Sheet-form structure of expandable thermoplastic resin, thermoplastic resin foam and methods for manufacturing thereof

Abstract

A sheet-form structure of expandable thermoplastic resin is provided which is capable of undergoing a pseudo-one-dimensional expansion in its thickness direction and which enables manufacture of thermoplastic resin foams having reduced variations in thickness and weight precisions, increased compressive strength, and excellent properties such as surface smoothness. A method of manufacturing the sheet-form structure, as well as such thermoplastic resin foams, are also provided. A sheet-form structure 1 of expandable thermoplastic resin including granules 2 of expandable thermoplastic resin arranged generally uniformly for integral connection thereof through a thin film 3 of expandable thermoplastic resin. A thermoplastic resin foam including a continuous, thermoplastic resin foam layer, a number of highly-expanded, thermoplastic resin portions provided on at least one surface of the continuous foam layer, and slightly-expanded, thermoplastic resin thin films for covering outer surfaces of respective highly-expanded portions.

1 . A sheet-form structure of expandable thermoplastic resin characterized as including granules of expandable thermoplastic resin planarly arranged in a generally uniform fashion and integrally connected to each other through a thin film of expandable thermoplastic resin.  
     
     
         2 . The sheet-form structure of expandable thermoplastic resin as recited in  claim 1 , characterized that said granules of expandable thermoplastic resin are arranged in a lattice-like fashion.  
     
     
         3 . The sheet-form structure of expandable thermoplastic resin as recited in  claim 1 , characterized that said granules of expandable thermoplastic resin are arranged in a zigzag fashion.  
     
     
         4 . The sheet-form structure of expandable thermoplastic resin as recited in any one of claims  1 - 3 , characterized that said granules of expandable thermoplastic resin are at their vertically near-centered portions integrally connected to each other through the thin film of expandable thermoplastic resin.  
     
     
         5 . The sheet-form structure of expandable thermoplastic resin as recited in any one of claims  1 - 4 , characterized as further including a planar member laminated onto said thin film of expandable thermoplastic resin.  
     
     
         6 . The sheet-form structure of expandable thermoplastic resin as recited in any one of claims  1 - 5 , characterized that said granule of expandable thermoplastic resin comprises a mixture of a blowing agent, highly-crosslinked thermoplastic resin composition and slightly-crosslinked or uncrosslinked thermoplastic resin composition, said thermoplastic resin compositions being substantially incompatible with each other.  
     
     
         7 . A method of manufacturing a sheet-form structure of expandable thermoplastic resin characterized in that a sheet-form expandable thermoplastic resin, while in a softened state, is introduced between a pair of counterrotating shaping rolls, which define therebetween a clearance having a dimension smaller than a thickness of said sheet-form expandable thermoplastic resin and at least one of which has a number of recesses provided generally uniformly on its peripheral surface, for compressively forcing portions of the sheet-form expandable thermoplastic resin in the softened state into said recesses, and is subsequently cooled and released.  
     
     
         8 . A thermoplastic resin foam characterized that the thermoplastic resin foam includes a continuous, thermoplastic resin foam layer, a number of highly-expanded, thermoplastic resin portions provided on at least one surface of said continuous foam layer, and slightly-expanded, thermoplastic resin thin films for covering outer surfaces of respective highly-expanded portions, and that said highly-expanded portions are thermally fused to each other through said slightly-exposed thin films.  
     
     
         9 . The thermoplastic resin foam as recited in  claim 8 , characterized that said highly-expanded portions are provided solely on one surface of said continuous foam layer and in a manner not to vertically overlap each other and to define a vertically single layer, and laterally fused to each other through said slightly-expanded thin films.  
     
     
         10 . The thermoplastic resin foam as recited in  claim 8 , characterized that said highly-expanded portions are provided on opposite surfaces of said continuous foam layer and in a manner not to vertically overlap each other and to define a vertically single layer, and laterally fused to each other through said slightly-expanded thin films.  
     
