US Patent 9060568 Article of footwear with insertable lightweight interior midsole structure

An article of footwear includes an upper that at least in part defines an interior chamber for receiving a foot; an insertable interior midsole component received within the interior chamber; and an exterior sole structure engaged with the upper, wherein the exterior sole structure includes: (a) an exterior midsole component and (b) optionally an outsole component that extends under the forefoot region, wherein the insertable interior midsole component is formed from a foam material comprising a reaction product of about 10 to about 100 phr hydrogenated or non-hydrogenated acrylonitrile butadiene copolymer, 0 to about 40 phr modified hydrogenated acrylonitrile butadiene copolymer, and 0 to about 90 phr alpha olefin copolymer, and at least one additive in an amount suitable to form the foam material; wherein the density of the foam material is less than 0.25 g/cm3.