Abstract: It is an object of the present invention to provide a method for manufacturing a high-quality foam that can be produced stably on an industrial scale and that affords excellent thermal insulation as a foam with thin cell membranes, which method ensures uniform molten mixture fluidity, which is an essential condition for achieving consistent foam quality, in the manufacture of a foam by mixing starch as one molten polymer compound with another polymer compound having a different melt viscosity, and to provide a foam manufactured by this method. Water is added to and mixed with a plant-derived fibrous material and starch to manufacture a foam of a plastic resin containing as compositional components starch and a plant-derived fibrous material such as pulverized paper, pulverized wood, or the like.

Abstract: It is an object of the present invention to provide a method for manufacturing a high-quality foam that can be produced stably on an industrial scale and that affords excellent thermal insulation as a foam with thin cell membranes, which method ensures uniform molten mixture fluidity, which is an essential condition for achieving consistent foam quality, in the manufacture of a foam by mixing starch as one molten polymer compound with another polymer compound having a different melt viscosity, and to provide a foam manufactured by this method. Water is added to and mixed with a plant-derived fibrous material and starch to manufacture a foam of a plastic resin containing as compositional components starch and a plant-derived fibrous material such as pulverized paper, pulverized wood, or the like.