PURPOSE: To provide the title compsn. which does not cause environmental pollution and has excellent shape retentivity during combustion, mechanical properties, low-temperature properties, chemical resistance and moldability, by blending a resin mixture of an ethylene polymer and a silane grafted polymer with a hydrated metallic compd.

CONSTITUTION: 100pts.wt. resin wherein the resin average density of an ethylene polymer has 0.890W0.915g/cm3, obtd. by mixing an ethylene polymer (A) mainly composed of an ethylene/α-olefin copolymer (e.g., linear low-density PE) with at least 2wt% silane grafted polymer (B) obtd. by dissolving a free radical generating compd. (a) (e.g., dicumyl peroxide) in an organosilane (b) of formula I (wherein R is a monovalent olefinically unsaturated hydrocarbon group or hydroxycarboxy; Y is a hydrolyzable group; R' is Y or a monovalent hydrocarbon group other than aliph. unsaturated hydrocarbon groups) and reacting it with at least one member selected from among component A is blended with 50W300pts.wt. compd. (C) having a decomposition initiating temp. of 150W450°C of formula II (wherein M is a metal; m and n are each a number of not smaller than 1; and X is the number of bound water molecules) or hydrated metallic compd. (C) composed of a double salt contg. said compd.