PROBLEM TO BE SOLVED: To develop a thermoplastic resin extrusion foaming heat insulation plate smaller in heat conductivity than a foaming heat insulation plate and more excellent in long-term insulation property.SOLUTION: A thermoplastic resin extrusion foaming heat insulation plate has thickness of 10 to 150 mm and apparent density of 20 to 50 kg/m. A thermoplastic resin constituting the plate is a mixture of a polystyrene resin and a polyethylene terephthalate copolymer (I) having melting heat amount of less than 5 J/g. The weight percentage of the polystyrene resin and the copolymer (I) is 85:15 to 50:50. In a transmission electron microscope picture of a cross section of an air bubble film of the extrusion foaming heat insulation plate, a stripe-like copolymer (I) phase having length in a direction along the air bubble film of 5 μm or more exists. The total area of the stripe-like copolymer (I) phase having length in the direction along the air bubble film of 5 μm or more is 15% or more of the total area of the cross section of the air bubble film.SELECTED DRAWING: Figure 1
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