| 摘要 |
The respective wall thicknesses of inner and outer layers in a multi-layer tube molded by an extrusion molding apparatus are made more accurate. The extrusion molding apparatus ( 1 ) comprises a plurality of extruders ( 6, 7 ) for thermally melting and extruding resins ( 3, 4 ) of different kinds, and a die ( 11 ) formed with an inner layer tube molding passage ( 9 ) for passing therethrough the resin ( 3 ) extruded from one extruder ( 6 ) of these extruders ( 6, 7 ) to enable the molding of an inner layer tube ( 2 a), and an outer layer tube molding passage ( 10 ) for passing therethrough the resin ( 4 ) extruded from the other extruder ( 7 ) to enable the molding of an outer layer tube ( 2 b) which is to be externally fitted integrally on the inner layer. tube ( 2 a), the die ( 11 ) enabling the molding of a multi-layer tube ( 2 ) by these inner and outer layer tubes ( 2 a, 2 b). Inner and outer extrusion ports ( 17, 18 ) constituting the respective front ends of the inner and outer layer tube molding passages ( 9, 10 ) are disposed radially close to each other and are opened forwardly from the front end surface ( 19 ) of the die ( 11 ) and separately from each other.
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