Resin composition, electric wire, method for producing resin composition, and method for producing electric wire

Abstract

To provide a resin composition producing less smoke when burned.SOLUTION: A resin composition comprising a first polyolefin resin grafted with silane, a second polyolefin resin not grafted with silane, and a process oil, wherein the content ratio of the process oil is 10 pts.mass or more and 35 pts.mass or less based on a total of 100 pts.mass of the first polyolefin resin and the second polyolefin resin, and wherein in an NBS smoke chamber smoke generation test, a smoke density during combustion is 150 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a resin composition, an electric wire, a method for producing a resin composition, and a method for producing an electric wire. [Background technology]

[0002] Patent Document 1 discloses a method for producing a heat-resistant resin composition, which is used for applications such as electrical wire insulators. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2013 / 147148 Summary of the Invention [Problem to be solved by the invention]

[0004] Resin compositions are used as insulating materials for electric wires for electrical equipment, and wire insulators are required to produce minimal smoke when burned.

[0005] An object of the present disclosure is to provide a resin composition that generates little smoke when burned. [Means for solving the problem]

[0006] The resin composition of the present disclosure includes a silane-grafted first polyolefin resin, a non-silane-grafted second polyolefin resin, and a process oil. The content of the process oil is 10 to 35 parts by mass per 100 parts by mass of the first and second polyolefin resins combined. The resin composition of the present disclosure exhibits a smoke density of 150 or less upon combustion in an NBS (National Bureau of Standards) smoke chamber test. [Effects of the Invention]

[0007] The resin composition of the present disclosure generates little smoke upon combustion. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the structure of an electric wire according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) The resin composition of the present disclosure comprises a silane-grafted first polyolefin resin, a non-silane-grafted second polyolefin resin, and a process oil. The content of the process oil is 10 to 35 parts by mass per 100 parts by mass of the first polyolefin resin and the second polyolefin resin combined. The resin composition of the present disclosure exhibits a smoke density of 150 or less upon combustion in an NBS smoke chamber test.

[0011] The resin composition of the present disclosure has a smoke density of 150 or less in an NBS smoke chamber smoke test, and therefore generates little smoke upon combustion. Furthermore, the resin composition of the present disclosure has excellent moldability due to the inclusion of a process oil. The moldability of the resin composition is improved by the content of the process oil being 10 parts by mass or more. The smoke generated upon combustion of the resin composition can be reduced by the content of the process oil being 35 parts by mass or less.

[0012] (2) In the resin composition of (1), the weight average molecular weight of the process oil is 0.75 × 10 3 Over 1.50 x 10 3 It may be the following:

[0013] When the weight average molecular weight of the process oil is within the above range, the moldability of the resin composition can be sufficiently maintained, and the smoke generated when the resin composition is burned can be more effectively reduced.

[0014] (3) In the resin composition of (1) or (2), the kinematic viscosity of the process oil at 40°C is 95 mm 2 / s or more 500mm 2 / s or less.

[0015] When the kinematic viscosity of the process oil is within the above range, the moldability of the resin composition can be sufficiently maintained, and the smoke generated when the resin composition is burned can be more effectively reduced.

[0016] (4) Any of the resin compositions (1) to (3) above may further contain an inorganic filler.

[0017] The resin composition (4) above can enhance the flame retardancy of the resin composition.

[0018] (5) In the resin composition of any one of (1) to (4) above, the second polyolefin resin may contain maleic anhydride-modified polyethylene.

[0019] The resin composition of (5) above can improve the tensile strength of the resin composition.

[0020] (6) In the resin composition of any one of (1) to (5) above, the second polyolefin resin may contain an ethylene acrylic acid copolymer.

[0021] The resin composition of (6) above can improve the tensile strength of the resin composition.

[0022] (7) The electric wire of the present disclosure includes a conductor and an insulator covering the conductor, the insulator being made of the resin composition according to any one of (1) to (6) above.

[0023] The electric wire of the present disclosure uses the resin composition of the present disclosure as an insulating material, and therefore generates little smoke upon combustion.

[0024] (8) A method for producing a resin composition according to the present disclosure includes the steps of: mixing a silane-grafted first polyolefin resin, a non-silane-grafted second polyolefin resin, and a process oil to obtain a resin material; mixing the resin material with a silanol condensation catalyst and then molding the mixture to obtain a molded product; and crosslinking the molded product. The process oil has a kinematic viscosity of 95 mm at 40°C. 2 / s or more 500mm 2 The process oil is mixed in a ratio of 10 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin.

[0025] The method for producing a resin composition according to the present disclosure can produce a resin composition that generates little smoke upon combustion. Furthermore, the method for producing a resin composition according to the present disclosure can easily produce a molded article from the resin composition.

