Fibers and nonwovens comprising polypropylene blends and mixtures
Fibers and nonwoven materials comprising polymeric blends and polymeric mixtures that incorporate a blend of a first metallocene polypropylene and a second polypropylene are described. The first and second polypropylenes have a predetermined relationship for the melt temperature and the melt flow rate of the individual polypropylenes. Also described are fibers (including bicomponent fibers) and nonwoven materials made from the fibers where the fibers are extruded using the polymeric blends, and/or the polymeric mixtures.
1. An extensible nonwoven material comprising:
a plurality of fibers, the fibers including a polymeric blend, wherein the polymeric blend comprises
(a) a first metallocene polypropylene having an average melt temperature T M1 and a melt flow rate MFR 1 ; and
(b) a second polypropylene having an average melt temperature T M2 and a melt flow rate MFR 2 ;
wherein the weight ratio of the first metallocene polypropylene to the second polypropylene is from about 1:4 to about 4:1 and wherein the polymeric blend has an average melt temperature T Mb of from about 125° C. to about 160° C., a melt flow rate MFR b of from about 15 g/10 minutes to about 35 g/10 minutes wherein:
T M1 <T Mb <T M2 ,
MFR 1 <MFR b <MFR 2 , and
MFR 2 /MFR 1 ≧2.0.
2. The nonwoven material according to claim 1 wherein: T M2− T M1 ≧10° C.
3. The nonwoven material according to claim 1 wherein the average melt temperature T M1 is from about 110° C. to about 135° C., said MFR 1 is from about 5 g/10 minutes to about 25 g/10 minutes, the average melt temperature T M2 is from about 135° C. to about 165° C. and the MFR 2 is from about 25 g/10 minutes to about 50 g/10 minutes.
4. The nonwoven material according to claim 1 wherein the first metallocene polypropylene is a random copolymer of propylene and ethylene.
5. The nonwoven material according to claim 1 wherein the first metallocene polypropylene is a copolymer of propylene and a comonomer selected from the group consisting of ethylene and a C 4 to C 20 α-olefin.
6. The nonwoven material according to claim 5 wherein the second polypropylene is a copolymer formed by the polymerization of propylene and C 4 to C 20 α-olefin.
7. An absorbent article comprising a nonwoven material according to claim 1 .
8. The nonwoven material according to claim 1 , wherein the fibers are bicomponent fibers.
9. The nonwoven material according to claim 8 , wherein the bicomponent fibers comprise:
(i) a first polymeric component comprising a polymeric blend according to claim 1 ; and
(ii) a second polymeric component comprising a compatible thermoplastic polymer.
10. The nonwoven material according to claim 9 , wherein the second polymeric component is selected from the group consisting of polyolefins and copolymers thereof, polyolefin blends, polyesters and polyamides.
11. The nonwoven material according to claim 9 , wherein the first polymeric component has a lower softening temperature than the second polymeric component.
12. The nonwoven material according to claim 1 , wherein the polymeric blend further comprises an adjunct.