Resin composition, cable, and method for manufacturing the cable

Abstract

To provide a resin composition with excellent mechanical properties. [Solution] A resin composition comprising polyurethane resin as the main component, having a tensile strength of 20 MPa or more, an elastic modulus of 20 MPa or less, and a Type A durometer hardness of 85 or less.

Description

Technical Field

[0001] The present disclosure relates to a resin composition, a cable, and a method for manufacturing a cable.

Background Art

[0002] Patent Document 1 discloses a wear-resistant rubber composition containing chloroprene rubber as a main component. This wear-resistant rubber composition is used for the sheath of a cable such as a cab tire cable.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Higher mechanical properties are required for the sheath of a cable such as a cab tire cable.

[0005] One of the objectives of the present disclosure is to provide a resin composition with excellent mechanical properties. Another objective is to provide a cable provided with a sheath made of the above resin composition. Still another objective is to provide a method for manufacturing a cable provided with a sheath made of a resin composition with excellent mechanical properties.

Means for Solving the Problems

[0006] The resin composition of the present disclosure contains a polyurethane resin as a main component, has a tensile strength of 20 MPa or more, an elastic modulus of 20 MPa or less, and a Shore A durometer hardness of 85 or less.

Effects of the Invention

[0007] The resin composition of the present disclosure has excellent mechanical properties. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing an example of a cable having a sheath made of the resin composition of the embodiment. [Figure 2] Figure 2 is a schematic diagram illustrating an example of a compound-making process in a method for manufacturing a cable having a sheath made of the resin composition of the embodiment. [Figure 3] Figure 3 is a schematic diagram illustrating the step of forming a sheath around an insulated wire in a method for manufacturing a cable having a sheath made of a resin composition of an embodiment. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0010] (1) The resin composition according to the embodiment of the present disclosure mainly comprises a polyurethane resin, has a tensile strength of 20 MPa or more, an elastic modulus of 20 MPa or less, and a Type A durometer hardness of 85 or less.

[0011] "Containing polyurethane resin as the main component" means that the proportion of polyurethane resin in the resin composition exceeds 50% by mass. Polyurethane resin accounts for the largest proportion of the resin composition. Resin compositions containing polyurethane resin as the main component tend to have improved tensile strength compared to those using chloroprene rubber. Resin compositions with a tensile strength of 20 MPa or higher have excellent mechanical strength. Resin compositions with an elastic modulus of 20 MPa or less have excellent flexibility.

[0012] (2) The resin composition described in (1) above may have a tear strength of 40 N / mm or more and an elongation of 300% or more at -40°C.

[0013] A resin composition with a tearing strength of 40 N / mm or more is excellent in mechanical strength. A resin composition with an elongation at -40° of 300% or more is excellent in low-temperature resistance.

[0014] (3) In the resin composition of (1) or (2) above, it may contain 5 to 100 parts by mass of a flame retardant with respect to 100 parts by mass of the polyurethane resin.

[0015] A resin composition containing a flame retardant within the above range is excellent in flame retardancy and heat aging resistance.

[0016] (4) In the resin composition of any one of (1) to (3) above, it may contain 0.1 to 2.0 parts by mass of a lubricant with respect to 100 parts by mass of the polyurethane resin.

[0017] A resin composition containing a lubricant within the above range is excellent in abrasion resistance.

[0018] (5) A cable according to an embodiment of the present disclosure is a cable including an insulated wire and a sheath covering the insulated wire, wherein the sheath is made of any one of the resin compositions of (1) to (4) above.

[0019] A cable provided with a sheath made of the above resin composition is excellent in mechanical properties.

[0020] (6) A method for manufacturing a cable according to an embodiment of the present disclosure includes a step of preparing an insulated wire, a step of putting a first polyurethane resin and additives into a mixer to produce a compound, and a step of putting a second polyurethane resin and the compound into an extruder to form a sheath around the insulated wire. The content ratio of each of the first polyurethane resin and the second polyurethane resin is set so that the tensile strength of the sheath is 20 MPa or more, the elastic modulus is 20 MPa or less, and the Shore A durometer hardness is 85 or less.

