Non-halogen resin composition, method for producing a silane-crosslinkable resin composition, electric wire and cable, and method for producing the same

Abstract

To provide a non-halogen resin composition which enables formation of a coating layer that can achieve both suppression in fusion of resin cured products at a use environmental temperature, and high flexibility of the resin cured products, and a wire / cable using the same.SOLUTION: A non-halogen resin composition contains a base polymer containing a high melting point non-halogen resin which contains an ethylene-ethyl acrylate copolymer and has a melting point of higher than 90°C, and an ethylene-α-olefin copolymer having a melting point of 70°C or lower, an aluminum hydroxide, and a silane compound for imparting silane crosslinkability to the base polymer, wherein 35 mass% or more and 65 mass% or less of the high melting non-halogen resin and the ethylene-α-olefin copolymer are contained in the base polymer, and 30 pts.mass or more and 150 pts.mass or less of the aluminum hydroxide is contained with respect to 100 pts.mass of the base polymer. The cable 1 has a conductor 2, an insulating layer 3 and a coating layer 4, and the coating layer 4 is composed of a resin cured product of the non-halogen resin composition.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a non-halogen resin composition, a method for producing a silane-crosslinkable resin composition, an electric wire and a cable, and a method for producing the same.

Background Art

[0002] In recent years, with the increasing awareness of environmental problems, non-halogen materials that do not contain halogen elements such as fluorine, chlorine, and bromine, which may generate harmful gases during combustion, have been widely used as coating materials for electric wires and cables. Furthermore, electric wires and cables are generally required to be flexible from the viewpoint of handleability. Since cables are thicker than electric wires in terms of structure and may have a high load depending on the conductor size, it is preferable to apply a flexible low-melting non-halogen resin as this coating material. As such low-melting non-halogen resins, ethylene-vinyl acetate copolymers, ethylene-α-olefin copolymers, etc. are known.

[0003] In addition, the coating material for electric wires and cables is generally subjected to a crosslinking treatment to chemically bond between molecules in order to impart heat resistance and toughness. As this crosslinking treatment, a continuous crosslinking extrusion method in which a coating extruder and a crosslinking tube are connected, an electron beam crosslinking method using an electron beam, a silane crosslinking method in which a silane coupling agent grafted to a resin is bonded with water, etc. are put into practical use. Among these, the silane crosslinking method is very useful from the economic and environmental viewpoints because it does not require large-scale dedicated equipment or large amounts of energy.

[0004] For example, a crosslinking method of a polyolefin-based resin is known in which a composition obtained by adding a radical generator and a silane compound to a polyolefin-based resin is subjected to a graft reaction and crosslinked by contacting with water under the action of a silanol condensation catalyst (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, a cable with a large conductor cross-sectional area has a relatively large current flowing through it during use. In some cases, the outer peripheral temperature of the cable rises to about 90°C due to significant conductor heating. For this reason, in the case of a cable coated with a low melting point non-halogen resin having a melting point lower than the use environment temperature, especially when cables with a large self-weight are laid multiple times and a large current is passed through, the surfaces of the cables (the resin cured products) may fuse together.

[0007] To address this problem, it is conceivable to replace the low melting point non-halogen resin, which is the cause of fusion, with a non-halogen resin having a melting point exceeding the use environment temperature. However, if such a replacement is simply made, although the fusion between the resin cured products within the use environment temperature can be suppressed, usually, the flexibility of the resin cured products is significantly impaired.

[0008] An object of the present invention is to provide a non-halogen resin composition capable of forming a coating layer that enables both suppression of fusion between resin cured products at or below the use environment temperature (90°C or below) and high flexibility of the resin cured products, and a wire or cable having a coating layer using the same. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

Means for Solving the Problems

[0009] Among the embodiments disclosed in the present application, the outline of typical ones will be briefly described as follows.

[0010] The non-halogen resin composition of the present invention comprises a high melting point non-halogen resin having a melting point exceeding 90 °C, which contains an ethylene-ethyl acrylate copolymer, and a base polymer containing an ethylene-α-olefin copolymer having a melting point of 70 °C or lower, aluminum hydroxide as a flame retardant, and a silane compound for imparting silane crosslinkability to the base polymer. The non-halogen resin and the ethylene-α-olefin copolymer are each contained in the base polymer in an amount of 35% by mass or more and 65% by mass or less, and the aluminum hydroxide is contained in an amount of 30 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the base polymer.

[0011] The method for producing a silane crosslinkable resin composition of the present invention comprises a step of kneading a base polymer containing a high melting point non-halogen resin having a melting point exceeding 90 °C, which contains an ethylene-ethyl acrylate copolymer, and an ethylene-α-olefin copolymer having a melting point of 70 °C or lower, aluminum hydroxide as a flame retardant, a silane compound, and a peroxide at a temperature equal to or higher than the melting point of the base polymer and lower than the decomposition temperature of the peroxide, and a step of heating to a temperature equal to or higher than the decomposition temperature of the peroxide after the kneading and introducing the silane compound into the base polymer by a graft reaction. The non-halogen resin and the ethylene-α-olefin copolymer are each contained in the base polymer in an amount of 35% by mass or more and 65% by mass or less, and the aluminum hydroxide is contained in an amount of 30 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the base polymer.

[0012] The electric wire or cable of the present invention has a conductor and a coating layer that coats and protects the conductor, and is characterized in that the coating layer is a cured product of the resin composition.