[0026] (9) A method for producing an electric wire according to the present disclosure includes the steps of: mixing a silane-grafted first polyolefin resin, a non-silane-grafted second polyolefin resin, and a process oil to obtain a resin material; mixing the resin material with a silanol condensation catalyst and then coating the mixture on a conductor to form a coating layer; and crosslinking the coating layer to form an insulator. The process oil has a kinematic viscosity of 95 mm at 40°C. 2 / s or more 500mm 2 The process oil is mixed in a ratio of 10 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin.

[0027] The method for manufacturing an electric wire according to the present disclosure can manufacture an electric wire that generates less smoke upon combustion. Furthermore, the method for manufacturing an electric wire according to the present disclosure makes it easy to form an insulator.

[0028] [Details of the embodiments of the present disclosure] Specific examples of the resin composition, electric wire, method for producing the resin composition, and method for producing the electric wire according to the present disclosure are described below. The sizes of components shown in the drawings are shown for the purpose of clarifying the description and do not necessarily represent the actual dimensional relationships. It should be noted that the present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0029] <Resin composition> The resin composition according to the embodiment includes a first silane-grafted polyolefin resin, a second non-silane-grafted polyolefin resin, and a process oil. One of the features of the resin composition according to the embodiment is that the smoke density upon combustion is 150 or less in an NBS smoke chamber test.

[0030] The resin composition of the embodiment includes a first polyolefin resin and a second polyolefin resin, thereby providing both strength and flexibility. The greater the proportion of the first polyolefin resin in the resin composition, the harder the resin composition becomes, improving its strength, such as tensile strength. The greater the proportion of the second polyolefin resin in the resin composition, the softer the resin composition becomes, improving its flexibility, such as elongation. The composition of the resin composition of the embodiment will be described in detail below.

[0031] (First polyolefin resin) The first polyolefin resin is a resin composition containing a polyolefin resin, a silane coupling agent, and an organic peroxide. The first polyolefin resin is obtained by grafting a polyolefin resin with a silane coupling agent. The composition of the first polyolefin resin is described in detail below.

[0032] <Polyolefin resin> The base resin of the first polyolefin resin is, for example, at least one polyolefin resin selected from the group consisting of polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and propylene-α-olefin copolymer. These polyolefin resins may be used singly or in combination of two or more. PE may be low-density polyethylene (LDPE) or high-density polyethylene (HDPE). LDPE includes linear low-density polyethylene (LLDPE) and very low-density polyethylene (VLDPE). PE is easily silane-grafted. PE also has high heat resistance and electrical insulation. When the polyolefin resin contained in the first polyolefin resin is PE, the heat resistance and electrical insulation of the resin composition are enhanced. When the polyolefin resin is LDPE, the flexibility of the resin composition is improved.

[0033] <Silane coupling agent> Examples of silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyldimethoxyethoxysilane, vinyltributoxysilane, vinyldimethoxybutoxysilane, vinyldiethoxybutoxysilane, vinyltriacetoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, and methacryloxypropylmethyldimethoxysilane.These silane coupling agents may be used alone or in combination of two or more.

[0034] The content of the silane coupling agent may be, for example, 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the polyolefin resin in the first polyolefin resin. If the content of the silane coupling agent is too low, the crosslinking reaction of the resin composition does not proceed sufficiently. If the content of the silane coupling agent is 0.1 parts by mass or more, the crosslinking reaction proceeds easily. If an excessive amount of the silane coupling agent is contained, aggregates formed by condensation of silane coupling agents are likely to be formed. If a large amount of such aggregates are formed, there is a risk of poor appearance of the molded article when the resin composition is molded. If the content of the silane coupling agent is 5 parts by mass or less, the formation of such aggregates is unlikely, thereby reducing poor appearance of the molded article. The content of the silane coupling agent may be 0.2 parts by mass or more and 4 parts by mass or less.

[0035] <Organic peroxide> Organic peroxides are catalysts that generate radicals by thermal decomposition and promote the grafting reaction of silane coupling agents to polyolefin resins. Examples of organic peroxides include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butylcumyl peroxide. These organic peroxides may be used alone or in combination of two or more.

[0036] The content of the organic peroxide may be, for example, 0.01 to 1 part by mass per 100 parts by mass of the polyolefin resin in the first polyolefin resin. If the content of the organic peroxide is too low, the graft reaction of the silane coupling agent to the polyolefin resin does not proceed sufficiently. If the content of the silane coupling agent is 0.01 parts by mass or more, the graft reaction proceeds easily. If an excessive amount of organic peroxide is contained, the condensation reaction between the silane coupling agents proceeds too much, making it easy for the above-mentioned aggregates to be formed. Therefore, when the resin composition is molded, there is a risk of the molded article having poor appearance. If the content of the organic peroxide is 1 part by mass or less, the above-mentioned aggregates are less likely to be formed, reducing the appearance of the molded article. The content of the organic peroxide may be 0.05 to 0.5 parts by mass.

