Footwear, and methods of preparing same
Footwear soles, footwear items and associated methods of manufacturing are provided. Some aspects of the invention provide a footwear sole in a form of a single unitary layer composed of a composition having unique and beneficial qualities. Some aspects of the invention provide a footwear sole wherein the composition comprising: ethyl vinyl acetate (EVA), and rubber. Some aspects of the invention provide a footwear sole wherein the composition comprising: EVA, rubber, and at least one agent selected from a bulking agent and a foaming agent. Some aspects of the invention provide a method of preparing a footwear sole composed of a single unitary layer, comprising: forming, by mixing while heating, a molten composition comprising: EVA, rubber, and at least one agent selected from a bulking agent and a foaming agent; inserting the molten composition to a mold; and forming the sole while curing the molten composition in the mold.
1. A footwear sole comprising a unitary sole which includes a top-facing surface configured to support the surface of a foot and a bottom-facing surface configured to contact a ground surface, said top-facing surface having a plurality of surface regions comprising at least one arrangement of a plurality of surface structures selected from the group of: apertures and grooves, and said bottom-facing surface comprising an arrangement of a plurality of recessed grooves, said unitary sole being in a form of a single unitary layer composed of a composition comprising: ethylene vinyl acetate (EVA) copolymer in the range of 32% to 60% of the weight of the composition, rubber in the range of 25% to 66% of the weight of the composition, wherein said rubber is not an ethylene vinyl acetate copolymer, and at least one agent selected from a bulking agent and a foaming agent,
wherein the footwear sole exhibits a density in the range of 0.2 to 0.45 mg per cubic millimeter, determined according to ASTM D297, an abrasion resistance in the range of about 0.1 to about 0.5 g after 10,000 cycles, determined according to ASTM D3886-99, and a compression set of not more than about 30%, determined according to SATRA TM156:2002,620n.
2. The footwear sole according to claim 1 , wherein the composition further comprises at least one of bridging agent and a color master agent.
3. The footwear sole according to claim 2 , wherein the composition comprises:
bulking agent in the range of 6% to 12% of the weight of the composition;
foaming agent in the range of 0.5% to 12% of the weight of the composition;
bridging agent in the range of 1% to 5% of the weight of the composition; and
color master agent in the range of 0% to 2% of the weight of the composition.
4. The footwear sole according to claim 2 , wherein the composition comprises:
EVA copolymer in the range of 42% to 46% of the weight of the composition;
rubber in the range of 38% to 42%, of the weight of the composition;
bulking agent in the range of 6% to 8% of the weight of the composition;
foaming agent in the range of 6% to 10% of the weight of the composition;
color master agent in the range of 0.5% to 1.5% of the weight of the composition; and
bridging agent in the range of 1% to 3% of the weight of the composition.
5. The footwear sole according to claim 2 , wherein the composition comprises:
44% ethylene vinyl acetate (EVA) copolymer, by weight of the composition;
40% rubber, by weight of the composition;
6% bulking agent, by weight of the composition;
8% foaming agent, by weight of the composition;
1% color master agent, by weight of the composition; and
1% bridging agent, by weight of the composition.
6. The footwear sole according to claim 2 , wherein the composition comprises:
ethylene vinyl acetate (EVA) copolymer in the range of 57% to 60% of the weight of the composition;
rubber in the range of 28% to 32% of the weight of the composition;
bulking agent in the range of 6% to 8% of the weight of the composition;
foaming agent in the range of 1% to 5% of the weight of the composition;
color master agent in the range of 0.5% to 2% of the weight of the composition; and
bridging agent in the range of 1% to 2.5% of the weight of the composition.
7. The footwear sole according to claim 2 , wherein the composition comprises:
59% ethylene vinyl acetate (EVA) copolymer, by weight of the composition;
30% rubber, by weight of the composition;
6% bulking agent, by weight of the composition;
3% foaming agent, by weight of the composition;
1% color master agent, by weight of the composition; and
1% bridging agent, by weight of the composition.
8. The footwear sole according to claim wherein the composition consists essentially of:
EVA copolymer in the range of 32% to 60% of the weight of the composition;
rubber in the range of 25% to 60% of the weight of the composition;
bulking agent in the range of 6% to 12% of the weight of the composition;
foaming agent in the range of 0.5% to 12% of the weight of the composition;
bridging agent in the range of 1% to 5% of the weight of the composition; and
color master agent in the range of 0% to 2% of the weight of the composition.
