Resin composition, resin composition molded article, power cable, and method for producing power cable

Abstract

A resin composition is coated around a long object, the resin composition containing propylene units. After a predetermined bending test, a molded body containing the resin composition contains no voids having a maximum length of 1 μm or more, and no crystals having a maximum length exceeding 10 μm. The bending test comprises: a first step of bending the molded body so that a bending ratio of a bending radius of the molded body relative to an outer diameter of the molded body is 7 or less; and a second step of bending the molded body in a direction opposite to the bending direction in the first step at the same bending ratio as that in the first step.

Description

Technical Field

[0001] The present disclosure relates to a resin composition, a resin composition molded article, a power cable, and a method for producing a power cable.

[0002] This application claims priority based on Japanese application No. 2020-211489, filed on December 21, 2020, and incorporates all the contents described in the aforementioned Japanese application by reference. Background Art

[0003] Cross-linked polyethylene has excellent insulating properties and is therefore widely used as a resin component constituting an insulating layer in power cables and the like (for example, Patent Document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 57-69611 Summary of the Invention

[0007] According to one embodiment of the present disclosure, a resin composition is provided, the resin composition being coated around a long object, the resin composition containing propylene units, and in a molded body containing the resin composition after a predetermined bending test, no voids having a maximum length of 1 μm or more are present, and no crystals having a maximum length exceeding 10 μm are present, wherein the bending test comprises: a first step of bending the molded body so that a bending ratio of a bending radius of the molded body relative to an outer diameter of the molded body is 7 or less; and a second step of bending the molded body in a direction opposite to the bending direction in the first step at a bending ratio identical to the bending ratio in the first step.

[0008] According to another embodiment of the present disclosure, a resin composition molded body is provided, wherein the resin composition molded body is coated around a long object, the resin composition molded body contains propylene units, and after a predetermined bending test, there are no voids with a maximum length of 1 μm or more, and no crystals with a maximum length exceeding 10 μm. The bending test comprises: a first step of bending the resin composition molded body so that a bending ratio of a bending radius of the resin composition molded body relative to an outer diameter of the resin composition molded body is 7 or less; and a second step of bending the resin composition molded body in a direction opposite to the bending direction of the first step at a bending ratio that is the same as the bending ratio of the first step.

[0009] According to another embodiment of the present disclosure, a resin composition molded body is provided, which contains propylene units, and the resin composition molded body satisfies the first necessary condition, the second necessary condition, and the third necessary condition in the distribution of the count number relative to the elastic modulus of the resin composition molded body obtained by micro-area elasticity measurement using a scanning probe microscope, wherein the elastic modulus is measured under the following conditions: at 25°C, the resin composition molded body is tapped 60,000 times within a range of 10 μm square by a cantilever composed of silicon and having a tip with a curvature radius of less than 20 nm, the first necessary condition is a normal distribution with only one peak appearing in the area where the count number becomes 4,000 times or more, the second necessary condition is that the elastic modulus at the peak of the normal distribution is less than 2,000 MPa, and the third necessary condition is that the count number at the peak of the normal distribution is less than 25% of the total tapping number.

[0010] According to another embodiment of the present disclosure, a resin composition molded body is provided, comprising: a resin A comprising a propylene unit; and a resin B comprising two or more monomer units, and being solid at 25°C. The storage modulus of the resin A at 25°C, as measured by a dynamic viscoelasticity measurement, is 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C, as measured by a dynamic viscoelasticity measurement, is 1 MPa or more and 200 MPa or less. When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0011] According to another embodiment of the present disclosure, a resin composition molded article is provided, comprising: a resin A comprising propylene units; and a resin B comprising two or more monomer units, the resin A being solid at 25°C, wherein a ratio of the storage modulus of the resin A at 25°C to the storage modulus of the resin B as measured by dynamic viscoelasticity measurement is 5 or more and 200 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0012] According to another embodiment of the present disclosure, a resin composition molded body is provided, comprising: a resin A comprising propylene units; and a resin B comprising two or more monomer units, wherein the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×104 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is greater than or equal to 1.1 and less than or equal to 3.0, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is greater than or equal to 52 parts by mass and less than or equal to 95 parts by mass, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0013] According to another embodiment of the present disclosure, a power cable is provided, comprising: a conductor; and an insulating layer covering the conductor, wherein the insulating layer contains propylene units, and after a predetermined bending test, the insulating layer contains no voids having a maximum length of 1 μm or more, and no crystals having a maximum length exceeding 10 μm.

[0014] According to another embodiment of the present disclosure, there is provided a power cable comprising: a conductor; and an insulating layer covering the conductor, wherein the insulating layer contains propylene units, and wherein the insulating layer satisfies the first, second, and third necessary conditions in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope.

[0015] According to another embodiment of the present disclosure, a power cable is provided, comprising: a conductor; and an insulating layer covering the conductor, the insulating layer comprising: a resin A comprising a propylene unit; and a resin B comprising two or more monomer units, the resin being solid at 25°C, the storage modulus of the resin A at 25°C measured by a dynamic viscoelasticity measurement being 600 MPa or more and 1200 MPa or less, the storage modulus of the resin B at 25°C measured by a dynamic viscoelasticity measurement being 1 MPa or more and 200 MPa or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0016] According to another embodiment of the present disclosure, a power cable is provided, comprising: a conductor; and an insulating layer covering the conductor, the insulating layer comprising: a resin A comprising a propylene unit; and a resin B comprising two or more monomer units, the resins being solid at 25°C, wherein a ratio of the storage modulus of the resin A at 25°C measured by dynamic viscoelasticity measurement to the storage modulus of the resin B is 5 or more and 200 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0017] According to another embodiment of the present disclosure, a power cable is provided, comprising: a conductor; and an insulating layer covering the conductor, wherein the insulating layer comprises: a resin A comprising propylene units; and a resin B comprising two or more monomer units, wherein the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is 1.1 or more and 3.0 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0018] According to another embodiment of the present disclosure, a method for manufacturing a power cable is provided, the method comprising the following steps: preparing a resin composition having a resin A and a resin B, wherein the resin A contains a propylene unit, the resin B contains two or more monomer units, and is solid at 25°C; and using the resin composition to cover an insulating layer around a conductor, wherein in the step of preparing the resin composition, the storage modulus of the resin A at 25°C measured by a dynamic viscoelasticity measurement is set to 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C measured by a dynamic viscoelasticity measurement is set to 1 MPa or more and 200 MPa or less, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less.

[0019] According to another embodiment of the present disclosure, a method for manufacturing a power cable is provided, the method comprising the following steps: preparing a resin composition having a resin A and a resin B, wherein the resin A contains a propylene unit, the resin B contains two or more monomer units, and is solid at 25°C; and using the resin composition to cover an insulating layer around a conductor, wherein in the step of preparing the resin composition, the ratio of the storage modulus of the resin A at 25°C measured by a dynamic viscoelasticity measurement to the storage modulus of the resin B is set to 5 or more and 200 or less, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less.

[0020] According to another embodiment of the present disclosure, a method for producing a power cable is provided, comprising the steps of: preparing a resin composition comprising a resin A and a resin B, wherein the resin A comprises a propylene unit and the resin B comprises two or more monomer units; and coating a conductor with an insulating layer using the resin composition, wherein in the step of preparing the resin composition, the peak molecular weight in the molecular weight distribution of the resin A is set to 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is set to be 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is set to be 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is set to 1.1 or more and 3.0 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing an example of the molecular weight distribution of each of resin A and resin B according to one embodiment of the present disclosure.

[0022] Figure 2 1 is a schematic cross-sectional view perpendicular to the axial direction of a power cable according to an embodiment of the present disclosure.

[0023] Figure 3 This is a diagram showing an example of the results of micro-region elasticity measurement. DETAILED DESCRIPTION

[0024] [Problems to be Solved by the Present Disclosure]

[0025] Cross-linked polyethylene is widely used as insulation for power cables, but due to age-related degradation, it cannot be recycled and must be incinerated, raising concerns about its impact on the environment.

[0026] Therefore, in recent years, resins containing propylene (hereinafter referred to as "propylene-based resins") have attracted attention as the resin component for insulating layers. Even when non-crosslinked, propylene-based resins can meet the insulation requirements for power cables. Specifically, they offer both insulation and recyclability.

[0027] An object of the present disclosure is to provide a technology capable of improving the insulation properties of a molded article containing a propylene resin.

[0028] [Effects of the Present Disclosure]

[0029] According to the present disclosure, the insulation properties of a molded article containing a propylene resin can be improved.

[0030] [Description of Embodiments of the Present Disclosure]

[0031] <Insights Obtained by the Inventors>

[0032] First, the findings obtained by the inventors will be briefly described.

[0033] Generally, polypropylene is harder than polyethylene, for example, as a single component.

[0034] Therefore, conventionally, resin components obtained by adding ethylene propylene rubber (EPR) or the like to polypropylene have been used in the technical field of automobile bumpers, etc. The addition of EPR or the like to polypropylene can soften the resin component.

[0035] Therefore, in the technical field of power cables, the inventors have tried to add a flexible resin such as EPR to a propylene-based resin as a resin component constituting the insulating layer in order to improve the flexibility of the insulating layer.

[0036] However, the inventors have conducted research on adding a flexible resin to a propylene-based resin in an insulating layer, and have found that the insulating properties of the insulating layer may be reduced after the power cable is flexed.

[0037] Analysis of the insulating layer whose insulation properties were reduced by flexing revealed that the reduction in insulation properties after flexing is caused by the following mechanism.

[0038] As mentioned above, the elastic modulus of flexible resin is lower than that of propylene resin. Each resin has a unique molecular weight distribution related to its elastic modulus. As a result, the molecular weight distribution of flexible resin and propylene resin are different from each other.

[0039] When two resins having different molecular weight distributions are mixed, at least one of the resins may be partially biased.

[0040] For example, a component with a high elastic modulus derived from a propylene resin may be locally concentrated. Hereinafter, a region where a component with a high elastic modulus is locally concentrated is also referred to as a "high elastic region." In the high elastic region derived from the propylene resin, crystallinity increases, and the high elastic region becomes hard.

[0041] On the other hand, for example, components with low elastic modulus derived from a flexible resin may be locally concentrated. Hereinafter, the region where the components with low elastic modulus are locally concentrated is also referred to as a "low elastic region." In the low elastic region derived from the flexible resin, crystallinity decreases (becoming amorphous), and the low elastic region becomes soft.

[0042] Even when the resin is locally distributed in the insulating layer as described above, there is no problem with insulation immediately after manufacture. However, when the resin is locally distributed in the insulating layer, the following phenomenon may occur when the power cable is bent.

[0043] When the power cable is bent, local stress is applied in the resin component. When local stress is applied, for example, inside the high elastic region, cracks or separations may occur between the crystals, and therefore a tiny void may be generated. Alternatively, at the interface between the crystalline high elastic region and the amorphous low elastic region, they may separate, and therefore a tiny void may be generated. Alternatively, even inside the amorphous low elastic region, particularly between materials with poor compatibility, separation or peeling may occur along the material interface, and therefore a tiny void may be generated. It should be noted that the "void" mentioned herein also includes cracks.

[0044] Furthermore, when local stress is applied to the resin component, for example, coarse crystals (spherulites) may be generated in the high elastic region derived from the propylene resin, triggered by mechanical deformation.

[0045] The tiny voids and coarse crystals created during flexing degrade insulation. Therefore, when a high electric field is applied to a power cable, the electric field concentrates on the tiny voids and coarse crystals within the insulation layer, potentially causing insulation breakdown.

[0046] As a result of intensive research as described above, the inventors have discovered that a decrease in insulation properties after flexing can be suppressed by suppressing the generation of microscopic voids and coarse crystals during flexing.

[0047] The present disclosure is made based on the above-mentioned findings found by the inventors.

[0048] <Embodiments of the present disclosure>

[0049] Next, embodiments of the present disclosure will be described by way of examples.