[0037] The content of the first polyolefin resin in the resin composition is, for example, 10 parts by mass or more and 60 parts by mass or less, where the total of the first polyolefin resin and the second polyolefin resin is 100 parts by mass. When the content of the first polyolefin resin is 10 parts by mass or more, the tensile strength of the resin composition is easily increased. When the content of the first polyolefin resin is 60 parts by mass or less, the flexibility of the resin composition is easily maintained. The content of the first polyolefin resin may be 15 parts by mass or more and 50 parts by mass or less, or even 20 parts by mass or more and 40 parts by mass or less.

[0038] (Second polyolefin resin) The second polyolefin resin is a polyolefin resin that is not silane-grafted. The base resin of the second polyolefin resin is, for example, at least one polyolefin resin selected from the group consisting of PE, PP, EVA, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer. These polyolefin resins may be used singly or in combination of two or more. The second polyolefin resin and the first polyolefin resin may contain the same type of polyolefin resin or different types of polyolefin resins. When the polyolefin resin contained in the second polyolefin resin is PE, the heat resistance and electrical insulation of the resin composition are enhanced. When the polyolefin resin is LDPE, the flexibility of the resin composition is improved.

[0039] The content of the second polyolefin resin in the resin composition is, for example, 40 parts by mass or more and 90 parts by mass or less, where the total of the first polyolefin resin and the second polyolefin resin is 100 parts by mass. When the content of the second polyolefin resin is 40 parts by mass or more, the flexibility of the resin composition is easily increased. When the content of the second polyolefin resin is 90 parts by mass or less, the tensile strength of the resin composition is easily maintained. The content of the second polyolefin resin may be 50 parts by mass or more and 85 parts by mass or less, or even 60 parts by mass or more and 80 parts by mass or less.

[0040] <Acid-modified polyethylene> The second polyolefin resin may contain acid-modified polyethylene. The acid-modified polyethylene is, for example, maleic anhydride-modified polyethylene. When the second polyolefin resin contains acid-modified polyethylene, the tensile strength of the resin composition can be improved.

[0041] The content of the acid-modified polyethylene is, for example, 5 parts by mass or more and 20 parts by mass or less, where the total of the first polyolefin resin and the second polyolefin resin is 100 parts by mass. When the content of the acid-modified polyethylene is within this range, the tensile strength of the resin composition is easily improved while maintaining the flexibility and heat resistance of the resin composition. The content of the acid-modified polyethylene may be 8 parts by mass or more and 16 parts by mass or less.

[0042] (Ethylene acrylic acid copolymer) The second polyolefin resin may contain ethylene acrylic acid copolymer (EEA), which can improve the tensile strength of the resin composition.

[0043] The content of EEA is, for example, 10 to 40 parts by mass, where the total of the first polyolefin resin and the second polyolefin resin is 100 parts by mass. When the content of EEA is within this range, the tensile strength of the resin composition is easily improved while maintaining the flexibility and heat resistance of the resin composition. The content of EEA may be 10 to 30 parts by mass, or even 15 to 25 parts by mass.

[0044] (process oil) The process oil not only improves the flexibility of the resin composition but also improves the moldability of the resin composition. By improving the moldability of the resin composition, it is possible to reduce defects in the appearance of molded articles of the resin composition. The process oil is, for example, a paraffin-based process oil.

[0045] The content of the process oil is 10 parts by mass or more and 35 parts by mass or less, relative to 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin. When the content of the process oil is 10 parts by mass or more, the moldability of the resin composition is improved. When the content of the process oil is 35 parts by mass or less, the smoke generated when the resin composition is burned can be reduced. Furthermore, when the content of the process oil is 35 parts by mass or less, the decrease in tensile strength of the resin composition can be reduced. The content of the process oil may be 10 parts by mass or more and 30 parts by mass or less, or even 10 parts by mass or more and 20 parts by mass or less.

[0046] <Weight molecular weight> The weight average molecular weight of the process oil is, for example, 0.75 x 10 3 Over 1.50 x 10 3 The larger the weight-average molecular weight of the process oil, the less likely the process oil is to vaporize when the resin composition is burned, and therefore less smoke is generated when the resin composition is burned. In other words, the smoke concentration when the resin composition is burned is lower. In addition, there is generally a correlation between the weight-average molecular weight of the process oil and the viscosity of the process oil, and the smaller the weight-average molecular weight of the process oil, the lower the kinematic viscosity of the process oil. The lower the kinematic viscosity of the process oil, the easier it is to mold the resin composition, and the moldability of the resin composition is improved. When the weight-average molecular weight of the process oil is 1.50 × 10 3 If the weight average molecular weight of the process oil is 0.75×10 or less, the kinematic viscosity of the process oil is not excessively high, and the influence on the moldability of the resin composition is small. 3 Over 1.50 x 10 3 When the weight average molecular weight of the process oil is 0.80×10 or less, the moldability of the resin composition can be sufficiently maintained, and smoke generated when the resin composition is burned can be more effectively reduced. 3 Over 1.40 x 10 3 The following is also acceptable.

