Fibers and Nonwovens with improved mechanical and bonding properties
The present invention relates to fibers, particularly to as-spun fibers, having improved properties, in particular improved bonding performance and mechanical properties. In particular, the present invention relates to fibers comprising a metallocene random copolymer of propylene and one or more comonomers, said metallocene random copolymer having a broader molecular weight distribution. The present invention further relates to nonwovens comprising such fibers and to a process for producing such fibers and nonwovens. The fibers and the nonwovens of the present invention are characterized by improved properties, in particular improved bonding performance and mechanical properties, when compared to the prior art fibers and nonwovens.
1. Fibers comprising only one polypropylene, wherein the polypropylene is a metallocene random copolymer of propylene and one or more comonomers, said comonomers being alpha-olefins different from propylene, wherein the metallocene random copolymer has a comonomer content of from 0.1 wt. % to 1.0 wt. % relative to a total weight of the metallocene random copolymer, a melting temperature of at least 147° C., an isotacticity of at least 90% mmmm pentads content as measured by 13 C-NMR, a percentage of 2,1-insertions relative to the total number of propylene molecules in the polymer chain of at most 1.0%, and a molecular weight distribution Mw/Mn of between 4.0 and 6.0, and wherein the fibers are as-spun fibers.
2. A nonwoven comprising the fibers of claim 1 .
3. The nonwoven of claim 2 , wherein the nonwoven is a spunbond nonwoven.
4. A laminate comprising the nonwoven of 2 .
5. As-spun fibers comprising only one polypropylene, wherein the polypropylene is a metallocene random copolymer of propylene and a comonomer, said comonomer being butene, wherein the metallocene random copolymer has a comonomer content of from 0.1 wt. % to 1.0 wt. % relative to a total weight of the metallocene random copolymer, a melting temperature of at least 147° C., an isotacticity of at least 90% mmmm pentads content as measured by 13 C-NMR, a percentage of 2,1-insertions relative to the total number of propylene molecules in the polymer chain of at least 0.7% and less than 1.2%, and a molecular weight distribution Mw/Mn of at least 2.5.
6. The fibers of claim 5 , wherein the metallocene random copolymer has a molecular weight distribution Mw/Mn of at least 4.0.
7. The fibers of claim 5 , wherein the metallocene random copolymer has a comonomer content of from 0.4 wt. % to 0.8 wt. % relative to a total weight of the metallocene random copolymer, an isotacticity of at least 97% mmmm pentads content, a percentage of 2,1-insertions relative to the total number of propylene molecules in the polymer chain of at least 0.7% and at most 1.0, and a molecular weight distribution Mw/Mn of at least 4.0 and at most 6.0.