[0021] The polyurethane resin undergoes a heat history in each of the steps of producing the compound and forming the sheath. That is, the polyurethane resin that has gone through the two steps of producing the compound and forming the sheath undergoes two heat histories. In the above cable manufacturing method, instead of putting all of the polyurethane resin that forms the sheath into the mixer in the step of producing the compound, the first polyurethane resin is put into the mixer in the step of producing the compound, and the second polyurethane resin is put into the extruder in the step of forming the sheath. By combining the first polyurethane resin and the second polyurethane resin, it becomes the polyurethane resin that forms the sheath. By putting the first polyurethane resin into the mixer and putting the second polyurethane resin into the extruder, the amount of the polyurethane resin that undergoes two heat histories can be reduced compared to the case of putting all of the polyurethane resin that forms the sheath into the mixer. By adjusting the amount of the polyurethane resin that undergoes two heat histories, the formed sheath can satisfy specific tensile strength, elastic modulus, and Type A durometer hardness.

[0022] (7) In the cable manufacturing method of (6) above, when the Type A durometer hardness of the first polyurethane resin and the second polyurethane resin is 68 or more and 76 or less, the content ratio of the first polyurethane resin may be 20 parts by mass or more and 60 parts by mass or less, and the content ratio of the second polyurethane resin may be 40 parts by mass or more and 80 parts by mass or less. When the Type A durometer hardness of the first polyurethane resin and the second polyurethane resin exceeds 76 and is 82 or less, the content ratio of the first polyurethane resin may be 30 parts by mass or more and 70 parts by mass or less, and the content ratio of the second polyurethane resin may be 30 parts by mass or more and 70 parts by mass or less. The content ratio of each of the first polyurethane resin and the second polyurethane resin is the ratio based on the total of the first polyurethane resin and the second polyurethane resin being 100 parts by mass.

[0023] By adjusting the content ratio of the first and second polyurethane resins according to the Type A durometer hardness of the polyurethane resins, the resulting sheath can easily meet specific tensile strength, modulus of elasticity, and Type A durometer hardness requirements.

[0024] [Details of the embodiments of this disclosure] Specific examples of the resin compositions, cables, and methods for manufacturing cables of this disclosure will be described with reference to the drawings. Identical reference numerals in the drawings indicate the same or corresponding parts. In each drawing, some parts of the configuration may be exaggerated or simplified for illustrative purposes. The dimensional ratios of parts in the drawings may also differ from those of the actual components. The present invention is not limited to these examples, but is indicated by the claims, and all modifications within the meaning and scope of equivalence to the claims are intended. First, the resin compositions will be described, followed by cables using the resin compositions and methods for manufacturing cables.

[0025] <Resin composition> The resin composition of the embodiment comprises a polyurethane resin and an additive. One of the features of the resin composition of the embodiment is that it contains polyurethane resin as the main component and has specific values ​​for tensile strength, elastic modulus, and type A durometer hardness.

[0026] The resin composition in this embodiment is used for the sheath 5 of the cable 1 shown in Figure 1. The sheath 5 is formed by mixing a first polyurethane resin 91 and an additive 95 in a mixer 7 to produce a compound 97, as will be described in detail later in the cable manufacturing method with reference to Figures 2 and 3, and then extruding this compound 97 and a second polyurethane resin 92 around the insulated wire 2 in an extruder 8.

[0027] Polyurethane resin Polyurethane resin is the main component of the resin composition. The content of polyurethane resin in the resin composition is more than 50% by mass, more specifically 60% by mass or more, or 70% by mass or more. The content of polyurethane resin in the resin composition is the ratio when the total mass of the constituent materials of the resin composition is taken as 100% by mass. Resin compositions containing polyurethane resin as the main component tend to have improved tensile strength.

[0028] Polyurethane resin is, for example, a thermoplastic, non-foaming type. A foamed type of polyurethane resin is also acceptable.

[0029] ≪Additives≫ The additives include at least one of the following: a flame retardant, a lubricant, a colorant, and an antioxidant.

[0030] The flame retardant is not particularly limited, and for example, halogen-based flame retardants such as chlorine-based or bromine-based ones, metal hydroxides such as aluminum hydroxide or magnesium hydroxide, or halogen-free flame retardants that do not contain halogens, such as phosphorus-based or nitrogen-based ones, can be used. One type of flame retardant may be used, or two or more types of flame retardants may be used in combination. The content ratio of the flame retardant is, for example, 5 parts by mass or more and 100 parts by mass or less per 100 parts by mass of polyurethane resin. A resin composition containing the flame retardant within the above range has excellent flame retardancy and heat aging resistance. The content ratio of the flame retardant may also be 10 parts by mass or more and 80 parts by mass or less per 100 parts by mass of polyurethane resin. In addition to the flame retardant, the additive may also include a flame retardant aid.