[0013] The method for manufacturing an electric wire or cable of the present invention includes a step of graft-treating and introducing a silane compound in the above non-halogen resin composition into a base polymer to obtain a silane crosslinkable resin composition, and extruding and coating the outer periphery of a conductor with the silane crosslinkable resin composition and a resin composition containing a silane crosslinking catalyst, and a step of curing the silane crosslinkable resin composition by silane crosslinking in the presence of the silane crosslinking catalyst and moisture, and is characterized by having the above steps. [Advantages of the Invention]

[0014] According to the non-halogen resin composition, electric wire / cable, and manufacturing method thereof of the present invention, it is possible to provide a non-halogen resin composition capable of forming a coating layer that enables both suppression of fusion between resin cured products at the use environment temperature (90°C or lower) and high flexibility of the resin cured products, and an electric wire / cable using the same.

[0015] Further, according to the method for manufacturing a silane crosslinkable resin composition of the present invention, it is possible to provide a silane crosslinkable resin composition capable of forming the coating layer of the above electric wire / cable. [Brief Description of the Drawings]

[0016]

Figure 1

Figure 2

[0017] Hereinafter, embodiments will be described in detail with reference to the drawings. In all the drawings for explaining the embodiments, members having the same function are denoted by the same reference numerals, and repeated explanations thereof are omitted. Further, in the following embodiments, explanations of the same or similar parts are not repeated in principle unless particularly necessary.

[0018] [Non-Halogen Resin Composition] The non-halogen resin composition according to this embodiment is a non-halogen resin composition containing a high melting point non-halogen resin having a melting point exceeding 90°C and containing an ethylene-ethyl acrylate copolymer, and a base polymer containing an ethylene-α-olefin copolymer having a melting point of 70°C or lower, aluminum hydroxide as a flame retardant, and a silane compound for imparting silane crosslinkability to the base polymer. Hereinafter, the components constituting this non-halogen resin composition will be described in detail respectively.

[0019] (Base polymer) The base polymer in this embodiment comprises a high melting point non-halogen resin having a melting point exceeding 90°C and containing an ethylene-ethyl acrylate copolymer, and an ethylene-α-olefin copolymer having a melting point of 70°C or lower.

[0020] The high melting point non-halogen resin used here has a melting point exceeding 90°C, and any non-halogen resin containing at least an ethylene-ethyl acrylate copolymer may be used. Here, having a melting point exceeding 90°C means that the resin constituting this high melting point non-halogen resin has a melting point exceeding 90°C. Here, the melting point of the high melting point non-halogen resin is preferably in the range of 90 to 110°C.

[0021] Since the ethylene-ethyl acrylate copolymer does not melt the crystalline component at 90°C and does not have an excessively high melting point (about 100°C), it is a component that plays a role in suppressing fusion in an environment of about 90°C and does not make the whole resin composition excessively hard. In addition, since it contains an acrylic group which is a polar group in the molecule, an improvement in oil resistance can also be expected.

[0022] Also, by using the ethylene-ethyl acrylate copolymer as the main component, for example, effects such as reducing the odor derived from the acetic acid component like the conventionally known ethylene-vinyl acetate copolymer, and enabling comfortable use even in applications with human contact can be expected. In this embodiment, it is preferably free of ethylene-vinyl acetate copolymer.

[0023] Here, as the high melting point non-halogen resin, in addition to the ethylene-ethyl acrylate copolymer, any non-halogen resin material having a melting point exceeding 90°C can be contained without any limitation. For example, resins having a hydrocarbon in a part of the molecular structure such as a molecular backbone or a molecular side chain and not containing halogen elements such as fluorine, chlorine, and bromine in the molecular structure can be exemplified.

[0024] Examples of high melting point non-halogen resins other than the ethylene-ethyl acrylate copolymer include, for example, ethylene-methyl acrylate copolymer, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, thermoplastic elastomer, polyamide-based polymer, or modified products thereof (for example, those obtained by modifying a part of the molecular structure with maleic acid or a silane coupling agent, etc.). These can be used alone or in a mixture of two or more.

[0025] Note that as the high melting point non-halogen resin, it is preferable to use the ethylene-ethyl acrylate copolymer alone. When using a high melting point non-halogen resin other than the ethylene-ethyl acrylate copolymer in combination, it is preferable to contain 50% by mass or more of the ethylene-ethyl acrylate copolymer in the high melting point non-halogen resin, and more preferably 80% by mass or more.

[0026] Next, the ethylene-α-olefin copolymer having a melting point of 70°C or lower contained in the base polymer is a copolymer of ethylene and α-olefin and is a compound having a melting point of 70°C or lower.

[0027] As the α-olefin component in this ethylene-α-olefin copolymer, there is no particular limitation as long as it is an α-olefin. For example, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. can be mentioned. Among them, in the application of coating materials for electric wires and cables, non-polar monomers such as 1-butene and 1-octene are preferred. This is because, for example, when having a polar group such as vinyl acetate like the conventionally known ethylene-vinyl acetate copolymer (EVA), it is necessary to pay attention to electrical insulation because the content of the polar group becomes high.

[0028] Also, the above-mentioned high melting point non-halogen resin and ethylene-α-olefin copolymer are each contained in the base polymer in an amount of 35% by mass or more and 65% by mass or less. By setting the content within this range, the fusion phenomenon can be suppressed and the desired flexibility and electrical insulation can be ensured at temperatures below the use environment temperature (90°C). Furthermore, it is preferable that the high melting point non-halogen resin is 35 - 50% by mass and the ethylene-α-olefin copolymer is 50 - 65% by mass. In this case, it can have a higher degree of flexibility and electrical insulation.

[0029] (Flame retardant) The flame retardant in this embodiment uses aluminum hydroxide. Aluminum hydroxide is preferred because it has a high flame retardant effect and does not generate deliquescent metal salts even when nitrogen oxides (NOx) and sulfur oxides (SOx) are present in the use environment atmosphere.

[0030] The aluminum hydroxide is not particularly limited as long as it can be used as a known flame retardant, and it may be surface-treated or not surface-treated. Examples of the surface treatment include fatty acid treatment and treatment with a silane coupling agent, etc., and fatty acid treatment is preferred.

