POLYPROPYLENE COMPOSITION FOR MELT SPUN FIBER APPLICATIONS
The present invention relates to a melt spun fiber comprising a propylene polymer composition comprising a terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms, wherein the propylene polymer composition has a melt flow rate MFR (230° C., 2.16 kg) of from 10 to 200 g/10 min and a melting temperature of less than 153° C., a spunbonded nonwoven fabric comprising the melt spun fibers, a process for producing said spunbonded nonwoven fabric, an article comprising said melt spun fiber and/or spunbonded nonwoven fabric, and the use of said terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms for increasing the spinnability of melt spun fibers and the mechanical properties of spunbonded nonwoven fabrics.
1 . A melt spun fiber comprising a propylene polymer composition comprising a terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms,
wherein the propylene polymer composition has a melt flow rate MFR (230° C., 2.16 kg) of from 10 to 200 g/10 min and a melting temperature measured according to ISO 11357-3 of less than 153° C.
2 . The melt spun fiber according to claim 1 , wherein the terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms has from 0.3 to 5.0 wt % of ethylene comonomer units and from 2.0 to 10 wt % of alpha-olefin comonomer units having from 4 to 12 carbon atoms, based on the total weight of the terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms.
3 . The melt spun fiber according to claim 1 , wherein the weight ratio of ethylene comonomer units (C2) to alpha-olefin comonomer units having from 4 to 12 carbon atoms (C4-20) [C2/C4-20] in the terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms is in the range of 1/6 to 1/2.5.
4 . The melt spun fiber according to claim 1 , wherein the terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms is a terpolymer of propylene with ethylene comonomer units and 1-butene comonomer units.
5 . The melt spun fiber according to claim 1 having a maximum take-up speed at a constant throughput of 2 kg/h of more than 4000 m/min.
6 . The melt spun fiber according to claim 1 having a tenacity of more than 2 cN/Dtex at a take-up speed of 1000 m/min and a tenacity of more than 3 cN/Dtex at a take-up speed of 4000 m/min.
7 . The melt spun fiber according to claim 1 having an elongation of not more than 250% at a take-up speed of 1000 m/min and an elongation of not more than 125% at a take-up speed of 4000 m/min.
8 . A spunbonded nonwoven fabric comprising the melt spun fibers according to claim 1 .
9 . The spunbonded nonwoven fabric according to claim 8 having a tensile strength in machine direction (TS-MD) of from 25 to 65 N/5 cm and a tensile strength in cross direction (TS-CD) of from 15 to 50 N/5 cm.
10 . The spunbonded nonwoven fabric according to claim 8 having elongation at break in machine direction (EB-MD) of from 70 to 150% and elongation at break in cross direction (EB-CD) of from 70 to 150%.
11 . The spunbonded nonwoven fabric according to claim 8 meeting the following relation
EB-CD>64+1.1·TS-CD−0.011·(TS-CD) 2 ,
wherein
EB-CD refers to the elongation at break in cross direction, and
TS-CD refers to the tensile strength in cross direction.
12 . A process for preparing a spunbonded nonwoven fabric according to claim 8 comprising the steps of
providing a propylene polymer composition comprising a terpolymer of propylene with ethylene comonomer units and alpha-olefin comonomer units having from 4 to 12 carbon atoms, which has a melt flow rate MFR (230° C., 2.16 kg) of from 10 to 200 g/10 min and a melting temperature measured according to ISO 11357-3 of less than 153° C.; and
spunbonding said propylene polymer composition by using a fiber spinning line at a maximum cabin air pressure of from 3,000 Pa to 10,000 Pa.
13 . An article comprising the melt spun fiber according to claim 1 or the spunbonded nonwoven fabric according to claim 8 .
14 . The article according to claim 13 being selected from filtration medium, diaper, sanitary napkin, panty liner, incontinence product for adults, protective clothing, surgical drape, surgical gown, and surgical wear.
15 . (canceled)
16 . (canceled)