Melt-spun multifilament polyolefin yarn formation processes and yarns formed therefrom
Disclosed is a method of forming multifilament polyolefin yarns and yarns formed according to the disclosed method. The yarns can be polypropylene yarns and can exhibit any of a high modulus, high tenacity, and a unique crystalline structure for multifilament polyolefin yarns. The process can generally include extruding a polymeric melt including the polyolefin at a relatively high throughput and low spinline tension and quenching the filaments in a liquid bath prior to drawing the fiber bundle at a relatively high draw ratio, for example greater than 10, in some embodiments.
1 . A method comprising:
forming a melted polymeric composition comprising at least one polyolefin;
extruding the melted polymeric composition through multiple orifices to form multiple filaments of the polymeric composition;
quenching the filaments in a liquid bath;
collecting the filaments to form a multifilament fiber bundle; and
drawing the multifilament fiber bundle with a draw ratio greater than about 6 to form a drawn multifilament yarn, wherein the multifilament fiber bundle is drawn while heated, the heat source being at a temperature of between about 80° C. and about 170° C.
2 . (canceled)
3 . The method of claim 1 , wherein the polymeric composition comprises at least two polyolefins.
4 . The method of claim 1 , wherein the polyolefin is a polypropylene.
5 . The method of claim 4 , wherein the polypropylene has a melt flow index of between about 0.2 and about 50.
6 - 8 . (canceled)
9 . The method of claim 1 , wherein each orifice defines a maximum cross-section of between about 0.002 inches and about 0.050 inches.
10 . The method of claim 1 , wherein the filaments are extruded at a rate of between about 1 meter per minute and about 25 meters per minute.
11 . The method of claim 1 , in which the liquid bath is heated.
12 . (canceled)
13 . The method of claim 1 , wherein the extruded filaments each describe a die swell adjacent to the orifice, the surface of the liquid bath being within the distance of the die swell.
14 - 15 . (canceled)
16 . The method of claim 1 , wherein the fiber bundle is drawn utilizing an oven or draw rolls heated to a temperature of between about 80° C. and about 170° C.
17 . (canceled)
18 . The method of claim 1 , wherein the draw ratio is between about 6 and about 25.
19 . The method of claim 1 , wherein the draw ratio is greater than about 10.
20 . The method of claim 1 , further comprising drawing the drawn multifilament yarn a second time, wherein the second draw ratio is less than the first draw ratio.
21 . The method of claim 1 , further comprising heat setting the drawn multifilament yarn.
22 . The method of claim 1 , wherein the ratio of the maximum cross-sectional dimension of a single orifice to the maximum cross-sectional dimension of the single drawn filament extruded from that orifice is between about 1 and about 10.
23 - 26 . (canceled)
27 . The method of claim 1 , further comprising forming a secondary product comprising the drawn multifilament yarn, the secondary product being selected from the group consisting of a rope, a woven fabric, and a nonwoven fabric.
28 . A method of forming a multifilament yarn comprising:
forming a melted polymeric composition comprising a polypropylene having a melt flow index of between about 2 and about 50;
extruding the melted polymeric composition through multiple orifices at a rate of between about 1 meter per minute and about 25 meters per minute to form multiple filaments of the polymeric composition;
quenching the filaments in a heated liquid bath;
collecting the quenched filaments to form a multifilament fiber bundle;
applying a lubricant to the fiber bundle; and
drawing the multifilament fiber bundle with a draw ratio greater than about 6 to form a drawn multifilament yarn, wherein the multifilament fiber bundle is drawn while heated, the heat source being at a temperature of between about 80° C. and about 170° C.
29 . The method of claim 28 , wherein each orifice defines a maximum cross-section of between about 0.002 inches and about 0.050 inches.
30 . (canceled)
31 . The method of claim 28 , in which the liquid bath is heated to a temperature of between about 50° C. and about 130° C.
32 . The method of claim 28 , wherein the fiber bundle is drawn utilizing an oven or draw rolls heated to a temperature of between about 80° C. and about 170° C.
33 - 36 . (canceled)
37 . The method of claim 28 , wherein the ratio of the maximum cross-sectional dimension of a single orifice to the maximum cross-sectional dimension of the drawn filament extruded from that orifice is between about 1 and about 10.
38 - 61 . (canceled)