[0031] Aluminum hydroxide whose surface is treated with fatty acids generally has increased affinity and dispersibility to the base polymer, thereby improving the flame retardancy, mechanical properties, etc. in the resin composition. As the fatty acid used for the surface treatment, a higher fatty acid having about 10 or more carbon atoms may be used, and any of saturated fatty acids and unsaturated fatty acids can be used. Specifically, examples of higher saturated fatty acids include lauric acid, palmitic acid, stearic acid, and arachidic acid, and examples of higher unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, myristoleic acid, palmitoleic acid, and eicosenoic acid, diunsaturated fatty acids such as linoleic acid, and triunsaturated fatty acids such as linolenic acid. In particular, stearic acid and oleic acid are widely used and preferred. These fatty acids are not limited at all and can be used alone or in combination.

[0032] The addition amount of aluminum hydroxide is preferably 30 to 150 parts by mass, more preferably 50 to 100 parts by mass, based on 100 parts by mass of the base polymer. By setting the content within such a range, it becomes possible to highly exhibit the flame retardancy, flexibility, and electrical insulation properties required for wire and cable coating materials.

[0033] (Silane compound) The silane compound in this embodiment is a compound for imparting silane crosslinkability by bonding to the resin constituting the base polymer by a graft reaction.

[0034] As this silane compound, any compound that can be bonded to the base polymer by a graft reaction to impart silane crosslinkability can be used without particular limitation, and examples thereof include silane coupling agents.

[0035] The silane coupling agent may be any one having a carbon-carbon double bond in its molecular structure. Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, etc. can be cited.

[0036] As the silane coupling agent, from the viewpoints of particularly excellent safety (high flash point) and economic efficiency during production, those containing a methacryl group are effective. Specific examples of this silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane. From the viewpoint of reactivity, 3-methacryloxypropyltrimethoxysilane is particularly preferred.

[0037] The addition amount of the silane compound is preferably 0.1 to 20 parts by mass, more preferably 1 to 10 parts by mass, based on 100 parts by mass of the base polymer. By setting the content within such a range, the silane compound can be introduced and sufficiently cured by silane crosslinking described later in the base polymer.

[0038] In addition, in order to subject the above-described silane compound to a graft reaction with the base polymer, for example, a peroxide may be contained. As the peroxide, those having a relatively high hydrogen abstraction ability and a half-life temperature of 120°C to 200°C for 1 minute (more preferably 150°C to 200°C in terms of production) are not problematic. Specifically, dicumyl peroxide, 1,1-di(t-butylperoxy)cyclohexane, 1,3-Bis(t-butylperoxyisopropyl)benzene, t-butylperoxyisopropyl carbonate, t-amylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, di-t-butyl peroxide, di-t-amyl peroxide, 1,1-di(t-amylperoxy)cyclohexane, t-butylperoxy-2-ethylhexyl carbonate, etc. can be used alone or in combination of two or more, but are not limited thereto.

[0039] The addition amount of the peroxide is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the base polymer, and more preferably 0.1 to 0.8 part by mass particularly when a silane coupling agent containing a methacryl group is used. By setting the content within such a range, the silane compound can be introduced and sufficiently cured by silane crosslinking described later in the base polymer.

[0040] In addition, the (grafted) base polymer obtained by the above graft reaction can contain a crosslinking catalyst in the resin composition in order to improve the crosslinking rate when subjecting it to silane crosslinking. Since the crosslinking starts when the crosslinking catalyst is present, it is preferably added at the timing of the crosslinking reaction.

[0041] Examples of the crosslinking catalyst include, specifically, elements containing metals such as Group II metals like magnesium and calcium, Group VIII metals like cobalt and iron, or metals such as tin, zinc, and titanium, metal compounds, metal salts of octylic acid or adipic acid, amine compounds, acids, etc. More specifically, dioctyltin dineodecanoate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, stannous caprylate, lead naphthenate, zinc caprylate, cobalt naphthenate, ethylamine, dibutylamine, hexylamine, pyridine, inorganic acids such as sulfuric acid and hydrochloric acid, organic acids such as toluenesulfonic acid, acetic acid, stearic acid, and maleic acid, etc.

[0042] The addition amount of the crosslinking catalyst is preferably 0.01 to 0.5 parts by mass, more preferably 0.02 to 0.1 parts by mass, based on 100 parts by mass of the base polymer. By setting the content within such a range, the silane compound introduced into the base polymer can be efficiently subjected to a crosslinking reaction to obtain a resin cured product.

[0043] Furthermore, as the non-halogen resin composition of this embodiment, known additive components can be blended within a range that does not inhibit the action of this embodiment. Examples of this additive component include, for example, antioxidants, lubricants, flame retardants, colorants, etc.

[0044] Examples of the antioxidant include, for example, phenolic antioxidants, sulfur-based antioxidants, phenol / thioester-based antioxidants, amine-based antioxidants, phosphorous acid-based antioxidants, etc.

[0045] Examples of the lubricant include, for example, fatty acid amide (amide)-based, zinc stearate, silicone, hydrocarbon-based, ester-based, alcohol-based, metal soap-based, etc.

[0046] Examples of the flame retardant include flame retardants other than the above aluminum hydroxide, such as metal hydroxides other than aluminum hydroxide, halogen-based, phosphorus-based, antimony-based flame retardants, etc.

[0047] As colorants, for example, when applied to electric wires and cables, the hue of the cured resin is often selected from black, yellow, and green. In this case, the colorant may be blended so as to obtain the above hue. As such colorants, for example, carbon black, inorganic pigments, organic pigments, or dyes can be used.

[0048] [Silane crosslinkable resin composition] The silane crosslinkable resin composition of the present embodiment is a resin composition obtained by graft-treating a silane compound onto a base polymer in the non-halogen resin composition described above.