[0031] The lubricant is not particularly limited, and for example, paraffin wax, polyolefin wax, fatty acid metal salt, fatty acid amide compound, fatty acid erate compound, or montanic acid ester wax can be used. One type of lubricant may be used, or two or more types of lubricants may be used in combination. The content ratio of the lubricant is, for example, 0.1 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of polyurethane resin. A resin composition containing the lubricant within the above range has excellent wear resistance. The content ratio of the lubricant may also be 0.2 parts by mass or more and 1.5 parts by mass or less per 100 parts by mass of polyurethane resin.

[0032] The coloring agent is not particularly limited, and for example, carbon can be used. The coloring agent is added for ultraviolet absorption. The content ratio of the coloring agent is, for example, 0.5 parts by mass or more and 5.0 parts by mass or 1.0 part by mass or more and 3.0 parts by mass per 100 parts by mass of polyurethane resin.

[0033] The antioxidant is not particularly limited, and for example, a phenolic antioxidant can be used. The antioxidant content is, for example, 0.1 parts by mass or more and 5.0 parts by mass or 0.5 parts by mass or more and 3.0 parts by mass per 100 parts by mass of polyurethane resin.

[0034] ≪Tensile Strength≫ The tensile strength of the resin composition is 20 MPa or higher. Resin compositions with a tensile strength of 20 MPa or higher have excellent mechanical strength. Resin compositions with a tensile strength of 20 MPa or higher are less likely to be damaged during use. The tensile strength may also be 21 MPa or higher, or 22 MPa or higher. If the tensile strength is too high, the relative modulus of elasticity and type A durometer hardness tend to be high. If the tensile strength is 35 MPa or lower, the relative modulus of elasticity and type A durometer hardness tend not to be excessively high. The tensile strength of the resin composition may be 20 MPa to 35 MPa, 21 MPa to 32 MPa, or 22 MPa to 32 MPa. The tensile strength can be measured according to JIS C3660-501:2019.

[0035] ≪Module of elasticity≫ The elastic modulus of the resin composition is 20 MPa or less. Resin compositions with an elastic modulus of 20 MPa or less have excellent flexibility. When the resin composition is used for the sheath 5 of cable 1, if the elastic modulus of the resin composition is 20 MPa or less, the cable is easy to handle. The elastic modulus may also be 19 MPa or less, or 18 MPa or less. If the elastic modulus is too low, the tensile strength tends to decrease relatively. If the elastic modulus is 1 MPa or more, the tensile strength does not decrease excessively relatively. The elastic modulus of the resin composition may be 1 MPa or more and 20 MPa or less, 2 MPa or more and 19 MPa or less, or 2 MPa or more and 18 MPa or less. The elastic modulus is measured by pulling a test specimen in the direction along its length at a tensile speed of 50 mm / min using a tensile testing machine, and the value obtained by dividing the load when the elongation rate becomes 2% by the cross-sectional area of ​​the test specimen is measured, and this value is multiplied by 50. This value is called the 2% secant modulus value. The size of the test specimen is 100 mm in length and 5 mm in width. The thickness of the test specimen is arbitrary.

[0036] Type A Durometer Hardness The Type A durometer hardness of the resin composition is 85 or less. Resin compositions with a Type A durometer hardness of 85 or less exhibit excellent flexibility. The Type A durometer hardness may also be 83 or less, or 80 or less. If the Type A durometer hardness is too low, the tensile strength tends to decrease relatively. If the Type A durometer hardness is 70 or higher, the tensile strength does not decrease excessively relatively. The Type A durometer hardness of the resin composition may also be between 70 and 85, between 72 and 83, or between 72 and 80. The Type A durometer hardness can be measured based on the hardness test of JIS K7311:1995.

[0037] Tear strength The tear strength of the resin composition is, for example, 40 N / mm or more. Resin compositions with a tear strength of 40 N / mm or more have superior mechanical strength. Resin compositions with a tear strength of 40 N / mm or more are less likely to be damaged during use. The tear strength may also be 41 N / mm or more, or 42 N / mm or more. If the tear strength is too high, the relative modulus of elasticity and type A durometer hardness tend to become high. If the tear strength is 100 N / mm or less, the relative modulus of elasticity and type A durometer hardness tend not to become excessively high. The tear strength of the resin composition may also be 40 N / mm or more and 100 N / mm or less, 41 N / mm or more and 90 N / mm or less, or 42 N / mm or more and 90 N / mm or less. The tear strength can be measured based on the tear test specified in IEC 62893-2:2017, assuming that the resin composition is used in the sheath 5 of cable 1.

