Abstract: A mandrel of a high frequency heating type, comprising a conductive layer comprising a metal member having an aspect ratio of at least 100, in a proportion of at least 60% by volume, and a surface layer formed thereon which is made from an organic polymer, and a method for producing a rubber hose using the mandrel. Inasmuch as the inventive mandrel enables heating the curable rubber extruded on the mandrel, from the inner surface side thereof, the curing time of the rubber can be drastically reduced. Moreover, since the surface layer of the mandrel is composed of an organic polymer, the mandrel can be easily pulled out from the cured rubber layer. The production method of the present invention is free of the difficulty in heating the inside of the rubber layer. The concurrent application of external heating has accomplished continuous production of rubber hose.

Abstract: The present invention relates to a composite flexible hose excellent in pliability without any adhesive layer between an innermost layer and an intermediate rubber layer. The hose consists of the innermost layer, the intermediate rubber layer, a fibrous reinforcement layer and an external rubber layer, each of which is formed in this order from the inside. The innermost layer is formed of a modified polyamide obtainable by blending of a polyamide and a carboxyl-containing modified polyolefin, and the intermediate rubber layer is formed of a rubber composition obtainable by a blend of 10 to 50 parts by weight of silicic acid or a salt thereof and 5 to 15 parts by weight of a brominated alkylphenol formaldehyde resin per 100 parts of the rubber material obtainable by blending butyl rubber and a halogenated butyl rubber at a weight ratio of 50/50 to 0/100. The composite flexible hose is completed by vulcanization after laminating each layer.