COMPOSITIONS AND METHODS OF MAKING THERMOSET FOAMS FOR SHOE SOLES

1 . A footwear article, comprising:

a shoe sole,

wherein the shoe sole comprises a crosslinked foam polyolefin elastomer having a density less than 0.88 g/cm 3 , the crosslinked foam polyolefin elastomer comprising:

a silane-grafted polyolefin elastomer, a silane-grafted olefin block copolymer, a polyolefin elastomer (POE), an olefin block copolymer (OBC), or a combination thereof;

an ethylene vinyl acetate (EVA) copolymer;

a crosslinker;

a condensation catalyst; and

a foaming agent,

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 footwear article of claim 1 , wherein the silane-grafted polyolefin elastomer and/or the silane-grafted olefin block copolymer comprises from about 60 wt % to about 97 wt % of an ethylene/α-olefin copolymer.

3 . The footwear article of claim 1 or claim 2 , wherein the crosslinker comprises one or more halogen molecules, azo compounds, carboxylic peroxyacids, peroxyesters, peroxyketals, and peroxides, and the crosslinker is present in an amount from greater than 0.15 wt % to about 2 wt % of the crosslinked foam polyolefin elastomer.

4 . The footwear article of claim 1 , wherein the condensation catalyst comprises an acidic catalyst and/or a tin-based catalyst and the condensation catalyst is present in an amount from about 1 wt % to about 4 wt % of the crosslinked foam polyolefin elastomer.

5 . The footwear article of claim 1 , wherein the density of the crosslinked foam polyolefin elastomer is from about 0.35 g/cm 3 to about 0.50 g/cm 3 .

6 . The footwear article of claim 1 , wherein the shoe sole exhibits an Asker C hardness of from about 20 to about 60, a rebound resilience of at least 60%, or both.

7 . The footwear article of claim 1 , further comprising a coloring agent.

8 . A crosslinked foam polyolefin elastomer composition comprising:

a silane-grafted polyolefin having a density less than 0.86 g/cm 3 ,

a crosslinker,

a condensation catalyst, and

a foaming agent,

wherein the polyolefin elastomer composition exhibits a compression set of from about 1.0% to about 50.0%, as measured according to ASTM D 395 (48 hrs @ 50° C.), and a density less than 0.88 g/cm 3 .

9 . The crosslinked foam polyolefin elastomer composition of claim 8 , wherein the silane-grafted polyolefin comprises a silane-grafted polyolefin elastomer, a silane-grafted olefin block copolymer, a polyolefin elastomer (POE), an olefin block copolymer (OBC), or any combination thereof.

10 . The crosslinked foam polyolefin elastomer composition of claim 8 , further comprising an ethylene vinyl acetate (EVA) copolymer, a coloring agent, or both.

11 . The crosslinked foam polyolefin elastomer composition of claim 8 , wherein the silane-grafted polyolefin comprises from about 60 wt % to about 97 wt % of an ethylene/α-olefin copolymer.

12 . The crosslinked foam polyolefin elastomer composition of claim 8 , wherein the crosslinker comprises one or more halogen molecules, azo compounds, carboxylic peroxyacids, peroxyesters, peroxyketals, and peroxides; and the crosslinker is present in an amount from greater than 0.15 wt % to about 2 wt % of the crosslinked foam polyolefin elastomer.

13 . The crosslinked foam polyolefin elastomer composition of claim 8 , wherein the condensation catalyst comprises an acidic catalyst and/or a tin-based catalyst, and the condensation catalyst is present in an amount from about 1 wt % to about 4 wt % of the crosslinked foam polyolefin.

14 . The crosslinked foam polyolefin elastomer composition of claim 8 , wherein the density of the polyolefin elastomer is from about 0.35 g/cm 3 to about 0.50 g/cm 3 .

15 . The crosslinked foam polyolefin elastomer composition of claim 8 , wherein the crosslinked foam polyolefin elastomer composition exhibits an Asker C hardness of from about 20 to about 60, a rebound resilience of at least 60%, or both.

16 . A method for making a shoe sole, the method comprising:

extruding a silane-grafted polyolefin, an ethylene vinyl acetate (EVA) copolymer, a crosslinker, 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;

crosslinking the crosslinkable polyolefin blend of the shoe sole element using a dual crosslinking system to form silane graft-silane graft crosslinks and carbon-carbon crosslinks at a temperature greater than 150° C. to form a shoe sole; and

catalyzing the dual crosslinking system of the crosslinking step by generating acetic acid in situ from the ethylene vinyl acetate (EVA) copolymer, 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.) and has a density less than 0.88 g/cm 3 .

17 . The method of claim 16 , wherein the silane-grafted polyolefin comprises a silane-grafted polyolefin elastomer, a silane-grafted olefin block copolymer, a polyolefin elastomer (POE), an olefin block copolymer (OBC), or a combination thereof.

18 . The method of claim 16 , wherein the silane-grafted polyolefin comprises from about 60 wt % to about 97 wt % of an ethylene/α-olefin copolymer.

19 . The method of claim 16 , wherein the crosslinker comprises one or more halogen molecules, azo compounds, carboxylic peroxyacids, peroxyesters, peroxyketals, and peroxides, the crosslinker is present in an amount from greater than 0.15 wt % to about 2 wt % of the crosslinkable polyolefin blend.

20 . The method of claim 16 , wherein the condensation catalyst comprises an acidic catalyst and/or a tin-based catalyst, and the condensation catalyst is present in an amount from about 1 wt % to about 4 wt % of the crosslinkable polyolefin blend.

21 . The method of claim 16 , wherein the shoe sole has a density from about 0.35 g/cm 3 to about 0.50 g/cm 3 .

22 . The method of claim 16 , wherein the foaming agent comprises a supercritical fluid, the crosslinkable polyolefin blend further comprises a coloring agent, or both.

23 . The method of claim 16 , wherein the shoe sole exhibits a rebound resilience of at least 60%, an Asker C hardness of from about 20 to about 60, or both.

24 . The method of claim 16 , further the method further comprises:

using a pull back and/or variotherm process to facilitate the crosslinking step.