Cross-linked polyolefin foams comprising cork particles

Abstract

The present invention provides a sheet of polymeric foam comprising chemically cross-linked, closed-cell, foam comprising at least one polyolefin; cork particles dispersed within said polymeric foam wherein said foam has a specific gravity of between 40-250 kg/m3 and is essentially free of visible perforations. Also provided by the present invention is a process for producing a continuous polymeric sheet said comprising a chemically cross-linked, closed-cell, polyolefin foam comprising at least one polyolefin and cork particles, homogenously dispersed within the polyolefin foam wherein once produced, said continuous polymeric sheet has a specific gravity of between 40-250 kg/m3 and is essentially free of visible perforations; the process comprising (i) continuously feeding into a mixing arrangement set at a temperature of between 60° C. and 200° C. a blend of at least one polyolefin resin, a blowing agent, a cross-linking agent and cork particles, to form therein a homogenous melt; (ii) transferring said melt into an extrusion line constructed to form a continuous sheet of said melt; (iii) conveying the continuous sheet into a heating module for heating said continuous sheet to a first temperature allowing cross-linking of said at least one polyolefin resin to obtain a cross-linked polyolefin sheet, said first temperature being lower than that required for activating said blowing agent; and (iv) heating the cross-linked polyolefin sheet to a second temperature allowing activation of said blowing agent, to obtain said continuous polymeric foam.

1 . A process for producing a continuous sheet of polymeric foam comprising:
 (a) chemically cross-linked, closed-cell, polyolefin foam comprising at least one polyolefin; and   (b) cork particles, homogenously dispersed within the polyolefin foam;   
       wherein once produced, said continuous polymeric sheet has a specific gravity of between 40-250 kg/m 3  and is essentially free of visible perforations; 
       the process comprising:
 i) continuously feeding into a mixing arrangement set at a temperature of between 60° C. and 200° C. a blend of at least one polyolefin resin, a blowing agent, a cross-linking agent and cork particles, to form therein a homogenous melt; 
 ii) transferring said melt into an extrusion line constructed to form a continuous sheet of said melt; 
 iii) conveying the continuous sheet into a heating module for heating said continuous sheet to a first temperature allowing cross-linking of said at least one polyolefin resin to obtain a cross-linked polyolefin sheet, said first temperature being lower than that required for activating said blowing agent; and 
 iv) heating the cross-linked polyolefin sheet to a second temperature allowing activation of said blowing agent, to obtain said continuous polymeric foam. 
 
     
     
         2 . The process of  claim 1 , comprising cooling said continuous polymeric sheet, once formed, followed by rolling the cooled continuous sheet to form rolled polymeric foam or followed by cutting the cooled continuous polymeric sheet into individual sheets. 
     
     
         3 . The process of  claim 1 , wherein said extrusion line comprises one or more of an extruder, a die or a calender. 
     
     
         4 . The process of  claim 1 , wherein said first temperature is between about 70° C. and about 160° C. 
     
     
         5 . The process of  claim 1 , wherein said second temperature is between about 150° C. and 250° C. 
     
     
         6 . The process of  claim 1 , wherein said at least one polyolefin is a copolymer of ethylene and an alpha-olefin selected from of iso-propene, butene, iso-pentene, hexane, iso-heptene and octane. 
     
     
         7 . The process of  claim 1 , comprising mixing said at least one polyolefin resin, 0.2-25 PHR blowing agent, 0.1-2 PHR cross linking agent, 0.1-25 PHR cork particles, and 0-3 PHR pigment. 
     
     
         8 . The process of  claim 1 , comprising feeding into the mixing arrangement an amount of cork particles to obtain in said sheet of polymeric foam 1-15 parts of the cork particles per 100 parts of the at least one polyolefin. 
     
     
         9 . The process of  claim 1 , wherein said cork particles have an average diameter of between 100 μm and 3000 μm. 
     
     
         10 . The process of  claim 1 , wherein said cork particles have an average diameter of between 500 μm and 2,000 μm.