[0047] <Kinematic viscosity> The kinematic viscosity of process oil at 40°C is, for example, 95mm 2 / s or more 500mm 2 / s or less. The unit of kinematic viscosity is millimeters per square second (mm 2 / s). The kinematic viscosity of the process oil is 95 mm 2 / s or more 500mm 2 / s or less, smoke generated when the resin composition is burned can be more effectively reduced while maintaining sufficient moldability of the resin composition. As described above, there is a correlation between the weight average molecular weight of the process oil and the viscosity of the process oil, and the higher the kinematic viscosity of the process oil, the larger the weight average molecular weight of the process oil. When the kinematic viscosity of the process oil is 95 mm 2 If the kinematic viscosity of the process oil is 500 mm / s or more, the weight average molecular weight of the process oil is relatively large, so that less smoke is generated when the resin composition is burned. 2 If the kinematic viscosity of the process oil is 100 mm / s or less, the resin composition can be easily molded. 2 / s or more 450mm 2 / s or less, and 120mm 2 / s or more 300mm 2 / s or less is also acceptable.

[0048] (inorganic filler) The resin composition of the embodiment may contain an inorganic filler. The inorganic filler is a substance that enhances the flame retardancy of the resin composition. For example, known inorganic fillers used as flame retardants for wire insulators can be used as the inorganic filler. Examples of materials for the inorganic filler include magnesium hydroxide, aluminum hydroxide, magnesium oxide, aluminum oxide, calcium oxide, magnesium carbonate, calcium carbonate, magnesium silicate, calcium silicate, silica, and talc. These inorganic fillers may be used alone or in combination of two or more.

[0049] The inorganic filler may be surface-treated with a silane coupling agent. The inorganic filler surface-treated with a silane coupling agent has excellent adhesion to the polyolefin resins contained in the first polyolefin resin and the second polyolefin resin, thereby increasing the bonding strength between the polyolefin resins and the inorganic filler.

[0050] The content of the inorganic filler is, for example, 50 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin. When the content of the inorganic filler is 50 parts by mass or more, the flame retardancy of the resin composition can be sufficiently improved. When the content of the inorganic filler is 200 parts by mass or less, the deterioration of the moldability of the resin composition can be reduced. The content of the inorganic filler may be 60 parts by mass or more and 180 parts by mass or less, or even 80 parts by mass or more and 150 parts by mass or less.

[0051] (Silanol condensation catalyst) The resin composition of the embodiment may contain a silanol condensation catalyst. The silanol condensation catalyst is a substance that crosslinks the silane-grafted first polyolefin resin. The silanol condensation catalyst functions to cause a condensation reaction of the silane coupling agent through the action of moisture. The silanol condensation catalyst functions to crosslink the polyolefin resin contained in the first polyolefin resin. Known silanol condensation catalysts, such as organotin compounds, can be used. Examples of silanol condensation catalysts include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctiate, dibutyltin diacetate, zinc stearate, lead stearate, barium stearate, calcium stearate, sodium stearate, lead naphthenate, lead sulfate, zinc sulfate, and organoplatinum compounds. These silanol condensation catalysts may be used alone or in combination of two or more.

[0052] The content of the silanol condensation catalyst is, for example, 0.001 to 1 part by mass per 100 parts by mass of the first polyolefin resin. When the content of the silanol condensation catalyst is within this range, the condensation reaction of the silane coupling agent proceeds quickly, and the first polyolefin resin is easily crosslinked uniformly. The content of the silanol condensation catalyst may be 0.01 to 0.5 parts by mass.

[0053] The resin composition of the embodiment may further contain additives such as an antioxidant, a processing aid, a colorant, etc. Known materials can be used as these additives.

[0054] (Smoke-producing) The resin composition of the embodiment has a smoke density of 150 or less when burned in an NBS smoke chamber smoke test. If the smoke density is 150 or less, the amount of smoke generated when the resin composition is burned is small. The smoke density may be 140 or less, or even 120 or less.

[0055] The NBS smoke chamber is equipped with a photometer and a heater within the chamber. The photometer has a light source and a photodetector. The heater irradiates a test piece of the resin composition with radiant energy, causing it to burn. The test piece is mounted vertically within the chamber. The photometer measures the smoke concentration by utilizing the attenuation of light intensity caused by the smoke generated when the test piece is burned, blocking the light. The smoke generation test is conducted in accordance with the test method of JCS 7508, specified in the Japanese Electric Wire and Cable Industry Standards.

