. "Materials preferred as the binder include any of conventionally known materials as they can be used so long as they have the above functions, and, for example, there can be used as desired, one or more of resins such as polyvinyl alcohol, acrylic resins, a styrene/acrylate copolymer, polyvinyl acetate, an ethylene/vinyl acetate copolymer, starch, polyvinyl butyral, gelatin, casein, ionomers, gum a" . . . .