Fibers for polyethylene nonwoven fabric

Abstract

The present invention relates to nonwoven webs or fabrics. In particular, the present invention relates to nonwoven webs having superior abrasion resistance and excellent softness characteristics. The nonwoven materials comprise monocomponent fibers having a surface comprising a polyethylene, said nonwoven material having a fuzz/abrasion of less than 0.7 mg/cm.sup.3. The present invention is also related to fibers having a diameter in a range of from 0.1 to 50 denier, said fibers comprising a polymer blend, wherein the polymer blend comprises: from 40 weight percent to 80 weight percent (by weight of the polymer blend) of a first polymer which is a homogeneous ethylene/α-olefin interpolymer having: a melt index of from about 1 to about 1000 grams/10 minutes, and a density of from 0.870 to 0.950 grams/centimeter.sup.3, and from 74 to 20 percent by weight of a second polymer which is an ethylene homopolymer or an ethylene/α-olefin interpolymer having a melt index of from about 1 to about 1000 grams/10 minutes, and preferably a density which is at least 0.01 grams/centimeter.sup.3 greater than the density of the first polymer.

Claims

1. A nonwoven material comprised of fibers having a surface comprising a polyethylene blend, said fibers being selected from the group consisting of monocomponent fibers, bicomponent fibers or mixtures thereof, said nonwoven material having a fuzz/abrasion less than or equal to 0.0214(BW)+0.2714 mg/cm.sup.2 when the material comprises monocomponent fibers and said nonwoven material having a fuzz/abrasion less than or equal to 0.0071(BW)+0.4071 mg/cm.sup.2 when the material consists of bicomponent fibers, wherein BW is the basis weight of the nonwoven material, wherein the fibers are from 0.1 to 50 denier and wherein the polymer blend comprises: a. from 40 weight percent to 80 weight percent (by weight of the polymer blend) of a first polymer which is a homogeneous ethylene/α-olefin interpolymer having: i. a melt index of from about 1 to about 1000 grams/10 minutes, ii. a density of from 0.915 to 0.950 grams/centimeter.sup.3, and iii. a molecular weight distribution, Mw/Mn, defined by the equation Mw/Mn≦(I10/I2)−4.63, wherein Mw is the weight average molecular weight and Mn is the number average molecular weight; and b. from 60 to 20 percent by weight of a second polymer which is an ethylene homopolymer or an ethylene/α-olefin interpolymer having: i. a melt index of from about 1 to about 1000 grams/10 minutes, and ii. a density which is at least 0.01 grams/centimeter.sup.3 greater than the density of the first polymer; wherein the overall melt index of the polymer blend is greater than 18 grams/10 min.

2. The nonwoven material of claim 1 wherein the material comprises monocomponent fibers and has a fuzz/abrasion less than or equal to 0.0214(BW)+0.0714 mg/cm.sup.2.

3. The nonwoven material of claim 1 wherein the material consists of bicomponent fibers and has a fuzz/abrasion less than or equal to 0.0143(BW)+0.1143 mg/cm.sup.2.

4. The nonwoven material of claim 1 further characterized as having a basis weight of less than 60 GSM.

5. The nonwoven material of claim 1 further characterized as having a tensile strength of greater than 10 N/5 cm in MD.

6. The nonwoven of claim 1 further characterized as having a consolidation area of less than 25%.

7. The nonwoven of claim 1 having a basis weight from about 20 GSM to about 30 GSM.

8. The nonwoven of claim 1 wherein the nonwoven is a spunbond fabric.

9. The nonwoven material of claim 1 wherein fiber is a spunbonded fiber.

10. The nonwoven material of claim 1 wherein the first polymer has a melt index greater than 10 g/10 minutes.

11. The nonwoven material of claim 1 wherein the first polymer has a density in the range of 0.915 to .925 grams/centimeter.sup.3.

12. The nonwoven material of claim 1 wherein the second polymer has a density which is at least 0.02 grams/centimeter.sup.3 greater than the density of the first polymer.

13. The nonwoven material of claim 1 wherein the material comprises monocomponent fibers and has a flexural rigidity (mN′cm) in the machine direction of less than or equal to 0.0286(BW)−0.3714 and the nonwoven has a basis weight in the range of 20-27 GSM.

14. The nonwoven material of claim 1 wherein the material comprises bicomponent fibers and has a flexural rigidity (mN.Math.cm) less than or equal to 0.0714(BW)−1.0786.

15. A fiber having a diameter in a range of from 0.1 to 50 denier, said fiber comprising a polymer blend, wherein the polymer blend comprises: a. from 40 weight percent to 80 weight percent (by weight of the polymer blend) of a first polymer which is a homogeneous ethylene/α-olefin interpolymer having: i. a melt index of from about 1 to about 1000 grams/10 minutes, ii. a density of from 0.915 to 0.950 grams/centimeter.sup.3, and iii. a molecular weight distribution, Mw/Mn, defined by the equation Mw/Mn≦(I10/I2)−4.63, wherein Mw is the weight average molecular weight and Mn is the number average molecular weight; and b. from 60 to 20 percent by weight of a second polymer which is an ethylene homopolymer or an ethylene/α-olefin interpolymer having: i. a melt index of from about 1 to about 1000 grams/10 minutes, and ii. a density which is at least 0.01 grams/centimeter.sup.3 greater than the density of the first polymer; wherein the overall melt index for the polymer blend is greater than 18 g/10 min.