[0038] <<Growth at -40℃>> The elongation of the resin composition at -40°C is, for example, 300% or more. A resin composition with an elongation of 300% or more at -40°C exhibits excellent low-temperature resistance. A resin composition with an elongation of 300% or more at -40°C is less prone to cracking even in low-temperature environments. The elongation at -40°C may be 310% or more, or even 320% or more. The elongation at -40°C can be measured based on the low-temperature elongation test of the sheath specified in JIS C3660-505:2019, assuming that the resin composition is used in the sheath 5 of cable 1.

[0039] <Cable> An example of cable 1 is shown in Figure 1. The cable 1 shown in Figure 1 is shown as a cross-section obtained by cutting the cable 1 in a direction perpendicular to the direction along the length of the cable 1. Cable 1 comprises insulated wires 2 and a sheath 5. Cable 1 comprises one or more insulated wires 2. Cable 1 in this example comprises three insulated wires 2. Each insulated wire 2 comprises a conductor 3 and an insulator 4 covering the conductor 3. The sheath 5 is made of the resin composition described above.

[0040] The constituent material of the conductor 3 is not particularly limited and may consist of, for example, copper, copper alloy, aluminum, or aluminum alloy. The cross-sectional shape of the conductor 3 is not particularly limited and may be, for example, circular. The conductor 3 may be a single wire or a stranded wire in which multiple strands are twisted together.

[0041] The insulator 4 is formed of an insulating resin material. The insulator 4 may also be formed of the resin composition described above.

[0042] The sheath 5 is formed by extruding the above-mentioned resin composition onto the outer circumference of multiple insulated wires 2 using the extruder 8 shown in Figure 3. The multiple insulated wires 2 are, for example, twisted together. The multiple insulated wires 2 may be bundled together with an insulating material (not shown). In this case, the multiple insulated wires 2 may be twisted together or strung together lengthwise. In the cable 1 equipped with an insulating material, the sheath 5 is placed on the outer circumference of the insulating material, and an insulating material (not shown) is filled between the multiple insulated wires 2 and the sheath 5.

[0043] Cable 1 is a power cable, such as a cabtyre cable. Cable 1 is used, for example, as a power supply cable in a factory or as a fast-charging cable for an electric vehicle. Cable 1 may also be a communication cable.

[0044] <Cable manufacturing method> A method for manufacturing a cable 1 having a sheath 5 made of the resin composition described above will be explained with reference to Figures 2 and 3. This method for manufacturing a cable 1 comprises a preparation step of preparing an insulated wire 2, a step of mixing the constituent materials of the sheath 5 to produce a compound 97, and an extrusion step of extruding the compound 97 to form the sheath 5 around the insulated wire 2. One of the features of the method for manufacturing a cable 1 in this embodiment is that in the mixing step, a first polyurethane resin 91 and an additive 95 are mixed to produce a compound 97, and in the extrusion step, a second polyurethane resin 92 is extruded together with the compound 97. The first polyurethane resin 91 and the second polyurethane resin 92 combine to form the polyurethane resin that forms the sheath 5.

[0045] For the sake of clarity, parts of the mixer 7 shown in Figure 2 and parts of the extruder 8 shown in Figure 3 are shown so that their internal components are visible. For clarity, in Figure 2, the first polyurethane resin 91 is shown as a circle and the additive 95 as a rectangle. In Figure 3, the second polyurethane resin 92 is shown as a circle. In both Figures 2 and 3, the compound 97 is shown as an elongated rectangle.

[0046] ≪Preparation process≫ In the preparation step, one or more insulated wires 2 are prepared. The multiple insulated wires 2 may be twisted together or bundled together with an insulating material (not shown). In this example, three insulated wires 2 are twisted together.

[0047] ≪Mixing process≫ In the mixing process, as shown in Figure 2, the first polyurethane resin 91 and additive 95 are put into the mixer 7 to produce a compound 97. The first polyurethane resin 91 is part of the polyurethane resin that forms the sheath 5. In the mixing process, not all of the polyurethane resin that forms the sheath 5 is put into the mixer 7. The remaining polyurethane resin that forms the sheath 5 is the second polyurethane resin 92 that is put into the extruder 8 in the extrusion process described later.

[0048] The mixer 7 is, for example, a twin-screw kneading extruder. The mixer 7 shown in Figure 2 is equipped with two screws 71 arranged inside a cylinder. The mixer 7 is equipped with a first inlet 70. The first polyurethane resin 91 and additive 95 are introduced through the first inlet 70. The first polyurethane resin 91 and additive 95 introduced through the first inlet 70 are kneaded by the two screws 71.

