Flame-retardant resin composition

1. A flame-retardant resin composition comprising:

a base resin containing a polypropylene homopolymer having a melt flow rate (MFR) at 230° C. of 0.5 g/10 minute and an olefin-based thermoplastic elastomer having a melt flow rate (MFR) at 230° C. of 9 g/10 minute,

a metal hydrate comprising magnesium hydroxide,

a phenol-based antioxidant, and

a metal soap,

wherein the blending ratio of the propylene homopolymer to the thermoplastic elastomer in the base resin is 7:3 in terms of a mass ratio,

into 100 parts by mass of the base resin are blended 75 to 100 parts by mass of the metal hydrate, 2 parts by mass of the phenol-based antioxidant, and 0.5 to 2 parts by mass of the metal soap, and

0.1 to 0.5 parts by mass of the metal soap based on 100 parts by mass of the base resin is magnesium behenate.

2. The flame-retardant resin composition according to claim wherein the metal hydrate is treated with a surface treating agent.

3. The flame-retardant resin composition according to claim 2 , wherein the surface treating agent comprises a long-chain fatty acid having 12 to 25 carbon atoms or an ester, an alkali metal salt or an alkaline earth metal salt thereof.

4. The flame-retardant resin composition according to claim 2 , wherein the surface treating agent comprises a chain alcohol having 6 to 30 carbon atoms.

5. The flame-retardant resin composition according to claim 1 , wherein the metal hydrate has an average particle diameter of 0.5 to 3 μm.

6. The flame-retardant resin composition according to claim 1 , wherein the metal soap comprises a combination of two different compounds.

7. The flame-retardant resin composition according to claim 6 , wherein the metal soap comprises magnesium behenate and calcium stearate.

8. The flame-retardant resin composition according to claim 1 , wherein the metal hydrate further comprises aluminum hydroxide.

9. The flame-retardant resin composition according to claim 1 , wherein the phenol-based antioxidant comprises tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane.

10. The flame-retardant resin composition according to claim 1 , wherein the magnesium behenate has a metal content of 2.9 to 3.7% by mass.

11. A non-halogen insulated electric wire for automobiles comprising:

a twisted wire composed of a plurality of conducting wires and

an insulating cover layer provided on an outer peripheral surface of the twisted wire and containing the flame-retardant resin composition according to claim 1 .

12. A wire harness for automobiles comprising:

an electric wire bundle containing a plurality of insulated electric wires and

an insulating protective material containing the flame-retardant resin composition according to claim 1 , which protects an outer periphery of the electric wire bundle.

13. A flame-retardant resin composition comprising:

a base resin containing a polypropylene homopolymer having a melt flow rate (MFR) at 230° C. of 0.5 g/10 minute, and an olefin-based thermoplastic elastomer having a melt flow rate (MFR) at 230° C. of 9 g/10 minute,

magnesium hydroxide,

a phenol-based antioxidant, and

magnesium behenate,

wherein the blending ratio of the propylene polymer to the thermoplastic elastomer in the base resin is 9:1 to 7:3 in terms of a mass ratio,

into 100 parts by mass of the base resin are blended 75 to 100 parts by mass of the metal hydrate, 0.5 to 2 parts by mass of the phenol-based antioxidant, and 0.1 to 0.5 parts by mass of magnesium behenate.

14. The flame-retardant resin composition according to claim 13 , wherein into 100 parts by mass of the base resin are blended 2 parts by mass of the phenol-based antioxidant,

and the blending ratio of the propylene polymer to the thermoplastic elastomer in the base resin is 7:3 in terms of a mass ratio.