[0050] [1] A resin composition according to one embodiment of the present disclosure is coated around a long object, the resin composition containing propylene units, and in a molded body containing the resin composition after a predetermined bending test, no voids having a maximum length of 1 μm or more are present, and no crystals having a maximum length exceeding 10 μm are present, wherein the bending test comprises: a first step of bending the molded body so that a bending ratio of a bending radius of the molded body relative to an outer diameter of the molded body becomes 7 or less; and a second step of bending the molded body in a direction opposite to the bending direction of the first step at a bending ratio identical to the bending ratio of the first step.

[0051] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0052] [2] A resin composition molded body according to one embodiment of the present disclosure is coated around a long object, the resin composition molded body containing propylene units, and in the resin composition molded body after a predetermined bending test, there are no voids with a maximum length of 1 μm or more, and no crystals with a maximum length exceeding 10 μm, wherein the bending test comprises: a first step of bending the resin composition molded body so that a bending ratio of a bending radius of the resin composition molded body relative to an outer diameter of the resin composition molded body becomes 7 or less; and a second step of bending the resin composition molded body in a direction opposite to the bending direction of the first step at a bending ratio identical to the bending ratio of the first step.

[0053] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0054] [3] In the resin composition molded body described in [2] above, the resin composition molded body satisfies the first, second and third necessary conditions in the distribution of the number of counts relative to the elastic modulus of the resin composition molded body obtained by micro-area elasticity measurement using a scanning probe microscope, wherein the elastic modulus is measured under the following conditions: at 25°C, the resin composition molded body is tapped 60,000 times within a 10 μm square range by a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm, the first necessary condition is a normal distribution having only one peak appearing in the area where the number of counts becomes 4,000 or more, the second necessary condition is that the elastic modulus at the peak of the normal distribution is less than 2,000 MPa, and the third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

[0055] According to this configuration, the generation of minute voids and coarse crystals during flexion can be suppressed.

[0056] [4] Another embodiment of the present disclosure is a resin composition molded body comprising propylene units, wherein the resin composition molded body satisfies a first requirement, a second requirement, and a third requirement in a distribution of count numbers relative to the elastic modulus of the resin composition molded body obtained by micro-area elasticity measurement using a scanning probe microscope, wherein the elastic modulus is measured under the following conditions: at 25°C, the resin composition molded body is tapped 60,000 times within a 10 μm square range by a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm, the first requirement is a normal distribution having only one peak appearing in an area where the count number becomes 4,000 or more, the second requirement is that the elastic modulus at the peak of the normal distribution is 2,000 MPa or less, and the third requirement is that the count number at the peak of the normal distribution is less than 25% of the total number of taps.

[0057] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0058] [5] The resin composition molded article according to any one of [2] to [4], comprising: a resin A comprising propylene units; and a resin B comprising two or more monomer units and being solid at 25°C.

[0059] According to this configuration, the molded body can be made soft.

[0060] [6] In the resin composition molded article described in [5] above, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, based on 100 parts by mass of the total content of the resin A and the resin B.

[0061] According to this configuration, the generation of minute voids and coarse crystals during flexion can be suppressed.

[0062] [7] In the resin composition molded body described in [5] or [6] above, the storage modulus of the resin A at 25°C measured by dynamic viscoelasticity measurement is 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C measured by dynamic viscoelasticity measurement is 1 MPa or more and 200 MPa or less.

[0063] According to this configuration, the resin A and the resin B can be uniformly mixed.

[0064] [8] Another embodiment of the present invention provides a resin composition molded body comprising: a resin A comprising a propylene unit; and a resin B comprising two or more monomer units, which is solid at 25°C, wherein the storage modulus of the resin A at 25°C measured by a dynamic viscoelasticity measurement is 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C measured by a dynamic viscoelasticity measurement is 1 MPa or more and 200 MPa or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0065] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0066] [9] In the resin composition molded article according to any one of [5] to [8] above, the ratio of the storage modulus of the resin A at 25°C to the storage modulus of the resin B measured by dynamic viscoelasticity measurement is 5 or more and 200 or less.

[0067] According to this configuration, the resin A and the resin B can be uniformly mixed.

[0068]

[10] Another embodiment of the present invention provides a resin composition molded body comprising: a resin A comprising a propylene unit; and a resin B comprising two or more monomer units, which is solid at 25°C, wherein the ratio of the storage modulus of the resin A at 25°C to the storage modulus of the resin B measured by dynamic viscoelasticity measurement is 5 or more and 200 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0069] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0070]

[11] In the resin composition molded article according to any one of [5] to

[10] , the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is greater than or equal to 1.1 and less than or equal to 3.0, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0071] According to this configuration, the resin A and the resin B can be uniformly mixed.

[0072]

[12] Another embodiment of the present disclosure provides a resin composition molded article comprising: a resin A comprising propylene units; and a resin B comprising two or more monomer units, wherein the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is greater than or equal to 1.1 and less than or equal to 3.0, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is greater than or equal to 52 parts by mass and less than or equal to 95 parts by mass, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0073] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0074]

[13] Another embodiment of the present invention provides a power cable comprising: a conductor; and an insulating layer covering the periphery of the conductor, wherein the insulating layer comprises propylene units, and after a predetermined bending test, there are no voids having a maximum length of 1 μm or more, and no crystals having a maximum length exceeding 10 μm in the insulating layer, wherein the bending test comprises: a first step of bending the power cable in such a manner that a bending ratio of a bending radius of the power cable relative to an outer diameter of the insulating layer becomes 7 or less; and a second step of bending the power cable in a direction opposite to the bending direction of the first step at a bending ratio identical to the bending ratio of the first step.

[0075] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0076]

[14] Another embodiment of the present invention relates to a power cable comprising: a conductor; and an insulating layer covering the periphery of the conductor, wherein the insulating layer comprises propylene units, and wherein the insulating layer satisfies a first requirement, a second requirement, and a third requirement in a distribution of counts relative to the elastic modulus of the insulating layer obtained by a micro-area elasticity measurement using a scanning probe microscope, wherein the elastic modulus is measured under the following conditions: at 25° C., the insulating layer is tapped 60,000 times within a 10 μm square range by a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm, the first requirement being a normal distribution having only one peak appearing in an area where the counts become 4,000 or more, the second requirement being that the elastic modulus at the peak of the normal distribution is less than 2,000 MPa, and the third requirement being that the counts at the peak of the normal distribution are less than 25% of the total number of taps.

[0077] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0078]

[15] Another embodiment of the present invention provides a power cable comprising: a conductor; and an insulating layer covering the conductor, wherein the insulating layer comprises: a resin A comprising a propylene unit; and a resin B comprising two or more monomer units, which is solid at 25°C, wherein the storage modulus of the resin A at 25°C measured by a dynamic viscoelasticity measurement is 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C measured by a dynamic viscoelasticity measurement is 1 MPa or more and 200 MPa or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0079] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0080]

[16] Another embodiment of the present invention provides a power cable comprising: a conductor; and an insulating layer covering the conductor, wherein the insulating layer comprises: a resin A comprising a propylene unit; and a resin B comprising two or more monomer units, which is solid at 25°C, wherein the ratio of the storage modulus of the resin A at 25°C to the storage modulus of the resin B measured by dynamic viscoelasticity measurement is 5 or more and 200 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0081] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0082]

[17] Another embodiment of the present disclosure provides a power cable comprising: a conductor; and an insulating layer covering the conductor, wherein the insulating layer comprises: a resin A comprising propylene units; and a resin B comprising two or more monomer units, wherein the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is greater than or equal to 1.1 and less than or equal to 3.0, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is greater than or equal to 52 parts by mass and less than or equal to 95 parts by mass, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0083] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0084]

[18] Another embodiment of the present disclosure provides a method for manufacturing a power cable, comprising the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A comprises a propylene unit, the resin B comprises two or more monomer units, and is solid at 25°C; and using the resin composition to coat an insulating layer around a conductor, wherein in the step of preparing the resin composition, the storage modulus of the resin A at 25°C measured by a dynamic viscoelasticity measurement is set to 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C measured by a dynamic viscoelasticity measurement is set to 1 MPa or more and 200 MPa or less, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less.

[0085] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0086]

[19] Another embodiment of the present disclosure provides a method for manufacturing a power cable, comprising the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A comprises a propylene unit, the resin B comprises two or more monomer units, and is solid at 25°C; and using the resin composition to coat an insulating layer around a conductor, wherein in the step of preparing the resin composition, the ratio of the storage modulus of the resin A at 25°C measured by a dynamic viscoelasticity measurement to the storage modulus of the resin B is set to 5 or more and 200 or less, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less.

[0087] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0088]

[20] Another embodiment of the present disclosure provides a method for producing a power cable, comprising the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A comprises a propylene unit and the resin B comprises two or more monomer units; and coating a conductor with an insulating layer using the resin composition, wherein in the step of preparing the resin composition, the peak molecular weight in the molecular weight distribution of the resin A is set to 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is set to be 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is set to be 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is set to 1.1 or more and 3.0 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0089] According to this configuration, a decrease in insulation properties after flexing can be suppressed.

[0090] [Details of the embodiments of the present disclosure]

[0091] Next, an embodiment of the present disclosure will be described below with reference to the accompanying drawings. It should be noted that the present disclosure is not limited to these examples, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0092] <One embodiment of the present disclosure>

[0093] (1) Resin composition molded body

[0094] The resin composition molded body of the present embodiment (hereinafter, also referred to as simply "molded body") contains, for example, a resin composition and is coated around a long object. Specifically, the resin composition molded body constitutes, for example, the insulating layer 130 of the power cable 10 described later. The object of the resin composition molded body is, for example, a long linear conductor 110. The resin composition molded body is, for example, extrusion-molded in a manner covering the outer periphery of the conductor 110. That is, the resin composition molded body has, for example, the same shape in the long dimension direction of the object. In addition, the length of the resin composition molded body in the long dimension direction of the object is, for example, more than 30 cm, preferably more than 50 cm. The thickness of the resin composition molded body coated on the object is, for example, more than 3 mm.

[0095] The resin composition molded article of this embodiment contains, for example, at least propylene units as a resin component. The "resin component" referred to herein refers to the resin material (polymer) constituting the main component of the resin composition molded article. The "main component" refers to the component with the largest content.

[0096] More specifically, the resin component constituting the resin composition molded body includes, for example, a propylene resin A and a flexible resin B. By mixing these, excessive crystal growth of the propylene resin can be inhibited, thereby improving the flexibility of the insulating layer.

[0097] In addition, the resin composition molded body of the present embodiment is, for example, non-crosslinked, or even if crosslinked, the gel fraction (crosslinking degree) is low. Specifically, the residue of the crosslinking agent in the resin composition molded body is, for example, less than 300 ppm. It should be noted that, when dicumyl peroxide is used as a crosslinking agent, the residue is, for example, cumyl alcohol, α-methylstyrene, etc. By making the molded body non-crosslinked or reducing the crosslinking degree as described above, the recyclability of the resin composition molded body can be improved.

[0098] (Resin A: acrylic resin)

[0099] As described above, the resin A of the present embodiment contains at least propylene units as a main component. Examples of the resin A include propylene homopolymers (homopolypropylene) and propylene random polymers (random polypropylene).

[0100] It should be noted that when the resin composition of the present embodiment is analyzed using a nuclear magnetic resonance (NMR) apparatus, at least propylene units are detected as monomer units derived from resin A. For example, when resin A is a propylene random polymer, propylene units and ethylene units are detected, and when resin A is a propylene homopolymer, only propylene units are detected.

[0101] In this embodiment, the stereoregularity of the propylene resin serving as resin A is preferably isotactic, for example. Propylene resins are polymerized using Ziegler-Natta catalysts and are general-purpose. The isotactic stereoregularity suppresses the melting point drop in a composition formed by mixing resin A with a low-crystalline resin B. As a result, stable use in non-crosslinked or lightly crosslinked conditions is possible.

[0102] It should be noted that, for reference only, other stereoregularities include syndiotactic and atactic, but neither is preferred as the stereoregularity of the propylene resin of this embodiment. In PP resins having these stereoregularities, the prescribed crystal structure cannot be obtained, and the melting point of a single component becomes low. In addition, in a composition formed by mixing the PP resin with resin B, the crystals of the PP resin are easily eroded by resin B. Therefore, the melting point of the composition is lower than the melting point of the PP resin as a single component. As a result, it is difficult to use the composition in a non-crosslinked or slightly crosslinked state. For these reasons, syndiotactic and atactic are not preferred.

