POLYPROPYLENE-COATED STEEL PIPE WITH HIGH RESISTANCE AGAINST DEGRADATION BY THERMAL OXIDATION, LOW TEMPERATURE EMBRITTLEMENT AND OUTSTANDING WATERPROOF SECONDARY WELDING PROPERTIES

摘要

PROBLEM TO BE SOLVED: To provide a polypropylene-coated steel pipe which is highly resistant against degradation by thermal oxidation and cathode separation and also is superbly waterproof with high secondary welding properties. ;SOLUTION: A maleic acid anhydride modified polypropylene layer and a polypropylene layer is an ethylene-propylene block copolymer containing 5-40wt.% of ethylene-propylene rubber for polypropylene. In addition, each of the maleic acid anhydride modified polypropylene layer and the polypropylene layer contains 0.03-1.8wt.% of each of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4- hydroxylbenzyl)benzene, tetrakis-(methylene-3-(3',5'-di-tert-butyl-4'-hydroxy-phenyl) propionate methane, and pentaerythritol-tetrakis-(β-lauryl-thiopropionate) as an antioxidant for polypropylene.;COPYRIGHT: (C)1997,JPO