[0049] The amount of the first polyurethane resin 91 to be introduced into the first inlet 70 is set so that a compound 97 can be produced together with the additive 95, and when combined with the second polyurethane resin 92, the proportion of polyurethane resin in the sheath 5 is set to a predetermined value. The respective proportions of the first polyurethane resin 91 and the second polyurethane resin 92 will be described later.

[0050] The amount of additive 95 added to the first inlet 70 is set so that the proportion of additive 95 in the sheath 5 is a predetermined value. In the mixing process, all of the additives forming the sheath 5 are put into the mixer 7.

[0051] The mixing process is carried out, for example, at a temperature between 120°C and 200°C. A temperature above 120°C facilitates the mixing of the first polyurethane resin 91 and the additive 95. A temperature below 200°C makes it easier to conserve energy without excessive heating energy. The mixer 7 may be a single-screw kneading extruder.

[0052] In this example, the compound 97 mixed in the mixer 7 is produced as pellets.

[0053] Extrusion Process In the extrusion process, as shown in Figure 3, the second polyurethane resin 92 and compound 97 are fed into the extruder 8 to form a sheath 5 around the insulated wire 2. The extruder 8 is, for example, a single-screw compounding extruder. The extruder 8 shown in Figure 3 has a single screw 81 located inside the cylinder. The extruder 8 has a second inlet 80. The second polyurethane resin 92 and compound 97 are fed in from the second inlet 80. The second polyurethane resin 92 and compound 97 fed in from the second inlet 80 are mixed by the single screw 81 and extruded around the insulated wire 2 as it passes through the extruder 8.

[0054] The extrusion process is carried out at a temperature of, for example, 120°C to 200°C. A temperature of 120°C or higher facilitates mixing of the second polyurethane resin 92 and the compound 97. A temperature of 200°C or lower makes it easier to conserve energy without excessive heating energy.

[0055] The respective content ratios of the first polyurethane resin 91 and the second polyurethane resin 92 are set so that the tensile strength of the sheath 5 is 20 MPa or more, the elastic modulus is 20 MPa or less, and the Type A durometer hardness is 85 or less. The respective content ratios of the first polyurethane resin 91 and the second polyurethane resin 92 are calculated as a ratio of 100 parts by mass to the total of the first polyurethane resin 91 and the second polyurethane resin 92.

[0056] The Type A durometer hardness of sheath 5 is determined by the Type A durometer hardness of the first polyurethane resin 91 and the Type A durometer hardness of the second polyurethane resin 92. The respective content ratios of the first polyurethane resin 91 and the second polyurethane resin 92 can be adjusted according to their respective Type A durometer hardnesses. By adjusting the content ratios of the first polyurethane resin 91 and the second polyurethane resin 92 according to their respective Type A durometer hardnesses, the resulting sheath 5 can more easily satisfy specific tensile strength, modulus of elasticity, and Type A durometer hardness.

[0057] For example, if the Type A durometer hardness of the first polyurethane resin 91 and the second polyurethane resin 92 is 68 or more and 76 or less, the content of the first polyurethane resin 91 is 20 parts by mass or more and 60 parts by mass or less, and the content of the second polyurethane resin 92 is 40 parts by mass or more and 80 parts by mass or less. For example, if the Type A durometer hardness of the first polyurethane resin 91 and the second polyurethane resin 92 is greater than 76 and 82 or less, the content of the first polyurethane resin 91 is 30 parts by mass or more and 70 parts by mass or less, and the content of the second polyurethane resin 92 is 30 parts by mass or more and 70 parts by mass or less.

[0058] The Type A durometer hardness of the first polyurethane resin 91 and the Type A durometer hardness of the second polyurethane resin 92 may be the same or different, as long as they satisfy the above range. If the Type A durometer hardness of the first polyurethane resin 91 and the Type A durometer hardness of the second polyurethane resin 92 are different, the Type A durometer hardness of the first polyurethane resin 91 and the Type A durometer hardness of the second polyurethane resin 92 should be set so that the sheath 5 formed by combining the first polyurethane resin 91 and the second polyurethane resin 92 satisfies a specific tensile strength, modulus of elasticity, and Type A durometer hardness. Alternatively, the content ratio of the first polyurethane resin 91 and the second polyurethane resin 92 should be set so that the sheath 5 formed by combining the first polyurethane resin 91 and the second polyurethane resin 92 satisfies a specific tensile strength, modulus of elasticity, and Type A durometer hardness.

