High crystalline olefin polymer for high speed spinning
A polymer composition includes a low ethylene random copolymer that can be used to form a meltspun or spunbond article at high spinning velocities. The polymer composition has a low xylene soluble content, a high crystallinity, or both, while having reduced spin-break at high spinning velocities. The polymer composition also exhibits good fiber tenacity and fabric softness.
1 . A polymer composition for forming a melt spun web, the polymer composition comprising: a propylene and α-olefin random copolymer; wherein: the random copolymer comprises α-olefin monomer units in an amount less than 1% by weight; the random copolymer having been peroxide cracked; the random copolymer exhibiting a rheological polydispersity index of 3 or less after peroxide cracking, a xylene solubles content of 2.7 wt. % or less prior to peroxide cracking, and a crystallinity of 55% or greater after peroxide cracking; and the polymer composition exhibits a melt flow rate of 20 dg/minute or greater (according to ASTM D1238, at 2300 C with a load of 2.16 kg).
2 . The composition of claim 1 , wherein the xylene solubles content is 2% or less.
3 . The composition of claim 1 , wherein the xylene solubles content is 1.8% or less.
4 . The composition of claim 1 , wherein the crystallinity is 60% or greater.
5 . The composition of claim 1 , wherein the crystallinity is 65% or greater.
6 . The composition of claim 1 wherein the α-olefin is ethylene.
7 . The composition of claim 1 , wherein the melt flow rate is 25 dg/min to 100 dg/min.
8 . The composition of claim 7 , wherein the melt flow rate is 35 dg/min to 65 dg/min.
9 . The composition of claim 1 , wherein the polydispersity index is 2.7 or less.
10 . The composition of claim 1 , wherein the polydispersity index is 2.5 or less.
11 . The composition of claim 1 , wherein the polymer composition includes an antacid and a stabilizer.
12 . The composition of claim 11 , wherein the polymer composition further comprises a lubricant, a processing aid, or a combination of any two or more thereof.
13 . The composition of claim 12 , wherein the lubricant comprises ethylene bis-stearamide, the processing aid comprises a fluoropolymer, the stabilizer comprises a phosphite, and the antacid comprises calcium stearate.
14 . The composition of claim 11 , wherein the stabilizer is present in a concentration of about 100 ppm up to about 2500 ppm.
15 . The composition of claim 1 , wherein the composition comprises a primary antioxidant, optionally a secondary antioxidant, and an antacid.
16 . The composition of claim 1 , wherein the composition comprises a primary antioxidant and an optional secondary antioxidant, wherein the primary antioxidant or the optional secondary antioxidant comprises a phenolic antioxidant; a lubricant comprising ethylene bis-stearamide; a processing aid comprising a fluoropolymer; a stabilizer comprises comprising a phosphite; and an antacid comprises comprising calcium stearate.
17 . A spunbond nonwoven web comprising, a plurality of fibers comprising the polymer composition of claim 1 , wherein the plurality of fibers are bonded together to form the web.
18 . The spunbond nonwoven web of claim 17 , comprising fibers having a linear mass density (denier, grams/9000 meters) of less than 2 denier per filament.
19 . A process for making a spunbond nonwoven web, the process comprising feeding the polymer composition of claim 1 into an extruder, the polymer composition being heated into a molten state and extruded through a die to form filaments, quenching the filaments, depositing the filaments on a moving belt, and bonding the filaments together to form a nonwoven web.
20 . The process of claim 19 , further comprising drawing the filaments at a high speed to a linear mass density (grams/9000 meters) of less than 2 denier per filament.