[0056] The smoke concentration is calculated using the following formula: Ds = (V / A·L) [log 10 (100 / T)] Ds is the smoke density. V is the volume of the chamber in cubic millimeters. A is the exposed area of ​​the test specimen in square millimeters. L is the optical path length in millimeters. T is the minimum light transmittance in percent.

[0057] <Electric wire> An electric wire according to an embodiment will be described with reference to Fig. 1. The electric wire 10 includes a conductor 11 and an insulator 12. Fig. 1 schematically shows a cross section perpendicular to the length of the electric wire 10. One of the features of the electric wire 10 according to the embodiment is that the material of the insulator 12 is the resin composition of the above-described embodiment. Since the insulator 12 of the electric wire 10 is formed from the resin composition of the above-described embodiment, the electric wire 10 generates little smoke when burned.

[0058] The electric wire 10 may be a round wire or a rectangular wire. The electric wire 10 shown in Fig. 1 is a round wire. The electric wire 10 is used, for example, for wiring of electric equipment, wiring inside control panels, and indoor wiring in buildings.

[0059] (conductor) The conductor 11 is made of, for example, pure copper, a copper alloy, pure aluminum, or an aluminum alloy. The conductor 11 may be a solid wire or a stranded wire. The cross-sectional shape of the conductor 11 may be circular or non-circular, such as oval, elliptical, or rectangular. The cross-sectional shape of the conductor 11 shown in FIG. 1 is circular. The nominal cross-sectional area of ​​the conductor 11 is, for example, 0.5 mm 2 Over 600mm 2 The diameter of the conductor 11 is, for example, 1 mm or more and 30 mm or less.

[0060] (insulator) The insulator 12 is provided so as to cover the outer periphery of the conductor 11. The thickness of the insulator 12 is, for example, not less than 0.5 mm and not more than 5 mm.

[0061] <Method of manufacturing resin composition> The resin composition of the embodiment described above can be produced by the production method described below. The production method of the resin composition of the embodiment includes, in order, Step 1A, Step 2A, and Step 3A. Each step is as follows.

[0062] Step 1A is a step for obtaining a resin material. Step 2A is a step of obtaining a molded body. Step 3A is a step of crosslinking the molded body. Each step will be described in detail below.

[0063] (Step 1A) In step 1A, a resin material is obtained by mixing a silane-grafted first polyolefin resin, a non-silane-grafted second polyolefin resin, and a process oil. Details of the first polyolefin resin, the second polyolefin resin, and the process oil are as described above.

[0064] The content ratio of the first polyolefin resin is, for example, 10 parts by mass or more and 60 parts by mass or less. The content ratio of the second polyolefin resin is, for example, 40 parts by mass or more and 90 parts by mass or less. The content ratios of the first polyolefin resin and the second polyolefin resin respectively indicate the parts by mass of each material when the total of the first polyolefin resin and the second polyolefin resin is 100 parts by mass.

[0065] The process oil is mixed in a ratio of 10 to 35 parts by mass per 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin. When the content of the process oil is 10 parts by mass or more, the melt viscosity of the resin material described below can be reduced. The lower melt viscosity of the resin material makes it easier to mold the resin material. As a result, the moldability of the resin composition is improved, and poor appearance of molded articles of the resin composition can be reduced. Furthermore, when the content of the process oil is 35 parts by mass or less, smoke generated when the resin composition is burned can be reduced.

[0066] The kinematic viscosity of the process oil at 40°C is 95mm 2 / s or more 500mm 2 / s or less. The kinematic viscosity of the process oil is 95mm 2 When the kinematic viscosity of the process oil is 500 mm / s or more, the smoke generated when the resin composition is burned can be effectively reduced as described above. 2 / s or less, the melt viscosity of the resin material described later can be reduced, and the moldability of the resin composition can be improved. 3 Over 1.50 x 10 3 The following is the result.

[0067] The first polyolefin resin is obtained by mixing a polyolefin resin, a silane coupling agent, and an organic peroxide, and grafting the silane coupling agent onto the polyolefin resin. The materials may be mixed using a mixer such as a kneader or a Banbury mixer, or a single-screw or twin-screw extruder. The mixing temperature when mixing the materials is equal to or higher than the melting point of the polyolefin resin and equal to or higher than the temperature at which the graft reaction of the silane coupling agent proceeds due to the action of the organic peroxide. The mixing temperature is, for example, 80°C or higher and 250°C or lower. The mixing temperature may also be 100°C or higher and 240°C or lower. The mixing time is appropriately set so that the graft reaction proceeds sufficiently. Known mixing conditions can be used.

[0068] The first polyolefin resin may be a commercially available silane-crosslinkable polyolefin resin, such as "Linkron," a product of Mitsubishi Chemical Corporation.