[0059] In this example, a pelletized compound 97 is produced in the mixer 7, and the pelletized compound 97 and the second polyurethane resin 92 are fed into the extruder 8. Although not shown in the diagram, the mixer 7 and the extruder 8 are configured as a single unit, and the compound 97 kneaded in the mixer 7 may be fed into the extruder 8 without being pelletized.

[0060] [Example Test] Several types of cables were fabricated, each equipped with a sheath made of a resin composition primarily containing polyurethane resin, and the characteristics of the sheath of each cable were investigated.

[0061] <Sample> In all samples, a compound was prepared by mixing polyurethane resin and additives in the mixing process, and a sheath was formed around an insulated wire by extruding the compound in the extrusion process. The mixing machine used in the mixing process was a twin-screw compounding extruder, with each of the two screws rotating at 300 rpm. The mixing process was carried out at a heating temperature of 160°C. The extruder used in the extrusion process was a single-screw compounding extruder, with one screw rotating at 12 rpm. The extrusion process was carried out at a heating temperature of 160°C. The content ratios of polyurethane resin and additives are shown in Table 1.

[0062] All samples were designed to resemble cabtyre cables, with a sheath formed around three twisted insulated wires. In each insulated wire, the conductor material is copper, and the insulator material is flame-retardant polyethylene. The nominal cross-sectional area of ​​the conductor is 50 mm². 2 The insulator thickness is 1.2 mm. The outer diameter of the sheath is 32 mm.

[0063] The polyurethane resin mixed in the mixing process is the first polyurethane resin, and the polyurethane resin mixed in the extrusion process is the second polyurethane resin. In Table 1, the respective content ratios of the first and second polyurethane resins are the ratios when the total of the first and second polyurethane resins is 100 parts by mass. In the columns for the first and second polyurethane resins, "A" indicates a polyurethane resin with a Type A durometer hardness of 68 to 74. The polyurethane resin labeled "A" used was Elastoran® ET870-11V manufactured by BASF. In the columns for the first and second polyurethane resins, "B" indicates a polyurethane resin with a Type A durometer hardness of 78 to 82. The polyurethane resin labeled "B" used was Elastoran® ET880 manufactured by BASF. In the column for the first polyurethane resin, "C" indicates a polyurethane resin with a Type A durometer hardness of 83 to 87. The polyurethane resin labeled "C" is Elastolane® ET885 manufactured by BASF. In the column for the first polyurethane resin, "D" refers to a polyurethane resin with a Type A durometer hardness of 88 to 92. The polyurethane resin labeled "D" is Elastolane® ET890 manufactured by BASF.

[0064] The additives include a flame retardant, lubricant, antioxidant, and colorant. The flame retardant is a hypophosphate, specifically Exolit® OP930 manufactured by Clariant Chemicals. The average particle size D50 of the flame retardant is 3 μm. The lubricant is a montanate ester, specifically LICOWAX® OP manufactured by Clariant Chemicals. The antioxidant is a phenolic antioxidant, specifically Irganox 1010 manufactured by BASF. The colorant is carbon, specifically Seest 3H manufactured by Tokai Carbon Co., Ltd. The respective content ratios of the flame retardant, lubricant, antioxidant, and colorant are expressed relative to 100 parts by mass of polyurethane resin. 100 parts by mass of polyurethane resin is the sum of the first polyurethane resin and the second polyurethane resin.

[0065] In samples No. 1, No. 8, No. 15, and No. 16, the entire amount of polyurethane resin forming the sheath was mixed during the mixing process to produce the compound. In samples No. 1, No. 8, No. 15, and No. 16, the content of the first polyurethane resin mixed during the mixing process is 100 parts by mass. Samples No. 1, No. 8, No. 15, and No. 16 have different Type A durometer hardness values ​​for the first polyurethane resin.

[0066] In samples No. 2 to No. 7 and No. 9 to No. 14, a compound was prepared by mixing a first polyurethane resin with an additive in the mixing step, and a sheath was formed by extruding a second polyurethane resin together with the compound in the extrusion step. In samples No. 2 to No. 7 and No. 9 to No. 14, the Type A durometer hardness of the first polyurethane resin mixed in the mixing step is the same as the Type A durometer hardness of the second polyurethane resin mixed in the extrusion step. The Type A durometer hardness of the polyurethane resins in samples No. 2 to No. 7 is different from that of the polyurethane resins in samples No. 9 to No. 14.