[0049] This graft treatment can be carried out, for example, by kneading a resin composition containing a high melting point non-halogen resin having a melting point exceeding 90 °C and containing an ethylene-ethyl acrylate copolymer and an ethylene-α-olefin copolymer having a melting point of 70 °C or lower, aluminum hydroxide as a flame retardant, a silane compound for imparting silane crosslinkability to the base polymer, and a peroxide at a temperature equal to or higher than the melting point of the base polymer and lower than the decomposition temperature of the peroxide, and after kneading, heating to a temperature equal to or higher than the decomposition temperature of the peroxide to introduce the silane compound into the base polymer by a graft reaction.

[0050] When producing a silane crosslinkable resin composition by the above graft treatment, first, the base polymer is melted, and aluminum hydroxide, which is a flame retardant, a silane compound, and a peroxide are kneaded in advance at a temperature lower than the decomposition temperature of the peroxide. Then, by heating and kneading to a temperature equal to or higher than the decomposition temperature of the peroxide to graft the silane compound onto the base polymer, it is possible to avoid applying an excessive amount of heat to the resin composition during or after the graft treatment.

[0051] If aluminum hydroxide is kneaded during graft treatment or at a high temperature after grafting, it may cause early cross-linking (originally cross-linking during wire and cable coating) to form in the resin composition, and the moldability during extrusion coating may be significantly reduced. Kneading aluminum hydroxide in a separate process after graft treatment or mixing aluminum hydroxide during extrusion coating is not economical and is not practical from the perspective of the homogeneous dispersibility of aluminum hydroxide.

[0052] Here, the decomposition temperature of the peroxide is defined as the temperature 30°C lower than the one-minute half-life temperature of the peroxide. That is, during kneading, by setting the temperature below the decomposition temperature of the peroxide, the components formulated as the temperature at which thermal decomposition of the peroxide is unlikely to occur are sufficiently kneaded, and then, in order to cause a graft reaction, heating is carried out above the decomposition temperature of the peroxide to decompose the peroxide and efficiently graft the base polymer.

[0053] At this time, the temperature of the graft treatment is preferably set to be equal to or higher than the one-minute half-life temperature of the peroxide. Also, the time of the graft treatment is preferably 3 times or more, more preferably 4 times or more, even more preferably 5 times or more, and particularly preferably 6 times or more the time it takes for the peroxide to decay (the half-life time of the peroxide) at the temperature of the graft treatment.

[0054] [Resin cured product] The silane-crosslinkable resin composition obtained as described above can be further made into a resin cured product by silane-crosslinking the base polymer grafted with a silane compound. Silane crosslinking can be formed by reacting the silyl group of the silane compound introduced into the base polymer in the presence of a silane crosslinking catalyst and moisture, whereby polymer molecules are crosslinked (cured) to obtain a resin cured product.

[0055] Therefore, the resin cured product obtained here is a resin cured product obtained by crosslinking a so-called non-halogen resin composition (the above non-halogen resin composition) in which halogen elements such as chlorine and bromine are not intentionally added to the resin itself or the compounding additives by the silane crosslinking method.

[0056] This resin cured product is a high melting point non-halogen resin containing an ethylene-ethyl acrylate copolymer having a melting point exceeding 90°C, an ethylene-α-olefin copolymer having a melting point of 70°C or lower and particularly excellent flexibility, and aluminum hydroxide having a high flame retardant effect and not generating deliquescent metal salts even when nitrogen oxides (NOx) and sulfur oxides (SOx) are present in the use environment atmosphere, each mixed in an appropriate amount. Therefore, when applied to a cable, even when the use environment temperature on the outer periphery of the cable is about 90°C, the resin cured product can maintain flexibility, flame retardancy, and moisture resistance while highly suppressing fusion at the use environment temperature.

[0057] Also, in this resin cured product, by suppressing the tensile peel strength after heat and pressure adhesion treatment at 90°C to 5 N or less, even if a fusion phenomenon occurs between the resin cured products, it can be peeled off with a very small force, and no fusion marks remain on the surface of the resin cured product after peeling, and the appearance is not damaged. Therefore, this resin composition does not cause problems in actual use as a coating layer of a cable.

[0058] Here, as specific pressurization conditions, about 3 MPa shown in this example is sufficient, and no change in adhesion density was observed even when processed at a pressure higher than this. Since there is a concern that the resin cured product becomes extremely thin and perforates when pressurized exceeding 5 MPa, it can be said that molding at 3 to 5 MPa is appropriate. In this specification, the tensile peel strength is the tensile peel strength of a sample obtained by pressure fusion of a resin cured product at 90°C, 3 MPa, and for 1 hour using a press machine.

[0059] In this resin cured product, the tensile strength at 100% elongation is preferably 7 MPa or less, and more preferably less than 6.5 MPa. This tensile strength is obtained by punching out a resin cured product cut to a thickness of 1 mm into the shape of a JIS No. 3 dumbbell piece, marking scale lines at an interval of 20 mm in the central part, measuring the tensile load at the time when the distance between the scale lines has elongated by 100% under the condition of a tensile speed of 200 mm / min, and using the following formula. δ = F / A (δ: Tensile strength (MPa), F: Tensile load (N), A: Cross-sectional area of test piece (mm 2 ))

[0060] In addition, in this cured resin, its oxygen index is preferably 21 or more, and more preferably 22 or more. The oxygen index represents the minimum oxygen concentration (volume %) required for the material to sustain combustion and serves as an index for evaluating the flammability of the material. This oxygen index is determined in accordance with JIS K 7201-2 (2007).