[0103] When resin A is a propylene random polymer, as described above, resin A comprises propylene units and ethylene units. The ethylene content (ethylene unit content) in the propylene random polymer is, for example, 0.5% by mass or more and 15% by mass or less. By setting the ethylene content to 0.5% by mass or more, spherulite growth can be suppressed. On the other hand, by setting the ethylene content to 15% by mass or less, the decrease in melting point can be suppressed, enabling stable use in non-crosslinked or slightly crosslinked conditions.

[0104] It should be noted that the storage modulus, molecular weight, and content of resin A will be described in detail below together with the storage modulus, molecular weight, and content of resin B.

[0105] (Resin B: flexible resin)

[0106] Resin B in this embodiment is, for example, a resin material having an elastic modulus lower than that of resin A and imparting flexibility to a resin composition molded article. Note that, from the perspective of suppressing excessive crystal growth of resin A, resin B can be considered a low-crystalline resin (amorphous resin).

[0107] Resin B in this embodiment, for example, comprises two or more monomer units. Specifically, Resin B is composed of a copolymer of at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene. The resin composition of this embodiment is analyzed using an NMR apparatus to detect the monomer units derived from Resin B.

[0108] In addition, the carbon-carbon double bond in the olefin-based monomer unit is preferably located at the α position, for example.

[0109] Furthermore, resin B is preferably solid at 25°C, for example. If resin B is liquid at 25°C, this corresponds to an excessively low molecular weight, as described below. In this case, it becomes difficult to uniformly mix resins A and B. In contrast, if resin B is solid at 25°C, an excessive decrease in molecular weight can be suppressed. This allows resins A and B to be uniformly mixed.

[0110] Examples of resin B that meet the above-mentioned requirements include ethylene propylene rubber (EPR), very low density polyethylene (VLDPE), and styrene resins (styrene-containing resins). Two or more of these resins may also be used in combination. It should be noted that the density of VLDPE is, for example, 0.855 g / cm 3 Above 0.890g / cm 3 the following.

[0111] From the viewpoint of compatibility with the propylene resin A, the resin B is preferably a copolymer containing propylene units, for example. Examples of the copolymer containing propylene units include EPR among those mentioned above.

[0112] Preferably, the ethylene content (ethylene unit content) of EPR is, for example, 20% by mass or more, preferably 40% by mass or more, and more preferably 55% by mass or more. When the ethylene content is lower than 20% by mass, the compatibility of EPR with respect to the propylene resin becomes too high. Therefore, even if the content of EPR in the molded body is reduced, the molded body can be softened. However, the effect of hindering the crystallization of the propylene resin (also called "crystallization hindering effect") cannot be manifested, and the insulation may be reduced due to microcracks of the spherulites. In contrast, in this embodiment, by setting the ethylene content to 20% by mass or more, the compatibility of EPR with respect to the propylene resin can be suppressed from becoming too high. Thus, the softening effect produced by EPR can be obtained, and the crystallization hindering effect produced by EPR can be manifested. As a result, the reduction in insulation can be suppressed. Moreover, by preferably setting the ethylene content to 40% by mass or more, more preferably to 55% by mass or more, the crystallization hindering effect can be stably manifested, and the reduction in insulation can be stably suppressed.

[0113] On the other hand, resin B may also be a copolymer containing no propylene units. For example, VLDPE is preferred due to its availability. Examples of VLDPE include PE composed of ethylene and 1-butene, and PE composed of ethylene and 1-octene. By adding a copolymer containing no propylene units as resin B, a predetermined amount of resin B can be mixed with the propylene resin while preventing complete compatibility. By setting the content of such a copolymer containing no propylene units above a predetermined amount, a crystallization-inhibiting effect can be achieved.

[0114] In addition, as mentioned above, resin B may also be a styrene resin, for example. Styrene resin is a copolymer comprising a styrene unit as a hard segment and at least one monomer unit of ethylene, propylene, butylene and isoprene as a soft segment. Styrene resin may also be referred to as a styrene thermoplastic elastomer. By comprising relatively soft monomer units and relatively rigid monomer units in styrene resin, formability can be improved. In addition, by comprising monomer units (such as butylene) having good compatibility with resin A as a PP resin, resin A and resin B can be uniformly mixed.

[0115] Examples of styrene-based resins include styrene-butadiene-styrene block copolymers (SBS), hydrogenated styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene copolymers (SIS), hydrogenated styrene-isoprene-styrene copolymers, hydrogenated styrene-butadiene rubber, hydrogenated styrene-isoprene rubber, and styrene-ethylene-butylene-olefin crystalline block copolymers. Two or more of these may be used in combination.

[0116] It should be noted that the term "hydrogenated" as used herein refers to hydrogenation of double bonds. For example, a "hydrogenated styrene-butadiene-styrene block copolymer" refers to a polymer obtained by hydrogenating the double bonds of a styrene-butadiene-styrene block copolymer. It should be noted that the double bonds of the aromatic rings of styrene are not hydrogenated. A "hydrogenated styrene-butadiene-styrene block copolymer" may also be referred to as a styrene-ethylene-butylene-styrene block copolymer (SEBS).

[0117] Among styrene resins, hydrogenated materials that do not contain double bonds in their chemical structure other than aromatic rings are preferred. Using non-hydrogenated materials can cause thermal degradation of the resin component during molding of the resin composition, potentially degrading the properties of the resulting molded article. In contrast, using hydrogenated materials improves resistance to thermal degradation, thereby maintaining high properties of the molded article.

[0118] The styrene content in the styrene-based resin (hereinafter simply referred to as "styrene content") is not particularly limited, but is preferably 5% by mass or greater and 35% by mass or less, for example. By setting the styrene content within this range, the material can be prevented from becoming excessively hard. This can also suppress separation and cracking between the PP-based resin and the styrene-containing resin.

[0119] (Molecular weight distribution)

[0120] As a result of intensive research, the inventors have found that the above-mentioned local imbalance of each of the resins A and B can be suppressed by adjusting the molecular weight distribution of each of the resins A and B as a single component.

[0121] Here, use Figure 1 The molecular weight distribution of each of resin A and resin B in this embodiment will be described. Figure 1 : is a graph showing an example of the molecular weight distribution of each of resin A and resin B according to this embodiment. Figure 1 In the figure, the vertical axis represents the differential distribution value (frequency) (%) normalized with respect to 100.

[0122] Figure 1 The molecular weight distribution of each of the resin A and the resin B in the above-mentioned formula is determined, for example, by gel permeation chromatography (GPC) based on a calibration curve prepared using polystyrene (PS) as a standard sample. Figure 1 As shown in FIG, the "molecular weight distribution" referred to herein refers to a distribution curve obtained by plotting differential distribution values ​​corresponding to the number of molecules against molecular weight.

[0123] In addition, below, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution. Mw / Mn is also called the polydispersity index (Polydispersity Index), which is defined as an index value (numerical value) representing the width of the above-mentioned molecular weight distribution. The larger the Mw / Mn, the wider the molecular weight distribution.

[0124] like Figure 1 As shown, in this embodiment, resin A and resin B have different molecular weight distributions. For example, at least a portion of the molecular weight distribution of resin A overlaps with the molecular weight distribution of resin B. On the other hand, the molecular weight distribution of resin A is relatively broad, while the molecular weight distribution of resin B is relatively narrow. These molecular weight distributions of resin A and resin B allow resin A and resin B to be uniformly mixed. This prevents localized imbalance between resin A and resin B within insulating layer 130. As a result, the formation of microscopic voids and coarse crystals during flexure can be suppressed.

[0125] Specifically, the peak molecular weight in the molecular weight distribution of resin A is, for example, 6×10 4 Above and 6×10 5 When the peak molecular weight of resin A is less than 6×10 4 When the peak molecular weight of resin A is set to 6×10 4 As a result, the embrittlement of resin A can be suppressed. Thus, resin A and resin B can be uniformly mixed. On the other hand, when the peak molecular weight of resin A exceeds 6×10 5 When the molecular weight of resin A is 6×10 5 Thus, the fluidity can be ensured, and the insulating layer 130 can be stably molded. In addition, the molecular weight distribution of resin A and the molecular weight distribution of resin B can be overlapped within a predetermined range. Thus, resin A and resin B can be uniformly mixed.

[0126] In addition, the Mw / Mn of resin A is, for example, greater than 3.0 and less than 8.0. When the Mw / Mn of resin A is less than 3.0, it is difficult to mold the insulating layer 130. In contrast, by setting the Mw / Mn of resin A to greater than 3.0, the insulating layer 130 can be stably molded. On the other hand, when the Mw / Mn of resin A exceeds 8.0, the molecular weight distribution of resin A becomes too wide. Therefore, the compatibility between resin A and resin B deteriorates locally. Therefore, it is difficult to mix them uniformly. In contrast, by setting the Mw / Mn of resin A to less than 8.0, the molecular weight distribution of resin A can be made wider than the molecular weight distribution of resin B, and the excessive expansion of the molecular weight distribution of resin A can be suppressed. Thus, the generation of portions where the compatibility between resin A and resin B is poor can be suppressed. As a result, resin A and resin B can be uniformly mixed.

[0127] On the other hand, the peak molecular weight in the molecular weight distribution of resin B is, for example, 4×10 4 Above and 4×10 5 When the peak molecular weight of resin B is less than 4×10 4 or more than 4×10 5 When the peak molecular weight of resin B is set to 4×10 4 Above and 4×10 5 This can suppress the generation of uneven portions caused by solidification of only one of the resin A and the resin B. In other words, the resin A and the resin B can be uniformly mixed.

[0128] In addition, the Mw / Mn of resin B is, for example, greater than 1.1 and less than 3.0. When the Mw / Mn of resin B is less than 1.1, the molecular weight distribution of resin B becomes too narrow. Therefore, an uneven portion solidified by only one of resin A and resin B may be generated. In contrast, by setting the Mw / Mn of resin B to greater than 1.1, the molecular weight distribution of resin B can be made narrower than the molecular weight distribution of resin A, and the excessive narrowness of the molecular weight distribution of resin B can be suppressed. Thus, the generation of uneven portions solidified by only one of resin A and resin B can be suppressed. That is, resin A and resin B can be uniformly mixed together. On the other hand, when the Mw / Mn of resin B exceeds 3.0, the molecular weight distribution of resin B becomes broad. Resins B, which are mixed with each other with a wide molecular weight distribution, are only mixed in a specific molecular weight region within resin A. Therefore, an uneven portion solidified by only one of resin A and resin B may be generated. In contrast, by setting the Mw / Mn of resin B to 3.0 or less, the molecular weight distribution of resin B can be made narrower than that of resin A. This can suppress the occurrence of uneven portions where only one of resin A and resin B solidifies. As a result, regardless of the local molecular weight within resin A, resin B, which is blended with a narrow molecular weight distribution, can be uniformly mixed throughout the entire resin A.

[0129] (Elastic modulus)

[0130] In this embodiment, as described above, the elastic modulus of resin B is lower than that of resin A. Furthermore, in this embodiment, resin A and resin B each satisfy the aforementioned molecular weight distribution requirements, and thus resin A and resin B each satisfy the storage modulus requirements measured by the following dynamic viscoelasticity measurement (DMA: Dynamic Mechanical Analysis).

[0131] It should be noted that in the following dynamic viscoelasticity measurement, for example, the storage modulus of the resin sample was measured while the temperature was increased from -50°C to 100°C while the sample was subjected to a 0.08% expansion and contraction (applied with a 0.08% expansion and contraction vibration). The measurement frequency was set to 10 Hz, and the heating rate was set to 10°C / min.

[0132] In the propylene resin resin A, as the molecular weight increases, the elastic modulus increases. Based on the molecular weight distribution of the resin A described above, the storage modulus of the resin A at 25°C measured by dynamic viscoelasticity measurement is, for example, 600 MPa or more and 1200 MPa or less. This achieves effects comparable to those obtained when the resin A satisfies the aforementioned molecular weight distribution requirements.

[0133] That is, the resin A and the resin B can be mixed uniformly.

