SHOE SOLES, COMPOSITIONS, AND METHODS OF MAKING THE SAME
A shoe sole composition and method for making a shoe sole are provided. The shoe sole includes a composition comprising a foamed silane-crosslinked polyolefin elastomer having a density less than 0.50 g/cm 3 . The shoe sole exhibits a compression set of from about 5.0% to about 20.0%, as measured according to ASTM D 395 (6 hrs @ 50° C.). The foamed silane-crosslinked polyolefin elastomer can be produced from a blend including a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin, having a crystallinity less than 40%, a silane crosslinker, a grafting initiator, a condensation catalyst, and a foaming agent.
1 . A shoe sole comprising:
a composition comprising a foamed silane-crosslinked polyolefin elastomer having a density less than 0.50 g/cm 3 ;
wherein the shoe sole exhibits a compression set of from about 1.0% to about 50.0%, as measured according to ASTM D 395 (48 hrs @ 50° C.).
2 . The shoe sole of claim 1 , wherein the density is less than about 0.30 g/cm 3 .
3 . The shoe sole of claim 1 , wherein the shoe sole exhibits a Asker C hardness of from about 50 to about 52.
4 . The shoe sole of claim 1 , wherein the compression set is from about 15.0% to about 20.0%.
5 . The shoe sole of claim 1 , further comprising:
a coloring agent.
6 . The shoe sole of claim 1 , wherein the silane-grafted polyolefin elastomer comprises a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin having a crystallinity less than 40%, a silane crosslinker, a grafting initiator, a condensation catalyst, and a foaming agent.
7 . The shoe sole of claim 1 , wherein the shoe sole exhibits a rebound resilience of at least 60%.
8 . A method for making a shoe sole, the method comprising:
extruding a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin, a silane crosslinker and a radical initiator together to form a silane-grafted polyolefin blend;
extruding the silane-grafted polyolefin blend, a foaming agent, and a condensation catalyst together to form a crosslinkable polyolefin blend;
injection molding the crosslinkable polyolefin blend into a shoe sole element; and
crosslinking the crosslinkable polyolefin blend at a temperature greater than 150° C. and an ambient humidity to form a shoe sole having a density less than 0.50 g/cm 3 .
9 . The method of claim 8 , wherein the shoe sole has a density of less than 0.35 g/cm 3 .
10 . The method of claim 8 , wherein the foaming agent comprises a supercritical fluid.
11 . The method of claim 8 , wherein the shoe sole exhibits a compression set of from about 1.0% to about 50.0%, as measured according to ASTM D 395 (48 hrs @ 50° C.).
12 . The method of claim 8 , wherein the shoe sole exhibits a rebound resilience of at least 60%.
13 . The method of claim 8 , wherein the silane-grafted polyolefin elastomer comprises from about 60 wt % to about 85 wt % of the first polyolefin and from about 10 wt % to about 35 wt % of the second polyolefin.
14 . The method of claim 8 , wherein the shoe sole exhibits a Asker C hardness of from about 50 to about 52.
15 . A method for making a shoe sole, the method comprising:
extruding a first polyolefin having a density less than 0.86 g/cm 3 , a second polyolefin, a silane crosslinker and a radical initiator together to form a silane-grafted polyolefin blend;
extruding the silane-grafted polyolefin blend, a foaming agent, and a condensation catalyst together to form a crosslinkable polyolefin blend;
compression molding the crosslinkable polyolefin blend into a shoe sole element; and
crosslinking the crosslinkable polyolefin blend at a temperature greater than 150° C. and an ambient humidity to form a shoe sole having a density less than 0.50 g/cm 3 .
16 . The method of claim 15 , wherein the foaming agent comprises a supercritical fluid.
17 . The method of claim 15 , wherein the shoe sole exhibits a compression set of from about 1.0% to about 50.0%, as measured according to ASTM D 395 (6 hrs @ 50° C.).
18 . The method of claim 15 , wherein the shoe sole exhibits a rebound resilience of at least 60%.
19 . The method of claim 15 , wherein the silane-grafted polyolefin elastomer comprises from about 60 wt % to about 85 wt % of the first polyolefin and from about 10 wt % to about 35 wt % of the second polyolefin.
20 . The method of claim 15 , wherein the temperature of the crosslinking step is about 180° C. and the crosslinking is performed in a time period from 40 seconds to 100 seconds.