[0069] The materials, such as the first polyolefin resin, the second polyolefin resin, and the process oil, may be mixed using a mixer such as a kneader or a Banbury mixer, or a single-screw or twin-screw extruder. The mixing temperature is equal to or higher than the melting temperature of the polyolefin resins contained in the first polyolefin resin and the second polyolefin resin. The mixing temperature is, for example, 80°C or higher and 250°C or lower. The mixing temperature may also be 100°C or higher and 240°C or lower. The mixing time is set appropriately so that the resin materials are mixed uniformly. Known mixing conditions can be used as the mixing conditions.

[0070] In addition to the resin material described above, an inorganic filler may be mixed. Details of the inorganic filler are as described above. The content of the inorganic filler is, for example, 50 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin.

[0071] In addition to the inorganic filler, additives such as antioxidants, processing aids, and colorants may also be mixed.

[0072] (2nd A process) In step 2A, the resin material and the silanol condensation catalyst are mixed and then molded to obtain a molded product. Details of the silanol condensation catalyst are as described above. The content of the silanol condensation catalyst is, for example, 0.001 to 1 part by mass per 100 parts by mass of the first polyolefin resin.

[0073] The resin material can be molded using, for example, an extruder. By using an extruder, the resin material and the silanol condensation catalyst can be mixed and molded continuously. The extruder is, for example, a single-screw extruder or a twin-screw extruder. The extrusion temperature is equal to or higher than the melting temperature of the polyolefin resins contained in the first polyolefin resin and the second polyolefin resin. The extrusion temperature is, for example, 80°C or higher and 250°C or lower. The extrusion temperature may also be 100°C or higher and 240°C or lower. Known extrusion conditions can be applied as the extrusion conditions.

[0074] The melt viscosity of a resin material is, for example, 3700 mPa·s or less. Melt viscosity is the viscosity of a resin material in a molten state. The unit of melt viscosity is millipascal seconds (mPa·s). The lower the melt viscosity of a resin material, the higher the fluidity of the resin material when it is molded. If the melt viscosity of a resin material is 3700 mPa·s or less, it is easier to mold the resin material. The melt viscosity can also be 3500 mPa·s or less. The melt viscosity is measured using a capillary rheometer. The melt viscosity measurement conditions are a resin material temperature of 190°C and a shear rate of 75 / s.

[0075] A catalyst masterbatch containing a silanol condensation catalyst may be mixed with a resin material. The catalyst masterbatch is a mixture of a matrix resin and a silanol condensation catalyst. The matrix resin is a polyolefin resin. The content of the silanol condensation catalyst in the catalyst masterbatch is, for example, 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the matrix resin. The content of the catalyst masterbatch to be mixed with the resin material is, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin. The catalyst masterbatch is adjusted so that, when mixed with the resin material, the content of the silanol condensation catalyst is 0.001 parts by mass or more and 1 part by mass or less per 100 parts by mass of the first polyolefin resin.

[0076] (3rd A process) In step 3A, the molded body is crosslinked. Crosslinking of the molded body is carried out by bringing the molded body into contact with moisture. When the molded body comes into contact with moisture, the polyolefin resin contained in the first polyolefin resin is crosslinked by a condensation reaction of the silane coupling agent. Crosslinking of the molded body progresses due to moisture in the air, even when the molded body is simply left in moist air at room temperature for a predetermined period of time. To promote crosslinking of the molded body, the molded body may be left in hot air, immersed in warm water, or exposed to high-temperature water vapor. Known crosslinking conditions can be applied.

[0077] <Wire manufacturing method> The electric wire 10 of the above-described embodiment can be manufactured by the manufacturing method described below. The manufacturing method of the electric wire of the embodiment includes, in order, a 1B step, a 2B step, and a 3B step. Each step is as follows.

[0078] Step 1B is a step of obtaining a resin material. Step 2B is a step of forming a coating layer on the conductor 11. Step 3B is a step of forming the insulator 12 by cross-linking the coating layer. Each step will be described in detail below.

[0079] (1B process) Step 1B is the same as step 1A in the above-mentioned method for producing a resin composition, and therefore a description thereof will be omitted.

[0080] (2nd B process) In step 2B, a resin material and a silanol condensation catalyst are mixed and then coated on the conductor 11 to form a coating layer. Step 2B is basically the same as step 2A described above, except that a resin material is coated on the conductor 11 to form a coating layer. The coating layer can be formed, for example, using an extruder. Specifically, a resin material and a silanol condensation catalyst are mixed using an extruder, and the mixture is extruded onto the surface of the conductor 11 to form a coating layer.

[0081] (3B process) Step 3B is a step of cross-linking the coating layer to form the insulator 12. The cross-linking of the coating layer is carried out by bringing the coating layer into contact with moisture. The cross-linking of the coating layer can be carried out by the same method as that for cross-linking the molded body described in Step 3A above.

[0082] [Test Example 1] In Test Example 1, the influence of process oil on the moldability and smoke generation of a resin composition was examined.