[0134] On the other hand, for resin B, which is a flexible resin, the relationship between molecular weight and elastic modulus depends on whether resin B is a styrene resin. When resin B is a non-styrene resin, the elastic modulus increases as the molecular weight increases. Conversely, when resin B is a styrene resin, the elastic modulus decreases as the molecular weight increases.

[0135] Regardless of the type of resin B, the storage modulus of resin B at 25°C, as measured by dynamic viscoelasticity measurement, is, for example, 1 MPa or more and 200 MPa or less, based on the molecular weight distribution of resin B described above. This achieves effects comparable to those achieved when resin B satisfies the aforementioned molecular weight distribution requirements. Specifically, resins A and B can be uniformly mixed.

[0136] Alternatively, based on the molecular weight distributions of each of the resins A and B, the ratio of the storage modulus of the resin A at 25°C measured by dynamic viscoelasticity measurement to the storage modulus of the resin B is, for example, 5 or more and 200 or less. This also provides an effect comparable to that obtained by satisfying the aforementioned molecular weight distribution requirement.

[0137] (Mix ratio)

[0138] In the present embodiment, it is more preferable that the mixing ratio of the resin A and the resin B satisfies the following requirements.

[0139] Specifically, when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is, for example, 52 parts by mass or more and 95 parts by mass or less.

[0140] When the content of Resin A is less than 52 parts by mass, the content of Resin B, a flexible resin, becomes relatively high. Consequently, low-elasticity regions, where Resin B is locally concentrated, are more likely to form. As a result, during flexion, tiny voids may form at the interface between the high-elasticity and low-elasticity regions, or at least within the low-elasticity regions. In contrast, by setting the content of Resin A to 52 parts by mass or greater, the excessive formation of low-elasticity regions can be suppressed. Consequently, the formation of tiny voids at the interface between the high-elasticity and low-elasticity regions, or at least within the low-elasticity regions, can be suppressed during flexion.

[0141] On the other hand, when the content of Resin A exceeds 95 parts by mass, the amount of Resin A, a propylene-based resin, becomes excessive relative to Resin B. Consequently, a high-elasticity region, where Resin A is locally concentrated, tends to form. As a result, during flexion, separation between crystals within the high-elasticity region may cause minute voids to form. By contrast, setting the content of Resin A to 95 parts by mass or less can suppress the excessive formation of high-elasticity regions. This can also suppress the formation of minute voids caused by separation between crystals within the high-elasticity region during flexion.

[0142] (Other additives)

[0143] The resin composition molded article may contain, in addition to the above-mentioned resin component, for example, an antioxidant, a copper damage inhibitor, a lubricant, and a colorant.

[0144] However, the resin composition molded article of this embodiment preferably contains less additives that function as nucleating agents for generating propylene crystals, for example. Examples of additives that function as nucleating agents include inorganic or organic substances such as flame retardants. Specifically, for example, when the combined content of the propylene resin and the low-crystalline resin is set to 100 parts by mass, the content of the additive that functions as a nucleating agent is preferably less than 1 part by mass. This can suppress the occurrence of unexpected abnormal crystallization caused by the nucleating agent, making it easier to control the amount of crystallization.

[0145] (2) Power cables

[0146] Next, use Figure 2 The power cable according to this embodiment will be described. Figure 2 This is a cross-sectional view perpendicular to the axial direction of the power cable according to the present embodiment.

[0147] The power cable 10 of this embodiment is configured as a so-called solid-insulated power cable. Furthermore, the power cable 10 of this embodiment is configured to be laid on land (in a pipeline), underwater, or underwater. Note that the power cable 10 is used, for example, for alternating current.

[0148] Specifically, the power cable 10 includes, for example, a conductor 110 , an inner semiconductive layer 120 , an insulating layer 130 , an outer semiconductive layer 140 , a shielding layer 150 , and a jacket 160 .

[0149] (Conductor (conductive part))

[0150] The conductor 110 is formed by twisting together a plurality of conductor core wires (conductive core wires) made of, for example, pure copper, copper alloy, aluminum, or aluminum alloy.

[0151] (Inner semiconducting layer)

[0152] Internal semiconductive layer 120 is provided to cover the outer periphery of conductor 110. Furthermore, internal semiconductive layer 120 is configured to have semiconductivity and to suppress electric field concentration on the surface side of conductor 110. Internal semiconductive layer 120 may include, for example, at least one of ethylene-based copolymers such as ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-butyl acrylate copolymer, and ethylene-vinyl acetate copolymer; an olefin-based elastomer; the aforementioned low-crystalline resin; and conductive carbon black.

[0153] (Insulation layer)

[0154] Insulating layer 130 is provided to cover the outer periphery of inner semiconductive layer 120 and is formed as a molded body of the resin composition described above. Insulating layer 130 is, for example, extrusion-molded from the resin composition as described above.

[0155] (Outer semiconducting layer)

[0156] External semiconductive layer 140 is provided to cover the outer periphery of insulating layer 130. Furthermore, external semiconductive layer 140 is configured to have semiconductivity and to suppress electric field concentration between insulating layer 130 and shielding layer 150. External semiconductive layer 140 is formed of, for example, the same material as internal semiconductive layer 120.

[0157] (Shielding layer)

[0158] Shielding layer 150 is provided to cover the outer periphery of outer semiconductive layer 140. Shielding layer 150 is formed, for example, by winding copper tape or as a wire shield formed by winding multiple soft copper wires. It should be noted that tape, such as adhesive tape, may be wound around the inside and outside of shielding layer 150.

[0159] (jacket)

[0160] The sheath 160 is provided to cover the outer periphery of the shield layer 150. The sheath 160 is made of, for example, polyvinyl chloride or polyethylene.

[0161] It should be noted that if the power cable 10 of this embodiment is an underwater cable or a bottom cable, it may have a so-called waterproof layer made of a metal such as aluminum or a wire armor outside the shield layer 150 .

[0162] On the other hand, the power cable 10 of the present embodiment may not have a waterproof layer outside the shield layer 150. In other words, the power cable 10 of the present embodiment may have a non-perfect waterproof structure.

[0163] (Specific dimensions, etc.)

[0164] The specific dimensions of power cable 10 are not particularly limited. For example, the diameter of conductor 110 is 5 mm to 60 mm, the thickness of inner semiconductive layer 120 is 0.5 mm to 3 mm, the thickness of insulating layer 130 is 3 mm to 35 mm, the thickness of outer semiconductive layer 140 is 0.5 mm to 3 mm, the thickness of shielding layer 150 is 0.1 mm to 5 mm, and the thickness of jacket 160 is 1 mm or more. The AC voltage applicable to power cable 10 of this embodiment is, for example, 20 kV or more.

[0165] (3) Cable characteristics

[0166] In this embodiment, as described above, by satisfying the requirements of the molecular weight distribution, elastic modulus, and compounding ratio of each of resin A and resin B, the following characteristics of insulating layer 130 can be obtained.

[0167] (Micro-area elasticity)

[0168] Measuring only the elastic modulus of a molded article by dynamic viscoelasticity measurement (DMA), which is a measurement of macroscopic hardness, cannot reveal the possibility of the generation of the aforementioned microscopic voids and coarse crystals during flexure.

[0169] Therefore, the inventors conducted intensive research and, as a result, attempted to measure the microscopic hardness of molded products by measuring the elasticity of microscopic regions. They found that it was possible to understand the possibility of the generation of microscopic voids and coarse crystals during flexure.

[0170] Here, use Figure 3 The measurement of micro-area elasticity will be described. Figure 3 This is a diagram showing an example of the results of micro-region elasticity measurement.

[0171] Figure 3 The "micro-area elasticity measurement" described in this document is performed using a scanning probe microscope (SPM). For example, in the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: 60,000 tappings are performed on a 10-μm square area of ​​the molded article at 25°C using a cantilever made of silicon (single crystal) and having a tip with a curvature radius of at least 1 nm and less than 20 nm. For example, a sheet of a predetermined thickness cut from the center of the insulating layer 130 in the thickness direction is used as the molded article for this measurement. This micro-area elasticity measurement yields a distribution of counts relative to the elastic modulus of the molded article.

[0172] For example, the insulating layer 130 of the present embodiment satisfies the first, second, and third requirements described below in the distribution of the number of counts obtained by micro-region elasticity measurement with respect to the elastic modulus of the insulating layer 130 .

[0173] First, a comparative example that does not satisfy at least any one of the first requirement, the second requirement, and the third requirement will be described.

[0174] As a comparative example, for example, Figure 3 As in (ii) of Figure 1, two or more peaks may appear in the region where the count number reaches 4000 or more. In this case, resins A and B are not uniformly mixed, and at least one of them is locally biased. In this case, tiny voids or coarse crystals may form during flexion.

[0175] In addition, as other comparative examples, for example, Figure 3 As in (iii), although the normal distribution has a single peak, the elastic modulus at the peak may exceed 2000 MPa. In this case, the resin A content is high, resulting in a high elasticity region where the resin A is locally concentrated. In this case, microscopic voids or coarse crystals may also form during flexion.

[0176] In addition, as other comparative examples, for example, Figure 3 As in (iv), sometimes, even though the normal distribution has only one peak and the elastic modulus at the peak is less than 2000 MPa, the number of counts at the peak of the normal distribution is more than 25% of the total number of taps (i.e., more than 15,000 times). In this case, for example, it is equivalent to the elastic modulus of resin B being too low, and resins A and B are not evenly mixed with each other. In this case, tiny voids or coarse crystals may also be generated during flexion.

[0177] In contrast, in this embodiment, for example, Figure 3 As in (i), as a first necessary condition, a normal distribution having only one peak appears in the region where the number of counts becomes 4000 or more.

[0178] As a second requirement, the elastic modulus at the peak of the normal distribution is 2000 MPa or less. In addition, as a third requirement, the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

[0179] Thus, in this embodiment, the distribution of the elastic modulus within the micro-regions of insulating layer 130 shifts toward the lower side, becoming broadly distributed from low to high elastic moduli. In other words, resin A and resin B are uniformly blended, resulting in uniform hardness even within micro-regions of the molded article. This prevents the formation of micro-voids and coarse crystals during flexure.

[0180] It should be noted that, in the second necessary condition, the lower limit of the elastic modulus at the peak of the normal distribution is not limited, for example, it is equivalent to the elastic modulus in the case of less propylene resin, which is 500 MPa. In addition, in the third necessary condition, the lower limit of the number of counts at the peak of the normal distribution is not limited. However, if the first necessary condition is met, the lower limit of the number of counts in the third necessary condition will not be less than the number of counts (4000 times) that serves as the benchmark for the first necessary condition. Therefore, the lower limit of the number of counts in the third necessary condition is, for example, 6.7% of the total number of taps.

[0181] (Flex tolerance)

[0182] In the present embodiment, the insulating layer 130 satisfies all the necessary conditions for the above-mentioned micro-region elasticity measurement, and thus has the resistance to the prescribed bending test.

[0183] The "bending test" referred to herein includes, for example, a first step of bending the power cable 10 so that the bending ratio of the bending radius of the power cable 10 (the bending radius of the molded body) to the outer diameter of the insulating layer 130 (the outer diameter of the molded body) becomes 7 or less; and a second step of bending the power cable in a direction opposite to the bending direction of the first step at the same bending ratio as the bending ratio of the first step. In a bending test under a conventional cable standard, the bending ratio of the bending radius of the power cable to the outer diameter of the insulating layer is set to, for example, approximately 20. In contrast, the bending ratio in the bending test in this embodiment is smaller than the bending ratio in the bending test under a conventional cable standard. Therefore, in this embodiment, the bending stress applied to the insulating layer 130 becomes stronger. Therefore, the bending test in this embodiment can be considered to be a strict test for the insulating layer 130.

[0184] As a resistance evaluation in this bending test, the presence of voids and coarse crystals in insulating layer 130 is evaluated. The voids are evaluated using, for example, a scanning electron microscope (SEM). The coarse crystals are evaluated using, for example, an optical microscope.

[0185] In this embodiment, after the aforementioned bending test, there are no voids with a maximum length of 1 μm or more, and no crystals with a maximum length exceeding 10 μm, within insulating layer 130. By suppressing the formation of microscopic voids and coarse crystals during flexure, a decrease in insulation properties after flexure can be minimized.