[0067] [Table 1]

[0068] The tensile strength, modulus of elasticity, type A durometer hardness, tear strength, and elongation at -40°C were examined for the sheath of each obtained cable sample. The results are shown in Table 2.

[0069] Tensile strength was measured in accordance with JIS C3660-501:2019. Specifically, a small dumbbell-shaped test piece was cut from the sheath of each cable sample, and a tensile test was performed at a tensile speed of 250 mm / min to determine the maximum tensile force. The tensile strength was then measured by dividing this maximum tensile force by the cross-sectional area of ​​the test piece before the test.

[0070] The modulus of elasticity was determined by cutting a strip-shaped test piece 100 mm long and 5 mm wide from the sheath of each cable sample, pulling the test piece along its length at a tensile speed of 50 mm / min using a tensile testing machine, and measuring the value obtained by dividing the load at which the elongation rate reached 2% by the cross-sectional area of ​​the test piece, and multiplying that value by 50.

[0071] Type A durometer hardness was measured by pressing a Type A durometer against the surface of the cable sheath of each sample, based on the hardness test specified in JIS K7311:1995. In Table 1, this is labeled as "hardness".

[0072] Tear strength was measured based on the tear test specified in IEC 62893-2:2017. Specifically, a strip-shaped test piece measuring 100 mm in length and 30 mm in width was cut from the sheath of each cable sample, and the load was measured when the test piece was torn from the first end to the second end along its length at a speed of 250 mm / min. The tear strength here is the average of the loads measured for three test pieces that were able to be torn to a position of 80 mm from the first end.

[0073] The elongation at -40°C was measured based on the low-temperature elongation test for sheaths specified in JIS C3660-505:2019. Specifically, a JIS No. 6 dumbbell-shaped test specimen was cut from the sheath of each cable sample that had been left standing at -40°C for 2 hours. The initial gauge length was set to 20 mm, and the test specimen was pulled at a speed of 25 mm / min. The elongation at the time the test specimen broke was measured.

[0074] [Table 2]

[0075] Table 2 shows that for samples No. 1 to No. 7, where the Type A durometer hardness of the polyurethane resin is between 68 and 74, the following can be observed. Samples No. 1 to No. 3 satisfy the requirement of an elastic modulus of 20 MPa or less, but the tensile strength does not satisfy the requirement of 20 MPa or more. It is thought that by mixing polyurethane resins with a Type A durometer hardness of 68 to 74 in samples No. 1 to No. 3, the Type A durometer hardness of the sheath becomes 76, and the elastic modulus of the sheath becomes 20 MPa or less. However, it is thought that the tensile strength did not satisfy the requirement of 20 MPa or more in samples No. 1 to No. 3 because the proportion of the first polyurethane resin was too high. Polyurethane resin undergoes a thermal history in both the mixing process and the extrusion process. In other words, polyurethane resin that has gone through the two processes of mixing and extrusion undergoes a thermal history twice. If the proportion of the first polyurethane resin is high, a large proportion of polyurethane resin undergoes a thermal history twice. It is thought that the tensile strength did not improve because the proportion of polyurethane resin undergoing a thermal history twice was too high.

[0076] Samples No. 4 to No. 6 satisfy the requirements of having an elastic modulus of 20 MPa or less and a tensile strength of 20 MPa or more. It is thought that the tensile strength improved in samples No. 4 to No. 6 because the proportion of the first polyurethane resin was relatively small, and the proportion of polyurethane resin that underwent two thermal histories was also relatively small.

[0077] In sample No. 7, the compound could not be molded because the proportion of the first polyurethane resin was too low during the mixing process. Therefore, a cable could not be manufactured using sample No. 7.

[0078] From the above, it can be seen that when the Type A durometer hardness of the first polyurethane resin and the second polyurethane resin is 68 or more and 76 or less, if the content of the first polyurethane resin is 20 parts by mass or more and 60 parts by mass or less, and the content of the second polyurethane resin is 40 parts by mass or more and 80 parts by mass or less, a sheath can be formed with an elastic modulus of 20 MPa or less and a tensile strength of 20 MPa or more.

