To provide an extrusion heat-insulating foam board of a polystyrene resin which has excellent flame retardancy, low heat conductivity, and excellent dimensional stability.
A manufacturing method, in which an expandable molten resin mixture, which is obtained by heating a polystyrene resin in an extruder and kneading together with blowing agents, flame retardants and cell regulators, is extrusion foamed into a low pressure sector through a die mounted on the extruder head, is characterized in that the blowing agents consist, per the total amount of the blowing agents, of 20-70 wt.% of isobutane (a), 10-65 wt.% of one or more aliphatic alcohol(s) (b) selected from 1-4C aliphatic alcohols, 5-50 wt.% of carbon dioxide (c), and 0-25 wt.% of other physical blowing agents (d) and that the weight ratio X (wt.%) of the aliphatic alcohol(s) and the weight ratio Y (wt.%) of carbon dioxide each against the total amount of the blowing agents satisfy equation (1): 7 ≥ X/Y ≥ 0.5.
COPYRIGHT: (C)2004,JPO
Naochika Kogure
Noritoshi Nishiyama
Teruyuki Akiyama
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