[0083] Samples of the resin compositions shown in Tables 1 and 2 were produced. The main components and content ratios of the resin compositions are shown in Tables 1 and 2. The content ratios of the materials are shown in parts by mass when the total of the first polyolefin resin and the second polyolefin resin is 100 parts by mass.

[0084] The resin composition samples were produced as follows. First, a first polyolefin resin, a second polyolefin resin, a process oil, and an inorganic filler were mixed to obtain a resin material. Next, the resin material was mixed with a catalyst master batch (catalyst MB) and then molded to obtain a molded body. This molded body was crosslinked by contacting it with moisture.

[0085] The content of the first polyolefin resin was 30 parts by mass. A commercially available VLDPE-based silane-crosslinkable resin was used as the first polyolefin resin. The first polyolefin resin used was Linkron SL800N manufactured by Mitsubishi Chemical Corporation. Linkron SL800N is a resin composition containing VLDPE, a silane coupling agent, and an organic peroxide.

[0086] The content of the second polyolefin resin was 70 parts by mass. Commercially available VLDPE, EEA, and maleic anhydride-modified polyethylene were used for the second polyolefin resin. The maleic anhydride-modified polyethylene used was LLDPE grafted with maleic anhydride (MAH-G-LLDPE). The content of VLDPE was 40 parts by mass. The content of EEA was 20 parts by mass. The content of MAH-G-LLDPE was 10 parts by mass.

[0087] Three types of process oils were prepared: Oil A, Oil B, and Oil C. All of these process oils are commercially available paraffin-based process oils. Oil A is Diana Process Oil PW-90 manufactured by Idemitsu Kosan Co., Ltd. Oil B is SUNPAR2100 manufactured by Japan Sun Oil Co., Ltd. Oil C is Diana Process Oil PW-380 manufactured by Idemitsu Kosan Co., Ltd. The kinematic viscosity and weight-average molecular weight of each process oil at 40°C are as follows: Oil A: kinematic viscosity 90.5mm 2 / s, weight average molecular weight 0.7×10 3 Oil B: kinematic viscosity 185mm 2 / s, weight average molecular weight 0.8×10 3 Oil C: kinematic viscosity 409mm 2 / s, weight average molecular weight 1.2×10 3

[0088] The kinematic viscosity of the process oil was measured in accordance with the test method specified in JIS K 2283:2000, a standard in the Japanese Industrial Standards. The weight-average molecular weight of the process oil was measured by dissolving the process oil in tetrahydrofuran (THF) and using gel permeation chromatography (GPC). The GPC used for the measurement was an HLC-8320GPC manufactured by Tosoh Technosystems Corporation.

[0089] The inorganic filler content was 100 parts by mass. Commercially available magnesium hydroxide was used as the inorganic filler. The inorganic filler used was surface-treated with vinylsilane. The volume average particle diameter of the inorganic filler was 1 μm.

[0090] Catalyst MB contains a silanol condensation catalyst. The catalyst MB content is 5 parts by mass. A commercially available catalyst MB was used. The catalyst MB used was LZ015H manufactured by Mitsubishi Chemical Corporation. LZ015H is a mixture of LDPE and a silanol condensation catalyst. The silanol condensation catalyst is an organotin compound.

[0091] (Sample No. 100, no process oil) Sample No. 100 shown in Table 1 is a resin composition produced without mixing in process oil, and does not contain process oil. In other words, the content of process oil in Sample No. 100 is zero.

[0092] (Sample A and oil A were used) Sample A is a resin composition using Oil A as the process oil. Samples A1 to A6 shown in Table 1 are samples A with different process oil content ratios.

[0093] (Sample B, Oil B used) Sample B is a resin composition in which Oil B is used as the process oil. Samples B1 to B6 shown in Table 2 are samples B with different process oil content ratios.

[0094] (Sample C and oil C used) Sample C is a resin composition in which Oil C is used as the process oil. Samples C1 to C6 shown in Table 2 are samples C with different process oil content ratios.

[0095] The moldability and smoke generation were evaluated for the resin composition samples shown in Tables 1 and 2. The moldability was evaluated based on the melt viscosity of the resin material and the appearance of the molded article of the resin composition.

[0096] <Evaluation of moldability: Melt viscosity of resin material> The melt viscosity of the resin material was measured using a capillary rheometer. The measurement conditions were a resin material temperature of 190°C and a shear rate of 75 / s. The capillary rheometer used for the measurement was an RH7 manufactured by Spectris Co., Ltd. The melt viscosity of each sample is shown in Tables 1 and 2.

[0097] <Evaluation of moldability: Appearance of molded product> Electric wires were manufactured with insulation formed from the resin compositions shown in Tables 1 and 2. The insulation was formed as follows: Using an extruder, a resin material and catalyst MB were mixed, and then the mixture was extruded onto a conductor to form a coating layer. This coating layer was crosslinked to form the insulation. The extruder used was a single-screw extruder with a screw diameter of 50 mm. Extrusion was performed at 20 meters per minute to achieve a coating layer thickness of 0.8 mm.

