To provide a polystyrene resin extruded foam plate produced by using isobutane having 0 ozone depletion potential and a small global warming potential as a blowing agent, having excellent flame retardance and low thermal conductivity.
The polystyrene resin extruded foam plate is obtained by extruding a foamable molten resin mixture comprising a mixed blowing agent containing the isobutane (except a chlorofluorocarbon and/or a fluorocarbon) and a polystyrene resin from a high-pressure zone to a low-pressure zone and has ≥10 mm thickness and 25-60 kg/m3 apparent density. The residual amount of the isobutane in the foam plate is 0.45-0.80 mol based on 1 kg of the foam plate. Furthermore, the foam plate has 0.05-0.18 mm average cell diameter in the thickness direction and 0.7-1.2 cell deformation ratio (the average cell diameter in the thickness direction/the average cell diameter in the horizontal direction) and satisfies type 3 of the flammability standard of the polystyrene extruded foam heat insulating plate described in JIS A9511(1995) and further has ≤0.028 W/mK thermal conductivity of the foamed plate.
KOGURE NAOCHIKA
TAKAHASHI SEIJI
IMANARI ONORI
NAITO MASATO
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