[0186] (Insulation)

[0187] In this embodiment, the AC breakdown electric field strength of the insulating layer 130 at room temperature (e.g., 25°C) before the aforementioned bending test is, for example, 60 kV / mm or greater. More specifically, at room temperature, an AC voltage of a commercial frequency (e.g., 60 Hz) is applied to a 0.2 mm thick sample under the following conditions: a voltage of 10 kV for 10 minutes, followed by a repeated 1 kV increase for 10 minutes. The AC breakdown electric field in this case is 60 kV / mm or greater.

[0188] Furthermore, in the present embodiment, even after the above-mentioned bending test, the AC breakdown electric field is maintained high.

[0189] That is, in this embodiment, the AC breakdown electric field strength of the insulating layer 130 at room temperature (e.g., 25° C.) after the bending test is, for example, 60 kV / mm or greater. Note that the testing method for the AC breakdown electric field strength after the bending test is the same as that before the bending test.

[0190] (4) Manufacturing method of power cable

[0191] Next, a method for manufacturing a power cable according to this embodiment will be described. Hereinafter, the step will be simply referred to as "S".

[0192] (S100: Resin Composition Preparation Step)

[0193] First, a resin composition containing propylene units is prepared.

[0194] In this embodiment, a resin component including a propylene resin resin A and a flexible resin resin B and other additives (such as an antioxidant) are mixed (kneaded) using a mixer to form a mixed material. Examples of the mixer include an open roll mill, a Banbury mixer, a pressure kneader, a single-screw mixer, and a multi-screw mixer.

[0195] In this case, the resin A and the resin B that satisfy at least one of the above-mentioned requirements for molecular weight distribution and elastic modulus are used.

[0196] Specifically, the peak molecular weight in the molecular weight distribution of resin A is set to 6×10 4 Above and 6×10 5Hereinafter, the Mw / Mn of the resin A is set to be 3.0 or more and 8.0 or less. In addition, the peak molecular weight in the molecular weight distribution of the resin B is set to be 4×10 4 Above and 4×10 5 Hereinafter, Mw / Mn of the resin B is set to 1.1 or more and 3.0 or less.

[0197] Alternatively, the storage modulus of resin A at 25°C measured by dynamic viscoelasticity measurement is set to 600 MPa to 1200 MPa, and the storage modulus of resin B at 25°C measured by dynamic viscoelasticity measurement is set to 1 MPa to 200 MPa.

[0198] Alternatively, the ratio of the storage modulus of the resin A at 25° C. measured by the dynamic viscoelasticity measurement to the storage modulus of the resin B is set to 5 or more and 200 or less.

[0199] In this case, when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less.

[0200] After the mixed material is formed, it is granulated using an extruder, thereby forming a granular resin composition that will constitute the insulating layer 130. It should be noted that a twin-screw extruder with a high mixing action can also be used to perform the steps from mixing to granulation at the same time.

[0201] (S200: Conductor Preparation Process)

[0202] On the other hand, a conductor 110 formed by twisting a plurality of conductor core wires is prepared.

[0203] (S300: Cable core forming process (extrusion process, insulation layer forming process))

[0204] After the resin composition preparation step S100 and the conductor preparation step S200 are completed, the above-mentioned resin composition is used to form the insulation layer 130 so as to cover the outer periphery of the conductor 110 with a thickness of, for example, 3 mm or more.

[0205] In this embodiment, the above-mentioned resin composition is used to form insulating layer 130 so that the first, second, and third requirements are satisfied in the distribution of counts with respect to elastic modulus obtained by micro-region elasticity measurement.

[0206] In this embodiment, the resin composition is used to form insulating layer 130 such that no voids having a maximum length of 1 μm or more and no crystals having a maximum length exceeding 10 μm exist in insulating layer 130 after the bending test.

[0207] In this embodiment, for example, a three-layer simultaneous extruder is used to simultaneously form the inner semiconductive layer 120 , the insulating layer 130 , and the outer semiconductive layer 140 .

[0208] Specifically, in a three-layer simultaneous extruder, for example, the resin composition for the internal semiconductive layer is fed into the extruder A for forming the internal semiconductive layer 120 .

[0209] The pelletized resin composition is fed into the extruder B for forming the insulating layer 130. The set temperature of the extruder B is set to a temperature that is 10°C higher than the desired melting point and 50°C lower. The set temperature is preferably adjusted appropriately based on the line speed and extrusion pressure.

[0210] The outer semiconductive layer resin composition containing the same materials as those of the inner semiconductive layer resin composition fed into the extruder A is fed into the extruder C for forming the outer semiconductive layer 140 .

[0211] Next, the extrudates from extruders A to C are directed to a common head, where the inner semiconductive layer 120, the insulating layer 130, and the outer semiconductive layer 140 are simultaneously extruded from the inside outward onto the outer periphery of the conductor 110. This forms an extruded material that will become the cable core.

[0212] The extruded material is then cooled, for example using water.

[0213] Through the above cable core forming step S300 , a cable core including the conductor 110 , the inner semiconductive layer 120 , the insulating layer 130 , and the outer semiconductive layer 140 is formed.

[0214] (S400: Shielding Layer Forming Step)

[0215] After the cable core is formed, the shielding layer 150 is formed by winding, for example, a copper tape around the outside of the outer semiconducting layer 140 .

[0216] (S500: Sheath Forming Step)

[0217] After the shield layer 150 is formed, vinyl chloride is fed into an extruder and extruded, thereby forming the sheath 160 on the outer periphery of the shield layer 150 .

[0218] In the above manner, the power cable 10 as a solid insulated power cable is manufactured.

[0219] (5) Effects of this embodiment

[0220] According to this embodiment, one or more of the following effects are achieved.

[0221] (a) In this embodiment, at least a portion of the molecular weight distribution of resin A overlaps with the molecular weight distribution of resin B. Meanwhile, the molecular weight distribution of resin A is relatively broad, while the molecular weight distribution of resin B is relatively narrow. This allows resins A and B to be uniformly mixed.

[0222] Here, a case where each of the resin A and the resin B does not satisfy the above-mentioned necessary conditions for molecular weight distribution is considered.

[0223] As a case where the above-mentioned molecular weight distribution requirements are not met, it is conceivable that the molecular weight distribution of resin A does not overlap with the molecular weight distribution of resin B. In this case, the compatibility of resin A and resin B is low, and they may not be fully mixed with each other.

[0224] Furthermore, it is conceivable that, while the molecular weight distribution of resin A overlaps with that of resin B, both the molecular weight distribution of resin A and the molecular weight distribution of resin B may be broadened. In this case, while resin A and resin B are expected to be uniformly mixed due to their mutually broad molecular weight distributions, in reality, resin A and resin B violate this expectation and become non-uniform. Specifically, there may be portions where resin A and resin B are not mixed, resulting in a localized bias in at least one of resin A and resin B. For example, it is conceivable that all of resin B is concentratedly mixed in a portion of resin A having a certain molecular weight.

[0225] In contrast, in this embodiment, the molecular weight distributions of resin A and resin B as described above allow resin B, which has a narrow molecular weight distribution, to be uniformly mixed throughout the entire resin A, regardless of the local molecular weight within resin A. This prevents local imbalances in resin A and resin B within insulating layer 130.

[0226] By suppressing localized imbalances in resin A and resin B, the elastic modulus can be shifted toward a lower value even in tiny regions of insulation layer 130, ensuring a uniform distribution of soft and hard areas. This prevents the formation of tiny voids and coarse crystals during flexure. Consequently, a decrease in the insulation properties of insulation layer 130 after flexure can be minimized.

[0227] (b) In this embodiment, the peak molecular weight in the molecular weight distribution of resin A is 6×10 4 Above and 6×10 5Below. Thus, resin A and resin B can be uniformly mixed together. In addition, the Mw / Mn of resin A is greater than or equal to 3.0 and less than or equal to 8.0. By setting the Mw / Mn of resin A to be greater than or equal to 3.0, the insulating layer 130 can be stably molded. In addition, by setting the Mw / Mn of resin A to be less than or equal to 8.0, the molecular weight distribution of resin A can be made wider than the molecular weight distribution of resin B, and the excessive expansion of the molecular weight distribution of resin A can be suppressed. Thus, the generation of parts with poor compatibility between resin A and resin B can be suppressed. As a result, resin A and resin B can be uniformly mixed.

[0228] In addition, the peak molecular weight in the molecular weight distribution of resin B is 4×10 4 Above and 4×10 5 The resin A and resin B are thus uniformly mixed. Furthermore, the Mw / Mn ratio of resin B is 1.1 or greater and 3.0 or less. By setting the Mw / Mn ratio of resin B to 1.1 or greater and 3.0 or less, the occurrence of uneven areas caused by solidification of only one of resin A and resin B can be suppressed. In other words, resin A and resin B can be uniformly mixed.

[0229] By satisfying the aforementioned molecular weight distribution requirements for resin A and resin B, local distribution of resin A and resin B can be suppressed in insulating layer 130. As a result, the generation of microscopic voids and coarse crystals during flexure can be suppressed.

[0230] (c) In this embodiment, based on the molecular weight distribution of resin A described above, the storage modulus of resin A at 25°C is 600 MPa to 1200 MPa. This provides an effect comparable to that achieved when resin A satisfies the aforementioned molecular weight distribution requirements. Specifically, resin A and resin B can be uniformly mixed.

[0231] Furthermore, based on the molecular weight distribution of resin B described above, the storage modulus of resin B at 25°C is 1 MPa to 200 MPa. This provides an effect comparable to that achieved when resin B satisfies the aforementioned molecular weight distribution requirements. Specifically, resins A and B can be uniformly mixed.

[0232] Alternatively, based on the molecular weight distributions of resins A and B, the ratio of the storage modulus of resin A to the storage modulus of resin B at 25°C is 5 to 200. This also provides effects comparable to those obtained by satisfying the aforementioned molecular weight distribution requirements.

[0233] (d) In this embodiment, when the combined content of resin A and resin B is 100 parts by mass, the content of resin A is 52 parts by mass or greater and 95 parts by mass or less. By setting the content of resin A to 52 parts by mass or greater, the excessive formation of low-elasticity regions can be suppressed. This can prevent the formation of microscopic voids at the interface between the high-elasticity region and the low-elasticity region, or at least at any location within the low-elasticity region, during flexion. On the other hand, by setting the content of resin A to 95 parts by mass or less, the excessive formation of high-elasticity regions can be suppressed. This can prevent the formation of microscopic voids caused by separation between crystals within the high-elasticity region during flexion.

[0234] (e) In this embodiment, because resins A and B satisfy the aforementioned requirements for molecular weight distribution, elastic modulus, and blending ratio, insulating layer 130 satisfies the aforementioned first, second, and third requirements in the distribution of the number of counts relative to the elastic modulus of insulating layer 130, as determined by micro-region elasticity measurement. Specifically, in insulating layer 130 of this embodiment, the distribution of the elastic modulus within micro-regions is shifted toward the lower side, with a broad distribution from low to high elastic moduli. In other words, by uniformly blending resins A and B, even micro-regions of the molded article achieve a uniform distribution of soft and hard areas. This suppresses the formation of micro-voids and coarse crystals during flexure.

[0235] (f) In this embodiment, after the aforementioned bending test, no voids with a maximum length of 1 μm or greater were present within the insulating layer 130, and no crystals with a maximum length exceeding 10 μm were present. By suppressing the formation of microscopic voids and coarse crystals during flexure, localized electric field concentration can be suppressed when a high electric field is applied. Consequently, a decrease in insulation properties after flexure can be suppressed.

[0236] <Other embodiments of the present disclosure>

[0237] As mentioned above, although embodiment of this disclosure was specifically described, this disclosure is not limited to the said embodiment, Various changes are possible within the range which does not deviate from the summary.

[0238] In the above embodiment, the resin composition molded article as the insulating layer is a resin composition molded article obtained by mechanical mixing and extrusion molding. However, the resin composition molded article may be a resin composition molded article obtained by polymerization and extrusion molding.

