Gel reduction in blends of thermoplastic polyurethane and hydroxyl functional polymers
Gas barrier layers and composites contain a low gel sheet produced from a composition containing a thermoplastic polyurethane (TPU), a hydroxyl functional copolymer, and a gel reducing additive. The gel reducing additive has functional groups that can react with isocyanate groups to reduce gel formation during the processing of blends of urethane containing polymers and hydroxyl functional polymers. Multilayer composites containing the low gel sheets can be made into inflatable membranes for containing an inflationary gas. In a particularly preferred embodiment, the membranes are used as bladders of cushioning devices in the soles of shoes, particularly athletic shoes.
1. A shoe, comprising an upper and a sole, wherein the sole comprises one or more inflatable membranes for containing an inflationary gas, wherein at least one of the membranes comprises a multilayer composite, wherein the composite comprises at least one flexible layer comprising a low gel sheet formed from a composition comprising a blend of thermoplastic polyurethane, hydroxyl functional copolymer, and a gel reducing additive, wherein the composition comprises 0.05% to 20% by weight of the gel reducing additive,
wherein the hydroxyl-functional copolymer comprises
a) a polymer having 10 mole percent or more of repeating units of structure
wherein n is 1, R1 and R2 are independently hydrogen, methyl, or ethyl, and R3 is hydrogen or C 1-3 alkyl, or
b) a copolymer of ethylene and vinyl alcohol with 25-60 mol % ethylene, and
wherein the gel reducing additive is selected from the group consisting of compounds with two or more hydroxyl groups, compounds with at least one primary amino group, compounds with at least one secondary amino group, compounds with at least one carboxyl group, and compounds with at least one carboxylic anhydride group.
2. A shoe according to claim 1 , wherein the composite further comprises at least one layer of ethylene vinyl alcohol copolymer and at least one layer of thermoplastic polyurethane.
3. A shoe according to claim 1 , wherein the composition comprises 0.5% to 20% by weight of the gel reducing additive.
4. A shoe according to claim 1 , wherein the composition comprises 1% to 20% by weight of the gel reducing additive.
5. A shoe according to claim 1 , wherein the hydroxyl functional copolymer comprises a copolymer of ethylene and vinyl alcohol.
6. A shoe according to claim 5 , wherein the molecular weight of the gel reducing additive is less than or equal to 2000.
7. A shoe according to claim 5 , wherein the molecular weight of the gel reducing additive is less than or equal to 200.
8. A shoe according to claim 5 , wherein the gel reducing additive comprises a compound having two or more hydroxyl groups.
9. A shoe according to claim 5 , wherein the gel reducing additive comprises a compound with two or more amino groups.
10. A shoe according to claim 5 , wherein the gel reducing additive is selected from the group consisting of ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, ditrimethylolpropane, pentaerythritol, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethylene glycol of molecular weight less than or equal to 400, propylene glycol, and dipropylene glycol.
11. A shoe according to claim 1 , wherein the composite comprises outer layers made of a blend of thermoplastic polyurethane, ethyl vinyl alcohol copolymer, and gel reducing additive, and the inner layers comprise alternating layers of ethylene vinyl alcohol copolymer and thermoplastic polyurethane.
12. A shoe according to claim 11 , wherein the composite comprises 10 or more inner layers.
13. A shoe according to claim 11 , wherein the composite comprises 30 or more inner layers.
14. A shoe according to claim 1 , wherein the composition comprises 0.05% to 5% by weight of the gel reducing additive.
15. A shoe according to claim 14 , wherein the hydroxyl functional copolymer comprises a copolymer of ethylene and vinyl alcohol.
16. A shoe according to claim 15 , wherein the composite comprises 10 or more inner layers.
17. A shoe according to claim 15 , wherein the composite comprises 30 or more inner layers.
18. A shoe according to claim 15 , wherein the gel reducing additive comprises a compound having two or more hydroxyl groups.
19. A shoe according to claim 15 , wherein the gel reducing additive comprises a compound with two or more amino groups.
20. A shoe according to claim 15 , wherein the gel reducing additive is selected from the group consisting of ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, ditrimethylolpropane, pentaerythritol, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethylene glycol of molecular weight less than or equal to 400, propylene glycol, and dipropylene glycol.
21. A shoe according to claim 14 , wherein the composite further comprises at least one layer of ethylene vinyl alcohol copolymer and at least one layer of thermoplastic polyurethane.
22. A shoe according to claim 14 , wherein the composite comprises outer layers made of a blend of thermoplastic polyurethane, ethyl vinyl alcohol copolymer, and gel reducing additive, and the inner layers comprise alternating layers of ethylene vinyl alcohol copolymer and thermoplastic polyurethane.