PURPOSE: To obtain the industrially advantageous foam having an extremely low shrinkability, excellent in dimensional stability and extremely rare migration properties of an additive to an article to be packaged by feeding plural esters into an extruder, heating and kneading the esters.
CONSTITUTION: This foam is obtained by feeding both of (A) an ester of a ≥21C fatty acid with a polyhydric alcohol having 3-7 OH groups and (B) an ester of a ≥18C fatty acid with the polyhydric alcohol having 3-7 OH groups, a foaming agent and a cell nuclear modifier, etc., into an extruder, heating and kneading the components and extruding the resultant molten gel into an area under a low pressure. Furthermore, the component (A) is preferably behenic acid monoglyceride and the component (B) is preferably stearic acid monoglyceride. The foaming agent is preferably a mixed foaming agent of 1,1-difluoroethane with isobutane.
MORITA KAZUHIKO
AOKI TAKESHI