[0239] In the above-mentioned embodiment, the case where the power cable 10 may not have a waterproof layer is described, but the present disclosure is not limited to this case. The power cable 10 may also have a simple waterproof layer. Specifically, the simple waterproof layer is composed of, for example, a metal laminate tape. The metal laminate tape has, for example, a metal layer composed of aluminum or copper and an adhesive layer provided on one or both sides of the metal layer. The metal laminate tape is, for example, wound to surround the outer periphery of the cable core (closer to the outer periphery than the outer semiconductive layer) by longitudinal addition. It should be noted that the waterproof layer can be provided on the outside of the shielding layer, or it can also serve as a shielding layer. With such a structure, the cost of the power cable 10 can be reduced.

[0240] In the above embodiment, the power cable 10 is described as being laid on land, in water, or on the bottom of the water, but the present disclosure is not limited to this case. For example, the power cable 10 may be configured as a so-called overhead wire (overhead insulated wire).

[0241] In the above embodiment, three layers are extruded simultaneously in the cable core forming step S300 , but they may be extruded layer by layer.

[0242] Example

[0243] Next, embodiments of the present disclosure will be described. These embodiments are examples of the present disclosure, and the present disclosure is not limited to these embodiments.

[0244] (1) Production of power cables

[0245] First, a predetermined resin composition was mixed using a Banbury mixer and granulated into pellets using an extruder. 2 conductor. After preparing the conductor, the resin composition for the inner semiconductive layer containing ethylene-ethyl acrylate copolymer, the above-mentioned resin composition, and the resin composition for the outer semiconductive layer composed of the same material as the resin composition for the inner semiconductive layer are respectively fed into extruders A to C. The extrudates from extruders A to C are guided to a common head, and the inner semiconductive layer, the insulating layer, and the outer semiconductive layer are extruded simultaneously from the inside to the outside to the outer periphery of the conductor. At this time, the thicknesses of the inner semiconductive layer, the insulating layer, and the outer semiconductive layer are set to 0.5 mm, 3.5 mm, and 0.5 mm, respectively. After extrusion, the extruded material is water-cooled. As a result, power cables of samples A1 to A7 and B1 to B9, each having a conductor, an inner semiconductive layer, an insulating layer, and an outer semiconductive layer from the center to the periphery, are manufactured.

[0246] [Samples A1 to A7, B1 to B9]

[0247] (Molding method)

[0248] Extrusion

[0249] Extrusion temperature: 170℃.

[0250] Thickness of insulation layer: 3.5mm.

[0251] The final outer diameter of the power cable is 20.3 mm.

[0252] (Resin A)

[0253] Content: 40 to 100 parts by mass.

[0254] (The total content of resin A and resin B is 100 parts by mass.)

[0255] PP1~PP3: propylene random polymer (random PP).

[0256] (Hereinafter, corresponding to PP1 to PP3 in the order of description)

[0257] Their respective stereoregularity: isotactic.

[0258] Styrene-equivalent molecular weight peaks: 230,000, 480,000, and 720,000.

[0259] Mw / Mn: 6.7, 6.2, 5.1.

[0260] The storage moduli of the single components at 25° C. measured by dynamic viscoelasticity measurement were: 850 MPa, 1050 MPa, and 1300 MPa.

[0261] Note that PP1 contains 10 mass % of EPR.

[0262] (Resin B)

[0263] Content: 0 to 60 parts by mass.

[0264] Material:

[0265] EPR1, EPR2: Ethylene propylene rubber (EPR)

[0266] (Hereinafter, corresponding to EPR1 and EPR2 in the order of description)

[0267] Ethylene content: 52% by mass, 68% by mass.

[0268] Styrene-equivalent molecular weight peaks: 200,000 and 700,000.

[0269] Mw / Mn: 2.3, 2.5.

[0270] The storage modulus of the single component at 25° C. measured by dynamic viscoelasticity measurement was 40 MPa and 210 MPa.

[0271] VLDPE1, VLDPE2: ultra-low density polyethylene

[0272] (Hereinafter, they correspond to VLDPE1 and VLDPE2 in the order of description)

[0273] Copolymers of ethylene and 1-butene, copolymers of ethylene and 1-octene.

[0274] 1-Butene content: 25% by mass, 1-octene content: 10% by mass.

[0275] Styrene-equivalent molecular weight peaks: 120,000 and 270,000.

[0276] Mw / Mn: 1.4, 1.7.

[0277] The storage modulus of the single component at 25° C. measured by dynamic viscoelasticity measurement was 80 MPa and 180 MPa.

[0278] SEBS1~SEBS3: Hydrogenated styrene butadiene styrene block copolymer

[0279] (Hereinafter, they correspond to SEBS1 to SEBS3 in the order described)

[0280] Styrene content: 40 mass%, 20 mass%, and 10 mass%.

[0281] Styrene-equivalent molecular weight peaks: 30,000, 70,000, and 150,000.

[0282] Mw / Mn: 1.2, 1.1, 1.1.

[0283] The storage moduli of the single components at 25° C. measured by dynamic viscoelasticity measurement were: 330 MPa, 70 MPa, and 5 MPa.

[0284] Butyl rubber 1, Butyl rubber 2: Isobutylene-isoprene copolymer

[0285] (Hereinafter, they correspond to butyl rubber 1 and butyl rubber 2 in the order of description)

[0286] Styrene-equivalent molecular weight peaks: 600,000 and 800,000.

[0287] Mw / Mn: 5.2, 5.2.

[0288] The storage modulus of the single component at 25° C. measured by dynamic viscoelasticity measurement was 230 MPa and 350 MPa.

[0289] Polybutene

[0290] Styrene-equivalent molecular weight peak: 10,000.

[0291] Mw / Mn: 2.1.

[0292] Storage modulus of a single component at 25° C. measured by dynamic viscoelasticity measurement: 0.1 MPa.

[0293] It should be noted that only polybutene is liquid at 25°C.

[0294] (2) Evaluation

[0295] [Resin Evaluation]

[0296] The following analysis was performed on each of the above-mentioned resin A and resin B.

[0297] (Molecular weight distribution)

[0298] The molecular weight distribution of each of resin A and resin B was measured by GPC under the following conditions based on a calibration curve prepared using PS as a standard sample.

[0299] Device: HLC-8321GPC / HT manufactured by Tosoh.

[0300] Eluent: o-dichlorobenzene.

[0301] Temperature: 145℃.

[0302] Concentration: 0.1wt% / vol%.

[0303] Flow rate: 1.0ml / min.

[0304] In addition, the calibration curve of PS was prepared based on the results within the range of molecular weight of 1,000 to 5,500,000.

[0305] (Storage modulus)

[0306] Resin A and resin B were used as single components to produce press sheets for evaluation. Dynamic viscoelasticity measurement (DMA) was performed on the press sheets of the resins used as the test. Specifically, the storage modulus of the press sheet was measured while the temperature was raised from -50°C to 100°C while applying 0.08% expansion and contraction to the press sheet. At this time, the measurement frequency was set to 10 Hz. In addition, the heating rate was set to 10°C / min. As the results of the measurement, the storage modulus at 25°C was compared.

[0307] [Post-manufacturing evaluation]

[0308] In each of the above-mentioned samples A1 to A7 and B1 to B9, two power cables were manufactured, and one of the two power cables was evaluated immediately after manufacturing, while the other was evaluated after the bending test.

[0309] (i) Evaluation immediately after manufacture (before bending test)

[0310] (Sample Collection)

[0311] The insulation layer of each of the power cables of Samples A1 to A7 and B1 to B9 was thinly sliced ​​along the circumferential direction, and a sheet was collected from the center portion in the thickness direction of the insulation layer. The thickness of the sheet was set to 0.5 mm.

[0312] (Gap Observation)

[0313] The insulating layer sheet was observed using a SEM. If voids were present in the observed image, the maximum length of the voids was measured. The results were evaluated as "A (good)" if the insulating layer sheet contained no voids with a maximum length of 1 μm or greater, and "B (poor)" if the insulating layer sheet contained voids with a maximum length of 1 μm or greater.

[0314] (Crystal Observation)

[0315] The insulating layer sheet was observed using an optical microscope. If crystals were present in the observed image, the maximum length of the crystals was measured. Note that if crystals overlapped, making it difficult to measure the maximum length of the lower crystal, the crystals exposed on the upper side were measured. The results were evaluated as "A (Good)" if the insulating layer sheet contained no crystals with a maximum length exceeding 10 μm, and "B (Poor)" if the insulating layer sheet contained crystals with a maximum length exceeding 10 μm.

[0316] (Storage modulus)

[0317] The dynamic viscoelasticity of the insulating layer sheet was measured in the same manner as the measurement of the single components of Resin A and Resin B. The storage modulus of the molded article was evaluated thereby.

[0318] (AC breakdown test)

[0319] At room temperature (25°C), an AC voltage of commercial frequency (e.g., 60 Hz) was applied to the insulating layer sheet. The voltage was applied at 10 kV for 10 minutes, followed by a repeated increase of 1 kV for 10 minutes. The electric field strength at which dielectric breakdown occurred in the insulating layer sheet was measured. An AC breakdown strength of 60 kV / mm or greater was rated as good, while an AC breakdown strength of less than 60 kV / mm was rated as poor.

[0320] (Micro-area elasticity measurement)

[0321] Micro-area elasticity measurements within the insulating layer sheet were performed using a scanning probe microscope (SPM). The SPM instrument used was a Bruker MultiMode 8. The elastic modulus of the micro-area elasticity measurement was measured under the following conditions: 60,000 taps were performed on a 10-μm square area of ​​the sheet at 25°C using a silicon cantilever with a tip curvature radius of less than 20 nm. This yielded a distribution of the number of taps relative to the sheet's elastic modulus.

[0322] As a result, the case where the following first, second, and third requirements are satisfied is evaluated as good, and the case where any of these requirements are not satisfied is evaluated as poor.

[0323] The first necessary condition is that a normal distribution with only one peak appears in the region where the number of counts becomes 4000 or more.

[0324] Second necessary condition: The elastic modulus at the peak of the normal distribution is 2000 MPa or less.

[0325] The third necessary condition: the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

[0326] Note that, in Table 2 described below, when the first requirement is not satisfied, the columns for the second and third requirements are omitted.

[0327] (ii) Evaluation after bending test

[0328] (Bending test: 7D bending test)

[0329] Bending tests were performed on the power cables of Samples A1 to A7 and B2 to B9 described above. Note that Sample B1 was poor in the evaluation immediately after manufacture, so no evaluation after the bending test was performed.

[0330] In the first step of the bending test, a power cable with an outer diameter of 20.3 mm was pressed along half the circumference of a SUS ring with a radius of 140 mm. Specifically, the power cable was bent so that the bending ratio of the power cable's bending radius relative to the outer diameter of the insulation layer (the outer diameter of the power cable) was 7 or less. In the subsequent second step, the power cable was bent in the opposite direction to the first step at the same bending ratio.

[0331] (Sample Collection)

[0332] In the power cables of Samples A1 to A7 and B2 to B9 after the bending test, sheets of the insulating layers were collected in the same manner as in the evaluation immediately after the above-mentioned production.

[0333] (Void Observation and Crystal Observation)

[0334] In the insulating layer sheet collected after the bending test, observation and evaluation of voids and crystals were performed in the same manner as the evaluation immediately after the above-mentioned production.

[0335] (AC breakdown test)

[0336] The insulating layer sheets collected after the bending test were subjected to an AC breakdown test in the same manner as the evaluation immediately after the above-mentioned production.

[0337] (3) Results

[0338] The results of the evaluation of each sample are described below using Tables 1 and 2. In Tables 1 and 2, the elastic modulus at the peak of the SPM measurement results is referred to as "peak elastic modulus," and the number of counts at the peak is referred to as "peak count."

[0339] [Table 1]

[0340]

[0341] [Table 2]

[0342]

[0343] (Sample B1 and Sample B9)

[0344] In the micro-region elasticity measurements of sample B1, which was not mixed with resin B, and sample B9, which had the content of resin A set to more than 95 parts by mass, a normal distribution with a single peak was obtained, but the elastic modulus at the peak was high, and the count number at the peak was also high. In sample B1, many gaps were generated before the bending test. As a result, the AC breakdown electric field was low in sample B1 before the bending test. In addition, micro-voids were generated in sample B9 during the bending test. As a result, the AC breakdown electric field was low in sample B9 after the bending test. It can be considered that in sample B1 and sample B9, high elastic regions derived from resin A were excessively formed, resulting in micro-voids when flexing.