[0061] Furthermore, in this cured resin, its volume resistivity is preferably 5.0×10 14 Ω·cm or more, and more preferably 1.0×10 15 Ω·cm or more. This volume resistivity is used to evaluate the electrical insulation of the cured resin and can be obtained from the current value after applying a voltage under predetermined conditions using an ultra-high insulation resistance measuring instrument.

[0062] As described above, by setting the formulation of the resin composition to a predetermined one, it is possible to obtain good flame retardancy and electrical insulation required for the coating material of electric wires and cables. Specifically, it is preferable that these properties are within the above-specified ranges of the oxygen index and volume resistivity, respectively.

[0063] [Electric wire and cable] The electric wire and cable in this embodiment has a conductor and a coating layer that coats and protects the conductor, and the coating layer is made of the cured resin of the non-halogen resin composition of this embodiment described above. The coating layer can directly coat the conductor to form an electric wire, or can indirectly coat the conductor on an insulating layer that coats the conductor to form a cable.

[0064] A cross-sectional view of the cable according to an embodiment of the present invention is shown in FIG. 1. As shown in FIG. 1, the cable 1 is composed of a conductor 2, an insulating layer 3, and a coating layer 4.

[0065] The conductor 2 can be a commonly used metal wire. For example, a copper wire, a copper alloy wire, an aluminum wire, a gold wire, a silver wire, etc. can be used. Further, as the conductor 2, a metal wire with a metal plating such as nickel applied around it may be used. Furthermore, as the conductor 2, a stranded conductor formed by stranding metal wires can also be used.

[0066] The insulating layer 3 only needs to be formed of an insulating material commonly used for cables and is not particularly limited. Examples of the insulating material for this insulating layer 3 include polyvinyl chloride, fluororesin, crosslinked polyethylene, natural rubber, synthetic rubber, etc.

[0067] The coating layer 4 is formed of a resin cured product of the non-halogen resin composition described in the above-described embodiment.

[0068] As a method for manufacturing this cable, the cable 1 can be manufactured by coating the outer periphery of the insulating layer 3 formed on the conductor 2 with the above-described non-halogen resin composition using an extruder. More specifically, in the extrusion coating process, a so-called two-shot silane crosslinking manufacturing method can be used in which a silane crosslinkable resin composition graft-treated with a silane compound and a resin composition containing a crosslinking catalyst are mixed. After the extrusion coating process, the final product can be obtained by allowing natural storage or placing it in a steam chamber at 100°C or lower to supply moisture to the coating material to advance the silane crosslinking reaction.

[0069] FIG. 2 is a diagram showing a schematic configuration of an extruder for manufacturing a cable in the present embodiment. As shown in FIG. 2, the extruder 11 includes a cylinder 20, a screw 13 rotatably provided in the cylinder 20, a hopper 12 for supplying a material into the cylinder 20, and a crosshead 16. Further, the extruder 11 includes a neck 15 between the crosshead 16 and the screw 13, and a breaker plate 14 between the neck 15 and the screw 13. The crosshead 16 has a die 17, and an electric wire 18 (a conductor covered with an insulator) passing through the crosshead 16 is covered with a sheath in the crosshead 16 and drawn out from the crosshead 16 as a cable 19 through the die 17.

[0070] The resin composition containing the crosslinking catalyst used here may be formed by mixing the crosslinking catalyst and the base resin. The base resin used here is not particularly limited as long as it does not inhibit the effects of the present invention, and it is preferably selected from the high melting point non-halogen resin and the ethylene-α-olefin copolymer described in the above resin composition. In addition to the base resin and the crosslinking catalyst, an antioxidant, a copper poisoning inhibitor, and the like can also be included.

[0071] Examples of the antioxidant include phenolic compounds such as 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (CAS No. 27676-62-6), pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS No. 6683-19-8), n-octadecyl 3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate (CAS No. 2082-79-3); amine compounds such as poly(1,2-dihydro-2,2,4-trimethylquinoline) (CAS No. 26780-96-1), ethoxyquin (CAS No. 91-53-2), 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (CAS No. 10081-67-1), N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (CAS No. 793-24-8); sulfur compounds such as pentaerythritol tetrakis[3-(dodecylthio)propionate (CAS No. 29598-76-3), ditridecyl 3,3'-thiobispropionate (CAS No. 10595-72-9), didodecyl 3,3'-thiobispropionate (CAS No. 123-28-4), dioctadecyl 3,3'-thiobispropionate (CAS No. 693-36-7); phenol-sulfur compounds such as 4,4'-thiobis(6-tert-butyl-m-cresol) (CAS No. 96-69-5); benzimidazole compounds such as 2-mercaptobenzimidazole (CAS No. 583-39-1); thiourea compounds such as 1,3,3-tributylthiourea (CAS No. 2422-88-0). These are not limited in their addition methods, such as being used alone, used in combination of two or more types, used as a mixture, or used as a masterbatch mixed with a non-halogen resin.

[0072] As a copper corrosion inhibitor, common heavy metal inactivators can be used. Specifically, compounds such as N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (CAS No. 32687-78-8), N-(2H-1,2,4-triazol-5-yl)salicylamide (CAS No. 36411-52-6), dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazide] (CAS No. 63245-38-5) can be mentioned. These can be in the form of a single substance or a mixture with other compounds, and their usage conditions are not limited.

[0073] The cable thus obtained is a cable having the configuration shown in FIG. 1, and its size is not particularly limited. For example, as an example, the diameter of the conductor 2 is 10.4 mm, the diameter including the insulating layer 3 is 13.4 mm, and the diameter of the cable 4 is 36 mm.

Examples

[0074] Next, this embodiment will be described in detail with reference to examples and comparative examples.

[0075] [Examples 1 to 10, Comparative Examples 1 to 5] The kneading of the silane coupling agent and various additives into the base polymer, the silane graft treatment, the preparation of the crosslinking catalyst masterbatch, and further the production of the cable using each of the prepared compounds and the crosslinking treatment were carried out as follows. The following conditions are an example and are not limited in any way.