16. A fiber having a diameter in a range of from 0.1 to 50 denier, said fiber comprising a polymer blend, wherein the polymer blend comprises: a. from 40 weight percent to 80 weight percent (by weight of the polymer blend) of a first polymer which is a homogeneous ethylene/α-olefin interpolymer having: i. a melt index of from about 1 to about 1000 grams/10 minutes, ii. a density of from 0.921 to 0.950 grams/centimeter.sup.3, and iii. a molecular weight distribution, Mw/Mn, defined by the equation Mw/Mn≦(I10/I2)−4.63, wherein Mw is the weight average molecular weight and Mn is the number average molecular weight; and b. from 60 to 20 percent by weight of a second polymer which is an ethylene homopolymer or an ethylene/α-olefin interpolymer having: i. a melt index of from about 1 to about 1000 grams/10 minutes, and ii. a density which is at least 0.01 grams/centimeter.sup.3 greater than the density of the first polymer.

17. The fiber of claim 15 or 16 wherein the fiber is a spunbond fiber.

18. The fiber of claim 15 or 16 wherein the first polymer comprises 40-60% of the blend.

19. The fiber of claim 15 or 16 wherein the second polymer is a linear ethylene polymer or a substantially linear ethylene polymer.

20. The fiber of claim 15 or 16 wherein the first polymer has a melt index greater than 10 g/10 minutes.

21. The fiber of claim 15 wherein the first polymer has a density in the range of 0.915 to 0.925 grams/centimeter.sup.3.

22. The fiber of claim 15 or 16 wherein the second polymer has a density which is at least 0.02 grams/centimeter.sup.3 greater than the density of the first polymer.

23. The fiber of claim 16 wherein the overall polymer blend has a melt index greater than 18 g/10 minutes.

24. A fiber of claim 15 or 16 wherein the fiber is selected from the group consisting of staple fibers and binder fibers.

25. The fiber of claim 24 wherein the fiber is a binder fiber and the binder fiber is in the form a sheath-core bicomponent fiber and the sheath of the fiber comprises the polymer blend.

26. The fiber of claim 25 wherein the sheath further comprises a polyolefin grafted with an unsaturated organic compound containing at least one site of ethylenic unsaturation and at least one carbonyl group.

27. The fiber of claim 26 wherein the unsaturated organic compound is maleic anhydride.

28. The fiber of claim 24 wherein the fiber is a binder fiber and the binder fiber is in an airlaid web, and the fiber comprises 5-35% by weight of the airlaid web.

29. The fiber of claim 24 wherein the fiber is a staple fiber and the stable fiber is in a carded web.

Description

EXAMPLES

(1) A series of fibers were used to make a series of nonwoven fabrics. The resins were as follows: Resin A is a Ziegler-Natta ethylene-1-octene copolymer having a melt index (I.sub.2) of 30 gram/10 minutes and a density of 0.955 g/cc. Resin B is a Ziegler-Natta ethylene-1-octene copolymer having a melt index (I.sub.2) of 27 gram/10 minutes and a density of 0.941 g/cc. Resin C is a homogeneous substantially linear ethylene/1-octene copolymer having a melt index (I.sub.2) of 30 gram/10 minutes and a density of 0.913 g/cc. Resin D is an ethylene/1-octene copolymer, comprising about 40 percent (by weight) of a substantially linear polyethylene component having a melt index of about 30 g/10 minutes and a density of about 0.915 g/cc and about 60 percent of a heterogenous Ziegler Natta polyethylene component; the final polymer composition has a melt index of about 30 g/10 minutes and a density of about 0.9364 g/cc. Resin E is an ethylene/1-octene copolymer, comprising about 40 percent (by weight) of a substantially linear polyethylene component having a melt index of about 15 g/10 minutes and a density of about 0.915 g/cc and about 60 percent of a heterogenous Ziegler Natta polyethylene component; the final polymer composition has a melt index of about 22 g/10 minutes and a density of about 0.9356 g/cc. Resin F is an ethylene/1-octene copolymer, comprising about 40 percent (by weight) of a substantially linear polyethylene component having a melt index of about 15 g/10 minutes and a density of about 0.915 g/cc and about 60 percent of a heterogenous Ziegler Natta polyethylene component; the final polymer composition has a melt index of about 30 g/10 minutes and a density of about 0.9367 g/cc. Resin G is an ethylene/1-octene copolymer, comprising about 55 percent (by weight) of a substantially linear polyethylene component having a melt index of about 15 g/10 minutes and a density of about 0.927 g/cc and about 45 percent of a heterogenous Ziegler Natta polyethylene component; the final polymer composition has a melt index of about 20 g/10 minutes and a density of about 0.9377 g/cc. Resin H is homopolymer polyproylene having a melt flow rate of 25 g/10 minutes in accordance with ASTM D-1238 condition 230° C./2.16 kg.