[0345] (Sample B3)

[0346] In sample B3, in which the content of resin A is set to less than 52 parts by mass, the storage modulus of the molded body is lower than that of the single component of resin A. However, in the micro-region elasticity measurement of sample B3, two peaks appeared. In sample B3, many micro-voids were generated during the bending test. As a result, the AC breakdown electric field after the bending test was low in sample B3. It can be considered that in sample B3, the low elastic region derived from resin B was excessively formed, so micro-voids were generated during bending.

[0347] (Sample B4)

[0348] The peak molecular weight of resin A exceeds 6×10 5 And in sample B4, in which the storage modulus of resin A exceeds 1200MPa, resin B with a low elastic modulus is used, so the ratio of the storage modulus of resin A to the storage modulus of resin B is within the specified range. In addition, the storage modulus of the molded body is lower than the storage modulus of resin A as a single component. However, in the micro-region elasticity measurement of sample B4, two peaks appeared. In sample B4, many tiny voids and coarse crystals were generated in the bending test. As a result, in sample B4, the AC breakdown electric field after the bending test was low. It can be considered that in sample B4, a high elastic region with an excessively high elastic modulus of resin A was formed, and therefore tiny voids and coarse crystals were generated when flexing.

[0349] (Samples B5 to B7)

[0350] The peak molecular weight of resin B exceeds 4×10 5In samples B5 to B7 where the storage modulus of resin B exceeds 200 MPa, the ratio of the storage modulus of resin A to the storage modulus of resin B is less than 5. It should be noted that the necessary conditions of Mw / Mn are also not met in samples B6 and B7. Therefore, two peaks appeared in the micro-region elasticity measurement of samples B5 to B7. In samples B5 to B7, many micro-voids were generated during the bending test. As a result, the AC breakdown electric field after the bending test was low in samples B5 to B7. It can be considered that in samples B5 to B7, since resin B does not meet the above-mentioned necessary conditions, resin A and resin B are not fully mixed, so micro-voids are generated during bending.

[0351] (Sample B2 and Sample B8)

[0352] The peak molecular weight of resin B composed of SEBS is less than 4×10 4 In sample B2, in which the storage modulus of resin B exceeds 200 MPa, the ratio of the storage modulus of resin A to the storage modulus of resin B is less than 5. Therefore, two peaks appeared in the micro-region elasticity measurement of sample B2. In sample B2, many micro-voids were generated during the bending test. As a result, the AC breakdown electric field after the bending test was low in sample B2. It can be considered that in sample B2, because resin B did not meet the above-mentioned necessary conditions, resin A and resin B were not fully mixed, and therefore micro-voids were generated during bending.

[0353] On the other hand, the peak molecular weight of the resin B composed of polybutene as liquid oil is less than 4×10 4 In sample B8, in which the storage modulus of resin B is less than 1 MPa, the ratio of the storage modulus of resin A to the storage modulus of resin B exceeds 200. In the micro-area elasticity measurement of sample B8, a normal distribution with one peak was obtained, but the number of counts at the peak was high. In sample B8, many tiny voids and coarse crystals were generated during the bending test. As a result, in sample B8, the AC breakdown electric field after the bending test was low. In sample B8, since the storage modulus of resin B is too low, resin A and resin B are not fully mixed, and only resin A, which is a PP-based resin, undergoes coagulation and crystallization. Therefore, it can be considered that tiny voids and coarse crystals are generated during bending.

[0354] (Samples A1 to A7)

[0355] In the micro-area elasticity measurement of samples A1 to A7 that meet the necessary conditions of molecular weight distribution, storage modulus and mix ratio, as the first necessary condition, a normal distribution with only one peak value appears in the area where the count number becomes more than 4000 times. In addition, as the second necessary condition, the elastic modulus at the peak of the normal distribution is less than 2000MPa. As the third necessary condition, the count number at the peak of the normal distribution is less than 25% of the total tapping number. In samples A1 to A7, there are no micro-voids and coarse crystals in the bending test. As a result, in samples A1 to A7, the AC breakdown electric field after the bending test is more than 60kV / mm.

[0356] For Samples A1 to A7, the content of resin A was set to 52 parts by mass or more and 95 parts by mass or less, based on the combined content of resin A and resin B being 100 parts by mass. By setting the content of resin A to 52 parts by mass or more, the excessive generation of low-elasticity regions was suppressed. This confirmed that the formation of microscopic voids during flexion could be suppressed. On the other hand, by setting the content of resin A to 95 parts by mass or less, the excessive generation of high-elasticity regions was suppressed. This confirmed that the formation of microscopic voids during flexion could be suppressed.

[0357] According to samples A1 to A7, the peak molecular weight in the molecular weight distribution of resin A was set to 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is set to be 3.0 or more and 8.0 or less. In addition, the peak molecular weight in the molecular weight distribution of the resin B is set to be 4×10 4 Above and 4×10 5 The Mw / Mn ratio of resin B was set to 1.1 or higher and 3.0 or lower. This allowed for stable molding of the insulation layer, uniform mixing of resin A and resin B, and suppressed localized imbalance between resin A and resin B. This also confirmed that the formation of microscopic voids and coarse crystals during flexure could be suppressed.

[0358] According to samples A1 to A7, the storage modulus of resin A at 25°C was set to 600 MPa or more and 1200 MPa or less, and the storage modulus of resin B at 25°C was set to 1 MPa or more and 200 MPa or less. Alternatively, the ratio of the storage modulus of resin A at 25°C to the storage modulus of resin B was set to 5 or more and 200 or less. This achieved an effect equivalent to that obtained when resins A and B satisfied the aforementioned necessary conditions for molecular weight distribution. In other words, resins A and B were uniformly mixed, and localized bias in each of resins A and B was suppressed. As a result, it was confirmed that the formation of microscopic voids and coarse crystals during flexure could be suppressed.

[0359] Thus, the results of Samples A1 to A7 confirmed that the decrease in insulation properties after flexing can be suppressed.

[0360] <Preferred embodiment of the present disclosure>

[0361] Preferred aspects of the present disclosure are described below.

[0362] (Note 1)

[0363] A resin composition is coated around a long object, the resin composition containing propylene units. After a predetermined bending test, a molded body containing the resin composition contains no voids having a maximum length of 1 μm or more, and no crystals having a maximum length exceeding 10 μm. The bending test comprises: a first step of bending the molded body so that a bending ratio of a bending radius of the molded body relative to an outer diameter of the molded body is 7 or less; and a second step of bending the molded body in a direction opposite to the bending direction in the first step at a bending ratio identical to the bending ratio in the first step.

[0364] (Note 2)

[0365] A resin composition molded article is coated around a long object, the resin composition molded article containing propylene units. After a predetermined bending test, the resin composition molded article contains no voids having a maximum length of 1 μm or greater, and no crystals having a maximum length exceeding 10 μm. The bending test comprises: a first step of bending the resin composition molded article so that a bending ratio of a bending radius of the resin composition molded article relative to an outer diameter of the resin composition molded article is 7 or less; and a second step of bending the resin composition molded article in a direction opposite to the bending direction in the first step at a bending ratio identical to the bending ratio in the first step.

[0366] (Note 3)

[0367] The resin composition molded body according to Note 2, wherein the resin composition molded body satisfies the first necessary condition, the second necessary condition and the third necessary condition in the distribution of the count number relative to the elastic modulus of the resin composition molded body obtained by micro-area elasticity measurement using a scanning probe microscope, wherein the elastic modulus is measured under the following conditions: at 25°C, the resin composition molded body is tapped 60,000 times within a 10 μm square range by a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm, the first necessary condition is a normal distribution with only one peak appearing in the area where the count number becomes 4,000 times or more, the second necessary condition is that the elastic modulus at the peak of the normal distribution is less than 2,000 MPa, and the third necessary condition is that the count number at the peak of the normal distribution is less than 25% of the total number of taps.

[0368] (Note 4)

[0369] A resin composition molded body comprising propylene units, wherein the resin composition molded body satisfies a first necessary condition, a second necessary condition, and a third necessary condition in a distribution of count numbers relative to the elastic modulus of the resin composition molded body obtained by micro-area elasticity measurement using a scanning probe microscope, wherein the elastic modulus is measured under the following conditions: at 25°C, the resin composition molded body is tapped 60,000 times within a 10 μm square range using a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm, the first necessary condition being a normal distribution having only one peak appearing in an area where the count number becomes 4,000 or more, the second necessary condition being the elastic modulus at the peak of the normal distribution being less than 2,000 MPa, and the third necessary condition being the count number at the peak of the normal distribution being less than 25% of the total number of taps.

[0370] (Note 5)

[0371] The resin composition molded article according to any one of Appendixes 2 to 4, comprising: a resin A containing propylene units; and a resin B containing two or more monomer units and being solid at 25°C.

[0372] (Note 6)

[0373] The resin composition molded article according to Supplementary Note 5, wherein the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, based on 100 parts by mass of the total content of the resin A and the resin B.

[0374] (Note 7)

[0375] The resin composition molded body according to Appendix 5 or 6, wherein the storage modulus of the resin A at 25°C measured by dynamic viscoelasticity measurement is 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C measured by dynamic viscoelasticity measurement is 1 MPa or more and 200 MPa or less.

[0376] (Note 8)

[0377] A resin composition molded article comprising: a resin A comprising propylene units; and a resin B comprising two or more monomer units, both being solid at 25°C. The storage modulus of the resin A at 25°C, as measured by a dynamic viscoelasticity measurement, is 600 MPa to 1200 MPa inclusive; the storage modulus of the resin B at 25°C, as measured by a dynamic viscoelasticity measurement, is 1 MPa to 200 MPa inclusive; and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass to 95 parts by mass inclusive.

[0378] (Note 9)

[0379] The resin composition molded article according to any one of Appendixes 5 to 8, wherein a ratio of the storage modulus of the resin A at 25° C. to the storage modulus of the resin B measured by dynamic viscoelasticity measurement is 5 or more and 200 or less.

[0380] (Note 10)

[0381] A resin composition molded article comprising: a resin A comprising propylene units; and a resin B comprising two or more monomer units, the resins being solid at 25°C, wherein a ratio of the storage modulus of the resin A at 25°C to the storage modulus of the resin B as measured by dynamic viscoelasticity measurement is 5 or more and 200 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0382] (Note 11)

[0383] The resin composition molded article according to any one of Appendix 5 to 10, wherein the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5Hereinafter, the Mw / Mn of the resin B is greater than or equal to 1.1 and less than or equal to 3.0, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0384] (Note 12)

[0385] A resin composition molded body comprising: a resin A comprising propylene units; and a resin B comprising two or more monomer units, wherein the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is greater than or equal to 1.1 and less than or equal to 3.0, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is greater than or equal to 52 parts by mass and less than or equal to 95 parts by mass, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0386] (Note 13)

[0387] The resin composition molded article according to any one of Appendixes 5 to 12, wherein the resin B is composed of a copolymer obtained by copolymerizing at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene.

[0388] (Note 14)

[0389] The resin composition molded article according to any one of Supplementary Notes 1 to 13, wherein an AC breakdown electric field at room temperature is 60 kV / mm or more.

[0390] (Note 15)

[0391] A power cable comprising: a conductor; and an insulating layer covering the conductor, the insulating layer containing propylene units, wherein after a predetermined bending test, the insulating layer contains no voids having a maximum length of 1 μm or more, and no crystals having a maximum length exceeding 10 μm. The bending test comprises: a first step of bending the power cable so that a bending ratio of a bending radius of the power cable relative to an outer diameter of the insulating layer is 7 or less; and a second step of bending the power cable in a direction opposite to the bending direction in the first step at a bending ratio identical to the bending ratio in the first step.

[0392] (Note 16)

[0393] A power cable comprises: a conductor; and an insulating layer covering the periphery of the conductor, the insulating layer containing propylene units, and the insulating layer satisfies a first necessary condition, a second necessary condition, and a third necessary condition in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope, wherein the elastic modulus is measured under the following conditions: at 25°C, the insulating layer is tapped 60,000 times within a 10 μm square range using a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm, the first necessary condition being a normal distribution having only one peak appearing in an area where the count number is 4,000 or more, the second necessary condition being the elastic modulus at the peak of the normal distribution being 2,000 MPa or less, and the third necessary condition being the count number at the peak of the normal distribution being less than 25% of the total number of taps.

