PIPE COVERING MATERIAL AND METHOD OF MANUFACTURING THE SAME, AND DUPLEX PIPE AND METHOD OF MANUFACTURING THE SAME

PROBLEM TO BE SOLVED: To provide a pipe covering material which has a superior appearance and can improve the expansion ratio of a foaming resin constituting the pipe covering material, to provide a duplex pipe and to provide a method of manufacturing the pipe covering material and the duplex pipe.SOLUTION: In a method of manufacturing a pipe covering material which is the method of manufacturing the pipe covering material made of a foaming resin with which a pipe is covered, a master batch preliminarily manufactured by mixing at least a base resin, a thermal expansion type capsule foaming agent and a chemical type heat decomposition type foaming agent and performing extrusion molding of the mixture is used, a foaming resin composition which does not contain olefin type crosslinking resin fine particles having the average particle size more than 300 μm is manufactured by mixing at least the master batch and a principal material resin and the foaming resin composition is formed by foaming extrusion molding while being heated. The method of manufacturing the duplex pipe is the method of manufacturing the duplex pipe 7b including a pipe main body 6b and a foaming resin protection layer 7a with which the circumference of the pipe main body 6b is covered, by the manufacturing method, the pipe covering material is manufactured and the manufactured pipe covering material is used as the foaming resin protection layer 7a.