Enhanced lubrication in polyolefin closure with polyolefin grafted cyclodextrin
Thermoplastic polymer compositions in a closure can comprise a polymer, a modified vinyl polymer and a slip agent or polymer lubricant said modified polymer having a moiety comprising a cyclodextrin compound. The cyclodextrin compound, locked into the polymer structure, can absorb impurities, permeants, or other undesirable volatile materials. The cooperation between the lubricant, the cyclodextrin grafted onto the thermoplastic polymer and the polymer structure can provide barrier properties to a film, web or other polymer structure and a surface with substantial lubricity.
1. A closure comprising a cap, the cap having a weight of about 0.75 to 1.25 grams and comprising a blend of a polyolefin resin, a lubricant and a modified polyolefin resin, the modified polyolefin resin comprising a polymethylene backbone having randomly substituted covalently bonded groups derived from a cyclodextrin compound, the cap comprising about 100 parts by weight of the polyolefin resin, about 0.05 to 4 parts by weight fatty acid amide lubricant and about 0.01 to 10 parts by weight of the modified polyolefin; wherein the cyclodextrin compound is substantially free of a compound in the central pore of the cyclodextrin ring and the concentration of lubricant at the surface of the cap is greater than the concentration of lubricant in the polyolefin resin.
2. The closure of claim 1 wherein the polyolefin comprises a melt index of about 0.5 to 100 g-10 min. −1 and the modified polyolefin is derived from a polyolefin with a melt index of 0.7 to 200 g-10 min −1 .
3. The closure of claim 1 wherein the polyolefin comprises a melt index of about 1 to 75 g-10 min. −1 and the modified polyolefin is derived from a polyolefin having a melt index of about 1 to 100 g-10 min. −1 .
4. The closure of claim 1 wherein the polyolefin comprises a polyethylene copolymer, a polypropylene copolymer or mixtures thereof.
5. The closure of claim 1 wherein the modified polyolefin comprises a modified polyethylene, a modified polypropylene or mixtures thereof.
6. The closure of claim 1 wherein the closure lubricant comprises about 0.1 to 3 wt % of a fatty acid amide based on the composition.
7. The closure of claim 6 wherein the fatty acid amide comprises a C 10-24 fatty acid amide, or mixtures thereof.
8. The closure of claim 4 wherein the polyolefin comprises a poly(ethylene-co-propylene).
9. The closure of claim 4 wherein the modified polyolefin comprises a modified poly(ethylene-co-propylene).
10. The closure of claim 1 wherein the modified polyolefin comprises a cyclodextrin bonded to a maleic acid modified polyolefin wherein the maleic acid modified polyolefin comprises about 0.02 to 5 weight percent maleic anhydride groups.
11. The closure of claim 1 wherein the modified polyolefin comprises a cyclodextrin bonded to a maleic acid modified polyolefin wherein the maleic acid modified polyolefin comprises about 0.02 to 2 weight percent maleic anhydride groups.
12. The closure of claim 4 wherein the polyethylene comprises a low-density polyethylene.
13. The closure of claim 4 wherein the polyethylene comprises a linear low-density polyethylene.
14. The closure of claim 4 wherein the polyethylene comprises a high-density polyethylene.
15. The closure of claim 1 wherein the cyclodextrin compound has a substituent substantially on at least one —OH group.
16. The closure of claim 1 wherein the cyclodextrin compound further has at least one substituent at the −2, 3 or the −6 position of a glucose moiety.