PURPOSE: To improve adhesive properties between a main material layer and a submaterial layer by extruding adhesives so that the contact surfaces of the main material layer and the submaterial layer blended with polyethylene and polyamide respectively are formed in irregular shapes and keeping the polyethylene at a temperature of 200-240°C.
CONSTITUTION: In a multilayer parison extruder 10, high-density polyethylene as a main material resin, with which adhesives are blended, is stored in a main- material resin storage chamber 17 at approximately 200-240°C while nylon as a submaterial resin, with which adhesives are blended, is stored in an accumulator 20 at 270°C. Extrusion pressure to the annular resin path 32 of high-density polyethylene is held at 400kgf/cm2, and the extrusion pressure of nylon is controlled so as to be periodically varied only by ±40kgf/cm2 centering around 400kgf/cm2. Only the thickness of a submaterial resin layer 3 between internal and external main material resin layers 2, 4 is altered with the change of extrusion pressure in a multilayer parison 1 extruded, irregularities are shaped in contact surfaces, and adhesive strength is increased largely.
OSUGI MASAKATSU
FUKUHARA KEIJI
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