An extruded styrene resin foam which is produced by using a blowing agent
imposing a reduced load on the environment and has outstandingly excellent
thermal insulating property and flame retardant property adapted for
construction use. The foam is obtained by extrusion-foaming of a styrene
resin and characterized by containing at least, one or more of saturated
hydrocarbons having 3 to 5 carbon atoms as a blowing agent, and containing
(A) a halogenated flame retardant, and (B) at least one compound selected
from the group consisting of phosphorus type flame retardants containing
nitrogen atom in a molecule; tetrazole compounds; specific
nitrogen-containing compounds; metal borates; boron oxides; phosphoric
acid ester compounds, and having a cell structure constituting the foam
wherein a cell anisotropic ratio k, which is defined by the formula:
k=a/(a.times.b.times.c).sup.1/3 wherein, in sections of the foam, a (mm)
is an average cell size in the thickness direction, b (mm) is an average
cell size in the transverse direction and c (mm) is an average cell size
in the longitudinal direction, satisfies the relationship: k.ltoreq.1.1,
and a satisfies the relationship: 0.05.ltoreq.a.ltoreq.0.30, and the
method for producing the same.