[0076] (Preparation of the resin composition and graft treatment) Into a pressure kneader with a capacity of 25 L (the kneader tank is set to a temperature equal to or higher than the melting point of the base polymer and lower than the decomposition temperature of the peroxide), based on the formulations shown in Tables 2 to 3, a base polymer, a silane coupling agent, a peroxide, a flame retardant, an antioxidant, a lubricant, and a colorant were charged and kneaded under pressure at a rotor rotation speed of 10 rpm for 10 minutes. Here, by previously dissolving the peroxide in the silane coupling agent, the dispersibility of the peroxide in the polymer can be improved. When charging, by immersing the silane coupling agent (dissolving the peroxide) in fillers such as the flame retardant, adsorption of the silane coupling agent to the kneader tank can be reduced. These conditions are just examples and are not limiting. For example, additives for expressing desired properties in the resin composition such as fillers and plasticizers may be added.

[0077] The graft treatment of the silane coupling agent is continuously carried out after pressure kneading. Specifically, the kneading temperature is raised until it reaches a temperature equal to or higher than the decomposition temperature of the peroxide (practically, higher than the one-minute half-life temperature), and kneading is continued until the peroxide is sufficiently decomposed. As the time for the peroxide to be sufficiently decomposed, it may be set to 6 times or more the half-life time of the peroxide at the kneading temperature. In this example and the comparative example, the graft treatment was carried out by raising the temperature to 180 °C for peroxide decomposition and holding at this temperature for 4 minutes. After the graft treatment, the material is quickly discharged from the kneader tank, extruded into strands, water-cooled, and then pelletized to produce pellets of the silane graft composition. Here, the granulation method is not limited to the above. For example, pellets may be produced using hot cut equipment without water cooling. Also, a release agent can be used to prevent adhesion between the pellets. The release agent may be in any form such as its components, powder, liquid, mist, etc. For example, considering economy, using talc, etc. is effective.

[0078] (Preparation of Crosslinking Catalyst Masterbatch) Note that the crosslinking catalyst masterbatch in Tables 2 to 3 was prepared as follows according to the formulation shown in Table 4.

[0079] A polymer (non-halogen resin), a crosslinking catalyst (silanol condensation catalyst), an antioxidant, and a copper poisoning inhibitor were kneaded in a 25-L pressure kneader (the kneader tank was above the melting point of the base polymer) at a rotor rotation speed of 20 rpm for 5 minutes. After kneading, the material was discharged from the kneader tank, extruded into strands, water-cooled, and pelletized to produce crosslinking catalyst masterbatch pellets.

[0080] Here too, the granulation method is not limited to the above. For example, pellets may be produced using hot cut equipment without water cooling. Also, a release agent can be used to prevent adhesion between the pellets.

[0081] (Manufacture and Crosslinking Treatment of Cables) In this example and comparative examples, the extruder 11 shown in Fig. 2 was used to manufacture cables as follows. Table 1 shows the extrusion conditions in the cable extrusion process. At this time, cylinders 1 to 5 are connected from the hopper side to the head side in this order to form cylinder 20, and the relationship between the length (L) and inner diameter (D) of cylinder 20 is expressed as L / D.

[0082] A conductor with a cross-sectional area of 100 mm 2 On a conductor (outer diameter 15.2 mm) formed by twisting a plurality of tinned soft copper wires, an ethylene-propylene rubber copolymer mixture was extruded and coated with a thickness of 2.0 mm as an insulator and crosslinked. Then, a dry blend of the resin composition (silane crosslinkable resin composition) after the graft treatment obtained above, a crosslinking catalyst masterbatch, and a pigment masterbatch (in cases other than black) was extruded and coated with a thickness of 2.6 mm using a single-screw extruder with a screw diameter of 90 mm to produce a cable having the configuration shown in Fig. 1. The produced cable was subjected to a crosslinking treatment by storing it in a saturated steam atmosphere at 60°C for 24 hours to obtain the final product.

[0083] In order to achieve the above kneading and grafting processes, any kneading and reaction apparatuses generally used, such as roll machines, extruders, mixers, and autoclaves, other than kneaders, are not particularly limited. Also, the kneading and grafting process conditions are not limited to the above in any way. Similarly, cable manufacturing is just an example. It may be formed into a wire shape by performing extrusion coating directly on the conductor. Moreover, the extruder, cable core, cable structure, and crosslinking process conditions are not limited to the above in any way.

[0084]

Table 1

[0085] [Evaluation of Properties] The kneaded compound and the cable after crosslinking treatment produced were evaluated as follows. The evaluation results are shown together in Tables 2 - 3.

[0086] [Peelability between Materials and between Cables] Here, the peelability of the material and the cable surface is evaluated by the peelability when they are brought into contact at 90°C (the material exposure temperature under normal use conditions).

[0087] The silane-grafted silane crosslinkable resin composition, crosslinking catalyst masterbatch, and pigment masterbatch were kneaded using a roll machine, and a 1 mm thick sheet was molded using a press machine. The obtained sheet was crosslinked by storing it in a 60°C saturated steam atmosphere for 24 hours, which is the same as the cable crosslinking conditions. The crosslinked sheet was cut into strips of 10 mm × 100 mm, two strips were overlapped, and a 10 mm × 60 mm portion was pressure-bonded at 90°C, 3 MPa, for 1 hour using a press machine to prepare a sample for the tensile peel test (the 10 mm × 40 mm non-bonded portion was used as the gripping part during the tensile test).

[0088] The tensile peel test was carried out by measuring the maximum load (tensile peel force) when the sample was peeled at a tensile speed of 200 mm / min using a tensilon-type tensile testing machine. The surface of the sheet after peeling was visually inspected. Those with no change before and after peeling were rated as "none" (qualified), and those with whitening on the sheet surface after peeling (change in material refractive index due to fusion) were rated as "yes" (unqualified).

