 1 part by weight per 100 parts by weight of the polyolefin. ing. For this reason, in Comparative Example 3, the crosslinking rate is increased, but the appearance is deteriorated.

Next, Examples 3 and 4 are compared with Comparative Examples 5 and 6. These samples have the same composition and amount of raw materials except for the amount of alkylated naphthalenesulfonic acid contained in the insulator 2. The amount of alkylated naphthalene sulfonic acid in Examples 3 and 4 is in the range of 0.1 to 1 part by weight with respect to 100 parts by weight of polyolefin. On the other hand, the amount of alkylated naphthalenesulfonic acid in Comparative Examples 5 and 6 is outside the above range. In Comparative Example 5, the amount of alkylated naphthalene sulfonic acid was less than the specified value of the present invention, so that a sufficient crosslinking rate could not be obtained. On the other hand, in Comparative Example 6, since the amount of alkylated naphthalenesulfonic acid exceeded the specified value of the present invention, the appearance of the insulator 2 was greatly deteriorated.
As a result, it was shown that the amount of the alkylated naphthalene sulfonic acid catalyst contained in the insulator 2 is not 0.1 to 1 part by weight, and the crosslinking speed and the appearance are not compatible.

  Also, Example 4 and Comparative Example 4 are compared. In Comparative Example 4, alkylated naphthalene sulfonic acid is contained only in insulator 2. Except this point, the composition and the amount of both raw materials are the same. When both are compared, in Comparative Example 4, a sufficient crosslinking rate is not obtained, whereas the crosslinking rate of Example 4 is improved. The reason for this is considered that the alkylated naphthalenesulfonic acid having a polar group and a nonpolar group exhibited affinity with a plasticizer having the same group, and both migrated to the polyolefin composition, resulting from the promotion of crosslinking.

Next, Examples 1 and 12 and Comparative Example 7 are compared. These samples have the same composition and amount of raw materials except for the amount of alkylated naphthalene sulfonic acid contained in the sheath 3. The amount of alkylated naphthalenesulfonic acid in Examples 1 and 12 is in the range of 0.1 to 3 parts by weight with respect to 100 parts by weight of PVC. On the other hand, the amount of alkylated naphthalenesulfonic acid in Comparative Example 7 is outside the above range (excess).
In Comparative Example 7, since the conductive sulfo group becomes excessive, the insulating property of PVC is lowered. As a result, it was shown that the above range of the addition amount is preferable in order to achieve both improvement in the crosslinking rate of the insulator 2 and insulation of the sheath 3.

Next, Example 4 and Comparative Example 8 are compared. In these samples, the composition and the amount of the raw material are the same except for the addition amount of the plasticizer in the sheath 3. The amount of the plasticizer added in Example 4 is in the range of 30 to 100 parts by weight with respect to 100 parts by weight of PVC. On the other hand, the addition amount of the plasticizer in Comparative Example 8 is outside the above range (too little). When the plasticizer was less than 30 parts with respect to 100 parts by weight of PVC, the catalyst moved together with the plasticizer from the sheath 3 into the insulator 2, and the crosslinking rate of the insulator 2 was improved. On the other hand, when it was out of the above range (too little), the catalyst transfer effect was not sufficiently observed. Similar to Comparative Example 4 in which no catalyst was added to the PVC composition as the sheath 3, the crosslinking rate was not improved in Comparative Example 8.
Also, Examples 1 and 13 are compared with Comparative Example 9. These samples have the same composition and amount of raw materials except for the amount of plasticizer added. The addition amount of the plasticizer in Examples 1 and 13 is in the range of 30 to 100 parts by weight with respect to 100 parts by weight of PVC. On the other hand, the amount of plasticizer added in Comparative Example 9 is outside the above range (excessive). When the plasticizer exceeded 100 parts by weight with respect to 100 parts by weight of PVC, the insulation property of the PVC composition was lowered. The reason for this is considered to be that the insulating property of the plasticizer itself is low, and the proportion of the plasticizer in the PVC composition becomes too high.
From the above results, it is shown that the plasticizer addition amount contained in the sheath 3 is preferably 30 to 100 parts by weight with respect to 100 parts by weight of PVC in order to achieve both improvement in the crosslinking rate of the insulator 2 and insulation of the sheath 3. It was.

  Next, Examples 1 and 14 and Comparative Examples 10 and 11 are compared. These samples have the same composition and amount of raw materials except for the added amount of stabilizer. The addition amount of the stabilizer in Examples 1 and 14 is in the range of 2.5 to 8 parts by weight with respect to 100 parts by weight of PVC. On the other hand, in Comparative Example 10, the added amount of the stabilizer is less than the specified value of the present invention, and in Comparative Example 11, the added amount of the stabilizer exceeds the specified value of the present invention. It was shown that the extrusion appearance of the sheath 3 deteriorated due to excessive nature.

