Method and mold for manufacturing biodegradable molded articles

Abstract

Using a metal mold ( 20 a ) consisting of a convex mold part ( 21 a ) and a concave mold part ( 22 a ), a molding material ( 14 ) is placed between a pair of coating films ( 12 ), and after claming, the molding material ( 14 ) and the coating film ( 12 ) are heated and molded to make a biodegradable expanded molded article, and at the same time, the coating film ( 12 ) is softened and pressure-bonded to a surface of the biodegradable expanded molded article. An exhaust hole ( 31 a ) and ( 32 a ) are provided on the convex mold part ( 21 a ) and the concave mold part ( 22 a ), respectively. At the time of heating and molding, gaseous matter existing between the coating film ( 12 ) and a surface of the metal mold ( 20 a ) is discharged out of the metal mold ( 20 a ) through the exhaust holes ( 31 a ) and ( 32 a ). Accordingly, it is possible to provide a method and a mold to manufacture a biodegradable expanded molded article easily and with excellent accuracy of dimension, having enough strength, enough water resistance, very excellent biodegradability and excellent surface smoothness even if the biodegradable molded article has a complicated shape.

1 .- 19 . (canceled) 
     
     
         20 . A mold to heat and mold a slurry or dough molding material mainly made of starch or a derivative thereof and obtained by adding water thereto through steam expansion,
 said mold made up of a plurality of mold parts that can fit together and form an internal given-shaped cavity,   each of said mold parts having an exhaust hole there through to discharge a gas in the cavity outside piercing through.   
     
     
         21 . A mold as set forth in  claim 20 , wherein inside the mold, an enclosed space is formed leading to the cavity through the exhaust hole and separated from outside the mold. 
     
     
         22 . A mold as set forth in  claim 20 , wherein the exhaust hole leads to outside the mold to discharge a gas in cavity to the outside the mold. 
     
     
         23 . A mold as set forth in  claim 20 , wherein
 the exhaust hole has a cross section between 0.12 mm 2  and 1.13 mm 2 .   
     
     
         24 . A mold as set forth in  claim 20 , wherein the mold parts are made of a metal and an insulator is placed between the mold parts to insulate the mold parts from each other. 
     
     
         25 . A mold as set forth in  claim 20 , used for a method to manufacture a biodegradable molded article by heating and molding the molding material with the coating film mainly made of a biodegradable plastic and having hydrophobicity through the steam expansion and at the same time softening and pressure-bonding the coating film to a surface of the biodegradable expanded molded article obtained through steam expansion molding,
 a fluoroplastic layer being formed on a surface contacting the coating film.   
     
     
         26 .- 41 . (canceled) 
     
     
         42 . A mold as set forth in  claim 21 , wherein
 the exhaust hole has a cross section between 0.12 mm 2  and 1.13 mm 2 .   
     
     
         43 . A mold as set forth in  claim 22 , wherein
 the exhaust hole has a cross section between 0.12 mm 2  and 1.13 mm 2 .