| abstract |
An extrusion foaming method for obtaining a styrene resin foam by introducing a blowing agent into the resin under pressure by which a foam having excellent heat insulating property and compressive strength can be produced with excellent stability using a blowing agent which is as environmentally safe as possible, characterized in that a foam is obtained by using a blowing agent comprising mainly less than 40% by weight and 5% by weight or more of an ether, and more than 60% by weight and not more than 95% by weight of a saturated hydrocarbon having 3 to 5 carbon atoms, based on the entire amount of the blowing agent, or as required, by using a blowing agent wherein a part of the saturated hydrocarbon in the foregoing blowing agent is replaced by a fluorinated hydrocarbon with concern for the environment, and preferably in that the ratio Z/X of cells constituting the foam wherein X is the average cell size in the direction of extrusion and Z is the average cell size in the direction of thickness is adjusted to 1 or less, preferably 0.8 or less by stretching the foam with heating after the extrusion. |