Core wire for multi-core cables and multi-core cable

A core wire for multi-core cables comprising:

• a conductor obtained by twisting a plurality of elemental wires;
• and
• an insulating layer coated on an outer peripheral surface of the conductor, the insulating layer containing polyethylene-based resin, the polyethylene-based resin being at least one selected from a group consisting of low-density polyethylene, linear low-density polyethylene and ultra-low-density polyethylene, wherein:
• a product of a linear expansion coefficient C1 of the insulating layer in a range of 25° C. to −35° C. and an elastic modulus E1 at −35° C., namely (C1×E1) is 0.01 MPaK−1 or more and 0.90 MPaK−1 or less,
• the linear expansion coefficient C1 of the insulating layer is 1.0×10−5 K−1 or more and 2.5×10−4 K−1 or less,
• the elastic modulus E1 at −35° C. is 1000 MPa or more and 3500 or less, and
• a melting point of the polyethylene-based resin is 80° C. or higher and 130° C. or lower.

A core wire for multi-core cables comprising:

• a conductor obtained by twisting a plurality of elemental wires;
• and
• an insulating layer coated on an outer peripheral surface of the conductor, the insulating layer contains polyethylene-based resin, the polyethylene-based resin being a combination of low-density polyethylene and high-density polyethylene, and a content of the high-density polyethylene relative to a total content of the polyethylene-based resins is 10% by mass or more and 50% by mass or less, wherein:
• a product of a linear expansion coefficient C1 of the insulating layer in a range of 25° C. to −35° C. and an elastic modulus E1 at −35° C., namely (C1×E1) is 0.01 MPaK−1 or more and 0.90 MPaK−1 or less,
• the linear expansion coefficient C1 of the insulating layer is 1.0×10−5 K−1 or more and 2.5×10−4 K−1 or less,
• the elastic modulus E1 at −35° C. is 1000 MPa or more and 3500 or less, and
• a melting point of the polyethylene-based resin is 80° C. or higher and 130° C. or lower.