[0394] (Note 17)

[0395] A power cable comprises: a conductor; and an insulating layer covering the conductor, wherein the insulating layer comprises: a resin A containing propylene units; and a resin B containing two or more monomer units, and is solid at 25°C. The storage modulus of the resin A at 25°C, as measured by a dynamic viscoelasticity measurement, is 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C, as measured by a dynamic viscoelasticity measurement, is 1 MPa or more and 200 MPa or less. When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0396] (Note 18)

[0397] A power cable comprises: a conductor; and an insulating layer covering the conductor, wherein the insulating layer comprises: a resin A containing propylene units; and a resin B containing two or more monomer units, and is solid at 25°C. The ratio of the storage modulus of the resin A at 25°C to the storage modulus of the resin B, as measured by dynamic viscoelasticity measurement, is 5 or more and 200 or less. When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less.

[0398] (Note 19)

[0399] A power cable comprises: a conductor; and an insulating layer covering the conductor, wherein the insulating layer comprises: a resin A comprising propylene units; and a resin B comprising two or more monomer units, wherein the peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is greater than or equal to 1.1 and less than or equal to 3.0, and when the total content of the resin A and the resin B is set to 100 parts by mass, the content of the resin A is greater than or equal to 52 parts by mass and less than or equal to 95 parts by mass, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0400] (Note 20)

[0401] A method for manufacturing a power cable comprises the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A comprises a propylene unit, and the resin B comprises two or more monomer units and is solid at 25°C; and using the resin composition to coat a conductor with an insulating layer. In the step of preparing the resin composition, the storage modulus of the resin A at 25°C, as measured by a dynamic viscoelasticity measurement, is set to 600 MPa or more and 1200 MPa or less, and the storage modulus of the resin B at 25°C, as measured by a dynamic viscoelasticity measurement, is set to 1 MPa or more and 200 MPa or less. When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less.

[0402] (Note 21)

[0403] A method for manufacturing a power cable comprises the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A comprises a propylene unit, and the resin B comprises two or more monomer units and is solid at 25°C; and coating a conductor with an insulating layer using the resin composition. In the step of preparing the resin composition, the ratio of the storage modulus of the resin A at 25°C, as measured by dynamic viscoelasticity measurement, to the storage modulus of the resin B is set to 5 or more and 200 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less.

[0404] (Note 22)

[0405] A method for producing a power cable comprises the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A comprises a propylene unit and the resin B comprises two or more monomer units; and using the resin composition to coat an insulating layer around a conductor, wherein in the step of preparing the resin composition, the peak molecular weight in the molecular weight distribution of the resin A is set to 6×10 4 Above and 6×10 5 Hereinafter, the Mw / Mn of the resin A is set to be 3.0 or more and 8.0 or less, and the peak molecular weight in the molecular weight distribution of the resin B is set to be 4×10 4 Above and 4×10 5 Hereinafter, the Mw / Mn of the resin B is set to 1.1 or more and 3.0 or less, and when the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is set to 52 parts by mass or more and 95 parts by mass or less, wherein the molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample, Mw is the weight average molecular weight in the molecular weight distribution, and Mn is the number average molecular weight in the molecular weight distribution.

[0406] Description of Reference Numerals

[0407] 10: Power cables

[0408] 110: Conductor

[0409] 120: Inner semi-conductive layer

[0410] 130: Insulation layer

[0411] 140: Outer semi-conductive layer

[0412] 150: Shielding layer

[0413] 160: Sheath.

Claims

1. A resin composition molded body having: Resin A comprising propylene units as a main component; and Resin B is composed of a copolymer of at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene, and is solid at 25° C. The storage modulus of the resin A at 25° C. measured by dynamic viscoelasticity measurement is 600 MPa or more and 1200 MPa or less, The storage modulus of the resin B at 25° C. measured by dynamic viscoelasticity measurement is 1 MPa or more and 200 MPa or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, A resin composition molded article comprising the resin A and the resin B satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the resin composition molded article obtained by micro-area elasticity measurement using a scanning probe microscope, in, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap the resin composition molded article within a 10 μm square area 60,000 times. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

2. The resin composition molded article according to claim 1, wherein The ratio of the storage modulus of the resin A at 25° C. measured by dynamic viscoelasticity measurement to the storage modulus of the resin B is 5 or more and 200 or less.

3. A resin composition molded body having: Resin A comprising propylene units as a main component; and Resin B is composed of a copolymer of at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene, and is solid at 25° C. The ratio of the storage modulus of the resin A at 25° C. to the storage modulus of the resin B measured by dynamic viscoelasticity measurement is 5 or more and 200 or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, A resin composition molded article comprising the resin A and the resin B satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the resin composition molded article obtained by micro-area elasticity measurement using a scanning probe microscope, in, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap the resin composition molded article within a 10 μm square area 60,000 times. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

4. The resin composition molded article according to any one of claims 1 to 3, wherein The peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 the following, The Mw / Mn of the resin A is 3.0 or more and 8.0 or less, The peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 the following, The Mw / Mn of the resin B is 1.1 or more and 3.0 or less, The molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample. Mw is the weight average molecular weight in the molecular weight distribution, Mn is the number average molecular weight in the molecular weight distribution.

5. A resin composition molded body having: Resin A comprising propylene units as a main component; and Resin B is composed of a copolymer of at least two of ethylene, propylene, butene, hexene, octene, isoprene and styrene. The peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 the following, The Mw / Mn of the resin A is 3.0 or more and 8.0 or less, The peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 the following, The Mw / Mn of the resin B is 1.1 or more and 3.0 or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, in, The molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample. Mw is the weight average molecular weight in the molecular weight distribution, Mn is the number average molecular weight in the molecular weight distribution, A resin composition molded article comprising the resin A and the resin B satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the resin composition molded article obtained by micro-area elasticity measurement using a scanning probe microscope, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap the resin composition molded article within a 10 μm square area 60,000 times. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

6. The resin composition molded article according to any one of claims 1 to 3 and 5, wherein In the resin composition molded body comprising the resin A and the resin B after a predetermined bending test, There are no voids with a maximum length of more than 1 μm. Furthermore, there are no crystals with a maximum length exceeding 10 μm. The bending test includes: a first step of bending the resin composition molded body so that the bending ratio of the bending radius of the resin composition molded body relative to the outer diameter of the resin composition molded body is less than 7; and a second step of bending the resin composition molded body in a direction opposite to the bending direction of the first step at a bending ratio that is the same as the bending ratio of the first step.

7. A power cable comprising: conductors; and An insulating layer, covering around the conductor, The insulating layer has: Resin A comprising propylene units as a main component; and Resin B is composed of a copolymer of at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene, and is solid at 25° C. The storage modulus of the resin A at 25° C. measured by dynamic viscoelasticity measurement is 600 MPa or more and 1200 MPa or less, The storage modulus of the resin B at 25° C. measured by dynamic viscoelasticity measurement is 1 MPa or more and 200 MPa or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, The insulating layer satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope, in, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap an area of ​​10 μm square on the insulating layer 60,000 times. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

8. A power cable comprising: conductors; and An insulating layer, covering around the conductor, The insulating layer has: Resin A comprising propylene units as a main component; and Resin B is composed of a copolymer of at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene, and is solid at 25° C. The ratio of the storage modulus of the resin A at 25° C. to the storage modulus of the resin B measured by dynamic viscoelasticity measurement is 5 or more and 200 or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, The insulating layer satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope, in, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap an area of ​​10 μm square on the insulating layer 60,000 times. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

9. A power cable comprising: conductors; and An insulating layer, covering around the conductor, The insulating layer has: Resin A comprising propylene units as a main component; and Resin B is composed of a copolymer of at least two of ethylene, propylene, butene, hexene, octene, isoprene and styrene. The peak molecular weight in the molecular weight distribution of the resin A is 6×10 4 Above and 6×10 5 the following, The Mw / Mn of the resin A is 3.0 or more and 8.0 or less, The peak molecular weight in the molecular weight distribution of the resin B is 4×10 4 Above and 4×10 5 the following, The Mw / Mn of the resin B is 1.1 or more and 3.0 or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less, in, The molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample. Mw is the weight average molecular weight in the molecular weight distribution, Mn is the number average molecular weight in the molecular weight distribution, The insulating layer satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap 60,000 times within a 10 μm square area of ​​the insulating layer. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

10. The power cable according to any one of claims 7 to 9, wherein: In the said insulation layer after the prescribed bending test, There are no voids with a maximum length of more than 1 μm. Furthermore, there are no crystals with a maximum length exceeding 10 μm. The bending test includes: a first step of bending the power cable in such a way that a bending ratio of the bending radius of the power cable relative to the outer diameter of the insulation layer becomes less than 7; and a second step of bending the power cable in a direction opposite to the bending direction of the first step at a bending ratio that is the same as the bending ratio of the first step.

11. A method for manufacturing a power cable, comprising the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A contains propylene units as a main component, and the resin B is a copolymer formed by copolymerizing at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene, and is solid at 25° C.; and The resin composition is used to coat an insulating layer around a conductor. In the step of preparing the resin composition, The storage modulus of the resin A at 25° C. measured by dynamic viscoelasticity measurement is set to 600 MPa or more and 1200 MPa or less, The storage modulus of the resin B at 25° C. measured by dynamic viscoelasticity measurement is set to 1 MPa or more and 200 MPa or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less. The insulating layer satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope, in, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap an area of ​​10 μm square on the insulating layer 60,000 times. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

12. A method for manufacturing a power cable, comprising the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A contains propylene units as a main component, and the resin B is a copolymer formed by copolymerizing at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene, and is solid at 25° C.; and The resin composition is used to coat an insulating layer around a conductor. In the step of preparing the resin composition, The ratio of the storage modulus of the resin A at 25° C. measured by dynamic viscoelasticity measurement to the storage modulus of the resin B is set to 5 or more and 200 or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less. The insulating layer satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope, in, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap an area of ​​10 μm square on the insulating layer 60,000 times. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

13. A method for manufacturing a power cable, comprising the following steps: preparing a resin composition comprising a resin A and a resin B, wherein the resin A contains a propylene unit as a main component and the resin B is composed of a copolymer obtained by copolymerizing at least two of ethylene, propylene, butene, hexene, octene, isoprene, and styrene; and The resin composition is used to coat an insulating layer around a conductor. In the step of preparing the resin composition, The peak molecular weight in the molecular weight distribution of the resin A was set to 6×10 4 Above and 6×10 5 the following, The Mw / Mn of the resin A is set to 3.0 or more and 8.0 or less, The peak molecular weight in the molecular weight distribution of the resin B was set to 4×10 4 Above and 4×10 5 the following, The Mw / Mn of the resin B is set to 1.1 or more and 3.0 or less, When the total content of the resin A and the resin B is 100 parts by mass, the content of the resin A is 52 parts by mass or more and 95 parts by mass or less. in, The molecular weight distribution of each of the resin A and the resin B is measured by gel permeation chromatography based on a calibration curve prepared using polystyrene as a standard sample. Mw is the weight average molecular weight in the molecular weight distribution, Mn is the number average molecular weight in the molecular weight distribution, The insulating layer satisfies the first, second, and third requirements in a distribution of count numbers relative to the elastic modulus of the insulating layer obtained by micro-area elasticity measurement using a scanning probe microscope, In the micro-area elasticity measurement, the elastic modulus is measured under the following conditions: at 25° C., a cantilever made of silicon and having a tip with a curvature radius of less than 20 nm is used to tap 60,000 times within a 10 μm square area of ​​the insulating layer. The first necessary condition is that a normal distribution with only one peak appears in the region where the count number becomes 4000 or more. The second necessary condition is that the elastic modulus at the peak of the normal distribution is 2000 MPa or less. The third necessary condition is that the number of counts at the peak of the normal distribution is less than 25% of the total number of taps.

Images