[0089] Also, for the cable after crosslinking treatment, two sets of two cables cut to a length of 300 mm and fixed (contacted) with wire were prepared. These were overlapped at right angles to each other and stored in a constant temperature bath at 90°C for 24 hours to prepare samples for confirming the peelability between cables. After taking them out of the constant temperature bath and leaving them at room temperature (23°C) for 1 hour, those where the contact part of the overlapped cables could be peeled off manually without fusion and no fusion marks were visually observed on the contact part after peeling were rated as "good" (qualified), and those with fusion at the contact part or whitening marks visually observed after peeling were rated as "bad" (unqualified).

[0090] <Flexibility (Tensile strength at 100% tensile elongation)> After peeling off the cured resin from the cable sheath after crosslinking treatment, a sample with a thickness of 1 mm cut from the sheath surface was punched into the shape of a JIS No. 3 dumbbell piece, and a tensile test piece marked with scale lines at 20 mm intervals at the center was prepared. The tensile load at the time when the distance between the scale lines reached 100% elongation was measured under the condition of a tensile speed of 200 mm / min, and the tensile strength was obtained by the following formula. δ = F / A (δ: Tensile strength (MPa), F: Tensile load (N), A: Cross-sectional area of the test piece (mm 2 ))

[0091] For the evaluation, those with a tensile strength at 100% elongation less than 6.5 MPa were rated as having sufficient flexibility and marked as "◎", those with a tensile strength between 6.5 MPa and 7.0 MPa were rated as having no practical problems such as wiring work and marked as "○", and those with a tensile strength exceeding 7.0 MPa were rated as having insufficient flexibility and marked as "×". The judgment criteria were that "◎" and "○" were qualified, and "×" was unqualified.

[0092] <Flammability (Oxygen Index)> A crosslinked sheet with a thickness of 3 mm was prepared by the same production method as the sample for the peel test between the above sheets. For this sheet, the oxygen index was measured by the method shown in JIS K 7201-2 (2007) using an OXYGEN INDEXER manufactured by Toyo Seiki. Those with an oxygen index of 22 or more were marked as "◎" indicating sufficient flammability, those with an oxygen index of 21 or more and less than 22 were marked as "○" indicating a level that can be practically applied without problems for applications where flammability is required under horizontal or 60-degree inclined test conditions in the cable flammability test, and those with an oxygen index of less than 21 were marked as "×" indicating insufficient flammability. The judgment criteria were that "◎" and "○" were considered qualified, and "×" was considered unqualified.

[0093] <Electrical Insulation (Volume Resistivity)> A crosslinked sheet with a thickness of 1 mm was prepared by the same production method as the sample for the peel test between the above sheets. For this sheet, the volume resistivity was determined from the current value after applying DC 500 V for 1 minute at room temperature (23°C) using an ultra-high insulation resistance measuring instrument R8340A manufactured by ADVANTEST. Those with a volume resistivity of 1.0×10 15 Ω·cm or more were marked as "◎" indicating sufficient insulation, those with a volume resistivity of 5.0×10 14 Ω·cm or more and less than 1.0×10 15 Ω·cm were marked as "○" indicating a level that can be generally applied without problems for those other than those requiring high insulation, and those with a volume resistivity of less than 5.0×10 14 Ω·cm were marked as "×" indicating insufficient insulation. The judgment criteria were that "◎" and "○" were considered qualified, and "×" was considered unqualified.

[0094] For the comprehensive judgment, those that passed all evaluation items were considered qualified, and those that failed even one item were considered unqualified.

[0095]

Table 2

[0096]

Table 3

[0097] Among the products shown in Tables 2 to 3, "Lex Pearl A3100" (melting point 104°C, vinyl acetate content 20% by mass) is manufactured by Ube Maruzen Polyethylene Co., Ltd., "Tufmer DF840" (melting point 66°C, ethylene-1-butene copolymer), "Tufmer DF940" (melting point 77°C, ethylene-1-butene copolymer) are manufactured by Mitsui Chemicals, Inc., "Evolue SP2520" (linear low-density polyethylene) is manufactured by Japan Polyethylene Corporation, "KBM-503" (3-methacryloxypropyltrimethoxysilane) is manufactured by Shin-Etsu Chemical Co., Ltd., "DCP" (dicumyl peroxide) is manufactured by NOF Corporation, "Antioxidant A" (sulfur-based secondary antioxidant) is manufactured by ADEKA Corporation, "Crodamide EBO" (ethylene bisoleic amide) is manufactured by CRODA, "BF-013 S" (aluminum hydroxide (fatty acid surface-treated grade)) is manufactured by Nippon Light Metal Co., Ltd., "Carbon Black" (Asahi Thermal Carbon) is manufactured by Asahi Carbon Co., Ltd., "Pigment Masterbatch (Yellow)" (condensed azo-based pigment blended masterbatch), "Pigment Masterbatch (Green)" (phthalocyanine blue, monoazo yellow-based pigment mixed blended masterbatch) are manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd.

[0098] [Table 4]

[0099] Among the products shown in Table 4, "Elvaloy 1125AC" is manufactured by DOW, "Antioxidant B" (hindered phenol-based primary antioxidant), "Heavy Metal Inactivator" are manufactured by ADEKA Corporation, "Neo-Stann U-830" (dioctyltin dineodecanoate) is manufactured by Nitto Denko Corporation.