Next, the condition that “the density of the polyolefin in the insulator 2 is 0.920 g / cm ³ or less” was examined.
As can be seen from Examples 4, 5, 10, and 11, the lower the density of the polyolefin, the higher the crosslinking rate. When the density is 0.920 g / cm ³ or less, high crosslinking performance that passes the hot set test is obtained even at a crosslinking time of 36 hours. It was. Therefore, in order to obtain high crosslinking performance, it was shown that the polyolefin density is more preferably 0.920 g / cm ³ or less.

Next, the condition that “the insulator 2 contains 1.5 to 5 parts by weight of the silane compound with respect to 100 parts by weight of the polyolefin” was examined.
As can be seen from Examples 1 and 6, when the silane compound is less than 1.5 parts by weight with respect to 100 parts by weight of polyolefin contained in the polyolefin composition of insulator 2, the hot set test is passed when the crosslinking time is 48 hours. However, it is rejected when the crosslinking time is 36 hours. As can be seen from Examples 3 and 7, when the amount of the silane compound was 6 parts by weight or more, the appearance was slightly deteriorated.
From the above results, it was shown that the amount of the silane compound is preferably 1.5 parts by weight to 5 parts by weight in order to achieve both the appearance and the crosslinking rate.

Next, the condition that “the insulator 2 has a weight ratio of silane compound to free radical generator (silane compound / free radical generator) of 25 to 100” was examined.
As can be seen from Examples 1, 2, 8, and 9, the lower the weight ratio (silane compound / free radical generator), the higher the crosslinking rate. In particular, when the weight ratio (silane compound / free radical generator) was 100 or less, high crosslinking performance sufficient to pass the hot set test was obtained even when the crosslinking time was 36 hours. On the other hand, when the weight ratio (silane compound / free radical generator) is less than 25, the extruded appearance of the insulator 2 is slightly deteriorated.
As a result, it was shown that the weight ratio (silane compound / free radical generator) is preferably in the range of 25 to 100 in order to achieve both the appearance and the crosslinking rate.

1 Conductor 2 Insulator 3 Sheath 10 Cable

Claims (5)

In a cable in which an insulator is provided on the outer peripheral side of the conductor and a sheath is provided on the outer peripheral side of the insulator,
The insulator is a Sn-free silane-crosslinked polyolefin composition. In the silane-crosslinked polyolefin composition, the alkylated naphthalene sulfonic acid is 0.1 to 1 with respect to 100 parts by weight of the polyolefin contained in the silane-crosslinked polyolefin composition. Part by weight,
The sheath is a Sn-free polyvinyl chloride composition, and in the polyvinyl chloride composition, alkylated naphthalene sulfonic acid is 0.1% with respect to 100 parts by weight of polyvinyl chloride contained in the polyvinyl chloride composition. A cable comprising: 3 parts by weight, 30 to 100 parts by weight of a plasticizer having a polar group and a nonpolar group, and 2.5 to 8 parts by weight of a stabilizer. The cable according to claim 1, wherein the density of the polyolefin is 0.920 g / cm ³ or less.   The silane compound is contained in an amount of 1.5 to 5 parts by weight with respect to 100 parts by weight of the polyolefin, and the weight ratio of the silane compound to the free radical generator (silane compound / free radical generator) is 25 to 25 parts. The cable according to claim 1, wherein the cable is 100. The alkylated naphthalene sulfonic acid in the insulator and the sheath is substituted with 1-2 sulfo groups, and is substituted with 1-4 alkyl groups;
The alkyl group is a straight chain or branched chain alkyl group having 5 to 20 carbon atoms,
The total number of carbon atoms in all substituted alkyl groups is 12 to 80;
The cable according to claim 1, wherein when there are a plurality of the alkyl groups, the types of the alkyl groups are different from each other. An insulator coating step of coating a conductor with a Sn-free insulator containing a polyolefin, a silane compound, a free radical generator, and an alkylated naphthalenesulfonic acid;
After the insulator coating step, a sheath coating step of covering the insulator with a Sn-free sheath containing polyvinyl chloride and alkylated naphthalenesulfonic acid;
After the sheath covering step, an insulator crosslinking step for performing silane crosslinking on the insulator;
Have
In the insulator coating step, the insulator is prepared by adding 0.1 to 1 part by weight of alkylated naphthalenesulfonic acid to 100 parts by weight of polyolefin,
In the sheath coating step, a plasticizer having a polar group and a nonpolar group is added to polyvinyl chloride, and alkylated naphthalenesulfonic acid is added in an amount of 0.1 to 3 with respect to 100 parts by weight of the polyvinyl chloride. A method for producing a cable, wherein the sheath is prepared by adding 30 to 100 parts by weight of a plasticizer having parts by weight, a polar group and a nonpolar group, and 2.5 to 8 parts by weight of a stabilizer.

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