Expandable thermoplastic resin molded product, method of producing expandable thermoplastic resin molded product and thermoplastic resin foam

Abstract

A thermoplastic resin foam, which is high in thickness-direction compressive strength and low in flexural modulus of elasticity, can be set pliably along a curved applicable portion such as body's outer surface, and can effectively absorb an impact force imparted from the outside; and an expandable thermoplastic resin molded product providing the above foam. An expandable thermoplastic resin molded product comprises an expandable thermoplastic resin sheet-form material of expandable thermoplastic resin having a sheet body and many projections formed scattered on at least one surface of the sheet body, and an elastic thermoplastic material layer laminated on at least one surface of the expandable thermoplastic resin sheet-form material so as to be spread over the outer surfaces of the projections; and a thermoplastic resin foam obtained by foaming the expandable thermoplastic resin molded product.

1 . An expandable thermoplastic resin product including: 
 a sheet-like structure of expandable thermoplastic resin having a base sheet and a plurality of raised portions provided in a distributed manner on at least one surface of said base sheet; and    a layer of elastic thermoplastic material placed on at least one surface of said sheet-like structure of expandable thermoplastic resin such that it covers outer surfaces of said raised portions.    
     
     
         2 . The expandable thermoplastic resin product as recited in  claim 1 , wherein said sheet-like structure of expandable thermoplastic resin contains a high crosslinked thermoplastic resin composition and a low crosslinked thermoplastic resin composition, which are little compatible with each other, and a heat decomposable blowing agent.  
     
     
         3 . The expandable thermoplastic resin product as recited in  claim 1  or  2 , wherein said elastic thermoplastic material has a flexural modulus in the range of 5 MPa-1,000 MPa.  
     
     
         4 . The expandable thermoplastic resin product as recited in any one of claims  1  - 3 , wherein said elastic thermoplastic material comprises a thermoplastic resin having an elastic property.  
     
     
         5 . The expandable thermoplastic resin product as recited in any one of claims  1 - 4 , wherein said plurality of raised portions are provided in a distributed manner on one surface of the base sheet.  
     
     
         6 . A method for manufacture of an expandable thermoplastic resin product comprising the steps of: 
 superimposing an elastic thermoplastic material or the like on a surface of an expandable thermoplastic resin sheet to provide a laminate sheet;    providing a pair of couterrotating shaping rolls spaced from each other by a clearance smaller in dimension than a thickness of said laminate sheet, a plurality of recesses being provided in a distributed manner on a periphery of at least one of said rolls;    introducing the laminate sheet while its surface is in a molten state into said clearance between said pair of shaping rolls and then withdrawing the laminate sheet from the pair of rolls so that the laminate sheet is shaped to define, on at least one surface thereof, projections corresponding to the recesses defined on the periphery of the shaping roll; and    cooling an expandable thermoplastic resin product having said projections.    
     
     
         7 . The method for manufacture of an expandable thermoplastic resin product as recited in  claim 6 , wherein said laminate sheet is introduced into the clearance between said pair of shaping rolls such that a layer of said elastic thermoplastic material is brought into contact with said plurality of recesses.  
     
     
         8 . A thermoplastic resin foam including: 
 a foam sheet composed of a thermoplastic resin and having a relative low expansion ratio;    a plurality of basic raised portions integrally provided on at least one surface of said foam sheet in a distributed manner and comprising a thermoplastic resin foam having a relatively high expansion ratio;    a low foamed layer having a relatively low expansion ratio and disposed to cover areas of the basic raised portions that exclude those in contact with the foam sheet so that the low foamed layer and the basic raised portions together constitute raised portions; and    a layer of elastic thermoplastic material disposed to cover the at least one surface of the foam sheet and the raised portions and also fill spaces between the raised portions.    
     
     
         9 . The thermoplastic resin foam as recited in  claim 8 , wherein said layer of elastic thermoplastic material has a foam structure.  
     
     
         10 . The thermoplastic resin foam as recited in  claim 8  or  9 , wherein said layer of elastic thermoplastic material has a flexural modulus of 5 MPa-1,000 MPa.  
     
     
         11 . The thermoplastic resin foam as recited in any one of claims  8 - 10 , wherein said elastic thermoplastic material comprises a thermoplastic resin produced via crosslinking of the thermoplastic resin which constitutes said foam sheet.  
     
     
         12 . The thermoplastic resin foam as recited in  claim 11 , wherein said crosslinking of the thermoplastic resin is achieved by a method using a silane-grafted polymer.  
     
     
         13 . A thermoplastic resin foam including: 
 a foam sheet-having a relatively low expansion ratio and composed of a thermoplastic resin;    a plurality of basic raised portions integrally provided on at least one surface of said foam sheet in a distributed manner and comprising a thermoplastic resin foam having a relatively high expansion ratio;    a low foamed layer having a relatively low expansion ratio and disposed to cover areas of the basic raised portions that exclude those in contact with the foam sheet so that the low foamed layer and the basic raised portions together constitute raised portions; and    a second foam layer disposed to cover the at least one surface of the foam sheet and said plurality of raised portions and also fill spaces between the raised portions.