[0100] From the examples, it was shown that if a base polymer contains 35 to 65% by mass of a high melting point non-halogen resin having a melting point exceeding 90°C and 35 to 65% by mass of an ethylene-α-olefin copolymer having a melting point of 70°C or lower, and 30 to 150 parts by mass of aluminum hydroxide, which is a flame retardant, is blended with respect to 100 parts by mass of the base polymer, no fusion phenomenon that causes practical problems occurs between the sheath materials at 90°C, which is the exposure temperature of the cable sheath in the use environment, and the flexibility, flame retardancy, and electrical insulation required for the cable can be satisfied.

[0101] Furthermore, from Example 4, as the high melting point non-halogen resin having a melting point exceeding 90°C, not only a single ethylene-ethyl acrylate copolymer but also a mixture of a plurality of polymers can be used. From Examples 9 and 10, it was shown that in addition to black, which is a common hue for the coating material of electric wires and cables, yellow and green can also be used.

[0102] In particular, from Examples 1 to 3, 35 to 50% by mass of a high melting point non-halogen resin having a melting point exceeding 90°C and 50 to 65% by mass of an ethylene-α-olefin copolymer having a melting point of 70°C or lower, and from Examples 5 to 8, 50 to 100 parts by mass of aluminum hydroxide were used, it was shown that higher levels of flexibility, flame retardancy, and electrical insulation can be achieved.

[0103] Also, it was found that even when cables come into contact with each other at 90°C, if the tensile peel force between the materials is about 5.0 N or less, it can be used practically without problems.

[0104] Note that the polymers and compounding additives used in this example are just examples and are not limited in any way. Also, the above resin composition is not limited to use in the form of a cable in which a sheath is coated on the outer periphery of an insulator as fabricated this time, and can also be used as the material for the coating in a so-called insulated wire or wire, which has a structure of only a conductor and a coating material (insulator).

[0105] From Comparative Example 1, when the high melting point non-halogen resin having a melting point exceeding 90°C is 30% by mass or less and the ethylene-α-olefin copolymer having a melting point of 70°C or less is 70% by mass or more, the materials fuse together during heating at 90°C, causing the cables to stick to each other. Also, when peeled, the fused parts turn white, significantly impairing the appearance. On the other hand, as in Comparative Example 2, when the base polymer having a melting point exceeding 90°C is 70% by mass or less and the ethylene-α-olefin copolymer having a melting point of 70°C or less is 30% by mass or more, it was found that the flexibility as a cable coating material significantly decreases.

[0106] From Comparative Example 3, when the melting point of the ethylene-α-olefin copolymer exceeds 70°C, even if an appropriate amount is blended, the flexibility decreases. Therefore, in the present invention, it can be said that it is important that the melting point of the ethylene-α-olefin copolymer is 70°C or less.

[0107] From Comparative Examples 4 and 5, it was found that when the addition amount of aluminum hydroxide blended as a flame retardant is 20 parts by mass or less, the flame retardancy significantly decreases. On the contrary, when added in an amount of 180 parts by mass or more, the flexibility and electrical insulation significantly decrease.

[0108] When manufacturing large-diameter wires and cables, the continuous cross-linking extrusion method and the electron beam cross-linking method require large-scale equipment and a huge amount of applied energy. In terms of equipment maintenance and the environment, the application of the silane cross-linking method is particularly effective. According to the present invention, a non-halogen-based environmentally friendly material composition can be manufactured by a process using the silane cross-linking method. Therefore, it enables not only economic advantages but also a wide range of developments of environmentally friendly products, which will become increasingly important in the future.

[0109] As described above, the invention made by the present inventors has been specifically described based on the embodiments. However, it goes without saying that the present invention is not limited to the above embodiments and can be variously modified without departing from the gist thereof.

Explanation of Reference Numerals

[0110] 1. 19 cables 2 conductors 3 insulating layers 4 coating layers 11 extruders 12 hoppers 13 screws 14 breaker plates 15 necks 16 crossheads 17 dies 18 electric wires 20 cylinders

Claims

1. A high melting point non-halogen resin containing an ethylene-ethyl acrylate copolymer and having a melting point exceeding 90°C, a base polymer containing an ethylene-α-olefin copolymer having a melting point of 70°C or lower, aluminum hydroxide as a flame retardant, and a silane compound for imparting silane crosslinkability to the base polymer, wherein the high melting point non-halogen resin and the ethylene-α-olefin copolymer are each contained in the base polymer in an amount of 35% by mass or more and 65% by mass or less, a step of graft-treating and introducing the silane compound in the non-halogen resin composition, which contains 30 parts by mass or more and 150 parts by mass or less of aluminum hydroxide with respect to 100 parts by mass of the base polymer, into the base polymer to obtain a silane crosslinkable resin composition; a step of extruding and coating the outer periphery of a conductor with the silane crosslinkable resin composition and a catalyst-containing resin composition containing a silane crosslinking catalyst, and curing the silane crosslinkable resin composition by silane crosslinking in the presence of the silane crosslinking catalyst and moisture; A method for manufacturing an electric wire or a cable, characterized by comprising the above steps.

2. A step of kneading a base polymer containing a high melting point non-halogen resin containing an ethylene-ethyl acrylate copolymer and having a melting point exceeding 90°C, an ethylene-α-olefin copolymer having a melting point of 70°C or lower, aluminum hydroxide as a flame retardant, a silane compound for imparting silane crosslinkability to the base polymer, and a peroxide at a temperature equal to or higher than the melting point of the base polymer and lower than the decomposition temperature of the peroxide; a step of heating to a temperature equal to or higher than the decomposition temperature of the peroxide after the kneading and introducing the silane compound into the base polymer by a graft reaction; A method for manufacturing a silane crosslinkable resin composition, characterized by comprising the above steps, wherein the high melting point non-halogen resin and the ethylene-α-olefin copolymer are each contained in the base polymer in an amount of 35% by mass or more and 65% by mass or less, and the aluminum hydroxide is contained in an amount of 30 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the base polymer.

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