Foam for footwear midsole and the like

Abstract

Embodiments herein provide high performance foam formulations and processing methods that address issues with traditional ethylene vinyl acetate (EVA) foams. In various embodiments, when used in midsoles, the high performance foam formulations may provide superior impact energy absorption per given load during compression, improved energy recovery during expansion, and reduced compression set over repeated impact cycles. In various embodiments, the high performance foam formulations may include a mixture of no more than about 75 PHR EVA foam and at least 15 PHR polyolefin foam.

What is claimed is: 
     
         1 . A high performance foam for a midsole comprising:
 at least 15 parts per hundred resin (PHR) polyolefin elastomer;   at least 5 PHR olefin block copolymer; and   no more than 75 PHR ethylene vinyl acetate (EVA).   
     
     
         2 . The high performance foam of  claim 1 , comprising:
 15-25 PHR polyolefin elastomer;   5-20 PHR olefin block copolymer; and   65-75 PHR EVA.   
     
     
         3 . The high performance foam of  claim 1 , comprising 18-22 PHR polyolefin elastomer. 
     
     
         4 . The high performance foam of  claim 1 , comprising 9-16 PHR olefin block copolymer. 
     
     
         5 . The high performance foam of  claim 1 , comprising 68-72 PHR EVA. 
     
     
         6 . The high performance foam of  claim 1 , comprising:
 18-22 PHR polyolefin elastomer;   9-16 PHR olefin block copolymer; and   68-72 PHR EVA.   
     
     
         7 . The high performance foam of  claim 1 , comprising:
 20 PHR polyolefin elastomer;   20 PHR olefin block copolymer; and   60 PHR EVA.   
     
     
         8 . The high performance foam of  claim 1 , comprising:
 20 PHR polyolefin elastomer;   10 PHR olefin block copolymer; and   70 PHR EVA.   
     
     
         9 . The high performance foam of  claim 1 , wherein the EVA is EVA 18%. 
     
     
         10 . The high performance foam of  claim 1 , wherein the high performance foam has a compression set of less than 45%, a resilience of greater than 45%, and a bonding strength of greater than 25 N/cm. 
     
     
         11 . A high performance foam for a midsole, comprising:
 ethylene vinyl acetate (EVA); and   25-50 PHR homogeneously branched, linear or substantially linear ethylene/alpha-olefin polymer, wherein the homogeneously branched, linear or substantially linear ethylene/alpha-olefin polymer has a density of from 0.85-0.92 g/cm 3 , and a melt index of 0.1-10 g/10 min.   
     
     
         12 . The high performance foam of  claim 11 , wherein the homogeneously branched, linear or substantially linear ethylene/alpha-olefin polymer comprises a polyolefin elastomer and/or an olefin block copolymer. 
     
     
         13 . The high performance foam of  claim 11 , wherein the high performance foam has a compression set of less than 45%. 
     
     
         14 . The high performance foam of  claim 11 , wherein the high performance foam has a resilience of greater than 45%. 
     
     
         15 . The high performance foam of  claim 11 , wherein the high performance foam has a bonding strength of greater than 25 N/cm. 
     
     
         16 . The high performance foam of  claim 11 , wherein the high performance foam has a compression set of less than 45%, a resilience of greater than 45%, and a bonding strength of greater than 25 N/cm. 
     
     
         17 . A high performance foam for a midsole comprising:
 at least 15 PHR polyolefin; and   no more than 75 PHR ethylene vinyl acetate (EVA), wherein the high performance foam has a compression set of less than 45%, a resilience of greater than 45%, and a bonding strength of greater than 25 N/cm.   
     
     
         18 . The high performance foam of  claim 17 , comprising:
 15-50 PHR polyolefin.   
     
     
         19 . The high performance foam of  claim 17 , wherein the polyolefin comprises a polyolefin elastomer and/or an olefin block copolymer. 
     
     
         20 . A method of making a high performance midsole comprising:
 mixing ethylene vinyl acetate (EVA), a polyolefin elastomer, and an olefin block copolymer to form an EVA/polyolefin mixture; and   compression molding the EVA polyolefin mixture to form the midsole.   
     
     
         21 . The method of  claim 20 , wherein mixing the EVA, polyolefin elastomer, and olefin block copolymer comprises mixing 65-75 PHR EVA, 15-25 PHR polyolefin elastomer, and 5-20 PHR olefin block copolymer.