(2) Resins D, E, F, and G can be made according to U.S. Pat. Nos. 5,844,045, 5,869,575, 6,448,341, the disclosures of which are incorporated herein by reference. Melt index is measured in accordance with ASTM D-1238, condition 190° C./2.16 kg and density is measured in accordance with ASTM D-792.

(3) Nonwoven fabric was made using the resins indicated in Table 1 and evaluated for spinning and bonding performance. The trials were carried out on a spunbond line which used a Reicofil III technology with a beam width of 1.2 meters. The line was run at an output of 107 kg/hour/meter (0.4 g/min/hole) for all polyethylene resins and 118 kg/hour/meter (0.45 g/min/hole) with the polypropylene resin. Resins were spun to make about 2.5 denier fibers, corresponding to the fiber velocity of about 1500 m/min at 0.4 g/min/hole output rate. A mono spin pack was used in this trial, Each spinneret hole had a diameter of 0.6 mm (600 micron) and a L/D ratio of 4. Polyethylene fibers were spun at a melt temperature of 210° C. to 230° C., and polypropylene fibers were spun at a melt temperature of about 230° C.

(4) The embossed roll of the chosen calendar had an oval pattern with a bonding surface of 16.19 percent, with 49.9 bond points per cm.sup.2, a land area width of 0.83 mm×0.5 mm and a depth of 0.84 mm.

(5) For the polypropylene resin the embossed calendar and smooth roll were set at the same oil temperature. For polyethylene resins the smooth roll was set 2° C. lower than the embossed roll (this was to reduce tendency of roll wrap). All calendar temperatures that are mentioned in this report were the oil temperature of the embossed roll. The surface temperatures on the calendars were not measured. The nip pressure was maintained at 70 N/mm for all the resins.

(6) TABLE-US-00001 Flexural Elongation Mono or Rigidity to Peak Tenacity Basis Bonding bicomponent Abrasion (mN.Math.cm) Force (N/5 cm); Softness Example # Resin Weight Temp ° C. filament (mg/cm.sup.2) MD; CD percent MD; CD (SPU) Comp. 1 100 percent H 20 145 mono 0.183 0.7; 63.8; 49.73; 0.7 0.3 78.25 37.18 Comp 2 100 percent A 20 130 Mono 0.831 0.11; 61.08; 14.61; 2.4 0.02 62.95 7.66 Comp 2 100 percent A 20 125 Mono 0.984 0.12; 32.63; 11.08; 2.6 0.02 45.06 5.56 Comp 2 100 percent A 20 120 Mono 0.997 0.13; 24.95; 9.32; 2.3 0.05 36.27 4.10 Comp 3 100 percent A 28 130 Mono 0.885 0.29; 65.07; 20.37; 2.2 0.03 72.81 11.42 Comp 4 100 percent B 21 125 Mono 0.678 0.08; 76.89; 13.72; 2.7 0.03 84.20 8.29 Comp 5 100 percent B 28 125 Mono 1.082 0.15; 71.50; 17.75; 2.6 0.02 74.32 10.45 Comp 6 80 percent 21 130 Mono 0.53 0.06; 63.14; 12.0; 2.9 A/20 percent C 0.03 91.56 8.8 Compounded Comp 7 80 percent 28 130 Mono 0.56 0.16; 86.02; 17.79; 2.4 A/20 percent C 0.07 109.51 13.22 Compounded Comp 8 80 percent 21 130 Mono 0.42 0.07; 57.98; 11.45; 3   A/20 percent 0.03 86.16 8.15 C Dry Blended 9 100 percent D 20 135 Mono 0.399 0.07; 71.3; 7.25; 3   0.02 100.16 5.90 10 100 percent D 27 135 Mono 0.491 0.14; 98.79; 11.28; NA 0.06 125.78 9.54 11 100 percent E 20 135 Mono 0.411 0.08; 69.35; 7.30; 4   0.03 97.99 6.09 12 100 percent E 27 135 Mono 0.653 0.22; 89.60; 11.33; NA 0.07 123.71 9.76 13 100 percent F 20 135 Mono 0.421 0.09; 75.04; 7.02; 3.7 0.03 105.15 6.15 14 100 percent F 27 135 Mono 0.534 0.22; 93.45; 11.36; NA 0.07 118.21 9.21 15 100 percent G 20 135 Mono 0.435 0.08; 59.55; 8.25; NA 0.03 96.78 7.12 16 100 percent G 27 135 Mono 0.625 0.19; 95.89; 13.26; NA 0.06 116.26 11.13 Comp 17 55 percent 20 125 Mono 0.487 0.07; 88.1; 12.32; NA A/45 percent 0.02 113.8 7.71 C Dry Blended Comp 18 55 percent 27 125 Mono 0.673 0.12; 103.0; 17.40; NA A/45 percent 0.03 139.5 11.60 C Dry Blended