[0079] Table 2 shows that for samples No. 8 to No. 14, where the type A durometer hardness of the polyurethane resin is between 78 and 82, the following can be observed. Samples No. 8 and No. 9 satisfy the requirement of an elastic modulus of 20 MPa or less, but their tensile strength does not satisfy the requirement of 20 MPa or more. It is thought that in samples No. 8 and No. 9, by mixing polyurethane resins with a type A durometer hardness of 78 or more and 82 or less, the type A durometer hardness of the sheath became 85, and the elastic modulus of the sheath became 20 MPa or less. However, it is thought that in samples No. 8 and No. 9, the proportion of the first polyurethane resin was too high, resulting in a large proportion of polyurethane resin undergoing two thermal histories, which is why the tensile strength did not meet the requirement of 20 MPa or more.

[0080] Samples No. 10 to No. 13 satisfy the requirements of having an elastic modulus of 20 MPa or less and a tensile strength of 20 MPa or more. It is thought that the tensile strength improved in samples No. 10 to No. 13 because the proportion of the first polyurethane resin was relatively small, and the proportion of polyurethane resin that underwent two thermal histories was relatively small. Compared to sample No. 3, sample No. 10 has a higher type A durometer hardness of polyurethane resin, so it is thought that the polyurethane resin did not deteriorate easily even with a larger proportion of polyurethane resin that underwent thermal histories, resulting in higher tensile strength.

[0081] In sample No. 14, the compound could not be molded because the proportion of the first polyurethane resin was too low during the mixing process. Therefore, a cable could not be manufactured using sample No. 14. Compared to sample No. 6, sample No. 14 has a higher Type A durometer hardness of the polyurethane resin, which is thought to be why the compound could not be molded even though the proportion of the first polyurethane resin was the same.

[0082] From the above, it can be seen that when the Type A durometer hardness of the first polyurethane resin and the second polyurethane resin is greater than 76 and less than or equal to 82, if the content of the first polyurethane resin is 30 parts by mass or more and 70 parts by mass or less, and the content of the second polyurethane resin is 30 parts by mass or more and 70 parts by mass or less, a sheath can be formed with an elastic modulus of 20 MPa or less and a tensile strength of 20 MPa or more.

[0083] In samples No. 15 and No. 16, the tensile strength was 20 MPa or higher, but the modulus of elasticity was not 20 Ma or lower. In samples No. 15 and No. 16, the high Type A durometer hardness of the polyurethane resin is thought to have improved the tensile strength but decreased the modulus of elasticity. [Explanation of Symbols]

[0084] 1 Cable 2 Insulated wires 3 conductors 4. Insulator 5 Sheath 7 Mixer 70 First input slot 71 Screw 8. Extruder 80 Second input slot 81 Screw 91 First polyurethane resin 92 Second polyurethane resin 95 Additives 97 Compound

Claims

1. It contains polyurethane resin as its main component, The tensile strength is 20 MPa or more. The modulus of elasticity is 20 MPa or less. Type A durometer hardness is 85 or less. Resin composition.

2. The tear strength is 40 N / mm or more. The resin composition according to claim 1, wherein the elongation at -40°C is 300% or more.

3. The resin composition according to claim 1, comprising 5 to 100 parts by mass of a flame retardant per 100 parts by mass of the polyurethane resin.

4. The resin composition according to claim 1, comprising 0.1 parts by mass or more and 2.0 parts by mass of a lubricant per 100 parts by mass of the polyurethane resin.

5. A cable comprising an insulated wire and a sheath covering the insulated wire, The sheath is made of the resin composition described in any one of claims 1 to 4. cable.

6. The process of preparing insulated wires, The first step is to put the polyurethane resin and additives into a mixer to produce a compound, The process includes the step of feeding a second polyurethane resin and the compound into an extruder to form a sheath around the insulated wire, The respective content ratios of the first polyurethane resin and the second polyurethane resin are set such that the tensile strength of the sheath is 20 MPa or more, the elastic modulus is 20 MPa or less, and the Type A durometer hardness is 85 or less. A method for manufacturing cables.

7. When the Type A durometer hardness of the first polyurethane resin and the second polyurethane resin is 68 or more and 76 or less, the content of the first polyurethane resin is 20 parts by mass or more and 60 parts by mass or less, and the content of the second polyurethane resin is 40 parts by mass or more and 80 parts by mass or less. When the Type A durometer hardness of the first polyurethane resin and the second polyurethane resin is greater than 76 and less than or equal to 82, the content ratio of the first polyurethane resin is 30 parts by mass or more and 70 parts by mass or less, and the content ratio of the second polyurethane resin is 30 parts by mass or more and 70 parts by mass or less. The method for manufacturing a cable according to claim 6, wherein the respective content ratios of the first polyurethane resin and the second polyurethane resin are such that the total amount of the first polyurethane resin and the second polyurethane resin is 100 parts by mass.

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