9. The footwear sole according to claim 1 , wherein the layer is generally homogeneous.
10. The footwear sole according to claim 1 , wherein each of said top-facing surface and said bottom-facing surface extend from an anterior end to a posterior end of a wearer's foot.
11. The footwear sole according to claim 1 , wherein a heel region in the top-facing surface comprises an arrangement of a plurality of apertures.
12. The footwear sole according to claim 1 , wherein at least one aperture in the plurality of apertures have a generally tapered shape extending inwardly with respect to a longitudinal plane of the sole layer.
13. The footwear sole according to claim 1 , wherein a first aperture in the plurality of apertures extends to an intra-layer depth that is less than a second aperture of the plurality of apertures.
14. The footwear sole according to claim 1 , wherein a toe region in the top-facing surface comprises an arrangement of a plurality of grooves.
15. The footwear sole according to claim 1 , formed by injection molding.
16. The footwear sole according to claim 1 , having one or more of the following properties:
Shore A hardness in the range of about 20H to about 35H, determined according to ASTM D2240;
Shore C hardness in the range of about 35H to about 48H, determined according to ASTM D2240; and
skid resistance on a dry surface in the range of u 0.30 to u 0.80, and skid resistance on a wet surface in the range of u 0.35 to u 0.60, determined according to F2913-2011.
17. The footwear sole according to claim 1 , having the following properties:
density in the range of about 0.26 to about 0.35 mg per cubic millimeter,
compression set not more than about 25%;
Shore C hardness in the range of about 38H to about 45H; and
skid resistance on a dry surface in the range of u 0.4 to u 0.67, and skid resistance on a wet surface in the range of u 0.35 to u 0.60, determined according to F2913-2011.
18. A method of preparing a footwear sole comprising a unitary sole which includes a top-facing surface configured to support the surface of a foot and a bottom-facing surface configured to contact a ground surface, said top-facing surface having a plurality of surface regions comprising at least one arrangement of a plurality of surface structures selected from the group of: apertures and grooves, and said bottom-facing surface comprising an arrangement of a plurality of recessed grooves, said unitary sole being composed of a single unitary layer, the method comprising:
forming, by mixing while heating, a molten composition comprising: ethylene vinyl acetate (EVA) copolymer in the range of 32% to 60%, rubber in the range of 25% to 66%, wherein said rubber is not an ethylene vinyl acetate copolymer, and at least one agent selected from a bulking agent and a foaming agent;
inserting the molten composition to a mold; and
forming the sole while curing the molten composition in the mold,
wherein the footwear sole exhibits a density in the range of 0.2 to 0.45 mg per cubic millimeter, determined according to ASTM D297.
19. The method according to claim 18 , wherein the composition further comprises at least one of a bridging agent and a color master agent.
20. The method according to claim 19 , wherein the composition comprises:
bulking agent in the range of 6% to 12% of the weight of the composition;
foaming agent in the range of 0.5% to 12% of the weight of the composition;
bridging agent in the range of 1% to 5% of the weight of the composition; and
color master agent in the range of 0% to 2% of the weight of the composition.
21. The method according to claim 18 , wherein the footwear sole is generally homogeneous.
22. The method according to claim 18 , wherein said sole forming step comprises forming a cross-linked foamed sole, by foaming while curing the molten composition in the mold.
23. The method according to claim 18 , further comprising at least one step of:
shaping the molten composition in a mold; and
cooling the sole in the mold to remove the sole from the mold.
24. The method according to claim 18 , wherein the preparing a footwear sole comprises one or more of the processes: injection molding, compression molding and single-step molding.
25. The method according to claim 18 , wherein the forming a molten composition is at a temperature in the range of 70 to 110° C., and the forming the sole is by molding at a temperature in the range of 160 to 190° C.
26. The method according to claim 18 , further comprising a two-step cooling step after the molding step, wherein a first cooling step is to a temperature in the range of 130 to 160° C. for a duration of time in the range of 5 to 20 minutes, and a second cooling step is to about room temperature for a duration of time in the range of 5 to 30 minutes.
27. The method according to claim 18 , wherein the sole obtained having a thickness in the range of 10 to 50 mm.
28. A sole formed by the method according to claim 18 .
29. The method according to claim 18 , wherein the composition comprises:
EVA copolymer in the range of 42% to 60% of the weight of the composition;
rubber in the range of 28% to 42% of the weight of the composition; and
foaming agent in the range of 7% to 12% of the weight of the composition.