[0098] The appearance of the molded resin composition was evaluated based on the surface roughness of the insulator. The arithmetic mean roughness Ra of the insulator surface was measured in accordance with JIS B 0601:2001. The surface roughness Ra of each sample is shown in Tables 1 and 2. If the surface roughness Ra of the insulator is 40 μm or less, the insulator can be evaluated as having good appearance.

[0099] <Smoke generation evaluation: smoke concentration> An NBS smoke chamber smoke test was conducted to measure the smoke concentration during combustion of the resin composition. The size of the test piece used in the smoke test was 76 mm in length, 76 mm in width, and 0.5 mm in thickness. The test conditions were a radiant heat of 2.5 W / cm 2The heating time was 20 minutes. The smoke concentration of each sample is shown in Tables 1 and 2.

[0100] <comprehensive evaluation> The resin compositions shown in Table 1 were evaluated comprehensively for moldability and smoke generation. The comprehensive evaluation was rated "A" when the surface roughness Ra was 40 μm or less and the smoke generation density was 150 or less, and "B" when the surface roughness Ra was more than 40 μm or the smoke generation density was more than 150. The comprehensive evaluation of each sample is shown in Tables 1 and 2.

[0101] [Table 1]

[0102] [Table 2]

[0103] Among Sample B, which uses Oil B, Samples No. B3 to No. B6, which contain 10 parts by mass or more of process oil, have a surface roughness Ra of 40 μm or less. Among Sample C, which uses Oil C, Samples No. C3 to No. C6, which contain 10 parts by mass or more of process oil, have a surface roughness Ra of 40 μm or less. Samples No. B3 to No. B6 and No. C3 to No. C6 have superior moldability compared to Sample No. 100, which does not contain process oil. Furthermore, the results of smoke generation tests on these samples show that the lower the process oil content, the lower the smoke concentration. Samples No. B3 to No. B5 and No. C3 to No. C5, which contain 35 parts by mass or less of process oil, have a smoke concentration of 150 or less, meaning that little smoke is generated during combustion.

[0104] The smoke generation of sample A, which uses oil A, is compared with that of samples B and C. When comparing samples with the same process oil content, it can be seen that samples B and C tend to have lower smoke concentrations than sample A. These results show that the higher the kinematic viscosity of the process oil or the larger the weight average molecular weight of the process oil, the more effectively the smoke generated when the resin composition is burned can be reduced. [Explanation of symbols]

[0105] 10 Electric wire 11 Conductor 12 Insulators

Claims

1. a silane-grafted first polyolefin resin; a second polyolefin resin that is not silane-grafted; process oil, the content of the process oil is 10 parts by mass or more and 35 parts by mass or less relative to 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin, In the NBS smoke chamber smoke test, the smoke density during combustion is 150 or less. Resin composition.

2. The weight average molecular weight of the process oil is 0.75×10 ３ Above 1.50 x 10 ３ The resin composition according to claim 1, wherein:

3. The process oil has a kinematic viscosity of 95 mm at 40°C. ２ / s or more 500mm ２ The resin composition according to claim 1, wherein the viscosity is 1 / s or less.

4. The resin composition according to claim 1 , further comprising an inorganic filler.

5. The resin composition according to claim 1 , wherein the second polyolefin resin comprises maleic anhydride-modified polyethylene.

6. The resin composition according to claim 1 , wherein the second polyolefin resin comprises an ethylene acrylic acid copolymer.

7. An electric wire comprising a conductor and an insulator covering the outer periphery of the conductor, The material of the insulator is the resin composition according to any one of claims 1 to 6. Electric wire.

8. a step of mixing a silane-grafted first polyolefin resin, a non-silane-grafted second polyolefin resin, and a process oil to obtain a resin material; a step of mixing the resin material with a silanol condensation catalyst and then molding the mixture to obtain a molded product; and crosslinking the molded body, The kinematic viscosity of the process oil at 40°C is 95 mm ２ / s or more 500mm ２ / s or less, the process oil is mixed in an amount of 10 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin; A method for producing a resin composition.

9. a step of mixing a silane-grafted first polyolefin resin, a non-silane-grafted second polyolefin resin, and a process oil to obtain a resin material; a step of mixing the resin material and the silanol condensation catalyst and then coating the mixture on a conductor to form a coating layer; and cross-linking the coating layer to form an insulator, The kinematic viscosity of the process oil at 40°C is 95 mm ２ / s or more 500mm ２ / s or less, the process oil is mixed in an amount of 10 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the total of the first polyolefin resin and the second polyolefin resin; Manufacturing method of electric wire.

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