     
         11 . A thermoplastic resin foam characterized that the thermoplastic resin foam takes the form of a plate and includes a continuous, thermoplastic resin foam layer, a number of highly-expanded, thermoplastic resin portions provided on at least one surface of said continuous foam layer, and slightly-expanded, thermoplastic resin thin films, together with respective highly-expanded portions, for enclosing peripheries of respective highly-expanded portions, and that at least one surface of the thermoplastic resin foam, located on a side where said highly-expanded portions are uncovered with respective slightly-expanded thin films, is configured in such a manner as to define concedes at highly-expanded portions covered with respective slightly-expanded thin films and concaves at portions located between neighboring highly-expanded portions.  
     
     
         12 . The thermoplastic resin foam as recited in  claim 11 , wherein one surface of the thermoplastic resin foam, located on a side where said highly-expanded portions are covered not with the continuous foam layer but with respective slightly-expanded thin films, is irregularly formed in such a manner as to define concedes at highly-expanded portions covered with respective slightly-expanded thin films and concaves at portions located between neighboring highly-expanded portions, and wherein another surface of the thermoplastic resin foam, located on a side where the highly-expanded portions are covered with the continuous foam layer, is configured in a manner as to define a number of concaves at least at portions corresponding in location to the highly-expanded portions.  
     
     
         13 . The thermoplastic resin foam as recited in  claim 11  or  12 , characterized said concedes defined by the highly-expanded portions covered with respective slightly-expanded thin films have heights of 1 mm or greater.  
     
     
         14 . The thermoplastic resin foam as recited in any one of claims  11 - 13 , characterized that a packing ratio, which is a proportion in volume of a circumscribing rectangular parallelepiped that is occupied by the circumscribed thermoplastic resin foam, is in the range of 50-90%.  
     
     
         15 . The thermoplastic resin foam as recited in any one of claims  11 - 14 , wherein said highly-expanded portions are thermally fused to each other through the slightly-expanded thin films.  
     
     
         16 . The thermoplastic resin foam as recited in any one of claims  11 - 14 , wherein the neighboring highly-expanded portions are spaced from each other, and connected to each other through the continuous foam layer.  
     
     
         17 . The thermoplastic resin foam as recited in any one of claims  11 - 16 , characterized that said highly-expanded portions are arranged in a lattice-like fashion.  
     
     
         18 . The thermoplastic resin foam as recited in any one of claims  11 - 16 , characterized that said highly-expanded portions are arranged in a zigzag fashion.  
     
     
         19 . The thermoplastic resin foam as recited in any one of claims  11 - 18 , characterized as further including a planar member laminated onto said continuous foam layer.  
     
     
         20 . A method of manufacturing a thermoplastic resin foam characterized as comprising the steps of: 
 heating a sheet-form structure of expandable thermoplastic resin, which includes granules of expandable thermoplastic resin containing a blowing agent and planarly arranged in a generally uniform fashion for integral connection to each other through a thin film of expandable thermoplastic resin, to a temperature sufficient to decompose said blowing agent to thereby effect foaming thereof; and    cooling the foam obtained in the first step.    
     
     
         21 . A method of manufacturing an irregularly-surfaced thermoplastic resin foam characterized as comprising the steps of: 
 heating a sheet-form structure of expandable thermoplastic resin, which includes granules of expandable thermoplastic resin containing a blowing agent and planarly arranged in a generally uniform fashion for integral connection to each other through a thin film of expandable thermoplastic resin, to a temperature sufficient to decompose said blowing agent to thereby effect foaming thereof; and    cooling the foamed, sheet-form structure of thermoplastic resin in a cooling unit which has a space more than sufficient to completely accommodate the sheet-form structure, while expanding, to define a clearance therebetween.    
     
     
         22 . The method of manufacturing an irregularly-surfaced thermoplastic resin foam as recited in  claim 21 , characterized that said granule of expandable thermoplastic resin comprises a mixture of a blowing agent, highly-crosslinked thermoplastic resin composition and slightly-crosslinked or uncrosslinked thermoplastic resin composition, said thermoplastic resin compositions being substantially incompatible with each other.