Fibers and Nonwovens with Improved Mechanical Properties
The present invention relates to fibers, particularly to as-spun fibers, having improved properties, in particular improved mechanical properties. In particular, the present invention relates to fibers comprising a metallocene polypropylene 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 nonwoven of the present invention are characterized by improved properties, in particular improved mechanical properties, when compared to the prior art fibers and nonwovens.
1 - 15 . (canceled)
16 . Fibers comprising a metallocene polypropylene, wherein the metallocene polypropylene has a molecular weight distribution M w /M n of at least 3.0.
17 . The fibers of claim 16 , wherein the metallocene polypropylene has a melting temperature of at least 135° C.
18 . The fibers of claim 16 , wherein the fibers are as-spun fibers.
19 . The fibers of claim 16 , wherein the metallocene polypropylene has a molecular weight distribution M w /M n of at least 3.5.
20 . The fibers of claim 16 , wherein the metallocene polypropylene has a molecular weight distribution M w /M n of at most 7.0.
21 . Nonwoven comprising the fibers of claim 16 .
22 . The nonwoven of claim 21 , wherein the nonwoven is a spunbond nonwoven.
23 . A laminate comprising the nonwoven of 21 .
24 . A process for the production of a spunbond nonwoven comprising:
(a) providing a blend comprising a metallocene polypropylene;
(b) feeding the blend of step (a) to an extruder;
(c) subsequently melt-extruding the blend to obtain a molten polymer stream;
(d) extruding the molten polymer stream of step (c) from a number of fine, usually circular, capillaries of a spinneret, thus obtaining filaments of molten polymer; and
(e) subsequently rapidly reducing the diameter of the filaments obtained in the previous step to a final diameter, wherein the metallocene polypropylene has a molecular weight distribution M w /M n of at least 3.0.
25 . A process for the production of multicomponent fibers and filaments comprising:
(a1) providing a first blend comprising a metallocene polypropylene;
(a2) providing at least one further blend comprising a thermoplastic polymer;
(b1) feeding each of the blends of steps (a1) and (a2) to a separate extruder;
(c1) consecutively melt-extruding the blends to obtain a molten polymer stream for each blend;
(d1) co-extruding the molten polymer streams of step (c1) from a number of fine capillaries of a spinneret, thus obtaining multicomponent filaments of molten polymer; and
(e) subsequently rapidly reducing the diameter of the filaments obtained in the previous step to a final diameter, wherein the metallocene polypropylene has a molecular weight distribution M w /M n of at least 3.0.
26 . The process of claim 24 , wherein the melt-extruding is done at a melt temperature in the range from 230° C. to 260° C.
27 . The process of claim 24 , further comprising:
(f) collecting the filaments obtained in step (e) on a support; and
(g) subsequently bonding the collected filaments to form a bonded nonwoven.
28 . The process of claim 24 , further comprising:
(h) laminating a film to the bonded nonwoven obtained in step (g).
29 . The process of claim 24 , wherein the bonded nonwoven is a spunbond nonwoven.
30 . The process of claim 24 , wherein the fibers and filaments are not subjected to a further drawing step.