Method for producing flame-retardant thermoplastic elastomer composition

A method for producing a flame-retardant thermoplastic elastomer composition, wherein the method comprises:

• step (1) of obtaining a thermoplastic elastomer composition by dynamically crosslinking a polymer mixture (A) comprising an ethylene-α-olefin-based copolymer rubber (A1) and a propylene-based polymer (A2) in the presence of a mineral oil-based softening agent (C) and a crosslinking agent (D), and
• step (2) of kneading the thermoplastic elastomer composition, a halogen-free flame retardant (E), zinc oxide (F), a thermoplastic resin with a polar group (G), and a polyhydroxy compound (H), wherein
• the amounts of the respective components at the time of starting the dynamic crosslinking in step (1) satisfy the following condition (p), and
• the amounts of the respective components at the time of starting the kneading in step (2) satisfy the following condition (q), and wherein
• condition (p) requires that when the combined amount of the ethylene-α-olefin-based copolymer rubber (A1), the propylene-based polymer (A2) and the mineral oil-based softening agent (C) is taken as 100% by weight, the amount of the ethylene-α-olefin-based copolymer rubber (A1) is 10 to 75% by weight, the amount of the propylene-based polymer (A2) is 10 to 50% by weight, and the amount of the mineral oil-based softening agent (C) is 1 to 60% by weight, and the amount of the crosslinking agent (D) is 0.001 to 5 parts by weight relative to 100 parts by weight of the combined amount of the polymer mixture (A) and the mineral oil-based softening agent (C), and
• condition (q) requires that the combined amount of the halogen-free flame retardant (E) and the zinc oxide (F) is 30 to 70 parts by weight, the amount of the thermoplastic resin with a polar group (G) is 0.5 to 10 parts by weight, and the amount of the polyhydroxy compound (H) is 0.5 to 10 parts by weight each relative to 100 parts by weight of the thermoplastic elastomer composition.