Molding base paper and molded paper vessel produced from it

Abstract

A molding base paper used for forming paper vessels such as a cup or tray for foods and various industrial products is disclosed which satisfies the following conditions (1) to (4): (1) a tensile strength (JIS-P 8113) of at least 2.0 kN/m, (2) an elongation at break (JIS-P 8113) of at least 1.5 %, (3) a critical compression stress, defined by the following formula, in the range of 1 to 10 MPa: critical compression stress = A/B wherein A represents the compression strength determined by JIS-P 8126, and B represents the area of loaded part of the test piece in the determination of the compression strength, and (4) an amount of the compression deformation, caused by applying compression stress of 20 kgf/cm 2 in thickness direction, of at least 10%. The paper vessels are prepared by controlling the water content of the molding base paper at 10 to 20% and then drawing the molding base paper at 100 to 150° C.

17 . A process for preparing a molded paper vessel, comprising draw-molding under heat and pressure, a molding base paper having the following conditions (1) to (4): 
 (1) a tensile strength (JIS-P 8113) of at least 2.0 kN/m,    (2) an elongation at break (JIS-P 8113) of at least 1.5%,    (3) a critical compression stress, defined by the following formula, in the range of 1 to 10 MPa:   Critical compression stress = A/B      wherein A represents the compression strength determined by JIS-P 8126, and B represents the area of loaded part of the test piece in the determination of the compression strength, and    (4) an amount of compression deformation, caused by applying compression stress of 20 kgf/cm 2  in thickness direction, of at least 10%, so as to form a vessel which satisfies the following formula (5):   0.15≦ H/ ( S   1 ) 1/2   (5)    wherein S 1  represents the bottom area of the vessel and H represents the height thereof.    
     
     
         18 . The process according to  claim 17 , wherein said molding base paper comprises a mechanical pulp selected from the group consisting of ground wood pulp, refiner ground wood pulp and thermomechanical pulp.  
     
     
         19 . The process according to  claim 18 , wherein said molding base paper comprises a mechanical pulp in an amount of 20 to 80%.  
     
     
         20 . The process according to  claim 17 , wherein said molding base paper further comprises a synthetic resin layer on at least one surface thereof.  
     
     
         21 . A process for preparing a molded paper vessel, comprising draw-molding a molding base paper under heat and pressure, so as to form a molded paper vessel which satisfies the following formula (1): 
       0.15≦ N/ ( S   1 ) 1/2   (1) wherein S 1  represents the bottom area of the vessel and H represents the height thereof,    said molding base paper comprising a high density layer having a density of 0.7 to 0.9 g/cm 3  and a low density layer having a density of lower than 0.7 g/cm 3 , and said molding base paper having a basis weight of 100 to 500 g/cm 2  and a density of 0.40 to 0.70 g/cm 3 .    
     
     
         22 . The process of  claim 21 , wherein said low density paper is mainly comprised of mechanical pulp.  
     
     
         23 . The process of  claim 22 , wherein said mechanical pulp is thermomechanical pulp.  
     
     
         24 . The process according to  claim 21 , wherein said molding base paper further comprises a synthetic resin layer on at least one surface thereof.